THE CHEMICAL NEWS. VOL. VII. No. 169.-February 28, 1863. SCIENTIFIC AND ANALYTICAL Researches on the Platinum Metals,* by WOLCOTT GIBBS, M.D. precipitated as sulphide, which is then treated in the manner already pointed out, so as to convert the rhodium into the double chloride of rhodium and ammonium. To remove the last traces of ruthenium, the rhodium salt may be a second time treated with nitrite of potash, as above, and again washed with alcohol. The presence of the least trace of ruthenium is easily ap-monium to the alcoholic solution. detected by adding a drop of colourless sulphide of amThe method of Iridium from Rhodium.—Iridium may be proximately separated from rhodium by the process recommended by Claus, which consists in taking advantage of the solubility of the double chloride of rhodium and ammonium, Rh,Cl3,3NH,Cl, in moderately strong solu tions of chloride of ammonium in which chloro-iridate of ammonium is nearly insoluble. This method is difficult of application when the quantity of rhodium is small, and is, at best, tedious and unsatisfactory. A better method is that given above for the separation of iridium from ruthenium. The mixed solutions of iridium and rhodium are to be treated as above mentioned with nitrite of soda, the rhodium precipitated by sulphide of sodium in slight excess, the liquid rendered slightly acid, filtered, and the dark brown sulphide of rhodium thoroughly washed. The filtrate is perfectly free from rhodium, and is to be treated in the manner already described. The sulphide of rhodium is to be oxidised in the same manner as the sulphide of ruthenium, and converted into the double chloride of rhodium and ammonium, Rh,Cl3,3NH,Cl, which is insoluble in a cold saturated solution of sal-ammoniac, in which it may be washed once or twice to remove alkaline salts and any traces of iridium which may be present as sulphate. The rhodium salt is then to be purified by crystallisation, or converted into the chloride of Claus's rhodium ammonia base by evaporation on a water bath with a solution of ammonia. The sulphate of iridium, Ir2O3,3 SO3, does not give a basic compound under these circumstances. The chloride 5NH,,Rh2Cl3, is then to be further purified by crystallisation. Rhodium from Ruthenium.-The separation of rhodium from ruthenium is best effected by means of nitrite of potash. The mixed solution of the two metals is to be boiled for a short time with an excess of the nitrite, together with a little carbonate of potash to keep the solution neutral or slightly alkaline. The yellow or orange-yellow solution is then to be evaporated to dryness upon a water bath, the dry mass rubbed to fine powder and then treated in a flask with absolute alcohol in the manner pointed out for the separation of platinum from ruthenium. After filtration and washing with absolute alcohol, the rhodium remains undissolved in the form of a mixture of the two double nitrites of rhodium and potassium. These may be ignited with a large excess of sal-ammoniac, so as to yield, after washing, metallic rhodium, or the nitrites may be dissolved in hot chlorhydric acid, ammonia added, and the rhodium * From the American Journal of Science, vol. xxxiv., page 341. obtaining pure ruthenium from the double nitrite of ruthenium and potassium has already been given. For the separation of osmium from the other metals of the group I have no better method to offer than that which is universally employed, namely, the volatilisation of the osmium in the form of osmic acid. The separation of palladium is in all cases also best effected by the processes commonly employed, especially by taking advantage of the solubility of the double salts of protochloride of palladium in solutions of the alkaline chlorides. With these preliminary and general statements, the method which I employ in separating the different metals of the platinum group from each other will be intelligible. The mass of double chlorides, obtained as already mentioned, is to be rubbed to a fine powder, mixed with four or five times its volume of boiling introduced into a deep porcelain evaporating dish, and water. A solution of nitrite of soda is then to be added in small quantities at a time, the solution being continually stirred and occasionally neutralised by addition of carbonate of soda. The liquid soon becomes olivegreen, and the greater part of the mass dissolves; it is advantageous, when the quantity of the mixed chlorides is large, to pour off the liquid as soon as it appears satuof water. The undissolved mass, which consists chiefly rated, and to repeat the operation with a fresh quantity of the impurities of the ore, when these have not been removed before the process of oxidation, is then to be thrown upon a filter, and washed with boiling water tion somewhat alkaline, the whole of the iron remains until the washings are colourless. By keeping the soluupon the filter as sesquioxide, with the other impurities. The filtrate contains iridium and rhodium as sesquichlorides, ruthenium partly as bichloride and partly as tions already mentioned have been well performed, no protochloride, platinum as bichloride. When the operadeterminable quantities of osmium and palladium are