Meteorology. AO} 
cannot bé ascribed to the account of tain ; 
for the summer period contains wet months 
as well as dry ; and in the London averages, 
the month of April is in the low period, 
though the driest in the year. It cannot be 
ascribed to temperature ; for the month of 
November is warmer than March; yet this 
‘Jast is m the high period by all the tables, 
and the former in the low period. Nothing 
appears to me indicative of the periods, but 
the declination of the sun; it seems that 
when the sun is north of the Equator, the 
weight of the atmosphere increases in these 
parts, and again diminishes when south of 
the Equator. 
The means by which the effect is produ- 
ced, I conceive, are these: thesun’s action is 
constantly increasing the mass of aqueous 
vapour in the atmosphere, during the period 
from the vernal to the autumnal equinox. 
That is, the whole mass of vapour existing 
in the atmosphere is daily increasing, not- 
withstanding the quantity precipitated. This 
fact is verified by the constant rise of the 
vapour point till the month of September, 
after which it commonly declines pretty ra- 
pidly. Now it is obvious that the addition of 
steam or aqueous vapour to the atmosphere, 
must add to the weight of the atmosphere; 
