305 
of Edinburgh, Session 1876-77. 
occur at Geneva, arising from its position with reference to Lake 
Geneva, and from the qualities of these winds as determined by 
the relative size of the lake. 
The hourly variations in the direction of the wind show that the 
land and lake breezes are strongly marked — the breeze from the 
lake prevailing during those hours of the day when the tempera- 
ture of the land is in excess of that of the lake, the land breeze 
during the rest of the day. In December, when the land is at no 
hour of the day warmer than the lake, no breeze from the lake sets 
in over Geneva, and also in January the breeze from the lake is 
but slight and of short continuance. These breezes leave their 
impress in a most distinct manner on the curves of the hourly 
variation of the vapour tension. During the winter months, when 
no breeze from the lake, or but a feeble one, sets in, the vapour 
curves show only one daily minimum, occurring about sunrise, and 
one maximum, about 2 p.m., whereas during the other months, from 
March to October, the vapour curves exhibit two daily minima, one 
about or shortly before sunrise, and the other from 2 to 4 p.m., and 
two maxima, one from 8 to 11 a.m., and the other from 6 to 10 p.m., 
according to season. Equally marked are the curves of the hourly 
variations of cloud, the maximum during the winter months occur- 
ring about sunrise, and the minimum about sunset. On the other 
hand, during the warm months there are two maxima and minima 
— the first maximum occurring about or shortly after sunrise, and 
the second, but by far the larger maximum, about 6 p.m., and the 
two minima shortly after midnight, and from 9 to 11 a.m. 
The explanation of these instructive phenomena is doubtless to 
be found in the size of Lake Geneva, which is large enough to 
occasion a strong breeze during the day from the lake all round its 
shores. On the setting in of the breeze, the air conveyed by it, 
having been resting sometime previously on the surface of the lake, 
is necessarily moist, and while this state of matters continues the 
first daily maximum of vapour tension is reached. As the breeze 
continues, the current is necessarily drawn from higher strata of 
the atmosphere, and being thus but a brief interval in contact with 
the lake the air becomes constantly drier till the second daily mini- 
mum occurs, from 2 to 4 p.m. The breeze then gradually diminishes 
in force, and the air consequently becomes moister, till the maxi- 
