496 



PROFESSOR FORBES ON THE DIMINUTION OF TEMPERATURE. 



The influence of humidity I believe to be very important in modifying the 

 results. The distribution of moisture as we rise in the atmosphere varies ex- 

 tremely at different seasons. In spring the hills are chiUed by continued con- 

 densations of moisture, whilst the plains are comparatively dry ; and in autumn 

 the reverse often occurs. I beheve that the actual fall of rain on low and high 

 grounds confirms this view, the autumnal rains being often heaviest in the plains, 

 whilst in spring and summer the excess is amongst the hills. 



The curve in Plate XX.,* representing the mean daily range for five years, is 

 deduced from careful observations made at Edinburgh by Mr Adie, with self- 

 registering instruments-! 



* The vertical lines in the plate correspond to the middle of each month. 



t The latter part of this paper has been remodelled since it was read — Dec. 1 839. 



