bable that certain vegetable products of deoxidised carbonic acid and water may have undergone a partial reoxidation, or even several alternate reoxidations and deoxidations, in the course of their history. Similarly in animals, although the ultimate process is one of oxidation, we know that some proximate principles of food experience an oxidation of certain of these constituents at the expense of the remainder, which consequently become deoxidised; and it is possible that some animal products may have undergone an entire deoxidation, or even several alternate deoxidations and reoxidations, before their final discharge from the body. On all these points very much yet remains to be learned; but still, the general position holds good, that vegetables effect a simultaneous deoxidation and intercombination of carbon molecules, while animals conversely effect their simultaneous reoxidation and separation. In many instances, also, the representatives of certain stages of building up and breaking up, in vegetable and animal life respectively, are closely allied to, or even identical with, one another. Oxalic acid, for instance, the simplest product of vegetable synthesis, and a frequent constituent of both the highest and lowest vegetable organisms, may be formed, as we have just seen, by a deoxidation of carbonic acid. But it also occurs abundantly in animal juices and secretions, not as a product of the deoxidation of carbonic acid, but as the last intermediate stage in the oxidation or downward transformation of more complex bodies into carbonic acid; just as the oxalic acid of commerce is obtained from sugar by a process of oxidation which, if carried too far, yields little else than carbonic acid. Benzoic acid, again, enjoys a wide distribution in the vegetable kingdom as a product of deoxidised carbonic acid, and is also a constant result of the natural and artificial oxidation of animal tissues. The power, then, of producing such bodies as benzoic acid and oxalic acid out of more complex bodies such as albumen and sugar, by artificial processes of oxidation more or less similar to the natural processes taking place in the animal body, has for a long time past been in the acknowledged possession of the chemist. Now, I propose to furnish you with illustrations of his inverse power, to which I have so often referred, of producing both animal and vegetable compounds by deoxidising, or synthetic, or vegetative processes-that is to say, of forming organic compounds without having recourse to living organisins or vital forces. I will first give you an account of the general processes employed for passing from a more simple to a more complex group, and then of the particular processes by which certain individual substances have been produced, interspersing some remarks upon the nature and relationship of the substances themselves. At starting, let me recall to your recollection the associated series of homologous fatty acids and alcohols, as written up on the table before you : Now, by a variety of processes, some new, some old, it is, and for a long time past has been, possible for us to fasten on to one or other of these or allied alcohol bodies an additional atom of carbon, in such a way as to produce the acid corresponding to the alcohol next in the series. Thus, by means of prussic acid CHN, or carbonic anhydride CO2, or phosgene COCl2, we can convert methylic alcohol into acetic acid, vinic alcohol into propionic acid, propylic alcohol into butyric acid, and so on; but until very lately we could not step from acetic to propionic acid, or from propionic to butyric acid,—that is to say, we could obtain butyric acid CHO, from certain members of the 3-carbon group, but not from those members which we had ourselves produced from the 2-carbon group; and, similarly, we could produce propionic acid C2H ̧Ó2, from certain members of the 2-carbon group, but not from those members which we had ourselves produced from the 1-carbon group. The series of synthetic operations by which it would be possible to pass from any group not merely to the next, but to the next but one, and so on ad libitum, was incomplete through a want of knowledge of the metamorphic relation subsisting between the acid and alcohol of the same group. The alcohol, and not the acid, being the plastic member of the group, we could convert the 1-carbon alcohol into the 2-carbon acid, and the 2-carbon alcohol into the 3-carbon acid, and so on; but being unable to convert the 2-carbon acid into the 2-carbon alcohol, we could not by any means pass from the 1-carbon to the 3-carbon group. Very