12 MR. G. V. VERNON ON THE IRREGULAR BAROMETRIC 



inches; and on an average of ii years, 117' 7 days are 

 rainy. The fall at Geneva is greatest in summer and 

 autumn,, hut at the Great St. Bernard it is greatest in 

 autumn and winter. The greatest monthly fall occurs in 

 October at Geneva, and in January upon the Great St. 

 Bernard, — the former being two months after the period 

 of minimum oscillation of the barometer, and the latter a 

 month later than the maximum period of oscillation. 



The conclusions which may be drawn from this investi- 

 gation are the following : — As we ascend in the atmo- 

 sphere, the amplitude of the irregular diurnal oscillations 

 of the barometer gradually diminishes, more especially in 

 the winter months, the summer months having an amount 

 of oscillation not differing much from that of less elevated 

 stations in nearly the same geographical position. Ex- 

 cessive rain-fall at stations of moderate elevation appears 

 to be accompanied by a larger amount of oscillation than 

 when the rain-fall is below the average : this law appears 

 to hold good in every month. 



At more elevated stations, the same law appears to 

 exist for the entire year ; but many of the months appear 

 to be subjected to some disturbing cause, and do not con- 

 form to this law. It remains to be seen whether a long 

 series of years would eliminate this disturbance, or whether 

 it may be owing to some other elements which, at the 

 higher station, produce effects dissimilar to those produced 

 at the lower station. Temperatures below the average of 

 the season greatly increase the amount of disturbance. 



Kamtz, in his ' Handbook of Meteorology,^ gives the 

 irregular oscillations for each month, and for various 

 places ; he, however, omits to state what particular years 

 were used, and how many years he deduced each mean 

 value from. The following small Table contains his values 

 for Geneva and the Great St. Bernard : — 



