124 



NATURE 



[April 12, 1917 



these things Mr. O'Malley gives a readable 

 description. 



The book is sure to be largely used in English 

 and Indian schools and should be in the hands 

 of every young officer posted to India, while, 

 studied by all who are interested in the progress 

 of the Empire, it should remove many current 

 misapprehensions and bring to the notice of home 

 readers some idea of the weighty and complex 

 problems which the Civil Service, patiently and 

 without advertisement, has hitherto solved with 

 conspicuous success. 



High-speed Internal-combustion Engines. By 

 A. W. Judge. Pp. ix + 350. (London: Whit- 

 taker and Co., 1916.) Price 155. net. 



This book opens with a general discussion on the 

 thermodynamic principles involved in the proper- 

 ties of gases and mixtures of gases, followed by a 

 chapter descriptive of experiments on rates of com- 

 bustion, etc., in the engine cylinder. Working 

 cycles and the conditions occurring in actual 

 engines are then treated ; this section has a useful 

 collection of experimental data on the losses due 

 to different parts of the engine mechanism and 

 to the friction of gases flowing along passages. A 

 section on pressures and temperatures follows, and 

 has many references to well-known experiments. 

 Chap. V. deals with indicators and indicator 

 diagrams, and has useful descriptions of modern 

 high-speed indicators. The remaining two 

 chapters deal with the mechanics of the engine 

 and with balancing. 



The volume is intended to form a companion 

 to one upon the design of high-speed internal- 

 combustion engines, and possibly this explains the 

 absence of drawings descriptive of typical engines. 

 We should hesitate to recommend the book to 

 students until the opportunity arises of examining 

 the proposed companion volume. The practical 

 engineer will not much appreciate the almost total 

 absence of reference to brake-horse-powers, and to 

 the special methods of measuring them which have 

 to be adopted in high-speed motors. There are 

 several minor blemishes. Thus on p. i various 

 heat units are defined, including the British 

 thermal unit, and omitting the Ib.-deg.-cent. heat 

 unit; J is given as 778 foot-pounds. But the 

 Centigrade system is employed throughout almost 

 the whole of the book. On p. 26 the symbols M 

 and m conflict; M appears in the text and m in 

 the equation. On p. 69 we read the loose state- 

 ment that " I cubic foot of petrol would require 

 for complete combustion . . . 45*4 1 cub. feet of 

 air"; and on the same page: "The volume of 

 the exhaust product ... is i4"7^ lbs." On p. 186 

 work is measured in "feet-lbs.," and elsewhere in 

 "foot-lbs." 



There are no exercises for the student to attempt 

 for himself, but there are a few worked-out ex- 

 amples in the text. The book, however, contains 

 a collection of matter which cannot fail to be of 

 service to anyone studying problems connected 

 with the changes occurring inside the cylinder of 

 internal-combustion engines. 



NO. 2476, VOL. 99I 



LETTERS TO THE EDITOR. 



[The Editor does not hold himself responsible for 

 opinions expressed by his correspondents. Neither 

 can he undertake to return, or to correspond with 

 the writers of, rejected manuscripts intended for 

 this or any other part of Nature. No notice is 

 taken of anonymous communications.] 



A Very Penetrating Radiation in the Atmosphere. 



It is noteworthy that English physicists have taken 

 very little interest in the progress which has been made 

 during the last ten years m atmospheric electricity. 

 This is the more remarkable seeing that some of the 

 problems are problems in pure physics, and there is 

 little doubt that they give evidence of phenomena of 

 fundamental importance. To take one or two examples. 

 There can now be no doubt that the earth is giving off 

 a constant stream of negative electricity which passes 

 at least into the upper atmosphere, and probably into 

 cosmical space. Are we justified in treating this result 

 of innumerable observations in all parts of the world 

 as something which will be explained in due time by 

 the old laws of physics, or should we not recognise the 

 possibility that we have here indications of a new pro- 

 perty of matter? The earth is a huge insulated mass 

 of matter moving unrestrained under cosmical forces, 

 and therefore may very well reveal a relationship be- 

 tween electricity and the motion of matter to which 

 laboratory experiments could give no clue. This 

 phenomenon is well worth the consideration of the 

 mathematical physicists who are at present throwing 

 all our preconceived ideas of electricitv, mass, motion, 

 and gravity into the melting-pot. 



Then, again, it is now no longer possible to treat 

 ball lightning as a figment of the imagination caused 

 by the bewilderment due to a near lightning flash. 

 What are these balls of light which travel and react 

 according to no laws of physics at present known ? 



The results of Vegard's and Stormer's work on the 

 aurora are probably too new to have attracted wide- 

 spread notice, but here we have indications of true 

 radio-active radiation penetrating our atmosphere and 

 producing the same apparent results as If the atmo- 

 sphere were being bombarded from outside by the 

 a radiation which is at present under Investigation in 

 our laboratories. 



The object of this note is to direct attention to 

 another phenomenon of atmospheric electricity which 

 is of first-rate physical importance. 



Until quite recently the most penetrating radiation 

 capable of lonlsinc: gases of which we have know- 

 ledge Is the y radiation emitted by radio-active sub- 

 stances. Balloon ascents, however, made in Germany 

 just before the outbreak of war have given almost In- 

 contestable proof of a radiation entering the atmo- 

 sphere from above which has ten times the pene- 

 trating power of the hardest radiation sent out 

 from radio-active substances. The method of 

 experiment is to carry up In a balloon a metal 

 box of y, mm. thick brass coated on the inside 

 with zinc and hermetically sealed. The ionlsatlon 

 within the box Is tested at each height bv means 

 of a central electrode connected to a Wulf 

 electroscope. It is found that the ionlsatlon within 

 such a box decreases at first after leaving" the ground 

 and then returns to lis original value at about 1500 

 metres altitude, after which It Increases raoidly to the 

 greatest height reached. The most oerfect set of 

 observations was made bvKolhorster in June, iqi4; the 

 most perfect In the sense that his apparatus had had 

 all the defects removed which previous ascents had 

 revealed, and the s^reatest heig-ht of anv ascent was 

 reached. The results are shown in the following table, 

 in which q Is the number of pairs of Ions generated 