recently, however, this difficulty has been overcome by the separate researches of Wurtz and Mendius, who have shown us how to transform any acid into its corresponding alcohol; whereby a continuous series of synthetic processes may now be carried on as far as we please. Without entering into purely chemical details, I may say that the process of Wurtz consists in transforming the aldehyd of the acid into the normal form of the alcohol; while that of Mendius consists in transforming the nitrile of the acid into the ammoniated form of the alcohol, by means of nascent hydrogen, as illustrated below in the case of ethylic alcohol, thus: Ethyl-amine. C2H,N or C2HS.H2N Ethyl-hydrate. C2HO or C2H.HO Ethyl-chloride. C2HCl or C2H.C1. The amine is readily convertible into the hydrate, and the hydrate into the chloride, bromide, or iodide; which last bodies, or their metal derivatives-such, for example, as sodium-ethylate C,H,NaO, and sodiumethyl C,H,Na-are the forms of alcohol most usually employed in actual synthetic processes. Prior, then, to this discovery by Wurtz and Mendius, of means for passing from the acid to its alcohol by hydrogenation, although many important syntheses had been effected, there had been no consecutive series of syntheses. The previously known processes would allow us to pass from certain mobile members of one group to certain immobile members of the next, but would carry us no further. Nowadays, however, by transforming the immobile acid into the mobile alcohol, we can proceed continuously through an apparently unlimited series of synthetic operations. Letting CO stand for the transferable part of carbonic anhydride CO2, phosgene COCl2, and hydrated prussic acid CHN.H2O, we should have the following series of operations leading to the production of fatty acids and alcohols of any degree of complexity, each of them capable of metamorphosis into scores of allied compounds, which again are capable of entering into combination with one another, as explained in my second lecture, to form still more numerous and complicated bodies. NEWS Propionic. C3H6O2 + H1 Propylic. C2HO + CO = Acetic. C2H402 Ethylic. H2O + C2HO. Propionic. C3H6O2. Propylic. H2O+CHO. Butyric. CHO.. 3-Carbon alcohol 4-Carbon acid Starting from the 1-carbon or methylic alcohol, we can convert it into the 2-carbon or acetic acid by wellknown processes. But in order to proceed from the 2-carbon acid, we must first transform it into the 2-carbon alcohol-the alcohol, in some or other of its forms, being the synthetic starting point, so to speak-and this we have very recently learned to do. Then, by affixing deoxidised carbonic anhydride on to the 2-carbon alcohol, we convert it into the 3-carbon or propionic acid. Then by acting upon propionic acid by deoxidised water, we transform it into propylic alcohol, upon which we again affix deoxidised carbonic anhydride to convert it into the 4-carbon or butyric acid, and so on continuously, by a series of deoxidising actions with carbonic oxide and hydrogen alternately. Now let us proceed to notice briefly, in the order of their complexity, some of the more interesting organic or carbon compounds which have been produced artificially by elementary synthesis. Among mono-carbon compounds we have first carbonic acid CH2O3, alike the most important product of animal oxidation and subject of vege table deoxidation. Associated with carbonic acid or hydrate, we have carbonic amide or urea CHAN,O, a body standing towards carbonic acid in the same relation that ammonia stands to water, and convertible into the acid by an exchange of certain elements of ammonia for the corresponding elements of water, thus: Urea. + (CO)”HN, + (Hạ)H,O, = (Hạ)HN, + (CO)”H,O. Carbonic acid is also met with in its dehydrated form as carbonic anhydride CO2, and as the sulphur derivative of that body or carbonic sulphanhydride CS2. These compounds are obtainable by burning charcoal in oxygen and sulphur respectively, the last of them, under the name of disulphide of carbon, being now produced on an enormous scale for certain manufacturing uses. The anhydride is readily procurable from the acid by dehydration, thus :Carbonic acid. Water. Carbonic anhyd. CH203 and reconvertible into the acid or its salts by actual or potential rehydration, thus :— Potash. Potas. bicarb. Potas. formiate. = CO2; Carb. anhyd. Lime. Formic acid. Water. Chalk. kingdom it has been occasionally recognised in human blood, urine, perspiration, and in the fluids of the spleen and muscles. It also exists largely in the juice of red ants from which it may be obtained by simple distillation, and