Mean of eight days The milk rendered was evidently the same as before the new ration. The estimation of the excrements rendered by the cow lasted four days, from the 24th to the 27th of January. To facilitate this estimation, the cow was put into a stall, the floor of which was covered with flag-stones. The humid dung was weighed every evening; after having been well mixed, a sample weighing 500 grammes was taken and afterwards dried on a stove. Thus was ascertained the quantity of dry matter contained in the humid excrements. Milk in 24 hours. 6.50 6.00 6:00 6:00 6:00 6.50 6.50 6.50 6.03 Beetroots 27.00 Aliments consumed by the cow in four days. Products rendered by the cow in four days. Nature of the Weight of Fatty matters Nature of the Weight of the Fatty matters aliments. the aliments. contained in the products. in products. contained aliments. After some remarks from M. GAY-LASSAC, M. DUMAS felt compelled to call to mind that Professor Liebig had sent to Paris an article in German, after his letter of March 6-in fact, his letter of this day. In the German article, which M. GayLussac appeared not to know, Professor Liebig states that M. Boussingault obtained from a cow which eat 7 kil. 500 of hay and 15 kilogrammes of potatoes, 64 lit. 92 of milk containing 3,116 grammes of butter; that from a second cow, which consumed 7 kil., 500 of after-grass, and 15 kilogrammes of potatoes, M. Boussingault obtained 4,000 grammes of dried excrements. Professor Liebig, having analysed hay of Giessen, and the dung of a Giessen cow, calculates from that, that the first cow of Bechelbronn received 756 grammes of fatty matter in six days, and that the second cow of Bechelbronn received 747; and he asks whence come the 3116 grammes of butter produced by the former. which had been admitted for the two cows of Bechelbronn. To avoid all new difficulty on this subject, I here give the literal translation of the first writing of Professor Liebig. It will be seen that no reference is made to the cow of M. Koch, and that all the discussion turns on the experiments of M. Boussingault. Professor Liebig thus expresses himself:"The experiments of M. Boussingault on the influence exerted by the aliments on the proportion and the principles of cows' milk go to furnish us with still more important arguments for establishing that the organism produces fat by means of alimentary substances which are not fats, or which do not contain fat.-—(Ann. de Chimie et de Phys. t. lxxi., p. 65.) "The experiments of M. Boussingault merit, I think, entire confidence; it is so much the more incomprehensible to see M. Boussingault associated with men of science who have made an object of doubt and of discussion of the opposite opinion. "In a series of experiments executed in winter on a cow, by M. Boussingault, the daily ration was 15 kilogrammes of potatoes, and 7 kil. 500 of hay. This combination of several experiments in one appeared to us valueless. I have reason to say so; and it is only astonishing to me that the cow belonging to Mr. Koch, now under consideration, furnished precisely in six days 64.92 of milk, containing 3,116 grammes of butter, and per diem 4,000 grammes of dry excrements, like the two preceding, and there should still be a ques-grammes of fresh potatoes, or 19 kil. 88 of tion concerning the 756 grammes of fatty dry potatoes, and, moreover, 45 kilomatters in the aliments, and of the 747 grammes of hay. grammes of fatty matters in the excrements The milk collected during six days was 64 lit. 92, containing 3 kil. 116 of butter. "In six days the cow received 90 kilo "Admitting that the 19 kil. 88 of potatoes furnished the 60 grammes of fatty matter which are contained in it, then the 3 kil. 056 of butter must come from the 45 kilogrammes of hay. Hay must therefore contain seven per cent. of fatty matter. "Now, this may be decided by experiment. The experiments made in my laboratory have shown that the best quality of hay, in the state in which it is eaten by the cow, gives 1.56 of its weight of matter, soluble in ether. "Supposing that hay contains 1.56 per cent. of butter, 45 kilogrammes of butter could produce only 691 grammes of butter in the cow. It remains to explain the origin of the 2 kil. 365 of butter, which M. Boussingault found in the milk. "Professor Liebig then renders an account the experiments made in his laboratory for determining the proportion of the fatty matters contained in excrements. The excrements of a cow fed with potatoes and after-grass were submitted to analysis: ether extracted from the dry matter 3 gr. 119 of fatty matter. Then he adds : : "As it must be admitted, according to M. Boussingault (Ann. de Chim. et de Phys. t. lxxi, p. 322), that the solid excrements in the dry state represent of the weight of dry provender, it is clear that those excrements contain the same quantity of fatty matter as the aliments swallowed. 7 kil. 50 of hay contain (at 1.56 per cent.) 116 gr. of fat. The 15 kilogrammes of potatoes, moreover, contain 10 grammes of fat-in all, 126 grammes. The excrements rendered each day weigh 4 kil.; they contain, at 3.119 per cent., 124.76 of fat. "A milch cow, which gives in six days 3 kil. 116 of butter, consumes in its aliments 756 gr. of matter soluble in ether; there enters into its excrements 747 gr. of similar fatty matter. It should, then, be concluded that these matters have not taken part in the formation of this 3 kil. 117 of butter." All the numbers which this article of Professor Liebig contains are therefore obtained from the two experiments of M. Boussingault, as I had advanced; and as they are perfectly identical with those of the letters of which Professor Liebig has addressed to the Academy, we should naturally conclude that there has been no new experiment until he assures us of the contrary. ON THE PRODUCTION AND PREVENTION OF SMOKE.