Features of the Earth's Surface. 355 
oping this structure, is always associated with plication; and 
both are associated with mountain chains 
A mashing together horizontally and an extension vertically, 
or an up-swelling of the mass, is therefore proved in slaty cleay- 
age, and thus also in mountain chains where slaty cleavage 
occurs. It only remains to show that the amount of mashin 
in one direction and extension in the other, absolutely pived 
in these cases, is fu/ly adequate to account for the upheaval of the 
greatest mountain chains. 
By the observations of Sorby and Haughton, taking an ideal 
cube of the original unsqueezed mass, the ratio of the greatest 
diameter (in the plane of cleavage), to the least diameter (per- 
pendicular to cleavage), becomes, after squeezing, sometimes 
21, sometimes 4:1, 6:1, 9:1, and even sometimes 1! : 1. 
According to Sorby, the average is 5 or 6: 1. Now it is evi- 
dent that of the three rectangular diameters of such a cube, 
one vertical and two horizontal, one of them, the horizontal in 
the direction of pressure, would be shortened, another, the ver- 
teal, would be elongated, while the third, the horizontal at right 
angles to pressure, would be unchanged, because in the rock- 
mass yielding could not take place in that direction. It follows 
then that the change of the original diameters in either diree- 
tion, by compression or elongation, would be the sguare roots of 
the ratios mentioned above. Thus if a cube of 3 inches diam- 
eter be crushed together horizontally, and allowed to exten 
only vertically, until its previously equal diameters become as 
‘1, it is evident that the vertical diameter has been increased 
and the horizontal diameter diminished 8 times. Taking 6:1 
ual: we may assert that a cleaved rocks the whole mass jas 
swelled up 24 (2°45) times ats original thickness. Suppose then a 
br ? 
10,000 feet thickness would be swelled to 25,000 feet, making an 
actual elevation of the surface of 15,000 feet. Now we actually 
~eed strata not only 10,000 but 20,000, and even 40,000 feet 
hick, 
I think, therefore, I am justified in asserting that the phe- 
rate 2? 
[To be concluded. ] 
ad 
