actually exist in the gas-pump) of separating the gaseous mixture from the liquid, and of renewing the vacuum, we should be able to determine (1) the total quantity of gases which the blood yields, and (2), by analysis, the proportion of each gas.

66

Now, with reference to the blood, by the application of the blood-pump," ," as it is called, we have learnt a great many facts relating to the nature of respiration, particularly that the difference of venous from arterial blood depends not on the presence of "effete matter," as used to be thought, but on the less amount of oxygen held by its colouring matter, and that the blood which flows back to the heart from different organs, and at different times, differs in the amount of oxygen and of carbonic acid gas it yields, according to the activity of the chemical processes which have their seat in the living tissues from which it flows.1 But this is not all that the blood-pump has done for us. applying it not merely to the blood, but to the tissues, we have learnt that the doctrine of Lavoisier was wrong, not merely as regards the place, but as regards the nature of the essential process in respiration. The fundamental fact which is thus brought to light is this, that although living tissues are constantly and freely supplied with oxygen, and are in fact constantly tearing it from the hæmoglobin which holds it, yet they themselves yield no oxygen to the vacuum. In other words, the oxygen which living protoplasm seizes upon with such energy that the blood which flows by it is compelled to yield it up, becomes so entirely part of the living material itself that it cannot be separated even by the vacuum. It is in this way only that we can understand the seeming paradox that the oxygen, which is conveyed in abundance to every recess of our bodies by the blood-stream, is nowhere to be found. Notwithstanding that no oxidation-product is formed, it becomes latent in every bit of living protoplasm; stored up in quantity proportional to its potential activity-i.e. to the work, internal or external, it has to do.

Thus you see that the process of tissue respiration-in other words, the relation of living protoplasm to oxygen-is very different from what Mayer, who localised oxidation in the capillaries, believed it to be. And this difference has a good Ideal to do with the relation of Process to Product in muscle. Let us now revert to the experiments on this subject which we are to take as exemplification of the truth of Mayer's forecasts.

The living muscle of a frog is placed in a closed chamber, which is vacuous-i.e. contains only aqueous vapour. The chamber is so arranged that the muscle can be made to contract as often as necessary. At the end of a certain period it is found that the chamber now contains carbonic acid gas in quantity corresponding to the number of contractions the muscle has performed. The water which it has also given off cannot of course be estimated. Where do these two products come from? The answer is plain. The muscle has been living all the time, for it has been doing work, and (as we shall see immediately) producing heat. What has it been living on? Evidently on stored material. If so, of what nature? If we look for the answer to the muscle, we shall find that it contains both proteid and sugar-producing material, but which is expended in contraction we are not informed. There is, however, a way out of the difficulty. We have seen that the only chemical products which are given off during contraction are carbonic acid gas and water. It is clear, therefore, that the material on which it feeds must be something which yields, when oxidised, these products, and these only. The materials which are stored in muscle are oxygen and sugar, or something resembling it in chemical composition.

And now we come to the last point I have to bring before you in connection with this part of my subject. I have assumed up to this moment that heat is always produced when a muscle does work. Most people will be ready to admit as evidence of this, the familiar fact that we warm ourselves by exertion. This is in reality no proof at all.

In

The proof is obtained when, a muscle being set to contract, it is observed that at each contraction it becomes warmer. such an experiment, if the heat capacity of muscle is known, the weight of the particular muscle, and the increase of temperature, we have the quantity of heat produced.

If you determine these data in respect of a series of contractions, arranging the experiments so that the work done in each contraction is measured, and immediately thereupon reconverted into heat, the result gives you the total product of the oxidation process in heat.

' Ludwig's first important research on this subject was published in 1862.

I now proceed abruptly (for the time at our disposal does not admit of our spending it on transitions) to the consideration of the other great question concerning vital motion, namely the question how the actions of the muscles of an animal are so regulated and co ordinated as to determine the combined move. ments, whether rhythmical or voluntary, of the whole body.

As every one knows who has read the "Lay Sermons," the nature and meaning of these often unintentional but always adapted motions, which constitute so large a part of our bodily activity, was understood by Descartes early in the seventeenth century. Without saying anything as to his direct influence on his contemporaries and successors, there can be no doubt that the appearance of Descartes was coincident with a great epochan epoch of great men and great achievements in the acquirement of man's intellectual mastery over nature. When he interpreted the unconscious closing of the eyelids on the approach of external objects, the acts of coughing, sneezing, and the like as mechanical and reflected processes, he neither knew in what part of the nervous system the mechanisms concerned were situated, nor how they acted. It was not until a hundred years after that Whytt and Hales made the fundamental experiments on beheaded frogs, by which they showed that the involuntary motions which such preparations execute cease when the whole of the spinal cord is destroyed-that if the back part of the cord is destroyed, the motions of the hind limbs, if the fore part, those of the fore limbs cease. It was in 1751 that Dr. Whytt published in Edinburgh his work on the involuntary motions of animals. After this the next great step was made within the recollection of living physiologists: a period to which, as it coincided with the event which we are now commemorating— the origin of the British Association-I will now ask your special attention.

