18 Scientific Proceedings, Royal Dublin Society. 
point out various probabilities which would tend in the other 
direction. According to one mode suggested as that in which the 
materials of the earth finally fell together, there would be two 
great reaches of the earth-nebula collapsing obliquely into each 
other, giving rise to tumultuous eddyings in the newly collected 
and defined mass, which would mingle together to a great extent, 
different parts thereof with their different temperatures. Another 
circumstance which would promote such mingling is the difference 
of specific gravity of the materials after condensation. If this 
were so, as is exceedingly probable, the enormous condensation in 
the inner parts of the newly-defined globular mass would liberate 
a vast amount of heat to raise the temperature of those parts ; 
and, as is evident, any heightening of temperature produced in 
this way would be unaffected by the remains of the eddyings just 
referred to, and by any convection currents (properly so called) ; 
it could itself produce no such currents as is evident. It could 
only be lowered by what would be really conduction, though 
acting under peculiar circumstances. We should thus have, 
though not an additional store, yet a more inward disposition or 
grouping of high temperature, favourable for rendering slower the 
cooling of the exterior parts of the globe beyond what is contem- 
plated by our opponents, and available, therefore, for lengthening 
the period of geological time. 
-If we knew accurately the present law of the increase of 
temperature per unit of depth, and the actual conditions of 
conductivity within the earth, supposing both to be approximately 
uniform round the centre, then the application of Fourier’s 
theorems would enable those competent to use such instruments, 
to decide whether the internal temperature of the earth at the 
commencement of geological operations proper was approximately 
uniform, or whether it increased towards the more inward parts. 
But the depth to which man has penetrated beneath the surface 
is utterly insufficient to shew the true law of increase of 
temperature, even independently of the numerous disturbing 
conditions at every place of observation. Without such inter- 
ferences the rise of temperature would be sensibly uniform down 
to a much greater depth than that of less than half a mile; and 
that would be so in either case, that is whether the temperature 
begins to be nearly uniform at a comparatively small depth of not 
