400 
ELEMENTS OE GEOLOGY. 
Fig. 429. 
stumps of no less than 73 trees with their roots attached ap¬ 
peared, as shown, in the annexed plan (Fig. 429), some of 
them more than 
eight feet in cir¬ 
cumference. The 
trunks, broken off 
close to the root, 
were lying pros¬ 
trate in every di- 
rection, often 
crossing each oth¬ 
er. One of them 
measured 15, an¬ 
other 30 feet in 
length, and others 
less. They w^ere 
invariably flatten- 
Groiiiid-plan of a fossil forest, Parkfielcl Colliery, near Wol- thick 
verhampton, showing the position of 73 trees in a quarter neSS 01 Olie Oi* tWO 
of an acre. inches, and con¬ 
verted into coal. Their roots formed part of a stratum of 
coal ten inches thick, which rested on a layer of clay two 
inches thick, below^ which was a second forest resting on a 
two-foot seam of coal. Five feet below this, again, was a 
third forest with large stumps of Lepidodendra^ Calamites^ 
and other trees. 
Blending of Coal-seams.—Both in England and North 
America seams of coal are occasionally observed to be part¬ 
ed from each other by layers of clay and sand, and, after 
they have been persistent for miles, to come together and 
blend in one single bed, which is then found to he equal in 
the aggregate to the thickness of the several seams. I was 
shown by Mr. H. D. Rogers a remarkable example of this in 
Pennsylvania. In the Shark Mountain, near Pottsville, in 
that State, there are thirteen seams of anthracite coal, some 
of them more than six feet thick, separated by beds of white 
quartzose grit and a conglomerate of quartz pebbles, often 
of the size of a hen’s egg. Between Pottsville and the Le¬ 
high Summit Mine, seven of these seams of coal, at first 
widely separated, are, in the course of several miles, brought 
nearer and nearer together by the '^gradual thinning out of 
the intervening coarse-grained strata and their accompany¬ 
ing shales, until at length they successively unite and form 
one mass of coal between forty and fifty feet thick, very 
pure on the whole, though with a few thin partings of clay. 
This mass of coal I saw quarried in the open air at Mauch 
