1877-] * Probable Origin and Age of the Sun. 311 
tuffs were so completely removed from the south side of the 
fault previous to the deposition of the Carboniferous Lime- 
stone series and the Coal-measures that not a fragment of 
them is anywhere to be seen between these latter formations 
and the old Silurian floor.” This enormous thickness of 
nearly 3 miles of Old Red Sandstone must have been de- 
nuded away during the period which intervened between the 
deposition of the Lower Old Red Sandstone and the accumu- 
lation of the Carboniferous Limestone. 
Near Tipperary, in the south of Ireland, there is a dislo- 
cation of the strata of not less than 4000 feet,* which brings 
down the Coal-measures against the Silurian rocks. Here 
1000 feet of Old Red Sandstone, 3000 feet of Carboniferous 
Limestone, and 800 feet of Coal-measures have been removed 
by denudation off the Silurian rocks. Not only has this 
immense thickness of beds been carried away, but the Silurian 
itself on which they rested has been eaten down in some 
places into deep valleys several hundreds of feet below the 
surface on which the Old Red Sandstone rested. 
Faults to a similar extent abound on the Continent and in 
America, but they have not been so minutely examined as 
in this country. In the Valley of Thessolon, to the 
north of Lake Huron, there is a dislocation of the strata to 
the extent of 9000 feet.t 
In front of the Chilowee Mountains there is a vertical 
displacement of the strata of more than 10,000 feet.J 
Prof. H. D. Rogers found in the Appalachian coal-fields 
faults ranging from 5000 feet to more than 10,000 feet of 
displacement. 
There are other modes than the foregoing by means of 
which geologists are enabled to measure the thickness of 
strata which may have been removed in places off the pre- 
sent surface of the country, into the details of which I need 
not here enter. But I may give a few examples of the 
enormous extent to which the country, in some places, has 
been found to have been lowered by denudation. 
Prof. Geikie has shown || that the Pentlands must at one 
time have been covered with upwards of a mile in thickness 
of Carboniferous rocks which have all been removed by de- 
nudation. 
In the Bristol coal-fields, between the River Avon and the 
Mendips, Prof. Ramsay has shown§ that about 9000 feet of 
* Jukes’s and Geikie’s Manual of Geology, p. 441. 
f Geology of Canada, 1863, p. 61. 
t Safford’s Geology of Tennessee, p. 309. 
|| Mem. to Sheet 32, Geol. Survey of Scotland. 
§ “ Denudation of South Wales.” Memoirs of Geol. Survey, vol. L 