in the corrosive fluid of certain caterpillars, &c. Now, by combining formic acid with ammonia, we obtain formiate of ammonia, which yields by dehydration that important organic compound met with in cherry-laurel water, bitter almond emulsion, &c., and known as prussic acid or cyanide of hydrogen, thus : This is the celebrated reaction by which urea was first produced artificially by Wöhler in 1828; but at that time the cyanogen of the cyanide of potassium employed was known only as a product of organic origin. You observe that by oxidising formic acid we obtain carbonic acid; and by oxidising the mon-ammoniated form of formic acidnamely, prussic acid-in presence of more ammonia, we obtain the di-ammoniated form of carbonic acid-namely, urea, which has since been produced by several other artificial processes. the methyl sub-group, and are, principally— The still less oxidised monocarbon compounds belong to Methyl hydride or marsh gas, CHO or CH,.HO Methyl-hydrate or wood spirit. CH,N or CH,H.,N Methyl-amine. These four bodies-the methyl varieties of hydrogen, hydrochloric acid, water, and ammonia--are mutually convertible by a variety of processes. Marsh gas, in addition to its occurrence as the chief constituent of coal gas, as the fire damp of coal mines, and as the gas of stagnant ponds or marshes, has recently been recognised by Pettenagain, is not only a product of destructive distillation, but kofer as a normal ingredient of expired air. Wood spirit, occurs in nature as a constituent residue of the essential oil of wintergreen, thus :— Water. Among other well known methyl compounds may be mentioned sarcosine, kreatine, caffeine or theine, theobromine, coniine, narcotine, &c., &c. The production of methylic from carbonic or formic compounds may be effected in a variety of ways. Thus prussic acid, by hydrogenation, yields methylamine : Prussic acid. Hydrogen. Methylamine. CHN + H4 = CH,N Formiate of barium is decomposed by heat with production of marsh gas; thus:Carb. Carb. anhyd. CO2+ KHOCKHO2, and CO2+ Ca′′O = CCa′′O3. The deoxidised forms of carbonic acid and anhydride, or formic acid CH2O2, and carbonic oxide CO, respectively, are readily procurable therefrom by processes of reduction, and are correlated with each other in a similar manner, thus:Carb. Potash. oxide. oxide. CO + KHO= CKHO2, and CH2O2 — H2O - CO. The production of formic acid or formiates by the reduction of carbonic acid with sodium (Kolbe), and by the combination of potash with carbonic oxide (Berthelot), being among the early examples of the formation of organic from inorganic compounds, excited on their first announcement a large amount of chemical interest. Altogether, formic acid enjoys a very extensive natural distribution. In the vegetable kingdom it occurs in the juice of the stinging nettle, in decaying pine needles, and as a product of the spontaneous oxidation of turpentine. In the animal' Barium formiate. Barium carb. Carb. anhyd. Marsh gas. CH + CH4 2 {CH 02 Ba" O2 2CBa"O3 + CO2 Marsh gas also results from passing a mixture of carbonic sulphanhydride and sulphuretted hydrogen over metallic copper heated to redness, thus:Carb. sulph. Hyd. sulph. Copper. Cupr. sulph. Marsh gas. CS2 + 2 H2S + Cus 4Cu2S + CHA Perhaps a still more interesting mode of obtaining methyl compounds consists in submitting disulphide of carbon to prolonged treatment with chlorine gas, whereby it is converted into perchloride of carbon, which by the 104 College of Physicians. continuous action of nascent hydrogen yields the following series of compounds :- Marsh-gas Derivatives. C Cl, Perchloride of carbon. CHA Methene, or marsh-gas. Thus among monocarbon compounds of purely artificial production we have the following interesting bodies, of which all save the last occur naturally in the vegetable or animal kingdom--namely, urea, formic acid, prussic acid, methylamine, marsh gas, and chloroform. The principal members of the dicarbon group, namely, alcohol and acetic acid, together with their respective congeners, are procurable from monocarbon compounds by a variety of processes. Thus, according to some observations of my own, on submitting a mixture of marsh-gas and carbonic oxide to a full red heat, acetylene or klumene is produced thus,— = Water. Klumene. Marsh-gas. Carb. oxide. со H2O + C2H2; CHA + and this klumene, when acted upon by nascent hydrogen, yields olefiant gas, or ethylene, thus :Klumene. Hydrogen. Ethylene. = C2H4 + C2H2 H2 Now, olefiant gas, as pointed out by Faraday and Hennell nearly fifty years ago, and as rediscovered and established beyond question by Berthelot