Mountain Building.—Reade. 241 
of 129.368 miles over every great circle of the sphere to dispose 
of in folds. 
Thus we see plainly that with the same loss of energy by the 
nucleus, very different effects are produced; the interception of 
the heat otherwise radiated into space, would provide lateral pres- 
sure by expansion compared to lateral pressure by secular cool- 
ing in the proportion of 129.368 to 1.96, or in round figures 
66 times as much. Itis worth noting that any effect in corrugat- 
ing the 20 miles shell produced by contraction in the first example 
would add to and intensify the effect in the second example. 
These two comparisons are given merely as extreme illustra- 
tions to enable others to grasp the essential difference between 
expansion and secular contraction as mountain building agents— 
neither case is reproduced in nature, but both partially so. In 
place of the absolute non-conductor assumed to envelope the 
globe in the last example, put sedimentary deposits over a portion 
of it. Under these portions a re-distribution of heat occurs in 
precisely the same manner, though in less degree than in our ex- 
ample, for the sediments do not stop all the heat—only a portion 
thereof. The globe goes on losing heat as before, but much less 
under the sedimentary areas than where denudation ‘is taking 
place, or where the condition of the crust is completely stationary, 
like in the non-sedimentary depths of the great oceans. It is to 
the relative distribution of heat in the earth and its crust that we 
must look for our mountain building agents and for the requisite 
stresses and strains. Some physicists, by a confusion of ideas, 
have supposed, that because there is no actual increase of heat 
under a sedimentary area simply through the raising of the iso- 
geotherms, no mountain building can in this way take place. If 
the idea had been properly thought out the fallacy would readily 
have been detected. 
I have dealt with this fundamental idea of the expansion of 
the crust through the interception of heat that would otherwise 
be wasted into space because it underlies my theory of mountain 
formation. I trust my readers will not therefore take this part 
for the whole of the theory for the rising of the isogeotherms is 
the ‘nitiatory precedent condition only. 
I have described fully in my Origin of Mountain Ranges and 
in the outline of my ‘‘Theory of the Origin of Mountain Ranges 
by cumulative recurrent expansion” published in this magazine 
