26 



SCIENTIFIC NEWS. 



[April ist, 1887. 



" In connection with the analysis for carbonic acid, the air is 

 pumped by a bellows into bottles with a capacity of a gallon 

 and a half, the air from different heights being obtained by 

 means of an adjustable india-rubber tube. In the analytical 

 process a solution of baryta is used. This poured into the 

 bottles containing the air absorbs the carbonic acid, and forms 

 a white powder at the bottom of the vessel. A given quantity 

 of baryta being capable of absorbing a given quantity of car- 

 bonic acid gas, the measurement of the baryta remaining in 

 solution in the bottle gives, on a simple calculation, the quantity 

 of carbonic acid gas which was in the amount of air sampled. 

 For the collection of those mysterious germs which are never 

 entirely absent from the atmosphere, and whose functions have 

 not yet been satisfactorily determined, a glass tube about 

 2 inches in diameter and 2-k feet in length is used. This, 

 coated internally with a transparent gelatine, in which the 

 germs can live and thrive, is brought to the place, the air of 

 which is to be tested, germ-free. A reversing aspirator is affixed 

 to it, and a measured quantity of air is then drawn through the 

 tube, on the sides of which the germs deposit themselves. At 

 first these are not distinguishable by the naked eye ; but in the 

 course of three or four days they have formed colonies and 

 multiplied so exceedingly that a glass is no longer needed to 

 pick them out. Ultimately they are subjected to examination 

 under high microscopic power, so as to determine, if possible, 

 their genera, and whether or not they are disease-producing 

 germs. They are mostly vegetable, and belong to the very 

 lowest order of things endowed with life. For determining the 

 amount of organic matter the apparatus used consists of a set 

 of six bottles filled with the purest distilled water, and connected 

 together by means of tubes. The aspirator is put on to one 

 end, and the air is then sucked into the bottles drop by drop, 

 and thoroughly washed in its passage through them. No per- 

 ceptible discolouration of the water ensues by this washing of 

 the air, but the water acquires a stuffy, disagreeable smell, the 

 same as is experienced in a badly ventilated chamber. The 

 water thus impregnated with organic matter is then emptied 

 into a vessel for analysis." 



The Microphone. — At a recent meeting of the Society 

 of Telegraph Engineers, Professor Hughes gave some 

 particulars of an experiment he had made by submerging 

 a microphone in a pubHc bath. By the unassisted ear no 

 sounds could be distinguished, but by the aid of the micro- 

 phone a great confusion of sounds was revealed, doors being 

 shut, footsteps, voices, water flowing, all mingled together. 

 This proved the vibratory power of water, and a practical 

 application of the phenomenon is found in the fact that the 

 microphone is now part of the regular equipment of officers 

 of certain water companies in Germany, where it is used to 

 detect leakage from the pipes by the noise of the waterflow. 



The British AssociAtioN. — The principal officers for the 

 Manchester meeting of the British Association, to begin on 

 August 31, under the presidency of Sir Henry Roscoe, have 

 now been selected. The following will be the Presidents of 

 the various Sections : — Section A, Mathematics and Physics, 

 Sir Robert S. Ball, Astronomer Royal for Ireland ; B, 

 Chemistry, Dr. Edward Schunck, F.R.S. ; C, Geology, Dr. 

 Henry Woodward, F.R.S. ; D, Biology, Prof. A Newton, 

 F.R.S. ; E, Geography, General Sir Charles Warren, R.E., 

 G.C.M.G. ; F, Economic Science, Dr. Robert Giffen ; G, 

 Mechanical Science, Prof. Osborne Reynolds, F.R.S. For 

 Section H, Anthropology, a President has not yet been 

 chosen. One of the public lectures will be given by Prof 

 H. B. Dixon, who has taken as his subject " The Rate of 



Explosions in Gases." The lecture to the working classes 

 will be given by Prof George Forbes. It is expected that, 

 socially, the Manchester meeting will be one of the most bril- 

 hant ever held. A very large sum has already been subscribed, 

 and liberal arrangements are being made for excursions and 

 other entertainments. 



Railway Brakes. — The paper read before the Society of 

 Arts on the 9th of March, by Mr. William P. Marshall, the 

 late Secretary of the Institution of Mechanical Engineers, 

 on Railway Brakes, forms an important addition to the 

 popular literature of the railway. The author gave simple 

 descriptions, such as could be understood by a plain man, of 

 the various kinds of brakes in use, commencing with the 

 simple brake, and treating of chain brakes, vacuum and 

 compressed-air brakes of various kinds, both automatic and 

 non-automatic, and the various adjuncts connected with 

 them. A good discussion followed, which extended over a 

 second sitting. The subject is an important one, to which 

 the general public might well turn their attention, consider- 

 ing how closely the efficiency of railway brakes affects their 

 safety and comfort. 



Sewing Machines afforded another mechanical subject of 

 popular interest for a paper read before the Society of Arts. 

 Mr. John W. Urquhart was the author, and he had a very 

 difficult task in putting the recent advances in sewing 

 machinery forward in a manner that could be understood 

 by any but experts. There is not, probably, above one user 

 of sewing machines in a thousand who has mastered the 

 principles of the mechanism, and for this reason Mr. Urqu- 

 hart's paper was additionally welcome. 



The Mineral Resources of the United States. — In a 

 report of the U.S. Geological Survey on the mineral re- 

 sources of the United States for 1885, it is stated that the 

 total mineral product is valued at 428,521,356 dols., an in- 

 crease of 15,306,608 dols. over 1884. Among seventy 

 mineral substances cited, coal is the most important, show- 

 ing a total value of 159,019,596 dols. An increase is shown 

 in the production of coke, natural gas, gold, silver, copper, 

 zinc, quicksilver, nickel, aluminium, lime, salt, cement, 

 phosphate rock, manganese, and cobalt oxide, while the 

 production of coal, petroleum, pig iron, lead, precious 

 stones, and mineral waters decreased. According to the 

 report, it is probable that the total output of 1886 was 

 much greater than that of 1885, and even larger than that of 



Artificial Rubies. — At a recent meeting of the Acade'mie 

 dcs Sciences, a report was read by M. Fremy on the artificial 

 production of rubies. We are indebted to our contemporary. 

 La Nature, for the following details. This subject has already 

 been treated with varying success by MM. Ebelmen, Gaudin, 

 CazoUj and Debray, and in 1877 M. Fremy himself obtained 



