1883.] Recent Literature. 525 
vey of Penna. series. The first view that Mr. Rand expresses is 
a“ regret that the publication was not delayed until the adjacent 
parts of Delaware county were examined.” This had been done 
before the issue of Cs, and we understand that the chief geologist 
is almost ready to issue C;, which is to be devoted to Delaware 
county. 
The criticisms as to location of the areas of serpentine, which 
Mr. Rand makes, are doubtless just, within the qualification pre- 
viously made, as a large portion of these outcrops are but a short 
distance from his residence, and it is not likely that he can be de- 
ceived about a subject to which he has given so much attention. 
At the same time it must not be forgotten that what one observer 
would regard as evidence of a Serpentine outcrop, another would 
not. In this respect Serpentine outcrops occupy almost a unique 
position. It would seem to be only thus that such wide diver- 
gences as are here noted are explicable. Professor Lesley’s 
remark that “ the Serpentine belt of Bryn Mawr instead of pass- 
ing in a straight line south-west * * * swings around south- 
ward in a curve towards Chester,” &c., which evoked criticism 
three months ago from another source)! is here also demurred to, 
as if it were a remark of Mr. Hall, whereas Mr. Hall nowhere 
appears to entertain such a view. The mistake which Mr. Rand 
ears to have made as to the true authorship of the remark, 
while quite natural, is a good illustration of one of the evils which 
result from too much editing and commenting by the superior 
officer of a geological survey. 
The last two pages contain the real gist of the paper, and merit, 
together with the map accompanying, a more detailed study. 
$ Mr. Rand regards what he terms the “ Eurite,” south of the 
air valley, “almost undoubtedly Potsdam sandstone,” but 
€ difficulty in the case is to account for outcrops of Potsdam 
sandstone of such widely different character existing so near 
yS ae ; 
Ayai, from Pomeroy to the Schuylkill, and beyond there, is 
°mposed of a white hard sandstone, making precipitous cliffs, 
: s 
far es and probably of a fault, and this line of trap continues 
nid the spot of which we are now talking; yet Mr, Rand 
Valley. ve us believe that the South-Valley-hill and the Noni 
cs ae long to the same formation. It is true that part o 
a. 8 culty is disposed of in assuming that to the Potsdam 
ferent patat of Rogers belong under and overlying schists dif- 
from the sandstone proper; but this will remove only part 
ee 
me Horizon of the South-Valley-Hill Rocks, Frazer, Proc. A, P. S., Dec. 15, 