within the last few years, is absorbed by oil of vitriol, and upon distilling the diluted acid, is liberated therefrom in the form of alcohol or spirit of wine, thus : Ethylene. Water. = Alcohol. C2H6O. You This production of alcohol from olefiant gas, or ethyJene, an important constituent of ordinary coal gas, is undoubtedly, in many points of view, a result of very great interest, but as a step in organic synthesis I think its importance has been somewhat over-estimated-alcohol and olefiant gas being closely allied members of the same carbon group. However, Berthelot's discovery of a process for obtaining alcohol by purely inorganic means naturally achieved considerable notoriety, and gave a great impetus to the general prosecution of synthetic methods. observe that the alcohol is produced from olefiant gas, which is itself produced from acetylene or klumene, which is itself produced from monocarbon compounds of strictly mineral origin. But a still more interesting way of obtaining acetylene has also been rediscovered and established by Berthelot, namely, the combustion, so to speak, of carbon in hydrogen gas. When charcoal is burnt in oxygen, the heat evolved by the initial combination is more than sufficient to maintain the combustion, and accordingly the piece of charcoal when once ignited continues to burn. But in the combustion of charcoal in hydrogen, if it may so be called, the piece of charcoal has to be maintained throughout in an intense state of ignition by means of the electric arc. When, for instance, the charcoal terminals of a moderately powerful battery, enclosed in a globe through which a current of dry hydrogen is passing, are approximated to each other so as to become ignited, as in the ordinary electric lamp, the hydrogen and ignited carbon combine with one another to form hydride of carbon or acetylene, much in the same way that oxygen and ignited carbon combine with one another But to form oxide of carbon or carbanhydride. oxidation tends to the separation, hydrogenation to the conjunction of carbon atoms; and accordingly, by the combustion of charcoal in oxygen we obtain only the mono-carbon compound CO2, whereas by its combustion in hydrogen we obtain the dicarbon compound C2H2, which is separated from the excess of hydrogen by transmission through an ammoniacal solution of the white or + Sept. 1, 1865. inferior chloride of copper, whereby it is retained in the Now, alcohol is procurable from acetic acid by the hydrogenising processes of Wurtz and Mendius, already described; while acetic acid is reprocurable from alcohol by oxidation, as in the ordinary manufacture of vinegar. Moreover, acetic acid C,H,O,, may be obtained synthetically from methyl alcohol CHO, by fixation of carbonic oxide CO, according to the previously mentioned general methods; and also from disulphide of carbon by Kolbe's historic process, referred to in my last lecture. The successive stages of this, the earliest unimpeachable process for obtaining an organic compound by strictly mineral means, are as follows:-Disulphide of carbon CS2, is first obtained by the combustion of charcoal in sulphur vapour. When this compound is acted upon by chlorine at a high temperature, it is converted into chloride of sulphur and chloride of carbon CC. Now, by transmission through red-hot tubes, this last compound is transformed, with evolution of chlorine, into the so-called sesquichloride of carbon, 2CC1=Cl2+ C2Cl, and eventually into the so-called bichloride of carbon or tetrachlorethylene, C,Cl, Cl2+ CCl4. In the course of his examination of this tetrachlorethylene, Kolbe observed that by exposure to chlorine in presence of water, it was decomposed into a mixture of trichloracetic and hydrochloric acid, thus :— which thus resulted from the series of transformations in- with as a glyceride in goat's butter, while amido-caproic dicated in the table before you : The disulphide of carbon, produced by the direct combination of sulphur and carbon, is converted, by treatment with chlorine, into tetrachloride of carbon; this, by heating to redness, into tetrachlor-ethylene; this, by the action of moist chlorine, into trichlor-acetic acid; and this, by means of nascent hydrogen, into ordinary acetic acid. By arresting the hydrogenation at a certain point, and treating the so-formed monochlor-acetic acid C2H,C1O2, with ammonia, we obtain glycocine, whereas by treating it with methylamine we obtain sarcosine, which, in combination with urea, constitutes kreatine, a compound, however, that has not yet beeno btained artificially. Thus, among 2-carbon products of the animal and