238 RAIN ON THE ALPS. 



arithmetical mean of the quantities fountl in 

 each; but it is only a quantity proportional to 

 the geometrical mean that can be supported in 

 the state of vapour, by the mean temperature : 

 and as the geometrical mean is always less than 

 the arithmetical mean, the excess must needs be 

 precipitated. 



This accounts for more rain falling in moup- 

 tainous countries than on plains; — but the 

 question at present is, how does it happen that 

 more falls on great elevations amongst the Alps 

 than on the plains below. 



To this it may be answered, that the Pass on 

 St. Bernard is not the highest point of land in 

 the vicinity, but rather the lowest, at least of the 

 ridge over which the road passes. Hence the 

 fall of rain, even in that elevated station is still 

 under the influence of superior currents of air 

 over the higher summits, and may still exceed 

 in quantity what falls on the distant plains. 

 The quantity of rain which falls at the foot of 

 the mountain, either on the Swiss or Italian 

 side, I have little doubt, will be found to be 

 still greater than that which falls at the Hospital 

 as related above. It would be very desirable 

 however to ascertain the fact; and more espe- 