Exactly forty-nine years ago Dr. Marshall Hall communicated to the Zoological Society of London the first account of his experiments on the reflex function of the spinal cord. The facts which he had observed, and the conclusions he drew from them, were entirely new to him, and entirely new to the physiologists to whom his communication was addressed. Nor can there be any reason why the anticipation of his fundamental discovery by Dr. Whytt should be held to diminish his merit as an original RELATION OF PRODUCT AND PROCESS IN MUSCLE (Result of one of Fick's experiments)

Total product reckoned as heat

6670 grammemillimeters. 156 milligrammeunits.

39'0 54'6

"

2 Descartes' scheme of the central nervous mechanism comprised all the " "reflex-action.' parts which we now regard as essential to Sensory nerves were represented by threads (filets) which connected all parts of the body to the brain ("Euvres," par V. Cousin, vol. iv. p. 359): motor nerves by tubes which extended from the brain to the muscles; motor centres by "pores" which were arranged on the internal surface of the ventricular cavity of the brain and guarded the entrances to the motor tubes. This cavity was supposed to be kept constantly charged with "animal spirits" furnished to it from the heart by arteries specially destined for the purpose. Any "incitation "of the surface of the body by an external object which affects the organs of sense does so, according to Descartes, by producing a motion at the incited part. This is communicated to the pore by the thread and causes it to open, the consequence of which is that the "animal spirit" contained in the ventricular cavity enters the tube and is conveyed by it to the various muscles with which it is connected, so as to produce the appropriate motions. The whole system, although it was placed under the supervision of the "âme raisonable" which had its office in the pineal gland, was capable of working independently. As instances of this mechanism Descartes gives the withdrawal of the foot on the approach of hot objects, the actions of swallowing, yawning, coughing, &c. As it is necessary that, in the performance of these complicated motions, the muscles concerned should contract in succession, provision is made for this in the construction of the systems of tubes which represent the motor nerves. The weakness of the scheme lies in the absence of fact basis. Neither threads nor pores nor tubes have any existence.

investigator. In the face of historical fact it is impossible to regard him as the discoverer of the "reflex function of the spinal cord," but we do not the less owe him gratitude for the application he made of the knowledge he had gained by experiments on animals to the study of disease. For no one who is acquainted with the development of the branch of practical medicine which relates to the diseases of the central nervous system will hesitate in attributing the rapid progress which has been made in the diagnosis and treatment of these diseases, to the impulse given by Dr. Marshall Hall to the study of nervous pathology.

In the mind of Dr. Marshall Hall the word reflex had a very restricted meaning. The term "excito-motary function," which he also used, stood in his mind for a group of phenomena of which it was the sole characteristic that a sensory impression produced a motor response. During the thirty years which have elapsed since his death, the development of meaning of the word reflex has been comparable to that of a plant from a seed. The original conception of reflex action has undergone, not only expansion, but also modification, so that in its wider sense it may be regarded as the empirical development of the philosophical views of the animal mechanism promulgated by Descartes. Not that the work of the past thirty years by which the physiology of the nervous system has been constituted can be attributed for a moment to the direct influence of Descartes. The real epochmaker here was Johannes Müller. There can be no doubt that Descartes' physiological speculations were well known to him, and that his large acquaintance with the thought and work of his predecessors conduced, with his own powers of observation, to make him the great man that he was; but to imagine that his ideas of the mechanism of the nervous system were inspired, or the investigations by which, contemporaneously with Dr. Marshall Hall, he demonstrated the fundamental facts of reflex action, were suggested by the animal automatism of Descartes, seems to me wholly improbable.

I propose, by way of conclusion, to attempt to illustrate the nature of reflex action in the larger sense, or, as I should prefer to call it, the Automatic Action of Centres, by a single example -that of the nervous mechanism by which the circulation is regulated.

The same year that J. R. Mayer published his memorable essay, it was discovered by E. H. Weber that, in the vagus nerve, which springs from the medulla oblongata and proceeds therefrom to the heart, there exist channels of influence by which the medulla acts on that wonderful muscular mechanism. Almost at the same time with this, a series of discoveries were made relating to the circulation, which, taken together, must be regarded as of equal importance with the original discovery of Harvey. First, it was found by Henle that the arterial bloodvessels by which blood is distributed to brain, nerve, muscle, gland, and other organs, are provided with muscular walls like those of the heart itself, by the contraction or dilatation of which the upply is increased or diminished according to the requirements of the particular organ. Secondly, it was discovered simultaneously, but independently, by Brown-Séquard and Augustus Waller, that these arteries are connected by nervous channels of influence with the brain and spinal cord, just as the heart is. Thirdly, it was demonstrated by Bernard that what may be called the heart-managing channels spring from a small spot of grey substance in the medulla oblongata, which we now call the "heart-centre"; and a little later by Schiff, that the artery-regulating channels spring from a similar head-central office, also situated in the medulla oblongata, but higher up, and from subordinate centres in the spinal cord.

