March 9, 19 16] 



NATURE 



45 



country for the general purposes of trade, but little 

 advantage has been taken of it, either in internal or 

 external trade. The system must be made compufsor}- 

 before the trading community as a whole will take 

 advantage of it. Several recent instances show that 

 the metric system can be introduced without the diffi- 

 culties which some people suppose would come with it. 



An article by Mr. R. G. Skerrett in the ScienHfic 

 American for February 12 describes Frickc's apparatus 

 for locating vessels at sea during fogs. It depends 

 on the difference in the time required for a wireless 

 signal and for a sound signal sent out from the same 

 point at the same instant to reach some distant point. 

 This difference is proportional to the distance apart of 

 the sending and receiving points. The receiving appa- 

 ratus consists of a wireless receiver and sixteen tele- 

 phones arranged at equal angular intervals round the 

 ship, and so protected that each will respond only to 

 sounds coming in approximately its direction towards 

 the ship. The arrival of the wireless signal starts 

 sixteen bands travelling outwards from a common 

 centre towards the sixteen corresponding telephones. 

 The arrival of the sound signal at the telephone 

 directed towards the quarter from which the sound 

 originates actuates a marking point carried by the 

 corresponding band, and a mark is made on the under 

 side of a piece of translucent paper placed over the 

 bands and ruled with concentric circles representing 

 the number of miles of the source from the vessel. 

 The marking points are brought back to the zero circle 

 after each observation, and a series of observations 

 gives the direction, distance, and course of the source 

 from the ship. 



In the last number of the Proceedings of the Geo- 

 logists' Association (December, 1915) Dr. A. Holmes 

 gives a useful summary account of the manner in 

 which the study of radio-active minerals can be applied 

 to the measurement of geological time. The science 

 of radio-activity has already destroyed the argument 

 by which Lord Kelvin deduced a relatively short age 

 for the earth from its apparent rate of cooling. But 

 the saine science also furnishes data for a direct esti- 

 mate of the age of a rock which contains radio-active 

 minerals. There is doubtless a considerable margin 

 of error, but the best results arc consistent, and seem 

 to be reasonable. Prof. Strutt's method was based 

 upon the accumulation of helium from the gradual 

 break-up of uranium and thorium. Dr. Holmes takes 

 instead the ratio of the final product, lead, to 

 uranium, and his results are in general higher than 

 Strutt's, probably owing to the loss of helium by 

 leakage. Various Carboniferous and Devonian intru- 

 sions are estimated to have an age of the order of 

 300 to 400 millions of years, and for granitic intru- 

 sions of the Middle pre-Cambrian is deduced an age 

 of the order of loco to 1200 millions of years. Such 

 figures will be comforting to geologists who dislike 

 hurrying unduly the operations of nature. 



In the current number of the Transactions of the 

 English Ceramic Society there are several important 

 papers, notably one by M. Bigot on the distribution 

 of heat in pottery ovens, and one on pottery pyrometr\- 

 by Mr. R. W. Paul. There is a memorial lecture on 

 the famous ceramic artist, M. Solon, by Mr. Hobson, 



Nrn OATCi ■\rr\-T r\>-r~\ 



of the British Museum, and a number of papers of purely 

 technical interest by Messrs. Audley, Dressier, Guy, Hill, 

 Mellor, Singleton, and Wilson. The English Society 

 is doing good work in getting the empirical expjerience 

 of the potters into, a systematic form, so that the 

 underlying principles may finalU- be made clear; and 

 it is gradually winning for itself general recognition 

 among the manufacturers who pay for the work of 

 abstracting the home and foreign pottery, clay, and 

 glass journals. These abstracts are an important 

 feature of the journal. 



The following forthcoming books of science are 

 announced, in addition to those referred to in recent 

 issues of Nature. By George Allen and Unwin, Ltd. 

 — Elements of Folk Psychology : Outlines of a Psycho- 

 logical History of the Development of Mankind, W. 

 Wundt, translated by E. L. Schaub ; Anthropo- 

 morphism and Science : A Study of the Development 

 of Ejective Cognition in the Individual and the Race, 

 O. A. Wheeler. By D. Appleton and Co.— The Book 

 of Forestry, F. F. Moon ; The Care and Culture of 

 House Plants, H. Findlay; The Fundamentals of Plant 

 Breeding, J. M. Coulter; Sanitation in Panama, W. C. 

 Gorgas; Irrigation Management, F. H. Xowell ; Irri- 

 gation in the United States, R. P. Teele; The Theon,' 

 of Steam Traction Engineering, S. R. Eighinger and 

 M. S. Hutton ; Minerals and Rocks, W. S. Bayley. 

 By .4. and C. Black, Ltd. — A Manual of Mendelism, 

 Prof. J. Wilson; First Principles of Evolution, Dr. S. 

 Herbert, new edition, illustrated; A Manual of Medicai 

 Jurisprudence, Toxicology, and Public Health, Dr. 

 W. G. A. Robertson, new edition, illustrated; Diseases 

 of Children, Dr. A. D. Fordyce, illustrated. By the Cam- 

 bridge University Press. — A Factorial Theor}- of Evolu- 

 tion, Prof. W. L. Tower ; Chemical Signs of Life, S. 

 Tashiro (University," of Chicago Science Series.) 

 By Cassell and Co., Ltd. — ^Alfred Russel Wallace: 

 Letters and Reminiscences, J. Marchant. By /. and 

 A. Churchill. — Handbook of Colloid Chemistry : the 

 Recognition of Colloids, Theorj- of Colloids, and their 

 General Physico-Chemical Properties, Dr. W. Ost- 

 wald, translated by Prof. M. H. Fischer. By John 

 Murray. — Agriculture after the War, A. D. Hall. By the 

 University of London Press. — The New Regional Geo- 

 graphies, L. Brooks, vol. i., The Americas, vol. ii., 

 Asia and Australia, vol. iii., Europe and Africa; An 

 Economic Geography of the British Empire, C. B. 

 Thurston. By Witherby atid Co., under the title, "A 

 Veteran Naturalist," a life of the late Mr. W. B. 

 Tegetmeier, by his son-in-law, Mr. E. W. Richardson. 



With reference to the note in N.-vture of March 2- 

 (p. 16), Mr. Perrycoste writes to say that he pointed 

 out not only the advantages consequent on the sug- 

 gested use of Latin, but the counterbalancing risks and 

 the necessity of discarding Latin " prose-composition," 

 as well as Latin verse. 



In the article on " The Utilisation of Peat " in Nature 

 of March 2, it should have been stated that the blocks 

 of Figs. I and 2 were lent to us by the Department 

 of Agriculture and Technical Instruction for Ireland, 

 which, as stated on p. 19, publishes the pamphlet from 

 which the article was abridged. Fig. 3 was from a 

 block lent by the Power Gas Corporation, Ltd., Stock- 

 ton-on-Tees. 