vegetable kingdom, that have been obtained by strictly mineral processes, may be mentioned alcohol, triethylamine, taurine, acetic acid, glycocine, sarcosine, and last, though not least important, oxalic acid; which results from the oxidation of alcohol, acetic acid, and glycolic acid, &c., and is producible synthetically from the mono-carbon formic and carbonic acids. By means of the general processes to which I directed your attention some time back, as well as by certain special processes, it is easy to pass from the 2-carbon to the 3-carbon group, upon which, however, we must rest satisfied with bestowing a very cursory glance. It comprises among its members glycerine CHO, the basic principle of the true fats, whether of vegetable or animal origin. Also lactic acid C,H,O,, an important constituent of the juice of flesh, and a product of that fermentation of grape-sugar and milk-sugar which is set up by putrefying curd. We have also the chief constituents of essential oil of garlic or allyl-sulphide (CH)2S, and of essential oil of mustard or allyl-sulphocyanate (C,H,) HCNS, to be included in the list of artificially-produced members of the propionic family. Passing on to the 4-carbon group, we have first butyric acid CH.2, a product of the destructive metamorphosis of sugar, mannite, &c. Combined with alcohol it forms butyric ether or essential oil of pine-apple, while combined with glycerine it forms that constituent of ordinary butter which is known as butyrine. Butyric is readily convertible into succinic acid CHO04, which bears to it the same relation that oxalic bears to acetic acid, and probably the most frequent artificial product of the oxidation of fatty matters. From succinic acid it is easy to procure in succession the well-known vegetable products, malic acid CHO, and tartaric acid CН ̧О6. The succinic and malic acids are very intimately associated with, and readily convertible into, one another. Thus asparagine CH,N2O3, the crystalline principle of asparagus and other etiolated plants, yields one or other of these acids, according to the treatment to which it is subjected. The 5-carbon compounds of artificial origin are of less general interest. I may mention fousel oil or amylalcohol CH12O, and valeric or valerianic acid C.H1002, a product originally obtained from essential oil of valerian. By combining amyl-alcohol with acetic acid we procure the pear flavour, and by combining it with valeric acid the apple or quince flavour used in confectionery, which are probably identical with the essential oils existing in the ripe fruits. Again, by combining valeric acid with glycerine we produce valerine, a constituent of whale oil. Of the 6-carbon fatty compounds which have been artificially obtained, the most interesting are caproic acid CHO, and leucic acid CH1203. Caproic acid is met acid or leucine is an occasional constituent of human urine, and a constant product of the metamorphosis of glandular tissue. Grape sugar C6H12O6, mannite CH1406, and a host of allied alimentary substances are also included in this group, though their exact relationship to the typi cal members is not as yet clearly established. Now, sugar has been obtained by Berthelot from glycerine, which is itself, as I have said, obtainable by purely inorganic means; so that, in one sense, sugar may be added to the list of artificially produced organic compounds. Still the means employed for effecting the conversion of the glycerine-namely, the action of putrifying animal tissue-must prevent our regarding the resultant sugar as being strictly of inorganic origin; although it is formed exclusively out of the glycerine, the animal tissue not contributing any actual material to its formation. However, if sugar has not yet been obtained by a satisfactory process, the recent formation of strictly allied bodies, such as the propylphycite of Carius, together with our increasing knowledge of the metamorphic relations of sugar itself, assures us that an unexceptionable means for producing this important alimentary principle cannot much longer escape us. The transformation of fatty into aromatic compounds has not yet been accomplished according to any definite reaction; but both phenene СHÅ, and phenol or carbolic acid C,H,O, are producible by transmitting the vapour of alcohol or fousel oil through red-hot tubes. From the former of these bodies we readily obtain aniline or phenylamine C,H,N, which is reconvertible into both phenene and phenol. The 7-carbon fatty acid and alcohol are usually obtained from castor oil. So far as I know, they have not been produced artificially from