PREFACE. THIS volume terminates with the five hundredth number of the "CHEMICAL NEWS," and we may, perhaps, at this juncture, not unfitly say a word or two concerning our enterprise. The reader cannot fail to have observed that we have recently made several important improvements in the "CHEMICAL NEWS." We have striven to make it not only a chemical newspaper, but a STANDARD WORK OF REFERENCE. Besides the original and critical papers proper to a journal, we are now giving, under the head of "Chemical Notices from Foreign Sources," the titles of all the contemporary chemical papers published throughout the world, and abstracts of the more important of them. Moreover, the Index has been very carefully compiled, and made much more copious and available for ready reference. We may fairly state that the two half-yearly volumes of the "CHEMICAL NEWS" represent essentially, in extent of material and facility of reference, the Jahresberichte der Chemie; and, in fact, we may claim for the "CHEMICAL NEWS" that its annual issue is a handy Yearbook of Chemical Science. It is a matter of gratification to the Editor to find that the "CHEMICAL NEWS" has attained so large a circulation in America. There it is re-printed in monthly numbers, to which is added a supplement to chronicle any scientific matters pertaining specially to America. Our circulation, including that of the American reprint, has risen to about 10,000 copies of each issue. This fact we are constrained to note, since, in the majority of instances, the only rewards the man of science can ever secure are the appreciation of his labours by fellow-workers and the consciousness of having served mankind. For more than a quarter of a century the "CHEMICAL NEWS" (with its predecessor, the Chemical Gazette), has faithfully recorded the progress of Chemistry and cognate sciences at home and abroad; so, in the future, our constant anxiety will be exercised to render it a still worthier representative of Chemical Science. THE CHEMICAL NEWS. VOLUME XIX. EDITED BY WILLIAM CROOKES, F.R.S., &c. No. 474.-FRIDAY, JANUARY 1, 1869. ACCURACY. ACCURACY and knowledge of detail are the great aims of modern scientific men. There may be much that is indefinite, but, when accuracy comes, every opposing speculation and supposed law or fact falls as hopelessly before it as that celebrated road to the skies which was felled to the earth by a well-aimed blow from Jack's Speculation in its early meaning is seldom heard. Thought must stand on scientific ground and follow a scientific line; if it is diverted it must be at angles which accord with the logic of nature. hatchet. We sometimes like before looking at our own age to glance at that which is past. It is pleasant to associate ourselves with our brethren, however far separated. If we wish to know the history of our own thoughts we trace them back in our minds, and if we wish to know how the world learned to think we must look to the ages which preceded the building of our ideas. There is, however, another reason not so purely logical, but perhaps more powerful. There is a richness in these early thoughts because they have a tint of the eastern sun which never fades, and we shall admire their brightness whilst time lasts, or until that day when the poet comes who shall exhaust in his writings the delight which children have in the fields and the sunshine. In early days of the world thoughts were not enchained by experiments, and great wide souls made boundless systems which endeavoured to include the infinite magnitudes that presented themselves to view in time and space. The warm colours were obtained from the fire in which they were smelted, although the heat itself has been quenched with an unheard hiss in the western seas. If we admire order, here is an idea stately and great; perhaps the formality, and, if we may add also, the imperial dignity, are among the early modes of seeking logical order and extreme accuracy. The Desatir is said to mention a system of the heavens in which each star reigns for a thousand years, and has besides one star for a prime minister; and when every heavenly body shall have gone through the two offices of minister and ruler one great heavenly period shall have been accomplished. Every year is made of days, which days again consist of one revolution of Saturn or nearly thirty years. Every year, therefore, was above 10,000 of our years. Precision in form was taken for accuracy. On this point it is to be feared that even chemists may err. Part of the above shows a desire to comprehend the infinite, and we do somewhat the same when we think of the most probableif not well proved-central kosmic sun round which our own system revolves. The classical ancients seemed to seek accuracy by a very different method, and, unable to comprehend the reasoning faculty has little reverence, and when it cannot grasp the wonderful it throws it aside, for the same reason as the hard uncle left the babes in the wood. The north, like the east, had no desire to diminish the For wonderful, but, perhaps, when they talked of the lights the moon, they meant no more by that great capacious of heaven being pursued by a wolf who would swallow up throat than our own stern Carlyle means when he uses such an expression as "infinite abyss." They must, however, bear