present. On cooling, the greater part of the platinum is deposited as PtCl2,KCl, mixed with a little of the corresponding iridium salt, and is to be separated by pouring off the olive-green supernatant liquid. The quantity of the alkaline nitrite to be added in this process need not exceed half of the weight of the mass of double chlorides, but with a little experience it will be found unnecessary to weigh the nitrite added, the process of the reduction of the iridium salt, IrCl2KCl, being evident to the eye. 98 On the Extraction, &c., of the Crystalline Principles of Opium. CHEMICAL NEWS, To the filtrate a solution of nitrite of soda is to be added, and the whole boiled until the liquid assumes a clear orange colour. Nitrite of soda should be used in this process because the resulting double nitrite of iridium and soda is easily decomposed by boiling with chlorhydric acid, which is not the case with the potash salt. When nitrite of potash is used, a small quantity of the white insoluble double salt already mentioned is usually formed and renders the solution turbid. To the clear yellow or orange-yellow boiling solution sulphide of sodium is to be added until a portion of the dark brown precipitate of the sulphides of ruthenium, rhodium, and platinum is dissolved with a brown-yellow colour, and an excess of the alkaline sulphide is, consequently, present. The liquid is then to be allowed to cool, and treated with dilute chlorhydric acid until a distinctly acid reaction is produced. In this manner the whole of the platinum, ruthenium, and rhodium present in the solution are thrown down as insoluble sulphides. After complete subsidence, the sulphides are to be thrown on a double filter and thoroughly and continuously washed with boiling water. When the operation is carefully performed, the filtrate and washings contain only iridium. It is best to neutralise this solution with carbonate of soda, boil a second time with a little additional nitrite of soda, and treat as before with sulphide of sodium and chlorhydric acid. In this manner very small additional quantities of the sulphides of platinum, ruthenium, and rhodium may sometimes be separated. The filtrate is to be evaporated and boiled with an excess of strong chlorhydric acid, which completely decomposes the double nitrite of iridium and soda, yielding the salt, IrCl2,NaCl, which is very soluble in water. An excess of a pure and strong solution of chloride of ammonium is then to be added, the whole evaporated to drvness, and the dry mass washed with cold water and then with a cold and strong solution of the ammonium salt. There remains a mass of pure chloro-iridate of ammonium, which may be advantageously rubbed to a fine powder, dissolved in boiling water, and allowed to crystallise. The resulting salt is chemically pure, and the crystals possess an extraordinary beauty and lustre. The mass of mixed sulphides, together with the filter, are to be treated with strong chlorhydric acid, and nitric acid added in small portions at a time. By the aid of a gentle heat the sulphides are readily oxidised and dissolved. After sufficient dilution, the liquid is to be filtered, the pulp of undestroyed filter-paper washed, the filtrate evaporated to dryness, the dry mass digested with concentrated chlorhydric acid, and again evapoated to dryness. The dry mass of chlorides and sulphates is to be re-dissolved in water, and the platinum, ruthenium, and rhodium precipitated by metallic zinc, after addition of chlorhydric acid. The finely divided metals, after filtration, washing, and drying, are then to be mixed with chloride of potassium, and treated with dry chlorine at a low red heat. In this manner the metals are again brought into the form of double chlorides, and the difficulties which arise from the presence of the sulphates are avoided. The mixed double chlorides are to be boiled with nitrite of potash, evaporated to dryness, and the soluble nitrite of ruthenium and potassium dissolved out with absolute alcohol in the manner described in speaking of the separation of platinum from ruthenium. The ruthenium may then be obtained pure by converting it into the double chloride of mercury and ruthen-diamin already mentioned, The mass undissolved by alcohol consists of chlorplatinate of potassium mixed with both the soluble and the insoluble double nitrites of rhodium and potassium. It is to be boiled with dilute chlorhydric acid, neutralised with carbonate of potash, again evaporated to dryness, after the addition of nitrite of potash, and again boiled with absolute alcohol, which sometimes dissolves a trace of ruthenium. The undissolved mass is then to be treated with hot water, and again evaporated to dryness, and this process repeated two or three times, so as to convert the whole of the soluble rhodium salt into the insoluble salt. The chlorplatinate of potassium may then, after reducing the mass to fine powder, be dissolved out by boiling water, when the rhodium salt remains pure as a fine orange-yellow crystalline powder. This may be dissolved in hot chlorhydric acid, evaporated to dryness with an excess of pure chloride of ammonium, and ignited in a clean porcelain crucible, when pure metallic