inorganic materials, but undoubtedly could be so produced at any moment. With the 7-carbon aromatic compounds the case is different. By the general processes already referred to, phenene has been converted into benzoic acid C-H6O2, by Harnitzky and Kekulé, and phenol into salicic acid CH6O3, by Kolbe. Benzoic acid readily yields benzoic aldehyd or essential oil of bitter almonds, and also glyco-benzoic or hippuric acid. Salicic acid, again, is readily oxidisable into gallic acid, of which tannin constitutes the natural glucoside, as shown by the following decomposition : = Glucose. Saligenine. C13H18O7+ H2O C6H12O6+ CH.02. Moreover, tyrosine,-a very remarkable product of tissue metamorphosis--though not yet produced from salicic acid, has much the same relation thereto that leucine has to caproic, and sarcosine and glycocine have to acetic acid, being, indeed, the ethyl-ammoniated form of salicic acid. Another 7-carbon compound of artificial production, and of great interest in an industrial point of view, is benzoene, or toluol C,H,, which Fittig and Tollens have recently obtained from phenene or benzol CH. Starting from these two bodies, we may procure all the so-called coaltar colours, with the brilliancy and variety of which most of us are now familiar. The red base or rosaniline CH,N3, the violet base or triethylrosaniline C6H31N3, and the blue base or triphenylrosaniline C3H31N3, being producible in this way from their constituent elements, furnish admirable illustrations of the constructive powers of modern organic chemistry. Thus have I illustrated to you the mode in which chemists can nowadays, without any recourse to vitality, build up primary molecules containing as many as seven atoms of carbon, either from carbonic acid, water, and ammonia, the materials out of which living organisms construct identical or similar molecules, or else from the elementary substances, carbon, hydrogen, oxygen, and nitrogen, upon which living organisms can exert no plastic action whatever. I might even proceed further, but should then be obliged to depart from that regular sequence I have hitherto followed. Moreover, my object has been rather to illustrate to you the general mode of procedure than to make known to you the utmost limits that have as yet been attained. Of the three great classes of alimentary substances, the oleaginous are quite, and the saccharine almost within our reach. The albuminous, indeed, are still far beyond us; and no wonder, since their very constitution is at present not only unknown, but unsuspected. In their case, however, as in that of many other bodies, so soon as we succeed in unravelling the mystery of their natural composition, so soon may we aspire confidently to the work of their artificial reconstruction. oil, after a time, oxidised faster in the dark than when exposed to coloured or white light. Oil heated. in atmospheric air oxidised much more rapidly than cold oil. The oxidation may be accelerated without heat by adding some oil already oxidised. M. Blomstrand presented a "Note on the Metals of the Tantalum Group." According to the author, only two metals exist in this group, Niobium and Tantalum. The acids also are only two in number, di- or tetratomic: tantalic acid TaO, or Ta0, and niobic acid NbO, or NbQ2. Rose's white hyponiobic chloride is an oxychloride, Nb,C,O, or the double. Hyponiobic acid prepared by the decomposition of the oxychloride is true niobic acid, NbO2. Kobell's dianic acid is, without doubt, niobic acid, either pure or perhaps mixed with a little tantalic acid, too small in quantity to interfere with the reaction with tin which Kobell considered characteristic of dianium, and which is also common to niobium. The author criticises M. Marignac's paper on the hyponiobic compounds, suggesting that the material M. Marignac experimented with was not pure, tantalum being present with the niobium. As we recently mentioned, Blomstrand has fixed the equivalent of true niobium at 39 (Nb 78). = Two other papers we may dispose of very shortly. M. Pécholier writes, that the reason absinthe produces worse effects than other alcoholic drinks of equal strength is, that the liquor is usually taken on an empty stomach. M. Donnet has made a microscopic examination of rotten eggs, to ascertain whether the putrefaction was caused by, or developed, infusoria. He found no trace of organisms at any stage of the putrefaction. This is an important fact for the opponents of spontaneous generation. Only a few words more, which I will borrow from my friend Dr. Frankland. "It would be difficult," said he. "to conclude a