Dee. 21, 1877.} 255 [Frazer. 
Remarks on Professor Prime's Paper. 
By PERstFoR FRAZER, JR. 
(Read before the American Philosophical Society, December 21, 1877.) 
The paper of Professor Prime is exceptionally interesting to me because 
similar, though (as I apprehend him) not identical and perhaps not céeval, 
deposits of limonite occur in many parts of the district which I have been 
studying for four years, and which includes Franklin, Adams, Cumber- 
land, York and Lancaster Counties. The two lines of limonite banks to 
which Professor Prime refers are also found there, and apparently in anal- 
ogous position, viz: at the upper and under surfaces of the calciferous 
formation (but not usually in the latter position when there is no represen- 
tation of the slates). Besides these two horizons of ore (if the term hori- 
zon may be applied to local deposits, in many cases principally produced 
long after the strata on the borders of which they lie) there are at least 
several others which cannot be referred either to the top or the bettom of 
the formation, but at various positions between the two. On the general 
maps accompanying my report of progress for 1874, there appear to be four 
or five such lines besides two principal ones nearly converging near Han- 
over, York County. 
This rough conformity of the limonite to the limits of the limestone rock 
indicates a connection between the two more close than can be attributed 
to accident. 
It has been often repeated before that the greatest exhibitions of iron 
ore of this character are almost invariably found directly in contact with 
the limestone, and one would naturally suppose that the cause was to be 
sought either in the action of one upon the other or in conditions which re- 
sulted in evolving both of them. It is true that the position of the clays in 
all these banks (including the larger ones just referred to), forbids the sup- 
position that the deposits have been entirely produced by infiltration from 
other points, for, as Dr. Hunt has long ago conclusively shown, there are 
strings and lenticular masses of iron hydrates, &c., which lie within, and, 
conformably to the edges of the kaolinized slates, repeating all the convo- 
lutions of the latter, and showing other unmistakable signs of contempo- 
raneous history. 
Nevertheless, the alteration of the ferriferous minerals which were the 
origin of these limonite nests has apparently gone forward more rapidly 
when there was an abundance of carbonate of lime present, than when this 
rock was represented by the argillaceous and schistose members of the 
series to which it gives its name. 
As to the amount of material necessary to produce all these beds, it 
might have been much more than furnished by the Pyrite alone, of which 
we know the former existence by the countless pits and casts which com- 
pletely permeate the strata ; as I endeavored to show several years ago. 