If I had the whole day at my disposal and your patience were inexhaustible, I might attempt to give an outline of the issues to which these five di coveries have led. As it is, I must limit myself to a brief discus ion of their relations to each other, in order that we may learn something from them as to the nature of automatic action.

Sir Isaac Newton, who, although be knew nothing about the structure of nerves, made some shrewd forecasts about their action, attributed to those which are connected with muscles an

The dates of the discoveries relating to this subject here referred to are as follows:-Muscular Structure of Arteries, Henle, 1841; Function of Cardiac Vagus, E. H. Weber, 1845; C nstricting Nerves of Arteries, B. Séquard, 1852, Aug. Waller, 1853: Cardiac Centre, Bernard, 18:8; Vascu. lar Centre, Schiff, 1858; Dilating Nerves, Schiff, 1854; Eckhard, 1864: Lovén. 1866. Of the more recent researches by which the further elucidation of the mechanism by which the distribution of blood is adapted to the requirements of each organ, the most important are those of Ludwig and his pupils and of Heidenhain.

alternative function. He thought that by means of motor nerves the brain could determine either relaxation or contraction of muscles. Now as regards ordinary muscles, we know that thi is not the case. We can will only the shortening of a muscle not its lengthening. When Brown-Séquard discovered the function of the motor nerves of the blood-vessels, he assumed that the same limitation was applicable to it as to that of mas cular nerves in general. It was soon found, however, that this assumption was not true in all cases-that there were certain instances in which, when the vascular nerves were interfered with, dilatation of the blood-vessels, consequent on relaxation of ther muscles, took place; and that, in fact, the nervous mechanis by which the circulation is regulated is a highly-complicated one, of which the best that we can say is that it is perfectly adapted to its purpose. For while every organ is supplied with mucur arteries, and every artery with vascular nerves, the influenes which these transmit is here relaxing, there constricting, acc ing (1) to the function which the organ is called upon to d charge; and (2) the degree of its activity at the time. At th same time the whole mechanism is controlled by one and the same central office, the locality of which we can determine wit exactitude by experiment on the living animal, notwithstanding that its structure affords no indication whatever of its fitness for the function it is destined to fulfil. To judge of the complicate nature of this function we need only consider that in no sing organ of the body is the supply of blood required always th same. The brain is during one hour hard at work, daring the next hour asleep; the muscles are at one moment in seve exercise, the next in complete repose; the liver, which before: meal is inactive, during the process of digestion is turgid blood, and bu ily engaged in the chemical work which beling to it. For all these vicissitudes the tract of grey substance wh we call the vascular centre has to provide. Like a s steward of the animal household, it has, so to speak, to exercise perfect and unfailing foresight, in order that the nutritive rial which serves as the oil of life for the maintenance of exc vital process, may not be wanting. The fact that this wonder function is localised in a particular bit of grey substance is whe is meant by the expression "automatic action of a centre." But up to this point we have looked at the subject from side only.

No state ever existed of which the administration was exch sively executive-no government which was, if I may be exeuse. the expression, absolutely absolute. If in the animal orga we impose on a centre the responsibility of governing a par lar mechanism or process, independently of direction from a ve we must give that centre the means of being itself influenced what is going on in all parts of its area of government. other words, it is as essential that there should be channels of formation passing inwards, as that there should be channels influence passing outwards. Now what is the nature of these channels of information? Experiment has taught us not mere with reference to the regulation of the circulation, but with re ference to all other automatic mechanisms, that they are various in their adaptation as the outgoing channels of influence Thus the vascular centre in the medulla oblongata is so cogni of the chemical condition of the blood which flows through it, that if too much carbonic acid gas is contained in it, the centre acts on information of the fact, so as to increase the velocity the blood-stream, and so promote the arterialisation of the blood. Still more strikingly is this adaptation arrangement by which the balance of pressure and resistance the blood-vessels is regulated. The heart, that wonderf muscular machine by which the circulation is maintained, is ra nected with the centre, as if by two telegraph wires-one which is a channel of influence, the other of information. Br the latter the engineer who has charge of that machine en information to headquarters whenever the strain on his machine is excessive, the certain response to which is relaxation of the arteries and diminution of pressure. By the former he is enable to adapt its rate of working to the work it has to do.

seen in the

If Dr. Whytt, instead of cutting off the head of his frog, removed only its brain-i.e., the organ of thought and conscions ness-he would have been more astonished than he actually at the result; for a frog so conditioned exhibits, as regar bodily movements, as perfect adaptiveness as a normal freg But very little careful observation is sufficient to show the fr

ence.

