LIMONITE AND LIMESTONES—GILPIN. 35 
sional undulations, until they pass beneath the later members of 
the same group, in the vicinity of Stellarton and New Glasgow. 
One is at once struck, when examining the sections of the 
Pictou Carboniferous, by the tremendous denudation they have 
been subjected to, which has dwarfed the Pictou Coal field to a 
tithe of its original dimensions, and in many places bared the 
Silurian rocks, which were once covered by thousands of feet of 
later formed strata. We find that the summits of anticlinals 
have been swept away, and that in places whole synclinal 
troughs have disappeared. 
The two following instances of this denudation are presented 
as examples of what has been going on all over the county. 
Thus, in the Pictou Coal field, we have in one section a breadth 
of outerop corresponding to a thickness of strata not less than 
3450 feet, which has disappeared. 
Similarly, in the Lower Carboniferous under discussion, we 
have at Bridgeville a thickness of 2500 feet, which has been 
swept away. These great masses of matter have gone to form 
the millstone grit, the Coal measures, the Upper Coal measures, 
and perchance have swelled the volume of that new continent 
which the sounding lead has discovered beneath the waves of the 
Atlantic. 
At first sight it may seem almost incredible that such. enor- 
mous masses could be swept away by the agencies we now see 
in action around us; but from the surveys of Prof. Lesley, in 
Huntington and Centre Counties, Pennsylvania, it appears that 
Lower Silurian measures, formerly towering to a height of 30 or 
40 thousand fect above the present sea level, are now but 2000 
feet above it, and that they have yielded to denuding forces 
thousands of cubic miles of material which compose the creta- 
ceous and tertiary deposits of New Jersey and Delaware. 
We have now reached:a point of importance, with regard to 
the origin of the Limonite ores, when we imagine that this great 
mass of Lower Carboniferous sediments, containing ferruginous 
shales and Limestones, formerly spread over a great part of the 
ground which now presents tg our gaze strata of Silurian.age. 
Everywhere in the Carboniferous, at a distance varying from 
