the April 21, 1876. calcium itself. Naturally we are unable to determine, for present, whether we have a lower molecular group of calcium, or whether the calcium itself is a compound of two distinct sub-elements, if the expression may be used. It seems that we can only undertake to solve this question by photographing the rays of calcium (H,H2) in different stars. If we find that they present always the same relative breadth and intensity there will be a strong presumption that we have met with a decomposition of calcium, or, in other terms, we shall have shown that a spectrum of rays is a spectrum due to different orders of molecular grouping. If, on the other hand, we find that these lines vary in breadth and in intensity, it will be difficult to explain this phenomenon except we admit that calcium, instead of being an element, is really composed of two substances. I must add that Prof. Stokes-whilst admitting that we have here a very convenient method for determining the power of dissociation existing in the sun, since we may find the extent of that power by the number of square inches of battery surface-does not believe that the evidence in favour of the dissociation of calcium is quite complete; and he believes it possible that with an increase of temperature the more refrangible lines increase in brilliance at the cost of the less refrangible, so that, if the quantity decreases gradually, we may obtain the results above described. I have, however, pointed out to him that this law does not hold good in other cases: for instance, with hydrogen an increase of temperature does not give a greater intensity to the red line C, and in case of sodium at the temperature of the sun we know that the absorption of the yellow line of sodium is more intense than that of any of the rays.-Comptes Rendus. REPORT DEVELOPMENT OF THE CHEMICAL ARTS By Dr. A. W. HOFMANN. (Continued from p. 144.) THE ammonia remains dissolved in the water only under the pressure at which it was saturated, and escapes in proportion as such pressure is diminished; at the same time the liquid is cooled in a corresponding degree, as during the evaporation of pure liquid ammonia. Mort and Nicolle produce this decrease of pressure by means of the air-pump. The ammonia removed is condensed by the return stroke of the piston and along with a corresponding amount of the diluted liquid simultaneously withdrawn from the evaporator is forced through a cooler This arrangement where re-absorption takes place. requires less motive power than a pure mechanical condensation. It is to be expected that this ammonia machine should be more efficient than the ether machine, but its performance falls short of that of Carré's machine. More exact accounts are hitherto not to be had. The machine works at lower pressure than the ether machine, and like this must be carefully protected against the influx of air. The danger of explosion is removed from the machine itself and transferred to the boiler of the engine. About the end of 1870 Mort and Nicolle have patented a new ammonia machine of which the only description in our hands is the English specification. It is described as the "low-pressure ice machine," and agrees in principle with Carré's machine, the air-pump being omitted. It differs, however, from the latter machine in as far as not liquid anhydrous ammonia, but a highly concentrated aqueous ammonia is produced and evaporated. This of course requires a much lower boiler pressure, the maximum tension being about 2 atmospheres at a steam * "Berichte über die Entwickelung der Chemischen Industrie 'Während des Letzten Jahrzehends." The arrangeheat of 107° C. The evaporation of course produces a much smaller reduction of temperature. ment is such that the ammoniacal liquid streaming from above into the ice generator, and flowing slowly over horizontal depressions gradually loses its ammonia, and arriving at the bottom in a very reduced state of concentration is drawn out by means of a pump, and in an especial vessel re-absorbs the ammonia which has been expelled by the heat. The liquid restored to its original degree of concentration is pumped back into the ice generator. The liquid escaping below from the kettle, and which is little more than water, serves as in Carré's machine for the re-absorption of the ammonia evaporating from the ice generator, and is driven back into the boiler by a second pump. It must be mentioned as a speciality that the ammonia evaporating in the boiler passes first into a cylinder with a piston, and furnishes the power for working the pumps, whereupon the absorption takes place. Air-pump Sulphuric Acid Machine, by Edm. Carré, of Moislains.