Geology. 285 
of area after area until a perfect map of the surface has been obtained ; 
and the patient underground working up of gangways and breasts, tun- 
nels and shafts, which reveal blunders no surface exhibitions could 
have corrected :—What is the best paleontological work in comparison 
with all this—for resulis ? What is even the patience, the skill and the 
in the table were all constructed with the very slightest references ‘ 
ble to paleontological evidence. The Free ort-Curlew limestone and the 
Ferriferous limestone are great lithological horizons, entirely established by 
sy. 
The opinion expressed by my friend Mr. Lesquereux “that coal No. 1, 
with its members B and C, and perhaps No. 2 subdivides, forming as man 
ers a 
feet of slate, The great Mauch Chunk Summit Mine Coal is, even to the 
uninstructed eye, a group of beds, spreading somewhat further asunder 
elsewhere. But that any one of the s 
should first so separate in parts as to obtain regularly lettered or num- 
red “members” and then these again split up until the one bed should 
be represented by a tall cross section containing eight separate beds of 
coal—I cannot easily believe it. 34s te 
_ In conclusion I wish to suggest to geologists who take a special interest 
in the carboniferous formation, that the term Mahoning sandstone bas be- 
come as unsafe a name for a horizon line, as is the term Conglomerate. 
uy surveys for the Pennsylvania Railroad Company some years ago, In 
ade me a 
important rocks in the Barren Measures by which that whole group, (and I 
must still consider it an interval separating most decidedly the upper and 
lower divisions of the true Coal Measures), can be d ussed intelligently. 
ne of these rocks is a conglomerate of weight and character, appearing 
over a considerable country, and forming as I believe, as general a hor- 
1zon ; Ss 
a 
the true place of which is from 
One to three hundred feet further down. But I shapes — to #4 
Philadelphia, Aug. 1, 1861. 
