and Volcanic Substances, 241 
crosses the river at Matson’s ford, about thirteen miles 
upward from Philadelphia. It cuts through all the strata in 
its road, to an unknown depth. I have not traced its termi- 
nation either way. It consists of a confused heap of figu- 
rate trap, many of the prisms clinkstones ; tetrahedral and 
pentagonal. ‘The large pentagonal prism which I caused 
to be brought to the Academy of Sciences in Race Street, 
from the Gulph mills, and which is now there, is a trap 
rock ; internally bearing no mark of igneous operation. It 
is more like a primitive than a fletz trap. It is found cut- 
ting through with its companions the limestone stratum of, 
the river Scuylkill about three miles above the Soapstone 
quarry. ‘This dyke is different from the rocks it adjoins, 
in-all its characters; it is a confused heap of unconformable 
basaltic prisms. The stone in question, is a pentagonal 
prism.~ It has been (from its internal appearance) consid- 
ered as a primitive trap. Who ever saw a Pentagonal primi- 
tive trap? Moreover, the rule of morals, is ‘the rule of 
Geology, nosciter a socio. 
‘Lhave no other information of any fleetz trap until we 
come to the basalt wall near the Yadkin in North-Carolina. 
I have specimens of this ; but I never have been at the spot. 
It is undoubtedly a basalt dyke. 
About a mile from Columbia, (South-Carolina) near 
Rocky branch, a few yards from Dr. Fisher’s mill dam in 
the high road, Mr. Vanuxem found a thin vein of trap, (a_ 
wacke as I think) cutting through the old granite. The 
depth unknown. The vein is about two inches over, 
While the fletz trap formation is referred to aqueous ori- 
gin, we shall never understand our country: but I appre- 
hend, that opinion has at present few supporters among well — 
informed Geologists in Europe. In this country Werner? oe 
theory prevails, but its downfal is not far distant. _ 
Indeed, the igneous origin of our Granite formation in its 
present form and appearance, has been made so probable . 
by the investigations of Hutton, Playfair, Sir James Hall, — 
and Dr. M’Culloch, that we shall in my opinion be driven 
to adopt it, notwithstanding the Me EInCICeS that as yet stand 
in ‘the way. iT C. : 
“Hip pinidial-De. T. D. Porter fils Wee so good as to : 
furnish me with the following additional information. — 