-We have still to mention a peculiar ice machine invented by the brother of the above-mentioned F. Carré, and also belonging to the class of absorption machines. Hitherto the idea has only been carried into practical execution on the small scale for domestic use. It was shown for the first time at Paris, in 1867, and has since been exhibited at Vienna. In principle it depends upon the cooling and freezing of water by its own evaporation in a vacuum-the well-known experiment of Leslie. E. Carré arranges his apparatus as follows:-A cylindrical vessel consisting of lead alloyed with 5 per cent of antimony is half filled with concentrated sulphuric acting from without. With the upper empty part of the acid which can be kept in motion by means of a stirrer vessel is connected on the one hand an air-pump, and on the other an ascending tube fitted with a cock and slightly bent, so that a flask filled with water may be placed in its end, and an elastic band serving for a lute. All the joints are very carefully adapted so as to prevent all access of air. When the air-pump is set in action the entire air is removed from the connected apparatus, the water evaporates and is absorbed by the sulphuric acid. After some time a crust of ice is formed in the flask, which increases more and more till the whole, which fills about half the flask, is frozen. The author succeeded in forming 340 evaporated. The duration of the operation increases grms. of ice in forty-five minutes, 60 grms. of water having when the sulphuric acid grows hot and becomes diluted. By the use of 1 litres of concentrated sulphuric acid, 12 flasks of ice, each amounting to 340 grms., can be obtained. The last flask required two hours in freezing, had then taken up one-third of its weight of water, and its and 75 grms. of water were absorbed. The sulphuric acid The cost of a flask of ice was 10 pfennige sp. gr. was 1·6. In this form the apparatus is excluto any further use. (about one penny, English) if the sulphuric acid is not put sively destined for the Carafe frappée, i.e., to cool drinking water by means of ice. The writer does not think the of air renders it useless, and satisfactory connectionConcentrated sulmachine fit for domestic use, since the smallest entrance materials are not easily met with. phuric acid also is an objectionable article in the house(To be continued.) hold.* ON CERTAIN CIRCUMSTANCES THE PURITY OF WATER By M. M. PATTISON MUIR, F.R.S.E., III. Influence of House Cisterns upon the Water Supply. 168 Treatment of Anthracen Oil. WCHEMICAL NEWS, April 21, 1876. against the use of cisterns in dwelling-houses, which is, I | a wooden cistern closed at the top. No. 8. From cistern suppose, chiefly due to the fact that the waste pipe from the cistern is generally in connection with the soil pipe which carries off the drainage of the house. The hurtful sewer gases may thus readily find their way into the cistern, and so contaminate the water therein stored. On the other hand, however, it may be urged that inasmuch as the water in cisterns is frequently changed there is no great probability that the water actually used for domestic purposes will be, at any rate largely, contaminated by sewer gas. I have attempted to obtain some definite measurements of the amount of contamination present in cistern waters, in so far as this may be estimated by the chemical processes at present in our possession. The method which I have adopted consists in measuring the amount of free and of albuminoid ammonia, and the amount of nitrogen existing as nitrates and nitrites; from these data we may deduce, at any rate comparative measurements, of the purity of various waters. In order to prove conclusively, for my own satisfaction, that if sewer gases be absorbed by water their presence will be indicated by a marked increase in the quantities of ammonia, free and albuminoid, obtained from that water on analysis, I carried out the following preliminary experiment: A quantity of distilled water, free from ammonia, was placed in a porcelain basin, which was covered with porous paper, and suspended at a short distance above the liquid in a sewer which received the refuse from a very large area, chiefly occupied by dwelling-houses, in Glasgow. After ninety-six hours the free and albuminoid ammonia were estimated with the following results:Free ammonia=0·60 mgm. per litre parts per million. Albuminoid,, =0'54 It is thus evident that the absorption of sewer gases by water causes a marked increase in the quantities of ammonia obtained on analysis. The method adopted for the estimation of ammonia was the well known one of Wanklyn and Chapman: the method for the estimation of nitrates was that described by Thorpe in the Journal of the Chemical Society for June, 1873. This method consists in evaporating the water, along with a fragment of ignited quicklime, to a small bulk, and then evolving the nitrogen, as ammonia, by the action of zinc, coated with a deposit of spongy copper, at a boiling heat. In selecting the waters for examination I endeavoured, as far as possible, to obtain typical samples; in this endeavour I was greatly aided by the kindness of Mr. Macleod, the Sanitary Inspector for Glasgow, who obtained for me samples of waters from various