* BY HENRY DIRCKS. THE question as to the cause of the production of smoke, its constitution and peculiarities, is one which, I am well aware, might be elaborated into a discourse of considerable length, but it is not my present object to go into these details. The subject is one of considerable importance, particularly as regards the health of towns, and the interests of manufacturers; I consider, therefore, that with this great public benefit in view, the object of this Association cannot be better carried out than by bringing forward, and subjecting to rigid investigation, any practical application of chemical theory which has been found to answer the proposed end. I may mention that the subject of smoke prevention was first laid before this Associa tion at the meeting in Glasgow, by Mr. CHARLES WYE WILLIAMS, whose views of the chemistry of combustion have been also published; yet it is not a little remarkable that even some who profess a knowledge of chemical science doubt the impossibility of economically burning smoke.† Having had very extensive intercourse with different manufacturers throughout the United Kingdom, I have generally found them doubtful as to what invention, or class of inventions, is most approved, or which theory of the many theories afloat is the soundest. If, therefore, the views now pro * In the discussion which followed the delivery of this paper, Mr. William West, chemist, of Leeds, emphatically said, in the course of his remarks, that "smoke CAN be burned"-and proceeded to ridicule the idea that smoke cannot be burned, which he stigmatised as "one of Mr. Williams's crotchets." He said he had early given a testimonial in favor of Mr. Williams's ar gand furnaces, every word of which he was still able to support! This quibbling on the part of Mr. West is what we were certainly not prepared to expect from him. Mr. Dircks replied by observing, that he could as boldly as Mr. West say, that smoke can be burnt. He considered, however, that the question before the Section was not whether smoke can be burnt; but, whether it is not more correct, more scientific, to prevent its formation; to burn the gas rather than the smoke. + Read before the Chemical Section of the British Association, at Cork, August 19, pounded are incorrect I seek nothing more earnestly than their unqualified condemnation; indeed, I am well persuaded that they cannot pass without censure if not chemically correct. Smoke, then, being nothing more than deposited carbon floating in incombustible gases and vapor, it is our interest to deal rather with the carburetted hydrogen than with the smoke. In practice, with large engine boiler and other furnaces, all that appears to be requisite is to consider the best mode of applying the air to the crude gaseous products of the coal. The gas not being under control we cannot obtain it conveniently in a divided form, as in the Argand lamp; but we can reverse the principle and divide the air into some hundreds of small streams, jets or films, showering it rapidly into the hot atmosphere of gas in such a manner as to secure intimate mixture. This plan has been extensively practised for the furnaces of land and marine engines, and found to answer in a most surprising and remarkable It will fully answer the purpose of this inquiry to define smoke to be the result of the imperfect combustion of the crude coal gas, eliminated on making each fresh charge, of fuel. The black vapor or smoke is only seen at the chimney top, and merely differs from the colorless vapor of a chimney not smoking by the deposited carbon of the carbonated hydrogen rendering it opaque. We have thus:-1st. In the furnace the crude coal gas distilling from the fuel, contaminated and colored by coal-tar vapor and other impurities, differing materially from smoke in quality, though not much unlike in appearance.-2nd. Given off at the chimney, we have the volume of black smoke arising from the incomplete combustion of the crude gas in the furnace and flues, owing to an imper-rangement is important to those who seek to fect supply of air, or oxygen. abate the nuisance of smoke on an economical system. It must appear strange to the body of scientific men whom I have the honor of addressing, that a chemical fact of this nature should be disputed to the extent of actually impeding the introduction of what appears scientifically to be the only means of effectually removing the smoke nuisance. manner. A knowledge of the necessity for this ar This is all I contend for, and I would sum up by making this general statement :--That, to prevent smoke being formed, it is requisite to supply air to the gaseous products of the coal, independant of the supply to the solid fuel in the grate.