rhodium remains as a porous mass mixed with chloride of potassium. When the process above described has been carefully conducted, and especially when the quantity of nitrite of soda added is sufficient, the mixed sulphides will be found to contain only platinum, rhodium, and ruthenium, and to be free from iridium. If, however, after converting the sulphides into double chlorides in the manner pointed out, iridium is found to be present, the process to be pursued is still the same so far as regards the separation of the ruthenium; the remaining mass is then to be dissolved in water with addition of chlorhydric acid, the solution nearly neutralised with ammmonia, the platinum and rhodium separated as sulphides in the manner already pointed out, brought into the form of double chlorides, and then separated by nitrite of potash as before. For the complete success of this method it is absolutely necessary that the mass of mixed double chlorides be freed from osmium as completely as possible. This is to be done in the usual manner by repeated evaporation with nitro-muriatic acid. PHARMACY, TOXICOLOGY, &c. Notes on the Extraction and Estimation of Some of the (Concluded from page 91.) merely the estimation of morphia. In addition to the the From the Transactions of the Medical and Physical Society of Bombay. † Pereira's "Materia Medica," 3rd ed., vol. ii., p. 2107. Geiger und Liebig's "Handbuch der Pharmacie," band i., s. 1191, § Pereira's " Mat. Med.," loco cit. Journal, vol. ix., p. 236; Liebig and Kopp's "Annual Report for 1849," Pharm. Journ., vol. xi., p. 418. * Ann. Ch. Phys., 2me. sie., tome v., p. 279. CHEMICAL NEWS, Feb. 28, 1863. On the Spectral Rays of Metallic Combinations. which form on cooling with ether to dissolve narcotine ; that of Thiboméry,tt who precipitates hot with ammonia; that of Fordos,‡‡ who mixes an aqueous infusion, without previous evaporation, with spirit, and precipitates cold with ammonia, separating the narcotine by washing with ether and chloroform; lastly, that of Merck,§§ a most trustworthy and practical experimenter, who evaporates the watery infusion to a small bulk, adds an excess of carbonate of soda, continues the evaporation to dryness, washes with water, then with spirit, and treats the residue with very weak acetic acid as long as it is neutralised, which dissolves morphia only and not narcotine, filters through pure animal charcoal, and precipitates with ammonia. But, whatever method is adopted, hurry is to be avoided. The thorough extraction of the opium requires time, and too much time, also, can hardly be allowed for the crystallisation of the morphia. Filtrations, too, are tedious operations if effectually performed. The use of spirit as the extracting agent is, on the small scale, much preferable to that of water for all purposes of analysis. It brings into solution all the crystalline principles, including the narcotine, and, by leaving undissolved much of the gummy matters, it renders the crystallisation and purification more easy and complete. By the process above described, I have repeatedly obtained crystals of morphia half an inch and upwards in length, even when operating upon as little as 300 grains of opium. The morphia is separated by this method with fully as much ease and accuracy as by any other, and certainly by no other means can the entire quantity of narcotine be so readily extracted-a matter of some interest now that the antiperiodic properties of this base are so fully established. Subjoined are the results obtained by the application of this process to some little-known varieties of opium : LIBRARY OF THE $99.99 VERSITY O PHYSICAL SCIENCE. TY OF MICHIG On the Spectral Rays of Metallic Combinations, by M. ALEXANDRE MITSCHERLICH. M. MITSCHERLICH has remarked that the spectrum given by chloride of barium in presence of excess of hydrochloric acid is quite different to the spectrum of barium itself. Inclined at first to attribute this fact to the presence of another metal, he examined this point synthetically. His arrangements are very simple; he places the solution to be examined in a glass tube, closed at its upper end, and having the other drawn to a point and bent nearly to a right angle; the liquid flows slowly through a bundle of fine platinum wires lodged in the point, and allowing at the same time the re-entry of air into the tube. He usually adds a salt of ammonia to the solutions, to facilitate the volatilisation of the dissolved salt. In studying the chloride of barium spectrum he filled one of these tubes with a solution of acetate of baryta, with the addition of acetate of ammonia, and he filled another tube with concentrated hydrochloric acid. He placed the extremity only of the first tube in a flame, and found it produced the rays characteristic of barium ; concentrated hydrochloric acid alone gave no ray; but on placing the bundles of platinum wire of these two tubes in the flame together, he saw the spectrum which he had obtained directly with chloride of barium. The author has noticed analogous facts with chlorides of calcium and strontium. Experiments with iodides, fluorides, and sulphides of alkaline earths have not been attended with the same results; the