Contrary to all preconceived ideas, experience proves that the brighter
the sky that shines above the camera the more tardy the action within
it. Italy and Malta do their work slower than Paris. Under the
brilliant light of a Mexican sun, half an hour is required to produce
effects which in England would occupy but a minute. In the burning
atmosphere of India, though photographical the year round, the process
is comparatively slow and difficult to manage; while in the clear,
beautiful, and moreover cool, light of the higher Alps of Europe, it
has been proved that the production of a picture requires many more
minutes, even with the most sensitive preparations, than in the murky
atmosphere of London. Upon the whole, the temperate skies of this
country may be pronounced favourable to photographic action; a fact
for which the prevailing characteristic of our climate may partially
account, humidity being an indispensable condition for the working
state both of paper and chemicals.--_Quarterly Review_, No. 202.