December 25, 1919] 



NATtfRE 



419 



Reviie generale des Sciences for October 15. The 

 three main divisions are tropical or zone mdga- 

 therinique, temperate or zone mesothennique, and 

 cold or zone microtherniique. These are based on 

 considerations of temperature. Two other divisions 

 are placed on the same level, one embracing hot 

 deserts and the other cold deserts, but in their case 

 amount of precipitation is an important determining 

 factor. Subdividing these zones, M. Koppen finds 

 eleven principal climates, which he names as follows : 

 (i) Tropical forests, (2) savannas, (3) steppes, (4) 

 deserts, (5) temperate with dry winter, (6) temperate 

 with dry summer, (7) temperate humid, (8) cold with 

 wet winter, (9) cold with dry winter, (10) tundra, 

 and (11) perpetual ice. In addition to these main 

 climates M. Koppen recognises a large number of 

 secondary and transition climates. With the help of 

 these lists he gives two or three reference letters to 

 every climate on the globe. We gather from the 

 summary that he distinguishes some fifty different 

 climates. Thus the climate of Brisbane is indexed as 

 C/a, which designates a warm temperate climate with 

 rainfall at all seasons, and the mean of the warmest 

 month not above 22° C. Cairo is indexed BW/i, 

 which means an arid climate of the desert type, with 

 a mean annual temperature above 18^ C. 



In a paper read before the London Mathematical 

 Society in 1903 Sir Joseph Larmor showed that when 

 the disturbance propagated into a medium is deter- 

 mined by considering each element of an advancing 

 wave-front to constitute a source of disturbance, as 

 Huygens did two centuries ago, the problem of 

 finding the strengths of these sources was indefinite 

 from an analytical point of view. Many distributions 

 could be found over the wave-front which would give 

 the same total effect. In a further paoer read before 

 the society on November 13 Sir Joseph shows that, 

 although analytically the problem is indefinite, 

 physically one specification only is permissible. 



In the Biochemical Joiimai for November Prof. 

 W. D. Halliburton and Messrs. J. C. Drummond and 

 R. K. Cannan describe some experiments made to 

 ascertain the food value, if any, of the synthetic pro- 

 duct prepared from olive oil and mannitol bv Lapwortli 

 and Pearson. The synthetic oil possessed a taste rnd 

 odour recalling those of olive-oil, but somewhat less 

 pleasant; insufficient oil was at hand to make experi- 

 ments on the higher animals, so rats were employed 

 in the work described. From the results so obtained 

 Halliburton, JDrummond, and Cannan conclude that 

 "mannitol olive-oil " is utilised by the animal organism 

 practically to the same extent as olive-oil itself, and 

 no toxic action was observed to follow its prolonged 

 administration to rats. 



A SHORT account of the methods used in France at 

 the present time for the production of radium bromide 

 and other radio-active substances is given bv M. 

 Demenitroux in La Nature for November i. Pitchblende 

 from Joachimsthal being no longer obtainable, the indus- 

 trv is dependent on carnotite from Colorado, autunite 

 from Portugal, and certain rare-earth minerals from 

 Madagascar. These contain fewer than 15, and in some 

 cases not more than 4, milligrams of active material 

 per ton. The first operation consists in the separation 

 of the barium, and this process is a long and costlv 

 one. The radio-active materials are separated with 

 the barium, and the second operation is the separa- 

 tion of the two from each other. This is done bv 

 fractional crystallisation, a tedious but certain process 

 which involves, as a rule, -joo successive crystallisa- 

 tions of the material. Finally, one of the tubes used 

 in medicine containing 100 milligrams of radium 

 bromide is obtained from 12 tons of the ore, 3 tons of 



NO. 2617, VOL. 104] 



hydrochloric and i ton of sulphuric acid, 5 tons 

 of carbonate of soda, and 10 tons of coal. The present 

 cost in France of the hydrated bromide of radium, 

 RaBrj,2H.O, is 500 francs per milligram. 



Hitherto it has been stated in the literature that 

 chloropicrin can be distilled unchanged at ordinary 

 pressure. Messrs. J. A. Gardner and F. W. Fox have 

 observed, however (Journal of the Chemical Society 

 for October), that when the pure anhydrous substance 

 is distilled at atmospheric pressure a small amount 

 of a yellowish-red gas, resembling diluted nitrous 

 fumes, is invariably produced, aqd ran be seen in 

 the atmosphere of the condenser and receiver. These 

 authors show that this is due to a slow decomposi- 

 tion of the boiling chloropicrin into carbonvl and 

 nitrosyl chlorides, according to the equation 



CCl3.NO, = COCI, + NOCI. 



If 200 c.c. of the substance are boiled gently, the 

 rate of decomposition is appro.ximatelv 2 c.c. per 

 day. This observation will account for the divergence 

 between statements made on the physiological activity 

 of chloropicrin. Further, the experiments of Frank, 

 land. Challenger, and Nicholls, showing that under 

 some conditions chloropicrin is quantitatively reduced 

 to methylamine, and under others to ammonia, would 

 be explained by the reduction in the first case of 

 chloropicrin per se, and in the second of its decom- 

 position products. In some reactions chloropicrin 

 seems to act as a nitro-compound, e.g. it can be <-ub- 

 stituted for nitrobenzene in Skraup's method of pre- 

 paring quinoline ; whilst in others the results can 

 be explained as due to the carbonvl and nitrosyl 

 chlorides. 



The latest catalogue of second-hand books of 

 Messrs. W. Heffer and Sons, Ltd., Cambridge (No. 

 184), comprises a number of works on history and 

 economics from the library of the late Rev. Dr. W. 

 Cunningham ; also books on architecture and archaeo- 

 logy, and old travels to the East. 



Mr. Fr.^xcis Edvv.-vrds, 83 High Street, Marylebone, 

 W.I, has just circulated a Catalogue (No. 396) of 

 autograph letters, historical documents, and manu- 

 scripts. Many of the letters are the work of ex- 

 plorers and men of science. The section devoted to 

 manuscripts contains several items of great historical 

 value. 



Among forthcoming books of science we notice the 

 following: — A "Peat Industry Reference Book," the 

 late F. T. Gissing {Charles Griffin and Co., Ltd.); 

 "The Life and Inventions of Sir Hiram S. Maxim," 

 P. F. Mottelay (John Lane); "Military Psychiatry in 

 Peace and War," Dr. C. S. Read (H. K. Lewis and 

 Co.. Ltd.); "The Life and Letters of Silvanus Phillips 

 Thompson, F.R.S.," Jane S. and Helen G. Thomp- 

 son (T. Fisher Unwin, Ltd.); and "The Life of Sir 

 William White, K.C.B., F.R.S.," F. Manning (John 

 Murray). 



In reference to our notice of the Daily Telegraph 

 Victorv .^t!as (November 13, p. 276), Messrs. Geo- 

 graphla, Ltd., take exception to the remark that "a 

 mistake is made in the area of the Slesvig plebiscite." 

 This criticism, which had reference to the course of 

 the frontier of that area, was based on the abstract 

 of the Treaty of Versailles published in Treaty Series, 

 No. 4, and our reviewer wishes to examine the German 

 large-scale maps of Slesvig before accepting the 

 boundary shown by Messrs. Geographia, Ltd. Mean- 

 while, we regret if his reading of the text and maps 

 of the abstract gave a wrong impression of the 

 arcuracv of the Daily Telegraph .^tlas. 