spectra were those characteristic of the metals themselves. The explanation may no doubt be found in the reducing action of the flame. Curious results are obtained from combinations of copper the chloride, iodide, and metallic copper give very different results; the chlorides and iodides of copper give distinct spectra, according to the order of combination to which they belong. Sulphide of copper gives no spectrum; this fact might be attributed to the fixity of this combination; but the following experiment puts this explanation out of the question:-A solution of chloride of potassium in presence of salammoniac and excess of hydrochloric acid gives no spectrum, in spite of the volatility of chloride of potassium; while this salt by itself, and much more diluted, gives the characteristic ray of potassium. This is accounted for by the reduction of the salt being in the latter instance effected by the flame, which in the first instance could not be the case. It is important to note the fact, that certain rays in the spectrum of a metal may be effaced by the presence of a different substance in the flame; thus, the blue ray of chloride of strontium disappears in presence of the spectrum produced by chloride of copper with addition of sal-ammoniac. Wishing to go still further, M. Mitscherlich sought to discover whether the rays are produced by the free metal itself or by its oxide; for this purpose it was requisite to avoid the reducing action of the flame. With this object, he heated the combination to redness in a porcelain tube closed at each end with glass; he commenced by receiving on the spectral apparatus the light emanating from the inside of the tube containing the combination partially reduced to vapour. This light being very feeble, he placed a bright flame at the other extremity of the heated tube, and thus the rays fur 100 On the Stratification of the Electric Light. nished by the substance were observable, only they were reversed. M. Mitscherlich's experiments were chiefly with soda, sodium, chloride of sodium, and carbonate of soda; sodium only gave a spectrum under these circumstances. The result of these researches is, that to the free metal alone are due its characteristic rays, and that, if they are seen with its combinations, reduction takes place by the carbon and hydrogen of the flame. It seems deducible from these experiments, that the solar atmosphere does not contain sufficient oxygen to oxidise all the sodium found in it, and that all the metals having less affinity for oxygen than sodium are free; it may, moreover, be admitted that if, in the solar atmosphere, there exist metals combined with electronegative elements, in spite of the presence of free sodium, their affinities are inverted at the high temperature of this atmosphere. Moreover, if the rays of certain metals are not observed, it is impossible to be certain of their absence; for they may exist in a state of combination like chloride of potassium, which, in the presence of some other bodies, as above shown gives no spectrum.-Bulletin de la Société Chimique de Paris. On the Stratification of the Electric Light, M. REITLINGER puts forward a new explanation of the phenomenon known as the "Stratification of the Electric Light," suggested by some observations with Geissler's tubes. Many of these tubes are formed of alternately wide and narrow portions, which emit distinctive coloured lights when traversed by the electric discharge. This curious phenomenon has probably been observed by most experimentors on the electric light. M. d'Ettingshausen has shown that the spectra of diversely luminous portions are of different constitution, and he mentioned this phenomenon to M. Reitlinger as an interesting subject for study, indicating, at the same time, the following arrangements as conducive to exact experi ments: Before a narrow slit a rectangular prism is placed so as to catch the lateral rays of light, which are wholly reflected on the face of the hypothenuse, and illuminate the upper portion of the slit, while the rays from another source fall directly on the lower portion. In this way, the spectra of the two lights may be easily compared, and their identity or their difference recognised. By this means, M. Reitlinger has shown that the spectra of narrow portions of a tube alternately widened and constricted, made and sold by M. Geissler as a hydrogen tube, showed the spectrum of pure hydrogen; while the spectrum of the wide portions showed that of oxygen. The diversity of the lights is caused, then, by the diversity of the luminous substances, and the passage of electricity seemed to separate the two mixed gases, at the same time rendering them luminous. The presence of oxygen in a hydrogen tube is probably owing to the method of preparation. M. Plücker says that aqueous vapour may be used for these tubes, and that the hydrogen is set at liberty by the first electric discharges. Such a separation of mixed gases seemed to M. Reitlinger to explain the stratification of the electric light. He admits, for instance, that in a tube prepared with aqueous vapour, hydrogen and oxygen are disposed in alternate layers, and that the hydrogen, a much better conductor than