1883.] Review of Report C, 2d Geol. Surv. of Penna. 1023 
the larger streams” (p. 60). So much for the text of Mr. Hall. 
There is not the slightest suggestion of a theory of any kind. It 
is in character like the record of facts contained in the “ Town- 
ship Geology,” and it is nothing else; nor is there one fact added 
which is new, unless it be the “laurentian syenite” which in divis- 
ion “A” is called “syenitic gneiss,” “syenitic rock” and “syenitic 
or granitoid rock.” These exposures, though not indicated on 
Dr. Frazer’s map, are described in the text of his Mémoire on 
this region printed in France and sent to the Geological Survey 
of Penna., in June, 1882, as well as in the township geology of 
the present volume. The reduced map of Mr. Hall has even 
less claim to originality than the “Notes,” because the colored 
map of Chester county, in which exists the “culpably copied” 
error of Northeast creek, was printed in 1880-81. This map 
contains all the data which are found on Mr. Hall’s map (except 
the areas of “ syenite”) and a great deal more beside. It is with 
the greatest respect for Mr. Hall, for his ability and for his work 
that the writer here says that the purpose that can be served by 
printing that part of the map opposite p. 6, which represents 
Chester county (a small part on the left), is very obscure. Of this 
map Professor Lesley says, “nothing is laid down which does not 
appear above the soil” (p. 33). However this may be (and it is 
not admitted), it is nevertheless true that many things appear 
above the soil which are not on Mr. Hall’s map. The same au- 
thority (p. 37) states: “ We owe to Mr. Hall's close and intelli- 
gent observation the collection of a large amount of satisfactory 
evidence for the general horizontality or low-dip angle of most 
of the rocks of this region [the “southern gneiss region” ], 
Whereas it had been taken for granted that a general steepness of 
dip prevailed.” 
Whatever may be Mr. Hall’s contributions towards this know- 
ledge the writer does not know, nor does he desire in the re- 
Motest degree to disparage them, yet the above editorial com- 
Ment is most unjust to the earlier worker, who already had 
Observed this fact in his study of Lancaster county, and sub- 
sequently made it a most important factor in the explana- 
tion of the intricate structure of Chester county near the 
Delaware State border. [See Mémoire sur la geologie de la 
Pennsylvanie. Lille, 1882. The horizon of the South Valley 
Hill rocks, Proc. Am. Phil. Soc., Dec. 15, 1882, pp. 322, 326, 
