Geology and Mineralogy. 389 
formity of shape than had hitherto been supposed, as irregularly 
in fact as a carpet crumpled together by a push from one side 
ments for working a mine are plainly set forth; and money need 
I 
h addition to the extremely valuable and elaborate under- 
stound map of the surface of the Mammoth Bed, on a scale of 
800 feet to an inch, there are three sheets of twelve cross sections 
ally seen throughout or not; and a small skeleton map of the 
basin (3200 feet to the inch) to show the places of the sections. All 
these sections across the basin are on the same scale vertically as 
horizontally, and hence show the geological structure undistorted, 
Which is of course their true object. 
But on such cross sections of the structure the scale has to be too 
showing the true relative order, thickness and distance apart, 0 
all the important beds, whether of coal or of rock of different 
inds. On the same sheets are added five similar columnar sec- 
Hons, on a smaller scale (100 feet to the inch), of the Pottsville 
Conglomerate underlying the set of workable coal beds; anc be- 
Sides, a diagram, on a scale but one-third as large, of twelve 
columnar sections of the Pennsylvania Geological Formation, No. 
AIT, and up to the Mammoth Coal Bed; also a convenient repeti- 
Hon of the little skeleton map to show the places of the sections. 
uch sections of course, if compared with what is found in a shaft 
°r boring or in natural exposures, show how vain it would be to 
: coal at many a point where perhaps a small 
_ Streak of coal or black slate, or dark colored earth, may (as so 
often has h ppened with consequent immense loss of money) 
ea for a time, illusory hopes of diseovering a valuable coa 
lhe 
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