Being incapable of the simplest ment 1 acts, this trac animal automaton has no notion of requiring food or of seeking it, has no motive for moving from the place it happens to

occupy, emits no utterance of pleasure or distress. Its life processes continue so long as material remains, and are regulated mechanically.

To understand this all that is necessary is to extend the considerations which have been suggested to us in our very cursory study of the nervous mechanism by which the working of the heart and of arteries is governed, to those of locomotion and voice. Both of these we know, on experimental evidence similar to that which enables us to localise the vascular centre, to be regulated by a centre of the same kind. If the behaviour of the brainless frog is so natural that even the careful and intelligent observer finds it difficult to attribute it to anything less than intelligence, let us ask ourselves whether the chief reason of the difficulty does not lie in this, that the motions in question are habitually performed intelligently and consciously. Regarded as mere mechanisms, those of locomotion are no doubt more complicated than those of respiration or circulation, but the difference is one of degree, not of kind. And if the respiratory movements are so controlled and regulated by the automatic centre which governs them, that they adapt themselves perfectly to the varying requirements of the organism, there is no reason why we should hesitate in attributing to the centres which preside over locomotion powers which are somewhat more extended.

But perhaps the question has alrea ly presented itself to your minds, What does all this come to? Admitting that we are able to prove (1) that in the animal body, Product is always proportional to Process, and (2), as I have endeavoured to show you in the second part of my discourse, that Descartes' dream of animal automatism has been realised, what have we learnt thereby? Is it true that the work of the last generation is worth more than that of preceding ones?

If I only desired to convince you that during the last halfcentury there has been a greater accession of knowledge about the function of the living organism than during the previous one, I might arrange here in a small heap at one end of the table the physiological works of the Hunters, Spallanzani, Fontana, Thomas Young, Benjamin Brodie, Charles Bell, and others, and then proceed to cover the rest of it with the records of original research on physiological subjects since 1831, I should find that, even if I included only genuine work, I should have to heap my table up to the ceiling. But I apprehend this would not give us a true answer to our question. Although, etymologically, Science and Knowledge mean the same thing, their real meaning is different. By science we mean, first of all, that knowledge which enables us to sort the things known according to their true relations. On this ground we call Haller the father of physiology, because, regardless of existing theories, he brought together into a system all that was then known by observation or experiment as to the processes of the living body. But in the "Elementa Physiologiæ " we have rather that out of which science springs than science itself. Science can hardly be said to begin until we have by experiment acquired such a knowledge of the relation between events and their antecedents, between processes and their products, that in our own sphere we are able to forecast the operations of nature, even when they lie beyond the reach of direct observation. I would accordingly claim for physiology a place in the sisterhood of the sciences, not because so large a number of new facts have been brought to light, but because she has in her measure acquired that gift of prevision which has been long enjoyed by the hi her branches of natural philosophy. In illustration of this I have endeavoured to show you that every step of the laborious investigations undertaken during the last thirty years as to the process of nutrition, has been inspired by the previsions of J. R. Mayer, and that what we have learnt with so much labour by experiments on animals is but the realisation of conceptions which existed two hundred years ago in the mind of Descartes as to the mechanism of the nervous system. If I wanted another example I might find it in the previsions of Dr. Thomas Young as to the mechanism of the circulation, which for thirty years were utterly disregarded, until, at the epoch to which I have so often adverted, they received their full justification from the experimental investigations of Ludwig.

But perhaps it will occur to some one that if physiology founds her claim to be regarded as a science on her power of anticipating the results of her own experiments, it is unnecessary to make experiments at all. Although this objection has been frequently heard lately from certain persons who call themselves philosophers, it is not very likely to be made seriously here. The

answer is, that it is contrary to experience. Although we work in the certainty that every experimental result will come out in accordance with great principles (such as the principle that every plant or animal is both, as regards form and function, the outcome of its past and present conditions, and that in every vital process the same relations obtain between expenditure and product as hold outside of the organism), these principles do little more for us than indicate the direction in which we are to proceed. The history of science teaches us that a general principle is like a ripe seed, which may remain useles and inactive for an indefinite period, until the conditions favourable to its germination come into existence. Thus the conditions for which the theory of animal automatism of Descartes had to wait two centuries, were (1) the acquirement of an adequate knowledge of the structure of the animal organism, and (2) the development of the sciences of physics and chemistry; for at no earlier moment were these sciences competent to furnish either the knowledge or the methods necessary for its experimental realisation; and for a reason precisely similar Young's theory of the circulation was disregarded for thirty years.