the blame of inaccuracy of words. The Greek mind reduces all wild solemnities to the most unromantic common place, and thereby brings us out of much folly into plain common sense. moon in the second century. "My patience is worn out Hear the complaint of the by the philosophers who are perpetually disputing about me-who I am, of what size, how it happens that I am sometimes round and sometimes full, at other times cut in half; some say I am inhabited, others that I am only to fit on me any notion they may have. a looking glass hanging-over the sea, and every one seems that my light is another's and stolen from the sun, not They even say hesitating to set me and my brother in opposition. it is not right that they should call the sun a stone or a red-hot clump." It was centuries before this that the sun had been called a red-hot stone as large as the Peleponesus. We in our time cannot differ far in principle from this view, and it has taken very long indeed to make steps in accuracy regarding the constitution of the heavenly bodies; still we tend to it. It would seem as if the world had always a large amount of matter standing for facts. We take pleasure in looking at an old chemical work," Dictionnaire de Chimie," of the "Encyclopédie Méthodique," begun in 1786 on such a scale that the first volume, quarto and double columned, and of 773 pages, goes only the length of the word "Airelle." Then knowledge was actually as bulky as now, although, perhaps, no sentence is written with accuracy. had enough to say to fill their minds;-nay, we may go They very much farther back, and for mere curiosity let us quite at random take up Pliny, who knew everything of his time in a rough way, and let us ask the cure for any common pain-say headache-we are not disappointed. The remedies are abundant. The heads of slugs or wool grease, or the bones of a vulture's head, or its brains mixed with oil and cedar rosin and applied to the head and nostrils; more are given equally promising, and some pretending to great accuracy, such as "the small bone from the head of a snail that has been found between two cart ruts, and after being passed through a gold ring with a piece of ivory, is attached to the patient in of dog's skin, a remedy well known to most always used with success." The whole course of thought is now changed among | men who have received even a tinge of science, but the .spirit of old times is not quite forgotten. There must be many men who remember in early days that it was enough to bring forward a good quotation when they wanted a proof, and there must be many who know minds incapable of seeking any other proof. There are in Europe superstitions exactly of the kind mentioned, some of them blended with forgotten knowledge, some wholly fantastic; it is the business of science to remove them and bring more accuracy. Modern astronomy is built on a basis of very careful observation and calculation, but we have never been able to find that modern astrology had even a semblance of a basis. It is even far behind the ancient in its attempts at proof. It seeks none, whereas in the East it is said that star watchers sat carefully observing the heavens whilst others gave notice of the birth of a child, in order to know exactly at what aspect of the skies it came into the world. This would produce a science founded on fact, or it would put an end to the whole. Without a trace of experiment, men wealthy enough to promise large sums come even now to astronomers to know the course of future events, but they will not give the money to a good tutor to relieve them of their ignor ance. It is difficult to measure the distance between this merchant consulting the astronomer, and the astronomer himself, who has a difficulty in making his visitor understand that he cannot read the future. Let us say the difference is two thousand years. Let us also pause a moment to consider the progress made by the astronomer in two thousand years. Perhaps the first man that counted by seconds was one who found the pendulum to be his own heart-a heart quietly beating after the violence of youth was over, sixty times a minute. The period of one beat has become for mankind a symbol of shortness; it is a length of time passing too rapidly to be calmly surveyed, and to speak of the movements in the sky to such accuracy was not to be thought of. There was no mode of measurement. Now the ear itself has become critical beyond the heart, and it dares to measure to one-tenth, whilst the intellect, with a refinement beyond its own full comprehension, divides the same period into a million, and the strange laws of nature placidly permit that mechanism shall be formed for the purpose. The man of the dark past, although he is living now amongst us, may have heard that from the great distances in space we see in stars that which has existed many years ago, and may think that we have only to turn the telescope and, by looking the other way, see equally far into the future. We have sympathy even with him, and we too would like to know the future of chemistry and even of man. But we are among chemists and not astronomers, although when we look far back chemistry offers us few illustrations. Since we first took up a piece of earth and said to ourselves" of what is this made?" we have a long line