houses situated in the lower parts of the town. The results are calculated as follows: situated just under the slates in a house in a lower locality than any of the preceding. No. 9. From cistern over water-closet in a dwelling-house. No. 10. From cistern similar to above. No. 11. From the cistern same as No. 9. but after stirring up the muddy deposit at the bottom. No. 12. From cistern near the slates in a house where there had been two cases of fever and where the water was complained of. Omitting for the present No. 11, it is found that No. 2 sample yields the highest number for free and for albuminoid ammonia, also for nitrates. Now this sample was taken from the cistern of a house in which the pipes have been recently entirely renewed, and in which the pipe leading from the water-closet to the main drain is thoroughly ventilated. The water in this cistern is, however, very rarely used; for all domestic purposes a supply is obtained directly from the main; it would therefore appear that sewer gases are slowly absorbed by water stored in such a cistern. That this absorptive action must take place slowly is evident if we look at the results obtained from the other waters. Although many of these waters were taken from badly situated cisterns, yet in none of them can the influence of sewer gases be distinctly traced. We must therefore conclude that the rapidity with which the water in the cistern has been changed has prevented any appreciable action of the gases upon these waters. There are, it is true, slight variations in the numbers obtained, but in no case do we find a notable increase as compared with water from the main pipe. The amount of ammonia, &c., obtained from a sample of the slimy matter found at the bottom of one of the cisterns (No. 11) indicates that a great part of the ammonium salts, &c., is concentrated therein; this matter may therefore perhaps exercise a certain beneficial effect upon the water. The general conclusions which I would draw from these results are :— (1.) That sewer gases are absorbed by water, but that this absorption takes place slowly. (2.) That in ordinary house cisterns the water is not contaminated to any great extent with sewer gases, probably because of the short time during which this water is allowed to remain in the cistern, and also perhaps because of the deposition of part of the impurities in the muddy substance which settles at the bottom of the cistern. The general problem of the influence of the means of I offer supply upon potable waters is a very wide one. these measurements as a contribution towards its solution. NEWS called residual method for some time, I may perhaps be permitted to speak from experience as to the practical mode of working it. Mr. Staveley has very correctly described the result of my first attempt to work the process on a large scale. I obtained a black greasy mass, full of pitch, and sufficiently uninviting to the eye. Having pressed a small quantity and submitted it to analysis, the result was so satisfactory that I was encouraged to make another trial with a second quantity of oil. For this purpose I selected a perfectly clean still, as I judged that the black colour of the deposit on the first trial was mainly due to the fact that the condensation had been conducted in a still previously used for tar distillations, and containing a quantity of pitch at the bottom. I now obtained a cake perhaps a shade darker in colour than is usually procured from the first crystallisation, but leaving little to complain of on that score. In order to ensure success in this mode of treatment, therefore, care should be taken in the outset to commence with a clean still, and the condensation should not be pushed too far. The crude anthracen obtained in this way is difficult to filter, but not more so than when the oil is distilled, and by proper means the filtration may be much facilitated. I was under the impression, when I stated that the solid residue contained 17 per cent anthracen, it would be fully understood by those to whom my article was addressed that the crude anthracen had previously been deprived, by filtration and pressure, of the oily matters associated with it; and I believe Mr. Staveley, although he finds fault with the obscurity of my description, perfectly comprehends my meaning. I am pleased to observe that Mr. Staveley's results on a small scale, as to quality and quantity of anthracen cake produced, are to a certain extent confirmatory of my own; and, should time permit, I hope hereafter to give further and more exact details of the process and its results.