66: 



NATURE 



[October 29, 1908 



Finallv we come to the " machines a explosion," 

 or balloons propelled by gas engines. Paul Haenlein 

 in 1S65 was the pioneer of this type, although he 

 seems to have had no practical success. The German 

 machines of Woelfert, Schwartz, and the first Zeppelin 

 .ire in turn described, though each of them proved 

 failures. The various vessels of Santos Duniont next 

 claim attention, especially his much-lauded trip round 

 the Eiffel Tower. More failures and catastrophes 

 followed with Rose, Severo, and De Bradsky, and 

 then came the successful essays of the Lebaudys. 

 The history of this type of airship is fully gone into, 

 from the first trials up to the unfortunate escape 

 of the Palrie. 



Then follow descriptions of the other French dirigi- 

 bles, the Vilh dc Paris, and that of Count de la 

 X'aulx. 



The modern airships of other countries are disposed 

 of in a few pages. The Zeppelin No. 3 is shortly 

 described, but its better-known successor, which has 

 since made its debut and taken its conge, is referred 

 to in the final pages of the book. Having described 

 the Polar explorations by balloon at some length, the 

 authors give a chapter on aeroplanes. The latter can 

 hardly be called up to date, since progress has been 

 so rapid during the last year or two. It is almost 

 amusing to read of M. Farman's record performance 

 of remaining in the air for 52 3 seconds w-hen to-day 

 we think nothing of Mr. Wright flying for more than 

 an hour with a passenger. In these circumstances of 

 kaleidoscopic changes it seems impossible to bring 

 out a book on aeronautics which shall be really up-to- 

 date, but the one before us is a good little history 

 which is fairly trustworthy, though it is not detailed 

 enough to be classed as a technical text-book. 



An Englisli Holiday with Car and Camera. By 

 James John Hissey. Pp. xviii-l-426; with 28 full- 

 page illustrations and a map of the route. (London : 

 Macmillan and Co., Ltd., 1908.) Price lox. net. 



It was scarcely necessary for Mr. Hissey to tell us, as 

 he does in his preface, that he travels purely for 

 pleasure and " in search of the picturesque." Those 

 readers who know the author's many pleasant, gossipy 

 books about English by-ways have long been aware, 

 from the optimistic wav in which rural England is 

 described, that Mr. Hissey loves exploring his native 

 land. This time the journey taken by the author and 

 his wife was confined to motoring in the country south 

 of a line joining the \\'ash to the Bristol Channel. 

 The account of the wanderings, with its many 

 glimpses of the home-life of the country people, and 

 the excellent illustrations, combine to make a very 

 interesting volume. 



Pearls and Parasites. By A. E. Shipley, F.R.S. 



Pp. xv + 232; with illustrations. (London: John 



Murray, 1908.) Price 7.9. 6d. net. 

 The title of Mr. .Shipley's book scarcely serves to indi- 

 cate the general character of the contents. The volume 

 contains nine essays, which, with one exception, deal 

 with problems of economic zoology. The subjects 

 introduced vary considerably among themselves, as 

 the following titles show: — Pearls and Parasites; the 

 Depths of the Sea; British Sea-fisheries; Zebras, 

 Horses, and Hybrids; Pasteur; Malaria; "Infinite 

 Torment of Flies"; and the Danger of Flies. The 

 concluding essay is an inquiry into the aims and 

 finance of Cambridge L?niversity. Most of the essays 

 have appeared previously in periodicals, and have been 

 read by many people interested in science. The sub- 

 jects discussed are sufficiently important to attract the 

 scientific as well as the general reader. 



NO. 2035, VOL. 78] 



.Architectural Education. By Wilfrid 1. Travers, 

 Pp. vii+119. (London : Harrison, Jehring and Co., 

 igo8.) Price 45. net. 



The subtitle of this book indicates its character with 

 fair precision; it runs: — " .\ history of the past and 

 some criticisms of the present system, upon which 

 are founded some suggestions for the future, with 

 particular reference to the position of the universities." 

 Mr. Travers has collected much information as to the 

 courses of training for architects and the syllabuses 

 of the examinations conducted by the Roval Institute 

 of British Architects and many universities, and also 

 offers useful suggestions for their improvement. 

 Many of the schemes of work here tabulated appear 

 to give little prominence to the training in the prin- 

 ciples of science which are necessary for an architect 

 to ensure successful work. 



LETTERS TO THE EDITOR. 



[The Editor does not hold himself responsible for opinions 

 expressed by his correspondents. Neither can he undertaJie 

 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 ationymous coniviunications.] 



A Suggested Explanation of the High Velocities of 

 Gases observed on the Solar Surface. 



The important discovery by Prof. Hale of the Zeenian 

 effect in sun-spot spectra proves the presence of extensive 

 areas on the solar surface in which ions of one kind 

 largely preponderate. This suggests the solution of one 

 great difficulty which has blocked the way in the attempts 

 that have been made to explain the very high velocities 

 which are not unfrequently observed near the solar surface 

 by spectroscopic and other means. For there is a limit 

 to the velocity of a gas impelled by pressure only, this 

 being the velocity with which it streams from a high 

 pressure into a vacuum, and we may put this limiting 

 velocity to be equal to that of propagation of sound in 

 the gas. Observation shows that the highest velocities 

 observed on the solar surface are about 200 times as great 

 as the velocity of sound in hydrogen at the temperature 

 of freezing water. 



If, then, these masses of moving matter are impelled 

 by pressure only, the number expressing their absolute 

 temperature divided by the density must be 40,000 times 

 greater than the corresponding number in the case of 

 hydrogen at 0° C. Taking the absolute temperature of 

 the sun to be forty times as great as that of freezing 

 water (which cannot be far from the truth), the observed 

 velocities would become consistent with our supposition of 

 pressure-motion only if the density of the gas were a 

 thousand times less than that of hydrogen. This brings 

 us down to the mass of the negative electron. As, how- 

 ever, spectroscopic evidence indicates the motion of ponder- 

 able matter (principally, if not solely, composed of 

 hydrogen), we must assume that gases are entangled in 

 tlie rush of electrons, but not to a sufficient degree to 

 alter the average density materially. In the case of matter 

 in which one kind of electrons preponderate, electric forces 

 may, of course, increase the velocities almost to any 

 extent, but the close agreement of the observed high veloci- 

 ties with the limiting velocity in a gas, having a density 

 equal to the thousandth part of that of hydrogen, and 

 being at a temperature agreeing, so far as we can tell, 

 with that of the solar surface, is highly suggestive. I 

 conclude, therefore, that if the observed velocities are real 

 — and there is good ground for believing them to be so — • 

 the prominences and other appearances in which velocities 

 of more than about 10 Icilometres a second are observed 

 are composed to a preponderating extent of electrons in 

 which gases are entangled to a sufficient degree to give 

 the spectroscopic test, but not sufficiently to alter materially 

 the average density. 



In conclusion, 1 should like to urge a word of caution 