oxygen, becomes less heated and less CHEMICAL NEWS, Feb. 28, 1863. luminous, that is to say, relatively obscure. Generally, stratification would result in the disposal in alternate layers of the two unequally conductive gases. Whatever may be thought of this hypothesis, the difficulty in understanding the disposition in alternate layers of the two diverse gases, the following experiments are worthy of attention : 1. A tube full of dry air, under a pressure of 15 mm. gave a spectrum characteristic of nitrogen only, with no signs of stratification. Moreover, no sensible difference was observed between the two large tubes and the capillary tube of communication forming the apparatus; only the spectrum of the capillary portion showed some rays which were absent in the spectrum of the large portions. The introduction of a little pure hydrogen produced stratification in the large tubes, without perceptibly modifying the corresponding spectra. At first, no sign of stratification appeared in the narrow tube, but on the nitrogen spectrum was superposed the more vivid spectrum characterising hydrogen. The introduction of hydrogen being continued, and the pressure increased to 6 millimètres, the light of the capillary tube stratified in its turn, and the tube presented somewhat the appearance of a chaplet of brilliant beads; at the same time, the hydrogen spectrum disappeared entirely, and the nitrogen spectrum alone was visible. 2. The electric light was developed in the barometric vacuum, the mercury supplying the place of one of the electrodes. Nothing appeared but a white, homogeneous light, without stratification. The introduction of airbubbles produced immediately a series of luminous layers, alternately more or less brilliant, but without approaching dimness. The spectrum of the light showed simultaneously the rays of both mercury and air. By properly regulating the intensity of the current and the elastic force of the air introduced, the less brilliant layers may be almost entirely obscured. The mercury rays of the spectrum at the same time lose the greater part of their brilliancy. 3. No stratification has been produced by simple gases.-Sitzungberichte der Raiserlichen Akademie der Wissenschaften, vol. xliii., p. 15. PROCEEDINGS OF SOCIETIES. PHARMACEUTICAL SOCIETY. Mr. P. SQUIRE, President, in the Chair. (Continued from page 81.) MR. C. H. WOOD called the attention of the meeting to a matter of some interest to the Society, as it related to a discovery by one of the members, announced some years ago at one of the meetings of the Chemical Discussion Association. At one of those meetings Mr. Robbins mentioned that he had found the black oxide of iron might be converted into a peroxide, which is attracted by the magnet. The fact of its being a peroxide was doubted at the time; but analysis left no doubt of its composition. + Recently M. Malaguti has announced the same discovery to the M. Reitlinger compares the arrangement of the two gases in alternate layers to the polarisation of the molecules of a compound body, preceding its electrolysis, A laboratory memorandum by Mr. Robbins, announcing the fact, was published three years ago in the first Number of the CHEMICAL Pure et Appliquée, and also into the Chemisches Centralblatt. This is another illustration of the way in which our neighbours, who ignore all sources of scientific information but the Comptes Rendus and the Annales de Physique et de Chimie, re-discover well known things. NEWS, and was translated, we believe, into the Repertoire de Chimie CHEMICAL NEWS Feb. 28, 1863. Chemical Society-Royal Institution of Great Britain. Academy of Sciences of Paris as something perfectly novel and original, and the Academy has granted a commission to investigate and report on the discovery. The only difference in the method given by M. Malaguti for the preparation of the peroxide, and that given by Mr. Robbins, is that the latter ignited the protoxide with nitrate of potash, while the former used chlorate of potash, Mr. Wood said he thought it was due to the Society and to Mr. Robbins to claim priority for the discovery. Mr. ROBBINS said that in the course of his experiments he had, of course, used chlorate of potash; but he gave nitrate of potash in his paper, because it answered equally well, and was a cheaper salt. Mr. CURTIS called the attention of the meeting to a bottle of aromatic confection on the table, and proceeded to make some remarks on a letter from Mr. Giles, of Clifton, in the Pharmaceutical Journal. The specimen of aromatic confection was of a bright yellow colour; and Mr. Curtis observed that a bright yellow colour was no proof of sophistication, as Mr. Giles seemed to allege. Dr. REDWOOD explained that Mr. Giles had made use of the words, "unsophisticated submission to the directions of the Pharmacopoeia." If the confection had been made precisely in the manner directed by the Pharmacopoeia it would not possess the bright yellow colour. Mr. WHIPPLE took the opportunity of remarking, that the confection on the table had not been prepared according to the Pharmacopoeia, and, therefore, it was not an article which a pharmaceutist should use. Mr. DEANE said that things made in large