-I am, &c., Turnchapel, Plymouth, April 6, 1876. A. MCDONALD GRAHAM. VANADIUM FOR ANILINE-BLACK. [We quote the following letter from the Textile Colourist : "Sir,-Having read your article on this most curious and interesting metal, in the March number of the Textile Colourist, with much interest, and in view of the most important part which it is destined to play, not only in medicines and photography, but eminently in the art of dyeing and printing silk, woollen, and cotton fabrics, a few words in reference to its recent discovery in greater abundance, and its application to calico-printing, may not be without interest to your subscribers, at the same time that it records historically the progress hitherto attained. "We are indebted to Prof. Roscoe for the discovery of vanadium in the residues left after the extraction of cobalt by the acid process as lately conducted at the works, Mottram St. Andrew's, Cheshire. 66 Availing himself of the use of our furnaces and utensils which were larger than the apparatus, &c., then at his command in the old Owens College, Quay Street, Manchester, a quantity of these residues were worked up early in the year 1867, and sufficient vanadic acid was made to enable him to conduct his exhaustive researches, and to determine once and for all the atomic weight and the true constituents of the various compounds of vanadium. "All the vanadic acid made having been used up by Dr. Roscoe in these original investigations early in the spring of the year 1870, a larger batch of the residues was put into work, and about 100 ozs. of vanadic acid was produced-the largest amount of vanadic acid there had been in the world up to that date. From this store of 100 ozs. Prof. Roscoe very liberally placed at our disposal about 30 ozs., the rest being required for his further experiments. In December of the same year it was sent up to London, to the eminent metallurgical firm of Johnson, Matthey, and Co., for sale, and it may be regarded as an evidence of the earnestness of purpose with which the late Mr. John Lightfoot, of Accrington, conducted his experiments, and watched the advent of any substance calculated to advance his discovery of the best method of working aniline-black; for there is little doubt that almost immediately afterwards he must have procured some vanadium oxide from this stock, for whilst in his original specification for printing and dyeing fabrics and yarns, and which is dated October 12th, 1870, vanadium is not mentioned, yet in the completed specification of his patent, dated April 12th, 1871, only a little over three months after the first lot of vanadium oxide was offered for sale, he states the fact that other metals and their compounds than To the Editor of the Chemical News. SIR,-In the CHEMICAL NEWS (vol. xxxiii., p. 140), in your summary of the contents of Reimann's Farber Zeitung (No. 11), you quote a letter from the French correspondent of that Journal in Rouen, in which he says that aniline-copper can be used to form aniline-black, and amongst the blacks with var.adium are there in use on a large scale. This is doubtless true. I should not have troubled you with this letter if your extract had ended with this statement, but you continue to quote some remarks made by the Editor of that Journal on this subject, in which he says "that it must be confessed that the colourists of Rouen produce far more novelties than their colleagues in all the rest of the world," and with a spirit of self-depreciation which is eminently characteristic of the English you continue "If Germany makes such a confession, what must England say?" Permit me to say that in this matter of the development of the use of "vanadium" for dyeing and printing cotton, woollen, and silk fabrics aniline-black, that neither French chemist nor French colourist has had anything to do with it. The first-published suggestion of the use of vanadium for aniline-blacks was made by the late John Lightfoot, of Accrington-an Englishman: it was worked out by Robt. Pinkney, Esq., of London-ar. other Englishman. Some of the best calico-printers in Lancashire have used vanadium instead of copper, in printing aniline-black, for three or four years past; and the various salts of vanadium, useful for this purpose, have only as yet been prepared on a commercial scale by myself.-I am, &c., SAML. MELLOR. Magnesium Works, Patricroft. rest he enumerates the oxide of vanadium; and in a small work by him on aniline-black, published May 1st, 1871, he records some interesting experiments made with various metals, and in it he states that the best black is obtained by the use of vanadium. "It was without doubt because of Mr. John Lightfoot's ignorance of the marvellous power possessed by the various Salts of vanadium when brought into contact with a mixture of aniline hydrochlorate, and the chlorates of sodium and potassium, to form aniline-black, that he did not introduce it into the original specification of his patent, but between the dates October 12th, 1870, and April 12th, 1871, he acquired this information when acting under the advice of his patent agent, who would inform him that the completed specification of his patent could only be an amplification of his original specification, but that no new matter could legally be introduced into it. Although he mentions that vanadium