I trust that the examples I have placed before you to-day may have been sufficient to show that the investigators who are now working with such earnestness in all parts of the world for the advance of physiology, have before them a definite and wellunderstood purpose, that purpose being to acquire an exact knowledge of the chemical and physical proces es of animal life, and of the self-acting machinery by which they are regulated for the general good of the organism. The more singly and straightforwardly we direct our efforts to these ends, the sooner we shall attain to the still higher purpo-e-the effectual application of our knowledge for the increase of human happiness.

The Science of Physiology has already afforded her aid to the Art of Medicine in furnishing her with a vast store of knowledge obtained by the experimental investigation of the action of remedies and of the causes of disease. These investigations are now being carried on in all parts of the world with great diligence, so that we may confidently anticipate that during the next generation the progress of pathology will be as rapid as that of physiology has been in the past, and that as time goes on the practice of medicine will gradually come more and more under the influence of scientific knowledge. That this change is already in progress we have abundant evidence. We need make no effort to hasten the process, for we may be quite sure that, as soon as science is competent to dictate, art will be ready to obey.

SECTION F GEOGRAPHY

OPENING ADDRESS BY SIR JOSEPH D. HOOKER, C.B., K.C.S.I., F.R.S., &c., PRESIDENT OF THE SECTION

On Geographical Distribution

IT has been suggested that a leading feature of the sectional addresses to be delivered on the occasion of this, the fiftieth anniversary of the meetings of the British Association, should be a review of the progress made during the last half century in the branches of knowledge which the sections respectively represent.

It has further been arranged that, at so auspicious an epoch, the sections should, when possible, be presided over by past Presidents of the Association. This has resulted in almost every sectional chair being occupied by a President eminent as a cultivator of the science with which his section will be engaged, though not the one I have the honour of filling, which, from the fact of there being no profes ed ge grapher amongst the surviving past Presidents, has been confided to an amateur.

Under these circumstances I should be untrue to myself and to you, if I presumed to address you as one conversant with geography in any extended signification of the word, or if I attempted to deal with that important and attractive branch of it, topographical discovery, which claims more or less exclusively the time and attention of the geographers of this country. It is more fitting for me, and more in keeping with the objects of this Association, that I be allowed to discourse before you on one of the many branches of science the pursuit of which is involved in the higher aims of geographers, and which, as we are informed by an accomplished cultivator of the science, are

integral portions of scientific geography. Of these none is more important than that of the distribution of animals and plants, which further recommends itself to you on this occasion from being a subject that owes its great progress during the last half-century as much to the theories advanced by celebrated voyagers and travellers as to their observations and collections. Before, however, I proceed to offer you a sketch of the progress made during the lifetime of the Association in this one branch, I must digress to remind you, however briefly, of the even greater advances made in others, in many cases through the direct or indirect instrumentality of the Association itself, acting in concert with the Royal and with the Royal Geographical Societies.

In topography the knowledge obtained during this half century has been unprecedently great. The veil has been withdrawn from the sources of the Nile, and the lake systems of Central Africa have been approximately localised and outlined. Australia, never previously traversed, has been crossed and recrossed in various directions. New Guinea has had its coasts surveyed, and its previously utterly unknown interior has been here and there visited. The topography of Western China and Central Asia, which had been sealed books since the days of Marco Polo, has been explored in many quarters. The elevations of the highest mountains of both hemispheres have been accurately determined, and themselves ascended to heights never before attained; and the upper regions of the air have been ballooned to the extreme limit beyond which the life-sustaining organs of the human frame can no longer perform their functions. In hydrography the depths of the great oceans have been sounded, their shores mapped, and their physical and natural history explored from the Equator to beyond both polar circles. In the Arctic regions the highest hitherto attained latitudes have been reached; Greenland has been proved to be an island; and an archipelago has been discovered nearer to the Pole than any other land. In the Antarctic regions a new continent has been added to our maps, crowned with one of the loftiest known active volcanoes, and the Antarctic ocean has been twice traversed to the 79th parallel. Nor have some of the negative results of modern exploration been less important, for the Mountains of the Moon and many lesser chains have been expunged from our maps, and there are no longer believers in the inland sea of Australia or in the open ocean of the Arctic pole. Of these and many others of the geographical discoveries of the last half-century full accounts will be laid before you, prepared for this section by able geographers; of whom Mr. Markham will contribute Arctic discovery; Sir Richard Temple, Asiatic; Lieut.-Col. Sir James Grant and Mr. H. Waller, African; Mr. Moseley, Australian; Mr. Trelawny Saunders, Syrian (including the Holy Land); the Hydrographer of the Admiralty will undertake the great oceans, and Mr. F. Galton will discuss the improvements effected in the instruments, appliances, and methods of investigation employed in geographical researches.

