310 



SCIENCE 



[N. S. Vol. LIII. No. 1370 



will probably derive the result that the state- 

 ment is not as hastily worded as it was first 

 thought to be. 



E. Lester Jones 



SCIENTIFIC BOOKS 



Physics of the Air. By W. J. Humphreys, 

 C.E., Ph.D., Professor U. S. Weatlier 

 Bureau, Philadelphia. Published for the 

 Franklin Institute by J. B. Lippincott Co., 

 1920. 



Professor Humphreys states in his intro- 

 duction that " it is obvious that an orderly 

 assemblage of all those facts and theories that 

 together might be called the Physics of the 

 Air, would be exceedingly helpful to the stu- 

 dent of atmospherics." 



Of this there can be no doubt, and the 

 author has rendered a great service by thus 

 bringing together and making easily available 

 material that otherwise would have remained 

 scattered through technical magazines, official 

 publications like the Monthly Weather Review 

 and journals of organizations like the Royal 

 Meteorological Society. 



The volume had its inception in a series of 

 lectures delivered by Dr. Humphreys at the 

 San Diego Aviation School in 1914. These 

 lectures revised and printed from month to 

 month in the Journal of the Franklin Insti- 

 tute, 191Y, 1918, 1919 and 1920, are now con- 

 solidated in one volume. 



As late as 1917 our military authorities 

 failed to appreciate the importance of a 

 knowledge of aerography, that is, the struc- 

 ture of the atmosphere. In June of that year 

 a high officer of the Signal Corps, at that 

 time entrusted with aviation, wrote: 



It has frequently happened in the past that men 

 who might otherwise have made good pilots became 

 so alarmed in advance over the subject of "holes 

 in the air ' ' and so impressed with the terrible 

 dangers of aerial navigation, that they never suc- 

 ceeded in gainiog the necessary confidence to be- 

 come good pilots, etc. 



This was given as a valid reason for re- 

 fusing to utilize recent advances in meteorol- 

 ogy ! And agairi : 



So little time is available and so great the neces- 

 sity for extreme haste in preparing aviators for 

 service overseas that there is no opportunity to 

 give more than the elements of meteorology in one 

 or two lectures. 



These views are referred to here, simply to 

 show in some measure the amount of official 

 inertia which had to be overcome. After 

 many promising lives had been sacrificed, the 

 need of the fullest knowledge possible was 

 manifest; and before the war ended aerog- 

 raphy had come into its own in both army 

 and navy schools of instruction. 



Professor Humphreys divides his treatise 

 into four main parts; mechanics and thermo- 

 dynamics; atmospheric electricity and auroras; 

 atmospheric optics; and factors of climatic 

 control. The author had the great advantage 

 of access to the Weather Bureau Library, and 

 critical readings by his colleagues. Fui'ther- 

 more, the text appeared in type before final 

 publication. The work is unusually free from 

 typographical errors. 



There are a few slips, however. On page 

 49 the symbol for temperature of the iso- 

 thermal region T might with advantage have 

 been placed in front of the radical, or at 

 least in some way separated more than at 

 present. Again, it would be a gain if instead 

 of saying that the temperature of a black 

 radiator, in this case the earth, was 259° C. 

 absolute, the author had used the more com- 

 mon form 259° A., adding if he thought it 

 necessary, in degrees C. It is desirable in a 

 text-book to avoid confusion, by using con- 

 sistent notation. The reviewer holds that it 

 is not good form to speak of a given tempera- 

 ture as 259° C. absolute on one page and on 

 the next page give a diagram exi>ressing the 

 same value in degrees Centigrade, that is, 

 — 14° C. One may expect to meet a slip 

 from such loose practise and sure enough it 

 occurs. On pages 75 and 76 it is stated: 



The effective absolute temperature of the earth 

 as a fuU radiator is approximately 260° C. 



Eather a warm condition; but of course the 

 author means that the effective temperature 

 on a certain approximate absolute scale is 



