118 Dr. C. Ricketts—Changes in the Earth's Crust. 
what would be the effects of contraction of the globe in cooling, 
upon the supposition of the temperature of solidification being 
respectively 7000° Fahr. and 4000° Fahr. The result arrived at is, 
that in the former case the contraction of the radius would be six 
miles, and in the latter two miles only; that the miean heights of 
the surface-elevation formed by compression would amount in the 
one to 19 feet and in the other to only two feet;! that is, as I 
understand him, the mountains caused by this supposed contraction 
of the earth in cooling might, in one case, be so high as a moderate 
sized cottage, in the other, as that of a dog-kennel. This being so, 
well may Mr. Fisher exclaim, ‘‘ Nascuntwr montes, genuit quos 
ridiculus mus!;’? which may be translated, “The mountains are 
born, an insignificant mouse is their mother!” This calculation 
corroborates what has been previously alluded to as to the com- 
paratively small effect subsidence has in causing lateral pressure or 
a tendency to cause contortions. ‘Too much, far too much, has been 
accredited to the effects these movements could produce in causing 
lateral pressure. Certainly in many instances where there has 
occurred great disturbance of the strata, by their becoming contorted 
and folded and dipping various ways, depression to a great extent 
has also taken place; whereas in others, where it can be proved 
that there has been at least as great an amount of subsidence, the 
strata continue as level or nearly so as when first deposited. The 
difference between the conditions in the different localities is so 
great, that the contortions cannot be referred to vertical movements 
common to each. 
There are other flexures dependent on minor local causes not 
necessary to be considered at the present time. 
An important step towards determining the causes of foldings in 
strata must be to ascertain, so far as is possible, at what period they 
were produced. Where they exist to the greatest extent, especially 
in deposits formed of fine mud, cleavage has also been frequently 
developed, and the particles have so changed their relative position 
that the embedded fragments of rock lie with their longer diameter 
obliquely to the stratification, and the flatter sides parallel to the 
direction of the cleavage; included fossils are distorted, the lower 
portions being often pressed into their substance, whilst the upper 
have become elongated ; indicating that the expansion has been from 
below upwards. Both contortion and cleavage arise from lateral 
compression ; it is therefore assumed that the same power that has 
caused the one has at the same time also caused the other. Such 
changes must have taken place before the original pasty condition of 
the strata became so consolidated as to prevent, on the application of 
pressure, movement of the particles of which the mass consists 
amongst themselves. This might be at any period prior to these 
clayey rocks becoming solidified by their being raised above the 
sea level, and the consequent drainage of their contained water, or 
from other causes. Great power has been exerted in the production 
of these flexures ; but there is no indication of violence; their state 
1 Phil. Mag. Jan. 1888; see also for Nov. 1887. 