Of other branches of science which are auxiliary to scientific geography, the majority will be treated of in the sections of the Association to which they belong; but there are a few which I must not, in justice to the geographers who have so largely contributed to their advance, leave unnoticed.

2

Such is Terrestrial Magnetism, which had as its first investigators two of our earliest voyagers, the ill-fated Hudson and Halley, who determined the magnetic dip in the north polar and tropical regions respectively. Theirs were the precursors of a long series of scientific expeditions, during which the dipping needle was carried almost from Pole to Pole, and which culminated in the establishment, mainly under the auspices of this Association, of the magnetic survey of Great Britain, of fixed magnetic observatories in all quarters of the globe, and of the Antarctic expedition of Sir James Ross, who, since the founda. tion of the Association, planted the dipping needle over the northern Magnetic Pole, and carried it within 200 miles of the southern one.

Major-General Strachey, in a lecture delivered before the Royal Geographical Society (Proceedings, vol. xxxi. p. 179, 1877), discusses, with just appreciation and admirable clearness, the interdependence of the sciences which enter into the study and aims of scientific geography, and which he enumerates under fourteen heads. This lecture contains the ablest review

of the subject known to me. It might very well be entitled "The whole duty of the Geographer." Every traveller's outfit should include a copy of it, and one should accompany every prize given by the Geographical Society to students for proficiency in geographical knowledge.

2 The subject of an able lecture "On the Magnetism of the Earth," delivered before the Royal Geographical Society by the Hydrographer of the Admiralty (Proceedings, vol. xxi. p. 20, 1876).

Nor is the geography of this half century less indebted physicists, geologists, and naturalists. It is to a most learne traveller, and naturalist, Von Baer, that the conception is du that the westward deflection of all the South Russian rivers i caused by the revolution of the globe on its axis.1 It was geologist, Ramsay, who explained the formation of so many lake beds in mountain regions by the gouging action of glaciers. I was a physicist and mountaineer, Tyndal, who discovered th properties of ice upon which the formation and movement glaciers depend. The greatest of naturalist-voyagers, Darwa within the same half-century has produced the true theory t coral reefs and atolls, showed the relations between volcan islands and the rising and sinking of the bottom of the ocean and proved that along a coast line of 2480 miles the southern part of the continent of South America has been gradually ele vated from the sea level to 600 feet above it. Within alm the same period Poulett Scrope and Lyell have revolutionised the theory of the formation of volcanic mountains, showing th.. these are not the long-taught upheavals of the crust of the earth but are heaped up deposits from volcanic vents, and they have largely contributed to the abandonment of the venerable the that mountain chains are sudden up-thrusts. Within the same period, the theory of the great oceans having occupied their pre sent positions on the globe from very early geological times was first propounded by Dana, the companion of Wilkes in his ex pedition round the world, and is supported by Darwin and by Wallace.

In Meteorology the advance is no less attributable to the labours of voyagers and travellers. The establishment of the Meteore logical Office is due to the energy and perseverance of a great navigator, the late Admiral Fitzroy.

Another domain of knowledge that claims the strongest synpathies of the geographer is Anthropology. It is only within the last quarter of a century that the study of man under hus physical aspect has been recognised as a distinct branch of science, and represented by a flourishing society, and by annual inter national congresses.

I must not conclude this notice without a passing tribute to a department of geography that has occupied the attention of too few of its cultivators. I mean that of literary research. Never theless, in this too the progress has been great; and I need only mention the publications of the Hakluyt Society, and two works of prodigious learning and the greatest value, "The Book of Marco Polo, the Venetian,' ," and "A History of Ancient Geography," ,"4 to prove to you that one need not to travel to new lands to be a profound and sagacious geographer.

I have asked you to accept the geographical distribution of organic beings as the subject which I have chosen for this address It is the branch with which I am most familiar; it illustrates extremely well the interdependence of those sciences which the geographer should study, and as I have before observed, its progress has been in the main due to the labours of voyagers and travellers.

In the science of distribution, Botany took the lead. Hun boldt, in one of his essays, says that the germ of it is to be fou in an idea of Tournefort, developed by Linnæus. Tournefort was a Frenchman of great learning, and, moreover, a great traveller. He was sent by the King of France in 1700 to explore the islands of Greece and mountains of Armenia, in the interest of the Jardin des Plantes, and his published narrative is full of valuable matter on the people, antiquities, and natural productions of the countries he visited. The idea attributed to him by Humboldt, is that in ascending mountains we meet successively with vegetations that represent those of successively higher lat tudes; upon which Humboldt observes: "Il ne fallut pas une grande sagacité pour observer que sur les pentes des hautes montagnes de l'Arménie, des végétaux des différentes latitudes suivent comme les climats superposés l'un sur les autres"; bat he goes on to remark, "cette idée de Tournefort developpée par Linné dans deux dissertations intéressantes (Stationes et Colone Plantarum), renferment cependant le germe de la Géographie

Von Baer, "Ueber ein allgemeines Gesetz in der Gestaltung der Fluss betten," St. Petersb. Bull. Sc. ii. (1860).