could be used, he does not claim its use in his patent. "The high price of vanadium oxide-then 6os. per oz. -and its exceeding rarity were reasons why he would decline to apply specially for a patent for its use in the formation of aniline-black; indeed it is on record that about this time he said that by far the best and most powerful agent to use in order to produce aniline-black was. vanadium, but that there was not sufficient vanadium in the world to supply the wants of one firm of calico 170 Chemical Notices from Foreign Sources. {CHEMICAL NEWS, April 21, 1876. printers, much less the requirements of the whole | I gave a summary (Comptes Rendus, liv., 782, 880, 949), I trade. "It was about this date that Mr. Robert Pinkney, of the firm of Blackwood and Co., London, requiring a substitute for copper for their marking-ink,-independent of and absolutely in ignorance that the late Mr. John Lightfoot was at the same moment engaged experimenting on the same substance, for the same purpose,-made some original investigations upon the use of the salts of vanadium in the formation of a permanent black. He found that only a few grains of the chloride of vanadium-say from 7 to 12 grains for 1 gallon of liquid, consisting of hydrochlorate of aniline and chlorate of soda-were sufficient for the formation of aniline-black; and, acting upon the belief that if vanadium was required it would be forthcoming, he applied for a patent for the use of the salts of vanadium in the formation of aniline-black, October 16th, 1871, and since then hundreds of thousands of bottles of marking-ink, called "Jetoline," have been sold by this firm, in all of which vanadium has been used. "At the time of the removal of the Owens College from its old premises, Quay Street, to its present palatial buildings, Dr. Roscoe very generously gave me all his stock of residues from the Mottram Mine, amounting to about I ton, and at the same time earnestly suggested that every effort should be made to obtain supplies from some other source, for, he argued, there was the requisite furnaces, utensils, and knowledge required to prepare the salts of vanadium, and if once a quantity of this substance, with its wonderful and quite unique properties, existed with reasonable probability of further supplies, many uses for it must sooner or later be developed. "This advice has been adopted, and in course of time control over the only known deposit of vanadium in the world has been obtained. "The results have abundantly vindicated the soundness of Dr. Roscoe's advice, and the number of applications opening out for this most marvellous substance has demonstrated the immense value of original researches, even upon substances which may seem to be amongst the rarest in nature. "Unfortunately the amount of vanadium found in the ore obtained from the deposit named is only a few ounces per ton, but as the properties possessed by the compounds of this metal are of the most extraordinary and valuable character, and as the smallest quantity of it performs a great amount of work, it may possibly suffice for present wants until other and richer deposits are found. Meanwhile, the many and important uses opening out for the salts of this metal in science, manufacture, and arts, mark another step onward in that ultimate victory of man over nature, which it is his privilege and birthright to assume, "Thanks to chemistry for having enabled us to score this additional victory. "Magnesium Works, Patricroft."] CHEMICAL NOTICES FROM "S. M. showed that the electro-positive elements of natural compounds do not enter indifferently into such compounds, but that some of these bodies belong in a manner virtually to a group of minerals marked out both atomically and crystallographically, and are, on the contrary, always strangers to other even closely approximating groups; but I showed that there exist most frequently between two neighbouring groups two minerals belonging respectively to each of the two groups, and characterised by one and the same basic element, playing this double part, and to which I gave the name of limitary or axial body. But of all the simple bodies calcium most frequently plays this strange part. Is this remarkable property in calcium of belonging at once to different types connected with its twofold behaviour under the influence of dissociating agents? Will the same hold good with titanium, iron, &c., which seem also to play a Protean part in the mineral kingdom? Report on a Memoir by M. E. Bourgoin, presented to the Academy, and entitled "Researches in the Succinic Series."-MM. Cahours and Berthelot.-M. Bourgoin has studied the conditions under which succinic acid may be directly converted into malic acid. The examination of these conditions has led to the discovery of two new acids, the oxymaleic and dioxymaleic. Study of Stratified Light.