Chemistry and Physics. 81 



7. JSfote on the computed drop of pressure in adiabatic expan- 

 sion ; by C. Baeus. — I have hitherto expressed my results for the 

 distribution of colloidal and other nuclei in a gas in terms of the 

 observed fall of pressure 8/> in the fog chamber. If under iso- 

 thermal conditions p is the pressure of the fog chamber, p' the 

 pressure of the vacuum chamber and^> 3 the common pressure after 

 exhaustion of the former, 8p=p-/j z . Recently I computed the 

 actual fall Ap=p-p li , where p 2 is the true isothermal pressure in the 

 fog chamber isolated from the vacuum chamber immediately after 

 exhaustion. The results are Sp — Ap=-225 Sp, nearly. 



Naturally I expected some appreciable correction in the final 

 reduction, but I did not anticipate so large a difference. The 

 result, however, is very interesting, for on applying it I find that 

 the distribution curves obtained in the use of very large fog 

 chambers now practically coincides with the curve which I 

 deduced from the data obtained by Wilson with his small and 

 unique apparatus. It appears furthermore that the successive 

 improvements which I have added to my fog chamber have for 

 some time reached a limit, and that its true efficiency is greatly 

 in excess of my estimate. 



8. Meteor ologische Optik • von J. M. Peentee. Mit zahl- 

 reichen Textfiguren. Ill Abschnitt: Seite 213-558. Wien und 

 Liepzig, .1906 (Wilhelm Braurnuller). — The opening section of 

 this important work was noticed in this Journal several years 

 since (see vol. xiii, p. 472), and now the third part is issued. It 

 discusses a very interesting series of phenomena, namely, those 

 due to the presence of minute foreign particles in the upper 

 atmosphere. Many different forms of halos and of coronas are 

 described and figured as well as discussed from a theoretical 

 standpoint ; in relation to these phenomena the varied forms of 

 snow and ice crystals are described in detail. The subject of 

 rainbows is very fully treated and illustrated. Altogether the 

 work is a very important contribution to our knowledge of a 

 peculiarly interesting but difficult subject. 



9. Leitfaden der Wetterkunde gemeinverstandlich bearbeitet / 

 von Dr. R. Boexsteix. Zweite umgearbeitete und vermehrte 

 Auflage. Pp. 230, with 22 tables. Braunschweig, 1906 (Fried- 

 rich Vieweg & Sohn). — After an interval of five years, the 

 author has brought out a second edition of his elementary work 

 on Meteorology. This is an indication of the success that the 

 book has had in meeting the needs of those for whom it was 

 expressly designed. The author states, as the fundamental prin- 

 ciple present in his mind, that any person may, if properly 

 instructed, become his own weather prophet, and with this before 

 him he has endeavored to treat the whole subject in such a man- 

 ner as to make it as intelligible as possible. This he has accom- 

 plished with marked success, but it still remains true that the 

 subject is one not without difficulty, and requiring much study 

 for even superficial mastery. Some of the new points introduced 

 into this edition concern the relation of the temperature of the 



Am. Jour. Scl— Fourth Series, Vol. XXII, No. 127.— July, 1906. 

 6 