quantity sometimes differed considerably in appearance from the same article made in small quantity. It was so in the confection of senna, and might be in many others; so mere difference in appearance could not be taken as a proof of adulteration. Rhubarb varied greatly in appearance when ground, and often gave rise to suspicions of adulteration when none had been practised. The Russian Government (Mr. Deane said) had now given up the monopoly of rhubarb, and, for the future, our supply will come to us through Canton. The conversation after this, we regret to say, became of more personal than general interest. [For the information of those of our readers who do not know how to make aromatic confection of a bright yellow colour, we may say that it is prepared by first steeping the saffron for a short time in a small quantity of boiling water, just enough to cover the saffron, in a mortar. A portion of the chalk is then added, and triturated with the saffron, until all trace of structure in the latter has disappeared. The mixture is then carefully dried at as low a temperature as possible, after which it is re-pulverised, and mixed with the rest of the chalk and other species.ED. CHEMICAL NEWS.] CHEMICAL SOCIETY. Thursday, February 19. Colonel PHILIP YORKE, F.R.S., Vice-President, in the Chair. Mr. David Brown was elected an Associate. ΙΟΙ The A paper, by Dr. A. W. HOFMANN, "On Formiamide," was read by the Secretary. The author adverted to the want of simple connecting links between the domains of mineral and organic chemistry, which often compelled the lecturer, for the sake of examples, to commence the history of carbon with the account of compounds higher in the series than those which formed the subject of the present communication. It was known that by extracting two equivalents of water from the formiate of ammonia, hydrocyanic acid was produced, but all attempts which had hitherto been directed to the preparation of formiamide by limiting the action to the removal of only one equivalent of water, appeared unsuccessful. author had succeeded, by the action of dry ammonia gas upon formic ether, in producing the compound in ques tion; for this purpose it was necessary to submit these bodies to the prolonged action of heat in sealed tubes-two days at the temperature of boiling water had converted but a small proportion of the ether into formiamide. When submitted to distillation, the excess of formic ether first passed over unchanged; but as the temperature approached 195°, a liquid was collected, which agreed both in properties and composition with formiamide. Analysis indicated the formula-CH,NO = CHO,NH2. The boiling point of this substance could not be determined with precision, on account of its tendency to decompose by heat into carbonic oxide and ammonia. By distillation at 140°, in a partial vacuum, it did not, however, undergo any change. The boiling point lies between 192° and 195°. Formiamide is soluble in water, alcohol, and ether; it remains permanently liquid when exposed to a freezing mixture, and does not exhibit any signs of crystallisation on standing at rest for a lengthened period of time. When treated with anhydrous phosphoric acid it yields hydrocyanic acid according to the following equation :CH,NO H2O + HЄN. = Dr. ODLING stated that, after the announcement of formiamide, he could not doubt the existence of formic aldehyde, which had never yet been isolated; also of the glyceric acid of the mono-carbon series, to which the same remark was applicable. The PRESIDENT then adjourned the meeting until March 5, when a paper by J. B. Lawes, F.R.S., "On the Assimilation of Nitrogen,' will be read. " Dr. WARREN DE LA RUE announced that Mr. Crookes' paper "On Thallium was about to be read before the Royal Society; and, inasmuch as the subject was one of great interest to chemists, he was commissioned by the President to invite the Fellows of the Chemical Society to attend the meeting of the Royal Society. This invitation was unanimously accepted and acted apon by the members assembled; an unusually large attendance was the result, and the arrangement generally appeared to give much satisfaction. ROYAL INSTITUTION OF GREAT BRITAIN. Friday Evening, January 23. Sir HENRY HOLLAND, Bart., M.D., D.C.L., F.R.S., VicePresident, in the Chair. A PAPER, by JOHN TYNDALL, Esq., F.R.S., Professor of Natural Philosophy, Royal Institution, was read “On Radiation through the Earth's Atmosphere." Nobody ever obtained the idea of a line from Euclid's definition that it is length without breadth. The idea is obtained from a real physical line drawn by a pen or pencil, and, therefore, possessing width; the idea being afterwards brought, by a process of abstraction, more nearly into accordance with the conditions of the definition. So also with regard to physical phenomena; we must help ourselves to a coninception of the invisible by means of proper images derived from the visible, afterwards purifying our conceptions to the needful extent. Definiteness of conceptions, even The CHAIRMAN gave notice of the changes which would be proposed at the anniversary meeting, March 30, regard to the election of members of the Council for the ensuing year. |