-M. Neyreneuff. Judging from his experiments on the action of electricity upon flames and gases, the author admits that there exist in a Geissler's tube traversed by discharges two forces which tend to impress a vibratory movement upon the gaseous mass within. He has found in studying the combustion of detonating mixtures the most important characteristics of electric stratification. The two series of phenomena may therefore be assimilated as regards their producing cause. Photo-micrographic Researches on the Transformation of Collodion in Photographic Operations. M. J. Girard.-The microscopic examination of collodion renders it practicable to distinguish the nature of the texture of the stratum, and to follow the reactions which take place in the production of the photographic image. When it is of good quality the layer is translucent, colourless, the cotton being perfectly dissolved. Among the most frequent modifications may be mentioned-First. Old collodion which still gives good impressions, but less rapidly than is to be desired; it contains liquid globules of modified ether. If too alcoholic it has the appearance of cellular tissue, and if water is present the fibrilla of cotton become apparent in the form of amorphous flocks. Second. Collodion which is too thick; it is intense, but without speed of action, having the appearance of a wavy cellulo-vascular tissue. This want of regularity in the stratum affects the distinctness of the impression which it ought to receive. Communications at a Distance by means of Water Courses.-M. Bourbouze.-This paper was deposited FOREIGN with the Academy in a sealed packet on November 28, 1870, and was now opened and read at the desire of the author. The experiments described show that it is possible to telegraph to considerable distances without wires; that NOTE. All degrees of temperature are Centigrade, unless otherwise telluric currents may be substituted for those of the expressed. Comptes Rendus Hebdomadaires des Seances, de l'Academie des Sciences. No. 13, March 27, 1876. Remark on the Recent Communication of Mr. Lockyer on the New Rays of Calcium.-M. C. Ste.Claire Deville.-The curious experiment described by Mr. Lockyer in his letter to M. Dumas on the property of calcium in presenting two distinct systems of rays according to the energy of the batteries applied has a profound interest for mineralogists. In a series of lectures which I delivered at the Collége de France, and of which | batteries generally employed, provided the immersed surfaces are duly varied, and that such currents may decompose the solutions of metallic salts. Exchanges of Ammonia between Natural Waters and the Atmosphere.-Th. Schloesing.-This paper is not suitable for abstraction. Sources of Carbonic Oxide: New Method of Preparing Highly Concentrated Formic Acid.—Mix formiate of soda with oxalic acid, both dry and in powder. On heating in the water-bath one obtains almost the theoretical quantity of an acid containing 99 per cent of actual formic acid. MISCELLANEOUS. The Radiometer.-Current literature, the faithful reflex of popular opinion, proves that the general interest in Mr. Crookes's remarkable discoveries concerning repulsion by radiation and the mechanical action of light continues unabated, notwithstanding the unusual degree of publicity accorded the successive researches of the discoverer, and the large number of recruits which have been thereby attracted to aid in the subjugation of the new territory and report to the less interested bystanders what they have seen. Thus in the last issue of the Quarterly Journal of Science will be found a report in extenso, with illustrations, of the lecture delivered by Mr. Crookes at the Royal Institution, already briefly summarised by us under the heading of "Weighing a Beam of Light." In Fraser's Magazine, also, there is an appreciative article on Mr. Crookes's discoveries, written in a fairly comprehensive and scientific, though essentially popular, manner. Indeed almost every periodical addressed to cultivated readers has had something to say upon the subject at one time or another; and this is true of France, Germany, and the States, no less than of our own country. It is not often that any discovery gives rise to a mass of criticism so large and varied in character as in the present instance. In the hands of a philosopher such as Herbert Spencer, these criticisms would afford fine illustrations of different kinds of bias, and of the errors resulting from each. Mr. Crookes in the hands of his critics is somewhat similarly placed to the member elect in some borough where party feeling runs high. His "friends" would push him ahead faster than he is prepared to go, whilst the other side would metaphorically "bonnet " him and hustle him out of sight with as little ceremony. According to the Athenæum, Professor Osborne Reynolds in a recent lecture, not merely ignored Mr. Crookes's labours, but re-christened the radiometer "Geissler's Light Mill," though the latter is in fact nothing but a Crookes's radiometer manufactured by Geissler, of Bonn. On the