486 



NATURE 



[July io, 1913 



Smith's contribution to the discussion of Mr. W. R. 

 Bower's paper on a graphical method of optical 

 imagery covers five pages, and contains all the essen- 

 tials of Gauss's analytical method and an example 

 of its use. A paper by Dr. W. H. Eccles deals with 

 the important question of the cause of the behaviour 

 of the light electrical contacts used as detectors in 

 wireless telegraphy. Dr. Eccles shows that nothing 

 further is required to explain the behaviour of the 

 different types of contacts than the laws of genera- 

 tion of heat in conductors by electric currents and 

 the laws of thermo-electricity. 



In a short note in the Gazzetta Cliimica Haliana 

 (vol. xliii., i., 197) Mr. A. Pieroni .describes a new 

 method of preparing colloidal solutions, which con- 

 sists in dissolving, for instance, silver nitrate or copper 

 sulphate in pyridine containing pyrogallol or tannic 

 acid, and subsequently diluting with water. Under 

 these conditions, colloidal solutions of copper or silver 

 are obtained which are much more concentrated than 

 colloidal solutions of the same metals in water only; 

 in the case of silver, for instance, relatively stable 

 solutions, containing 0-05 to 0064 per cent, of the 

 metal, can be obtained. 



We have received from the United Tanners' Federa- 

 tion of Great Britain and Ireland a copy of "The 

 Tanners' Yearbook" (3s., post free), which, besides 

 containing a report of the work of the central com- 

 mittee of the Tanners' Federation during 1912, con- 

 tains statistics of leather and of materials emploved 

 in the leather industry, and a number of articles on 

 matters of technical interest. Some of these are of 

 scientific importance ; for instance, the article on the 

 mimosa-bark industry of South Africa, by Dr. J. 

 Gordon Parker, and that on the new synthetic tannin, 

 'Neradol D," manufactured by the Badische Co., 

 Ltd. 



The Journal of the Marine Biological Association 

 (vol ix., No. 41 contains an important paper bv the 

 late 'Mr. G. H. Drew on the precipitation of calcium 

 carbonate by marine bacteria. Evidence is brought 

 forward to show that the chalky mud flats forming 

 thi Great Bahama Bank and those which are found 

 in the neighbourhood of the Florida Keys are now 

 being precipitated bv the action of a new bacterium, 

 to which, owing to its power of precipilating calcium 

 carbonate from dilute solutions of calcium salts, the 

 name Bacterium calcis is given. The isolation and 

 characteristics of the bacterium are described and the 

 hypothesis put forward thai in the formation of the 

 various chalk and oolite strata the Bacterium calcis 

 or similar bacteria have played an important part, as 

 well as the Foraminifera and larger organisms; if 

 such a view be correct these strata must have been 

 deposited in comparatively shallow- water, the tempera- 

 ture of which approximated to that of the modern 

 tropii al seas. 



The second Gustave Canet lecture, delivered bv 

 Dr. Dugald Clerk, before the Junior Institution of 

 Engineers, on June 30, dealt with the present state 

 of our knowledge of the working fluid of internal- 

 combustion engines. The combined work of English 

 NO. 228o, VOL. 91] 



and Continental physicists and engineers has thrown 

 much light upon the physical and chemical behaviour 

 of flame, and it is now possible to give an approxi- 

 mately accurate account of the leading phenomena of 

 combustion, explosion, and expansion, so far as con- 

 cerns the engineer. Dr. Clerk gave a useful sum- 

 mary, together with the principal results, of modern 

 experiments on temperatures in the gas-engine 

 cylinder, on the internal energy of gas-engine mix- 

 tures, on explosions in closed vessels, on turbulence, 

 and on radiation. With the view of testing the 

 accuracy of the data thus accumulated, there are 

 several . trials on gas-engines included, together with 

 the reduction of the results. The information thus 

 given presents a very full statement of our know- 

 ledge, as might be expected from Dr. Clerk's personal 

 connection with the British Association committee 

 formed in order to study this subject. In Dr. Clerk's 

 opinion, practical men very greatly underrate their 

 indebtedness to theory. Some practical men have 

 gone so far as to say that gas-engine designers have 

 brought internal-combustion engines to their present 

 state of efficiency without any aid from scientific 

 theory. The increasing efficiency of the internal- 

 combustion engine has put great pressure upon steam- 

 engine builders, and recent steam turbine efficiencies 

 have attained such figures that it becomes necessary 

 for the gas-engine designer to attempt further 

 economies in order to keep ahead of his steam rival. 

 This he can do only by exact knowledge of his heat 

 losses and properties of his working fluid. 



We have received from Messrs. Gallenkamp and 

 Co., 19 and 21 Sun Street, E.C., a catalogue of 

 laboratory outfit for the bacteriological and patho- 

 logical laboratory. All the general and special appa- 

 ratus, as well as the necessary fittings, are included 

 in the list, which is fully illustrated. 



Catalogue No. 319, just issued by Mr. E. Baker, 

 14 and 16 John Bright Street, Birmingham, includes 

 a number of rare and interesting works on many 

 branches of science, offered at low prices. Librarians 

 and others requiring volumes to complete sets or 

 series, or papers on particular subjects, should see 

 the catalogue. 



Three new volumes in Prof. Ostwn'd's series of 

 scientific classics — "Klassiker der ex.-. '-.ten Wissen- 

 schaften " — published by Mr. W. Engelmann, of Leip- 

 zig, have recently been received. No. 1S8 (price 1.80 

 marks) is entitled, "Die Druckkrafte des Lichtes," 

 and contains two papers by P. Lebedew on the pressure 

 of light, with notes by P. Lasareff. A translation 

 into German of A. C. Clairaut's work, published in 

 1743, on the theory of the shape of the earth, based 

 upon hydrostatic principles, appears as No. 189 (price 

 4.60 marks), under the title, " Theorie der Erdgestalt 

 nach Gesetzen der Hydrostatik," with notes by 

 P. E. B. Jourdain and A. v. Oettingen. Similar valu- 

 able notes are contributed by R. Anschtitz to No. 190 

 (price S marks), which contains J. Loschmidt's " Kon- 

 stitutions-Formeln der organischen Chemie in graph- 

 ischer Darstellung." Each of the volumes has a por- 

 trait of the original author as a frontispiece. 



