240 Proceedings of the Royal Physical Society. 
whether that vapour occupies a chamber by itself in the 
form of steam, or is diffused through the air. It is equally 
well known, that heated air, whether it be moist or dry, pro- 
duces warmth ; and it is therefore evident to any one who 
reflects on the subject, that the warm vapour raised from 
the equatorial oceans, and carried to the poles, must contri- 
bute, in a greater or less degree, to elevate the temperature 
of the Arctic regions. 
In a lecture delivered at the Eoyal Institution, and pub- 
lished in the "Keader" in February 1864, as " a contribution 
of great suggestiveness " Professor Frankland advocates a 
very different theory. He maintains that " the sole cause 
of the phenomena of the glacial epoch was a higher tempe- 
rature of the ocean than that which obtains at present." In 
supporting this view, he assumes that the effects of the 
glacial period were felt over the entire globe ; that it was 
preceded by a period of indefinite duration, in which gla- 
cial action was altogether awanting, or was at least com- 
paratively insignificant ; and that, in the course of the gra- 
dual cooling of the earth, the land had cooled more rapidly 
than the sea. He afterwards adduces some experiments, by 
which he endeavours to show that heat is more rapidly ra- 
diated from watery vapour than from dry air of equal tem- 
perature, and that the interposition of vapour diminishes the 
radiation from the surface of water much more than that 
from granite. He then proceeds to argue that the watery 
exhalations from a tepid ocean, condensed by the rapid radia- 
tion from the polar circles, produced the remarkable cold of 
the glacial epoch. 
In his address to the British Association at Bath, Sir C. 
Lyell speaks of warm moist air from the south producing 
cold in the north, as if that were an opinion that is generally 
entertained by geologists. In referring to the influence of 
the sirocco, or wind from the desert of Africa, in melting 
the snows of the Alps, he adduces arguments which show 
that that desert had in the post-tertiary period been covered 
with the deep. He then goes on, without any reasoning in 
support of his statement, to say — " What mighty effects may 
we not imagine the submergence of the Sahara to have pro- 