* III. PHARMACY, MATERIA MEDICA, THERAPEUTICS, &c. ON MEDICINAL EXTRACTS. BY G. M. MOWBRAY. (Concluded from page 472.) WE now come to a consideration of that method of evaporation which has been termed spontaneous, and which, if rapidly conducted, equals any method that we have considered; still, the difficulties to be overcome are not trifling. The most recent modification of this method is that described in the "Pharmaceuti * The views of the author were supported by the several speakers who entered into a discussion of the subject, with the solitary exception of Mr. West, who seemed to prefer haggling about terms rather than confining his attention to the chemical fact that the only combustible portion of smoke is the carbon, which is suspended in so much incombustible matter, that, as far as economy is concerned, its combustion is most difficult, and can only be effected at the expense of fuel to burn it; whereas gas with a due admixture of air affords smokeless flame. Pro cal Transactions," p. 638, vol. 2, by Mr. Hooper, and illustrated by a wood engraving. The objections which have deterred me from practising this plan are— 1st. Cost of the vessels, steam-boiler, leaden vitriol pans, manual labor, and fuel. 2nd. Inconvenience of dabbling in sulphuric acid, or permitting workmen to do so. 3rd. Cost of reduction of the vitriol to a concentrated state. fessor Apjohn, president of the chemical section, spoke in very high terms of Mr. Williams's treatise on The Combustion of Coal, in which, as it appeared to him, he had entirely exhausted the subject; he fully coincided in all that was advanced, and considered it best to prevent the formation of smoke. In reply to an inquiry from the chairman, Mr. Dircks stated that the principle he advocated was that practically carried out by the Argand furnace, the invention of Mr. C. W. Williams. 4th. Loss of acid and disagreeable odor given off as the vitriol becomes dilute and acts upon the lead. 5th. The length of time required for the operation. Against all these objections, the extract produced does not surpass that procured by exposing the juice on dishes in a room through which a current of air is impelled by a blower, such air having been heated by a charcoal brazier. I must be allowed to express my conviction that Mr. Hooper (I cannot believe unconsciously) has either resolved to monopolise" Vitriol Spontaneous Extracts," or that he is rather deeply indebted to Drs. Prout, Pereira, Hodgkin, and Julius Jeffreys, Esq., for a severe quizzing than for useful suggestions, and I am sure no more severe punishment could be inflicted upon these gentlemen and Mr. Hooper than to require from each of them the manufacture of one ton of extract by the method to which their suggestions have contributed so much, even if four times the present market price were offered as a fee for the product. Taking Mr. Hooper's data, the following is an estimate of the cost of manufacturing 164lbs. of extract of henbane by this pro cess: Mr. Hooper states that with a surface of 7200 inches superficial, one man working at the blower for 12 hours can evaporate six pints of liquid. After vitriol has absorbed thrice its weight of moisture, it requires to be concentrated. Then Dr. Hooper's charge for ext. hyoscyaine is 1s. 4d. per oz. I cannot conceive how our friend can designate his arrangement as possessing advantages over the common method of spontaneous evaporation, with such an estimate of expenditure, neither can I understand how the terms "simple in construction and easily managed" apply; but the extent to which Mr. H. has pushed his method of manufacture, a fact known only to himself, would perhaps best solve this question. Strictly speaking, the term spontaneous does not apply where heat is used, yet as explained in reference to the term in vacuo, we must accept terms as usually understood. Figs. 5 and 6 represent a blower which I have attached by a band to the flywheel of a steam-engine; the fans of this revolve about 320 times in a minute, and send through a cast-iron pipe, heated to redness, laying under the boiler of the steam-engine, a powerful blast of heated air into a small chamber; this blast will support a pressure of two ounces to the inch at the end of the conducting tube, and extracts thus prepared are very excellent; I find the temperature of the chamber is maintained at about 100° F., although at first it rapidly rises to 140° F. I have also adapted to the exit tube of the vacuum pumps a pipe passing through the furnace of the steam-boiler, and by opening the connection so that air may be drawn freely from the atmosphere have forced such air through the heated pipe into the upper part of Fig. 9 at A, allowing the partitions to dip in the liquid to be evaporated. Extracts thus prepared yield to none in point of flavor, medicinal efficacy, and strength. The last method which I have adopted has been by filling a cast iron chamber whose height is seven feet four inches, width five feet, and depth two feet, with dishes piled on each other, and filled alternately with chloride of calcium and the liquid or liquids to be evaporated, then exhausting by means of the air pumps such chamber, until the barometrical indicator stands at 28 inches, the torricellian vacuum being 30 inches, then cutting off the communication with the pumps and allowing the vacuum chamber to remain undisturbed for four days, occasionally shutting off the suction pipe from the vacuum pau, and letting it on to the vacuum chamber for five, ten, or fifteen minutes, or |