194 



NA TURE 



[December 28, 1905 



is one, however, that requires extended quantitative 

 and qualitative treatment. The supposition that an 

 action is entirely due to a colloid, because the action 

 ceases on separation of the colloid from the system, 

 is an error commonly made by physiologists, due to 

 the omission of taking into account phenomena of 

 adsorption, and the complete alteration of conditions 

 produced by the change. 



There can be no doubt as to the value of this work 

 in its completed form ; it traverses practically the 

 whole of physiology in its chemical aspect, so far as 

 it is now possible to do so, and illustrates in an 

 excellent manner the results that have been produced 

 through application of chemical methods to physio- 

 logical problems; it is the first extended treatise of 

 the biochemistry of plants, and as such fills a void 

 that was distinctly appreciable, and moreover fills it 

 in a manner that places all vegetal physiologists 

 under great obligation to its author. 



F. Escombe. 



EXPERIMENTS Willi EXPLOSIVES. 

 New Methods of Testing Explosives. By C. E. 

 Bichel. Translated and edited by Axel Larsen. 

 Pp. 62. (London: Chas. Griffin and Co., Ltd.) 

 Price 6s. net. 



IN collecting together and translating the papers 

 on the researches carried out in the laboratory 

 of the Carbonite Explosives Company, Hamburg, the 

 translator .has given to English readers a valuable and 

 interesting little volume. The title is perhaps a trifle 

 misleading, but the whole -scope of the work may be 

 seen from the following quotation : — " (i) Why does 

 a smaller quantity of one explosive than another cause 

 ignition of fire-damp? (2) What are the incidental 

 phenomena and the influences tending to promote 

 such result? (3) In what manner do they co-operate 

 in producing it? " 



Appreciating the fact that it is desirable to work 

 with quantities as nearly as possible approaching those 

 employed in actual practice, special apparatus has 

 been constructed, so that for the particular explosives 

 dealt with we now have details obtained from ex- 

 periment on a much larger scale than any hitherto 

 adopted. In some cases charges of gunpowder as 

 great as 1500 grams were exploded, and for the 

 higher explosives often 300 grams. Even for the 

 calorimetric determinations the bomb had a capacity 

 of 30 litres, which was capable of taking a charge 

 of 100 grams. There must always, however, be 

 some risk with heavj charges of recording undue 

 pressures, a point to which Noble has directed atten- 

 tion. 



The actual pressures, gas volumes and composi- 

 tion of the products were determined from charges 

 fired in Bichel 's apparatus, the pressure being 

 recorded by a piston indicator working on a drum. 

 The record is really in excess of the true pressure, but 

 it is stated that the indicated pressure is rarely more 

 than two or three per cent, from the actual. The 

 apparatus permits of variations of surface area for a 

 definite charge, and so the cooling effect of the 

 chamber may be eliminated. It appears that with 

 NO. 1887, VOL. J 3] 



this allowance the pressure at a given density of 

 loading is proportional to that with higher densities. 

 This, however, may not be strictly true with very 

 high densities. 



The actual temperature at the moment of explosion 

 was calculated from the heat developed, the composi- 

 tion of the products and their specific heat, in the 

 usual manner, but all such calculations are uncertain 

 owing to doubt as to the specific heats of gases at 

 these high temperatures, and the impossibility of 

 taking into account dissociation. The possibility of 

 fitting a thermo-junction into the Bichel apparatus 

 might be worthy of consideration, for although the 

 results cannot approach actual values, yet the relative 

 temperatures recorded would probably serve as a 

 useful check on those calculated. Macnab has already 

 employed the thermo-junction for this purpose. 



In connection with the safety of explosives for 

 mining, undoubtedly the length of the flame, its 

 duration and temperature are of the greatest import- 

 ance. The two former were recorded photographi- 

 cally, a quartz lens being used. Some excellent 

 plates of the flames are reproduced. A factor deduced 

 from the ratio of the flame duration to the detonation 

 time, termed the " after-flame ratio," is shown to 

 have the greatest influence on the ignition of fire- 

 damp, and a most instructive diagram shows the 

 temperature developed, the length of flame, and the 

 " after-flame ratio " for the explosives examined. 



In considering the efficiency of an explosive the 

 author makes a distinction between the dynamic 

 action, due to the projectile-like action of the products 

 on the surrounding surfaces, and the static energy, 

 deduced in the usual manner from the volume 

 occupied by the products at the calculated temperature 

 of explosion. It certainly seems that a more rational 

 classification is thus possible than when the two are 

 considered together, and the results are claimed to 

 be fairly in accordance with those obtained in actual 

 practice. 



The general bearing of the work on the question 

 of safety is clearly dealt with, and four very complete 

 tables give a mass of information relating to the 

 explosives examined. 



Sufficient has been said of the contents of the book 

 to convince those interested in the subject of its great 

 value. It deals almost exclusively with mining 

 explosives, but it would certainly be of very great 

 interest if the investigations could be extended to 

 military explosives, for the author has such valuable 

 apparatus at his disposal that experiments on this 

 large scale could not fail to give much valuable 

 information. J- S. S. B. 



CM SALITY AND THE HUMAN WILL. 

 The New Science of Causation. By H. Croft Hiller. 

 Pp. xiii + 386. (London: The Walter Scott Pub- 

 lishing Company, Ltd., 1905.) Price 10s. net. 

 IF intrepidity were the prime essential of a philo- 

 sopher, this work would be epoch-making, and 

 its author would be a thinker of the first rank. He 

 claims to have formulated a case — to his mind, abso- 