other hand, some of Mr. Crookes's friends write as if, before his researches, nothing whatever was known of the influence of radiation on delicately suspended bodies, and so lay the one they would befriend open to the charge of ignorance or suppressio veri, though his first paper, read before the Royal Society, is prefaced by a most scrupulously detailed list of his predecessors' researches in the same field, and a full acknowledgement of his obligations where such were due. Again, many of his well-wishers reason as if it were a matter of life and death to Mr. Crookes's fame to maintain that the phenomena discovered by him are due to light alone, and that all cause for wonder would cease if it were admitted that heat had anything to say to them. We noticed how very careful Mr. Crookes was to avoid committing himself to any theory when lecturing at the Royal Institution, and fully appreciating the intention and importance of this reserve, we found space even in our brief notice of the lecture, to record the fact that Mr. Crookes styled the force neither light nor heat, but a "function of the refrangibility." His views on this point are very clearly set forth in the Quarterly Journal of Science. "The human eye," says Mr. Crookes, "by what we may term a physiological accident, is sensitive to but the central portion of the solar spectrum; the part at the red end possesses in the greatest degree the property of causing the sensation of warmth, and of dilating the mercury in a thermometer, and of doing other things which are conveniently classed among the effects of heat; the centre part affects the eye, and is therefore called light; whilst the part at the other end of the spectrum has the greatest energy in producing chemical action. But it must not be forgotten that any ray of the spectrum, from whatever part it is selected, will produce all these physical actions in more or less degree. A ray in the orange, for instance, if concentrated on the bulb of a thermometer, will cause the mercury to Perhaps fully one-half of the voluminous correspondence on Mr. Crookes's discoveries would never have seen the light if the writers had been possessed of that small modicum of modesty or self-mistrust necessary to make them doubt whether their own intellectual calibre was such that they knew more of the subject by intuition than another man, a gold medallist of the Royal Society, did after many months' laborious and indisputably skilled research. Had they asked themselves that question, the public would have been spared many folios of turgid truisms, and themselves the shame of advancing theories which had been disproved by experiment perhaps years before. A week or two ago a letter, written evidently in the highest possible spirits, appeared in the columns of a contemporary, announcing that, interesting and important as Mr. Crookes's researches were, his alleged discovery of the mechanical action of light had been anticipated by some forty years. We need hardly remark that if the writer of the letter had read Mr. Crookes's résumé of previous investigations, he would have found the experiment referred to duly recorded, though it affects as little the question of priority as Puck's offer to " put a girdle round about the earth in forty minutes " does the originality of the modern system of laying submarine telegraph cables. So long as poor human nature remains what it is, and what it ever has been, it is hopeless to expect that discussions on a new discovery will be conducted without animus and upon merits alone. Lord Brougham, writing in the Edinburgh Review, likened Dr. Young's hypothesis of the undulatory theory of light to "the unmanly and unfruitful pleasure of a boyish prurient imagination, or the gratification of a corrupted and depraved appetite." Public opinion no longer admits of such unbridled license in criticism as this, but that the snake though scotched retains his venom fangs, the tone of some criticisms of Mr. Crookes's labours clearly proves. Some allowance should undoubtedly be made for disappointed physicists. As remarked in Fraser's Magazine-" The general surprise was not lessened by the fact that the announcement of this mechanical action of light came from an unexpected quarter; for although Mr. Crookes, as the discoverer of thallium and as an original investigator, was well known even outside scientific circles, the public at large would have rather looked for an announcement of this character from one of the more popular exponents of science whom they had delighted to honour." Prof. Huxley has likened the progress of science to that of a nail in the wheel of a coach, since to one sitting on the coach, and regarding the nail alone, the movement appears at times to be retrograde in character, although to one standing afar off each part undoubtedly shares in the general progress of the whole. We may expand the simile, and remark that it is not the big wheels which lead and guide the coach. |