2 Dana in American Journal of Science, ser. 2, vol. iii. p. 352 (1847), and various later publications.

3 By Colonel Henry Yule, C. B. (ed. 1, 1871; ed. 2, 1875).

4 By S. H. Bunbury (1879).

5Sur les lois que l'on observe dans le distribution des formes végétalts" (Mémoire lu à l'Institut de France, January 29, 1816).

6 I have been unable to find any such idea expressed in Tournefort's works. Edward Forbes, however, also attributes the idea to Tournefort (Memoirs of the Geology Survey, vol i. p. 351).

Botanique." Tournefort's idea was, however, an advanced one for the age he lived in, and should not be judged by the light of the knowledge of a succeeding century. He had no experience of other latitudes than the few intervening between Paris and the Levant. Humboldt himself did not suspect the whole bearing of the idea on the principles of geographical distribution, and that the parallelism between the floras of mountains and of latitudes was the result of community of descent of the plants composing the floras, not that it was brought about by physical causes. The idea of the early part of the eighteenth century is, when rightly understood, found to be the forerunner of the matured knowledge of the middle of the nineteenth.

The labours of Linnæus, himself a traveller, and whose narratives give him high rank as such, paved the way to a correct study of botanical geography. Before his time little or no attention was paid to the topography of plants, and he was the first to distinguish, to lay down rules, and to supply models for these two important elements in their life-history- namely, their habitats or topographical localisation, and their stations, or the physical nature of their habitats. In his "Stationes Plantarum,"1 Linnæus defines with precision twenty-four stations characterised by soil, moisture, exposure, climate, &c., which, with comparatively slight modifications and improvements, have been adopted by all subsequent authorities. Nor, indeed, was any marked advance in this subject made, till geological observation and chemical analysis supplemented its shortcomings. In his essay "De coloniis plantarum," published fourteen years after the "Stationes," he says, "Qui veram cunque et solidam plantarum scientiam aucupatur, patriam ipsarum ac sedem cujusque propriam haud sane ignorabit," and he proceeds to give an outline of the distribution of certain plants on the globe, according to climate, latitude, &c., and to indicate their means of transport by winds, birds, and other agencies. India (meaning the tropics of both worlds) he characterises as the region of palms; the temperate latitudes, of herbaceous plants; the northern, of mosses, algæ, and conifere; and America, of ferns;-thus preparing the way for the next great generaliser in the field.

4

This was the most accomplished and prolific of modern travellers, Humboldt, who made botany a chief pursuit during all his journeys, and who seems, indeed, to have been devoted to it from a very early age. His first work was a botanical one, the "Flora Friburgensis," and we have it on his own authority that three years before its publication, when he was only just of age (in 1790) he communicated to his friend G. Förster, the companion of Cook in his second voyage, a sketch of a geography of plants. It was not, however, till his return from America that his first essay on Botanical Geography appeared, which at once gave him a very high position as a philosophical naturalist. Up to the period of its appearance there had been nothing of the kind to compare with it for the wealth of facts, botanical, meteorological, and hypsometrical, derived from his own observations, from the works of travellers and naturalists, and from personal communication with his contemporaries, all correlated with consummate skill and discussed with that lucidity of exposition of which he was a master. The great feature of this essay is the exactness of the methods employed for estimating the conditions under which species, genera, and families are grouped geographically, and the precision with which they are expressed. This was succeeded in 1815, and subsequently, by four other essays on the same subject. Of these the most valuable is the Prolegomena,' ,"5 in which he dwells at length on the value of

I

Amanitates Academicæ, vol. iv. p. 64, 1754.

2 Ibid. vol. viii. p. 1, 1768.

3 Between the dates of the writings of Linnæus and Humboldt,_two notable works on geographical distribution appeared. One by Frid. Stromeyer ("Commentatio inauguralis sistens Historia Vegetabilium Geographicæ specimen," Göttingen, 1800), is an excellent syllabus of the points to be attended to in the study of distribution, but without examples; the other is a too general work by Zimmermann, entitled, "Specimen Zoologiæ Geographicæ, Quadrupedum Domicilia et Migrationes sistens," Lugd. Bat. 1777, which he followed by "Geographische Geschichte des Menschen und der allgemein verbreiteten vierfüssigen Thiere, nebst einer hieher gehörigen zoologischen Weltcharte, Leipzig, 1778-1783.'

