SHORT MEMOIRS ON METEOROLOGICAL SUBJECTS. 393 



will certainly in the future be felt as a disastrous neglectj'wbich in most cases can never 

 be made np. 



No. 5. This limitation was selected with reference to the diurnal turning-points of 

 barometric pressure; it also agrees well with the time during which the ascending cur- 

 rent of air is active. Cases of rain continuing more than three hours are so rare that 

 no averages are to be taken. 



No. 6. Properly this is the hour between which and the following that rainfall is 

 measured which has been entered under the first hour of rain. 



No. 7. Even J. Miiller, in his Cosmical Physics, has taken no notice of the necessary 

 cooling, and, moreover, has introduced into the computation the latent heat of a kilo- 

 gram instead of a gram of vapor (3d ed., page 678). 



No. 8. Wettstein has used somewhat different numbers for the maximum weight of 

 aqueous vapor in a cubic meter of saturated air. I know not whence they come ; they 

 are neither the ordinary numbers nor those given in Zeuner's Grundziige, table I, page 

 8. For the sake of uniformity with subsequent computations, I have throughout sub- 

 stituted the values given by the ordinary formula 



q = 0.623 -7—, — r • ;=7vi • 

 •^ 1 + at iW 



No. 9. Espy, also, in his Philosophy of Storms, guided by similar computations, 

 has, like Wettstein, rejected Hutton's theory of rain. 



c. 



lu reply to some remarks by Captain Hoffmeyer, Dr. Hann publishes 

 the following additional note : 



ATi\rOSPHERlC PEESSURE AIS^D EAINFALL. 



[Translated by Cleveland Abbe from the Journal of the Austrian Meteorological Association, x, p. 11, 



1875, January 1.] 



Captain Hoffmeyer criticises a partially unjustifiable generalization 

 from the result of observations, which in strictness only holds good for 

 localities on the north side of the Alps. To this note, Captain Hoff- 

 meyer adds a series of remarks and conclusions that are the more valua- 

 ble in the theory of storms, inasmuch as they rest upon the unprejudiced 

 daily study of facts, which at present are scarcely found collected to- 

 gether and collated at any other place in such abundance as at the 

 Meteorological Institute in Copenhagen. 



I can almost perfectly accede to the views of Captain Hoffmeyer, and 

 this will be evident to every reader of my essay published in vol. ix of 

 this journal ; but my objection to the theory of Espy and Eeye, that the 

 ascending current of air is the only or the chief cause of the barometric 

 minimum at the storm center, seems to me not thereby disturbed. Ac- 

 cording to my way of thinking, the position of the question is at present 

 as follows: Observations show that the heaviest rains in the tropics 

 have so slight an influence on the atmospheric pressure that they are 

 unable in the least to disturb the regular diurnal variation of iiressure. 

 Xow, it seems to me illogical to assume that the same cause can under 

 quite analogous conditions be accompanied by opposite consequences. 