subject like the present without some notice of the considerations which naturally suggest themselves regarding the possibility of economically replacing natural processes by artificial ones in the formation of organic compounds. At present, the possibility of doing this only attains to probability in the case of rare and exceptional products of animal and vegetable life. By no processes at present known could we produce sugar, glycerine, or alcohol from their elements at one hundred times their present cost, as obtained through the agency of vitality. But, although our present prospects of rivalling vital processes in the economic production of staple organic compounds, such as those constituting the food of man, are exceedingly slight, yet it would be rash to pronounce their ultimate realisation impossible. It must be remembered that this branch of chemistry is as yet in its merest infancy; that it has hitherto attracted the attention of but few minds; and further, that many analogous substi-A tutes of artificial for natural processes have been achieved. In such cases where contemporaneous natural agencies have been superseded, we have almost invariably drawn upon that grand store of force collected by the plants of bygone ages and conserved in our coal-fields." . ACADEMY OF SCIENCES. August 21. M. DAMOUR presented a memoir "On the Chemical Composition of the Stone Implements of Pre-historic Times." In this first part of the memoir the author gives a very good account of quartz, agate, flint, jaspar, obsidian, and fibrolite, all well-known substances that have been employed in the manufacture of stone implements. The account of the examination of the implements is to come, we suppose, in the next part. M. Cloez contributed a second memoir "On the Oxidation of Fatty Vegetable Oils." In this memoir he treats of the influence of light and heat on the oxidation. The author's results are of much interest. He exposed oils to the air in colourless glass vessels, and also in vessels of red, yellow, green, and blue glass, and also left some oil exposed to air in total darkness. After ten days' exposure the increase of weight was greatest in the colourless glass vessel; it was rather less in the blue glass; was very small in the red, yellow, and green; and no increase of weight at all was observed in the oil exposed in the dark. Like results were found after twenty days; but after thirty days' exposure the results were somewhat different. The increase of weight was greater in the coloured glasses than in the uncoloured, green showing the largest increase after 150 days' exposure. It is worthy of notice that poppy NOTICES OF BOOKS. Diamonds and Precious Stones: their History, Value, and COMPLETE account of diamonds and precious stones in relation to chemistry, geology, art, morals, and political economy, would form one of the most interesting books ever written. The author of the work under notice does not pretend to anything so ambitious as this, and yet has produced a book of very considerable value. The scientific account of the several stones, indeed, is in most cases imperfect, and in many inexact; art is scarcely noticed, and the special history is, we fear, not always to be relied upon; but, in spite of this, the general reader will find much that is novel and interesting, and those who wish for commercial information much that is valuable. Diamonds and precious stones have in all ages possessed a high exchangeable value-not entirely, it would seem, from their rarity. Ancient superstitions ascribed to certain stones occult virtues which modern intelligence would appear to not altogether discredit. The author of this work, in his evidence in the case Emanuel v. Wilbraham, said that it was customary in these days for a gentleman when engaged to present his fiancée with three rings, an emerald, a ruby, and a diamond. These, which would at first sight appear merely as offerings to the lady's vanity, may perhaps have another signification. For we learn from this and other books that the emerald was regarded as preservative of female chastity, while the ruby was supposed to ward off evil company and unpleasant dreams, and the diamond was potent against all sorts of poisons. Potent or not, diamonds and rubies are now of more value than they ever were, and, as the author hopes in his preface, this book "will prove useful to the merchant in supplying him without trouble with the distinguishing characteristics of each gem, and to the amateur as affording him simple and easy means of distinguishing the false from the real, and the valuable from the worthless." |