SHORT MEMOIRS ON METEOROLOGICAL SUBJECTS. 421 



to substitute for the density p in equation (2), which determines the 

 diminution of pressure with altitude, the specific gravity of moist air, or 



where p is expressed in kilograms per square meter. By this step, the 

 only change in the preceding equation is that dh everywhere receives 



the additional factor f 1 — 0.377- V Therefore in this case the dimi- 

 nution of temperature is that given by equation (I) multiplied by the 

 same factor, or, 



(ll)=S(^-«--|)- 



The introduction of the specific gravity p' of moist air instead of dry 

 in this case is analogous with the consideration of the moisture of the 

 air in barometric hyi)sometry, and means the ascent of moist air in the 

 midst of air equally moist, providing that under these circumstances an 

 ascent on a large scale actually occurs. 



In the preceding example ( „ H r-r-r. mm ) ? we find by formula (II) 



(I) =-0.00332, 

 or scarcely an appreciably different result. 



RAINFALL AND BAROMETKIC MINIMA. 

 By Prof. Dr. Theo. Reye. 



[Translated by Cleveland Abbe from the Zeitschrift d. Oest. Gesell. Meteorologie, 1375, x, p. 65-70.] 



From one of the recent memoirs of Dr. Hann I perceive, to my delight, 

 that in the most important points our views as to the cause of whirlwinds 

 already agree. [Hann's memoir was written in December, 1874, before 

 the publication of his review of Ferrel's theories.] We both recognize 

 the latent heat of the condensed vapor as the moving force in whirl- 

 winds; this gives to the air a stronger or weaker ascensive force, and 

 thereby causes a continuous inflow of air toward the rain-cloud. In 

 general, I agree with what Hann says: "The atmospheric pressure sinks 

 first when an extended whirl has formed in whose center the air proba- 

 bly is rising with increased vehemence." For I also am persuaded^ 



[Note by the Transi^vtor. — A.s there is frequently much coufuaion of ideas as to 

 tlie part played by aqueous vapor in storras, the translator hopes to contribute some- 

 what toward clearer views by adding to the present collection this paper of Reye's with 

 Hann's foot-notes.] 



' See my " Wirbelsturme," page 138. 



