xxviii Appendix. 
rock, could only be relieved by the whole stratum bulging upwards and 
forming an arch, or more properly a dome; and as we know the rate of 
expansion, we can calculate what the elevation would have to be on a sphere 
the size of the earth, for various temperatures and for different areas, in order 
to relieve the pressure. This is exhibited in the following table, which is part 
of a larger table that I have calculated.* In it the upper line is the thickness 
in feet of the deposit, while the second line is the temperature due to that 
thickness. The left-hand column is the diameter, or breadth, in miles of the 
heated area, while the other columns show the elevation in feet that would 
take place :— 
Thickness ak sie 500 feet 2,500 feet 10,000 feet 25,000 feet 
Temperature... ae 10° 50° 200° 500° 
Breadth, 100 miles... 1,140 feet 3,700 feet 8,700 feet 14,600 feet 
Sree o pape 7,220 ,, 24,200 ,, 49,300 ,, 
a EON = 5, Fi 1,570 ,, LW © 53 28,600 ,, 65,400: ,, 
we OO ee 1,900 ,, Ta <5, 30,700 ,, 74,400 ,, 
From this table it will be seen that formations no thicker nor more 
extensive than those that we know to have been deposited, are pee capable 
of being elevated far above the highest known mountains. 
It may have occurred to you that a bed of limestone would not be capable 
of supporting itself as an arch, and, therefore, that instead of being elevated 
it would break up into fragments ; this is very true, if the arch was entirely 
unsupported, but as soon as the expansion overcame the rigidity of the crust, 
and movement commenced, the underlying superheated rocks, being relieved 
from pressure, would rise up and still press upwards on the rising arch, so 
that the pressure expended in elevation would be that capable of overcoming 
the rigidity only of the crust, and not its weight. You may also have 
noticed that unless the rate of deposition was greater than the rate of the 
conduction of heat outwards, no deposit would rise above the surface of the 
sea, for as soon as deposition ceased the increase of temperature would cease — 
also ; and conversely, the greater the difference between the rates the greater 
would be the rise, for the longer would be the time before the deposit attained 
its normal temperature. 
The data to estimate these rates are not very exact, more especially the 
rate of PANES but the following is the “best information that I can 
collect :— 
Monsieur Joseph Fourier has calculated that the earth decreases in tem- 
Tha hki 
hat the earth is a sphere, with a radius 
3958 miles, and that rocks expand ‘000005 for 1° Fahr. 
