3S4 Clayfole on the Interior of the Earth. 
being found totally inadequate to explain the phenomena as 
they appear at the surface. 
As this opinion waned there rose in its place another directly 
opposed to it. Ushered in under the shadow of great names in 
the world of science it taught us to believe that the globe was 
solid from core to crust. We were told that all our geological 
theories must be reconstructed on the basis of a solid globe. 
The authority of Thomson, of Hopkins and of Pratt, secured 
for this new doctrine a respectful hearing and a wide acceptance. 
It was a not unnatural reaction from the opposite extreme which 
had preceded it. It afforded for a while great hope of a final 
solution of the problem. But it has been ti'ied and found want- 
ing. Like its predecessor it has failed to explain the phen- 
omena. 
No other extreme being possible most of the later theories 
have been modifications or combinations of these two, with 
qualifying additions intended to explain special difficulties or 
fill inconvenient gaps. 
Without going into detail, which would be foreign to the 
purpose of this paper, it will suffice to say that most of the more 
recent theories involve the presence of a layer of imperfectly 
liquid matter between a solid nucleus and a solid crust. This 
layer is by some supposed to be continuous and by others to be 
divided into lakelets of greater or less extent. Both these views 
are held by geologists well qualified to form and well entitled 
to express an opinion. Each is intended to account for certain 
phenomena which have proved difficulties in the way of the 
adoption of the other. 
This viscous layer is not only a result of a compromise be- 
tween two opposing theories but is also a result of a compro- 
mise between the two great solidfying forces of pressure and 
cold. It appears to be a necessary result of the evolution of the 
terrestrial sphere. Looking back to the time when the earth 
existed as a molten globe it is evident that the constant radiation 
of heat from its surface into space must have steadily though 
slowly, cooled the outer layer. This as fast as it grew cool 
and perhaps solid sank into the heated mass in consequence of 
its greater density. There it was remelted but at the expense of 
the internal store of heat. This process continued until the 
