134 



NATURE 



[March 31, 1910 



be otherwise compatible with their business require- 

 ments. As it. is, there appears to be no such induce- 

 ment in England for anyone to initiate, undertake, 

 and publish original work, whether on stability, 

 stream lines, propellers, motors, or strength of 

 materials. Indeed, there are very strong inducements 

 for having such work undone, unwritten, and un- 

 published.i 



The next two chapters deal, respectively, with the 

 dirigible balloon and the flying machine. In the 

 former we have an illustrated historic description, 

 tracing the gradual progress that has been made in 

 dirigibles since the first idea of one was suggested 

 by Franklin in 1784; while in the latter the evolution 

 of the power-driven machine from the mere glider is 

 briefly but sufficiently well discussed. '"The Future 

 of Aerial Navigation " is a subject on which anyone 

 with an imaginative mind can write something which 

 people will read with eagerness, and this being the 

 case, we think that Mr. Rotch has been wise in only 

 devoting twenty pages to it, in preserving the historic 

 order, and in giving numerous references to what has 

 been written. The book is, of course, much smaller 

 and less compendious than M- Turner's. 



(4) That such English f l^^ie as are able, in spite 

 of their national disabiiities, to undertake original 

 work find their efforts appreciated in Germany is 

 well shown by the publication, by the Teubner Press, 

 of a translation of part i. of Mr. Lanchester's book 

 within a comparatively short time of its appearance 

 in England. The English preface is dated October, 

 1907, the German preface, by Prof. C. Runge, August, 

 1909, none too long for the work of the translators 

 and printer. We cannot do better now than quote 

 from Prof. C. Runge 's German preface in the follow- 

 ing terms : — 



"The present book contains so many important 

 original ideas and investigations for the development 

 of free flight that German engineers and men of 

 science will be grateful to the publishers for having 

 provided a translation of it. 



The author has in some places altered the text, and 

 in others the text has been altered by the translators 

 in consultation with the author, so that the translation 

 may be regarded as a revised edition. A complete 

 retrospect of existing literature was, however, not 

 attempted; this would have altered the character of 

 the whole book and necessitated completely re-writing 

 it, which was not contemplated by the translator. 



For men of science the principal charm of the book 

 lies in the ideas on fluid resistance, and the expression 

 of these by exact mathematical formulae should be 

 the next problem of hydrodynamics." 



Does not the last sentence confirm what has been 

 stated above as to the need of prizes for which 

 mathematicians as well as physicists and engineers 

 are eligible? G. H. Bryan. 



E. H. Harper. 



B' 



PROF. K. J. ANGSTROM. 



[Y the death of Prof. Knut Johan Angstrom, phy- 

 sical science has lost a conscientious and capable 

 worker, in a field which requires long and continuous 

 experience before . success can be achieved. For this 

 reason his departure will be felt more severely than 

 that of many men, who perhaps have gained a greater 



1 Mr. Alexander has offered a prize of looo/. to the Aerial League for the 

 best and most trustworthy motor of 20 h.p. capable of running unattended 

 for twenty-four hours. While fully appreciating the importance and value 

 of such prizes, it should be pointed out that the worker who attempts to 

 penetrate more deeply into the thermodynatnics ox general theory of the 

 internal combustion engine, with the view of paving the way for future im- 

 provements, has no prospect of reward, whereas the successful competitor 

 for such a prize may have other prospects of a return for his exertions in 

 the form of patents. 



NO. 2109, VOL. 83] 



reputation, but have been fortunate enough to interest 

 others in the line of research they have been pur- 

 suing. . ■ 



Knut .Angstrom bore an honoured name. Those 

 who still remember the early days of spectrum 

 analysis know how much that science owed to the 

 pioneer work of his father, Anders Johan Angstrom, 

 whose map of the solar spectrum remained until Row- 

 land's time the standard to which all wave-lengths 

 were referred. 



The son was born on January 12, 1857, and re- 

 ceived his school and university education at Upsala, 

 where he spent almost his entire life. He was 

 appointed assistant in the physical laboratory of that 

 university in 1882, graduated as Doctor of Philosophy 

 in 1885, and became lecturer in physics in the same 

 year. In 1895 he was appointed to the chair of 

 physics, and at the time of his death occupied the 

 position of pro-rector of the university. 



So far back as 1889 we find Knut Angstrom investi- 

 gating absorption phenomena in the infra-red by 

 means of the spectro-bolometer, and during the follow- 

 ing two years he obtained valuable results on the 

 absorption spectrum of carbonic oxide, carbonic acid, 

 and marsh gas. He also discovered the similarity in 

 the characteristic absorption of the same substances 

 (ether, benzene, bisulphide of carbon) in their liquid 

 and gaseous states. 



We owe to him, further, a valuable investigation on 

 the infra-red absorption of aqueous vapour, carbonic 

 acid and ozone. All these gases are constituents of 

 our atmosphere, and the effect of the two latter on the 

 temperature of the earth may be considerable, not so 

 much because they absorb a certain portion of the 

 solar radiation, but chiefly on account of their much 

 greater comparative influence in preventing the heat 

 radiated from the earth from being dissipated into 

 space. An interesting and instructing controversy took 

 place in connection with the effect of carbonic acid. 

 Arrhenius in 1896 had given a very ingenious ex-g 

 planation of the Glacial period by assuming that thej 

 quantity of carbonic acid in the atmosphere had in-i 

 creased since that time. If it be assumed that thej 

 absorption is proportional to the total quantity pre-i 

 sent, it can indeed be shown that a small variation in; 

 quantity would exercise a very considerable effect on 

 the temperature; but, as pointed out by Knut 

 Angstrom, the proportionality between absorption and 

 quantity only holds when the quantities are sufficiently 

 small, and he showed that the quantity of carbonic! 

 acid in the atmosphere must be reduced to about! 

 20 per cent, of its present value before an appreciable- 

 effect in the total absorption can take place. 



In the course of the further discussion of the sub- 

 ject Angstrom carried out important observations on 

 the effect of pressure, and showed that by increasing the 

 pressure, but diminishing the thickness of the_ layer 

 so that the total quantity of absorbing material re- 

 mains constant, a marked increase of absorption is 

 noticed at the higher pressure. It follows that in 

 order to find by optical means the quantity of car- 

 bonic acid in our atmosphere, it is not sufficient tc 

 determine the amount of gas necessary in our atmo- 

 sphere, it is not sufficient to produce the same absorp- 

 tion as shown by the atmosphere, but account rnusl 

 be taken of the conditions of pressure. Observations 

 on the absorption of ozone also led to the interesting 

 result that there must be considerable quantities o: 

 that gas in the upper regions of the atmosphere. 



Knut Angstrom's name has become rnore particu- 

 larly associated with recent researches in the mea 

 surement of solar radiation. He constructed ar 

 instrument, the essential portions of which consis 



