238 Proceedings of the Royal Physical Society. 
I, On the Natural Agencies at present in operation, to which the 
Phenomena of the Glacial Epoch may he ascribed. By the Rev. 
James Brodie, Monimail, Fife. 
Of all the discoveries which geologists have made, there 
are none that have excited greater interest, or given rise to 
more varied discussion, than those which relate to the glacial 
epoch. 
Confining our view to the British Islands, we find that, 
after the lapse of many ages, during which the temperature 
seems to have heen as warm, or even warmer, than that 
which now prevails, the country had been subjected for a 
lengthened period to all the rigours of a polar climate. 
This severity of climate had again been gradually amelio- 
rated, till at last it gave place to the equable warmth which 
we now enjoy. 
We need not, therefore, wonder that a lively interest has 
been excited in the various endeavours that have been 
made to discover the causes to which these phenomena are 
to be attributed. 
In the following observations, it is our object to show 
that the changes to which we have alluded may all be ex- 
plained by a reference to the varying effect of the natural 
agencies by which the solar heat, communicated to the in- 
tertropical regions, is afterwards distributed over the earth ; 
and we hope, by a little careful consideration, to establish 
the accuracy of our views. 
These agencies are three in numbers — I. The air which 
covers the land ; 11. The air that covers the sea ; and III. The 
surface water of tbe ocean. 
I. The Jlrst of the natural agencies by which the equato- 
rial heat is distributed over the globe, is that of the air which 
covers the land within the torrid zone. 
A part of the heat communicated to the intertropical 
lands passes by radiation into space. Another part is com- 
municated by contact to the air which lies above them. 
This latter part we know to be very considerable, though it 
is difficult to determine the proportion it bears to - that 
which is given ofi" by radiation. The air, thus warmed and 