of men, each striving to be more accurate than his neighbour. We do often wish that we could take up a history of these later men, written not merely in English but by Englishmen who had read and weighed everything for themselves. For our facts we must go either to the originals or to the Germans. We find in these rich volumes by Kopp abundance of matter well weighed, perhaps with as much justice to Englishmen as they could do themselves, but we should like to see it written with a warm heart towards our fellows, seeking out every corner as justice alone cannot, but as kindness only can. We turn to France and there we find a history truly original also, but with a name that sounds surely German-it is Hoefer. Well, we cannot blame them: we are thankful. We cannot see the tendency towards exactness and clearness better than by taking a chemist's view. Air was once the soul of the world, it was the life of man, it was a spirit including intellect, it was a ghost, it was capable of turning into water, which again became earth, and it was in itself nothing material, and had no weight or substance. CHEMICAL NEWS, Jan. 1, 1869. Now it has fallen into the ranks of ordinary things, although not less wonderful. It has been divided into parts, although unseen. This very spirit of the world has been dissected, and chemists treat it without reverence, measuring it out in tubes or weighing it on balances. Now we can scarcely tell how various its composition. It has two principal parts, but a third was soon added, whilst a fourth, under the name of ozone, has been followed by the scent for many years-we may even say since those ancient days when the smell was observed after violent lightning. Now we have plants and animal diseases almost endless, and strange influences accompanying every wind. These by degrees the scientific enquirer is hunting down, and preparing for the world new museums in nature where we shall see, by the aid of magic eyes, forms of disease lurking around and capable of being successfully attacked instead of insidiously entering and finding no one to struggle against them. The air has been, and will long be a study worthy of the greatest and the most acute, but the progress made is a great triumph, and shows that scientific men in many departments are reasoning, on the whole, rightly and fairly, gaining a victory over the world. We may say that all organic matter comes from the air, the trees, and the lower animals, and man himself; and when we have viewed this proof which chemistry has made we almost return to the original idea that the air is the life of the world, not by general and vague reasons but by careful analyses. Out of air we may form or see formed by natural means thousands of bodies, each varied in in its structure as we can prove, although air itself is invisible; and out of it will come many thousands more-movements of unseen bodies, directed by unseen forces, and observed by unseen minds. It is to this that we have come by accuracy to a world that was as unknown as if it were in Saturn, whereas we are in its midst and the scales of our eyes only want removal to shew us the irresistible intelligences at work. The wide and hasty flights of thought are past in many departments. The workers must walk softly. Our trail is not the broad foot of the elephant on the mud, but the slightly displaced leaf of the forest. With patience the chemist watches the drops from his filter and walks up and down on guard; with patience he observes that onethousandth of the weight has been lost and that he ought to have lost less; he begins again. We do not wonder at Professor Rose being excited when a courtier walking about in his laboratory touched with exquisite forefinger a transparent precipitate of alumina on a filter. Stateli ness of manners was forgotten. The chemist seized the offending finger and never ceased to wash it with a jet of water till the earth was all returned to the funnel; nor could he venture to explain, since the jet was driven by his own mouth and swollen cheeks. The idea of cleanliness in all its accuracy is known only to chemists. When preparing a substance for analysis is there any trouble that we avoid if we can aid success. What! in a vile laboratory? Yes; no foul air must touch these bodies. Air, that which the most sensitive persons would consider sweet, would be poison. The slightest trace of carbonic acid or moisture, things found in all breezes, would make some analyses imperfect. We can well remember when in that stage of learning when sulphur and hydrogen are so much employed for metals we rushed forward to seek advice, but were driven back from the sanctum by the usually most urbane and pleasant friend. What could that mean? he was preparing a silver salt in order to obtain an important atomic weight. We are obliged to use not only pure air, but sometimes artificial atmospheres, and sometimes the entire absence of atmosphere. As to analysis generally, most chemists have seen in their own day the rise of the methods of Fresenius. It was no easy matter to learn from that of Rose. The information was great, but the system deficient. Now the details and system of Fresenius seem to form an embodiment of logic itself, and if any one learns them he must have learned to reason in such a way that he will |