"

4 "Essai sur la Géographie des Plantes," par A. de Humboldt et Aimé Bonpland; rédigée par A. de Humboldt, lu à la Classe des Sc. Phys. et Math. de l'Institut Nationale, 17 Nivôse de l'An 13, 1805.

5 "De Distributione Geographica plantarum secundum Cali temperiem et altitudinem Montium, Prolegomena." This appeared in quarto in the first volume of the "Nova Genera et Species Plantarum" in 1815, and separately in an octavo form in 1817. Humboldt's other works on geographical distribution are "Notationes ad Geographiam Plantarum spectantes," 1815; 'Ansichten der Natur," 1808, and ed. 2, 1827; "Nouvelles Recherches sur les lois que l'on observe dans la Distribution des formes végétales" (1816); and an article with a similar title in the "Dictionnaire des Sciences Naturelles,' vol. xviii p. 422, 1820.

numerical data, and explains his "Arithmeticæ botanices," which consists in determining the proportion which the species of certain large families or groups of families bear to the whole number of species composing the floras in advancing from the Equator to the Poles, and in ascending mountains. Some kinds of plants, he says, increase in numbers relatively to others in proceeding from the Equator to the Poles, as ferns, grasses, amentiferous trees, &c.; others decrease, as Rubiaceæ, Malvacea, Compositæ, &c.; whilst others still, as Labiata, Cruciferæ, &c., find their maximum in temperate regions, and decrease in both directions. He adds that it is only by accurately measuring this decrease or increase that laws can be established, when it is found that these present constant relations to parallels of temperature. Furthermore, he says that in many cases the whole number of plants contained in any given region of the globe may be approximately determined by ascertaining the number of species of such families.

The importance of this method of analysing the vegetation of a country in researches in geographical botany is obvious, for it affords the most instructive method of setting forth the relations that exist between a flora and its geographical position and climatal conditions.

Humboldt's labours on the laws of distribution were not limited to floras, they included man and the lower animals, cultivated and domesticated, as well as native; they may not be works of the greatest originality, but they show remarkable powers of observation and reflection, astonishing industry, conscientious exactitude in the collection of data, and sagacity in the use of them; he is indisputably the founder of this department of geographical science.

No material advance was made towards improving the laws of geographical distribution so long as it was believed that the continents and oceans had experienced no great changes of surface or of climate since the introduction of the existing assemblages of animals and plants. This belief in the comparative stability of the surface was first dispersed by Lyell, who showed that a fauna may be older than the land it inhabits. To this conclusion he was led by the study of the recent and later tertiary molluscs of Sicily, which he found had migrated into that land before its separation from the continent of Italy. Just, he adds, as the plants and animals of the Phlegræan fields had colonised Monte Nuovo since that mountain was thrown up in the sixteenth century; whence, he goes on to say, we are brought to admit the curious result, that the fauna and flora of Val de Noto, and of some other mountain regions of Italy, are of higher antiquity than the country itself, having not only flourished before the lands were raised from the deep, but even before they were deposited beneath the waters. The same idea occurred to Darwin, who, alluding to the very few species of living quadrupeds which are altogether terrestrial in habit, that are common to Asia and America, and to these few being confined to the extreme frozen regions of the North, adds, "We may safely look at this quarter (Behring's Straits), as the line of communication (now interrupted by the steady progress of geological change), by which the elephant, the ox, and the horse entered America, and peopled its wide extent.

The belief in the stability of climatal conditions during the lifetime of the existing assemblages of animals and plants was also dispelled by the discovery, throughout the northern temperate regions of the old and new worlds, of Arctic and boreal plants on all their mountains, and of these fossilised on their lowlands, and which discoveries led to the recognition of the glacial period and glacial ocean.

The first and boldest attempt to press the results of geological and climatal changes into the service of botanical and zoological geography was that of the late Edward Forbes, a naturalist of genius, who, like Tournefort, chose the Levant as the field for his early labours. In the year 1846, Forbes communicated a paper to the Natural History section of this Association, on the distribution of endemic plants, especially those of the British

1 Humboldt's isothermal lines and laws of geographical distribution are obviously the twin results of the same researches, one physical, the other biological.

2 I do not hereby imply that no progress was made in the knowledge of the facts of distribution, for, over and above many treatises on the distribution of the plants of local floras, there appeared, in 1816, Schouw's "Dissertatio de sedibus plantarum originariis"; which was followed in 1822 by his excellent "Grundtrack til el almendelig Plante-Geographie," of which the German edition is entitled, "Grundzüge einer allgemeinen Pflanzengeographie." 3 ** Principles of Geology," ed. 3, vol. iii. p. 376, 1834.

4 Journal of Researches in Geology and Natural History, &c., p. 151 1839.