No. 384.] JAMES HALL AND AMERICAN GEOLOGY. 897 
the look of perplexity and bewilderment on the faces of the 
audience. Guyot was sitting immediately behind me. He 
leaned forward and whispered in my ear, ‘ Do you understand 
anything he is saying?’ I whispered back, ‘ Not a word. 
This was scarcely a reflection on the intonation of the reader, 
but a truthful picture of mental consternation. Yet physico- 
chemical and mathematical obscurities could hardly be expected 
from Hall. The promulgation of his theory of mountain- 
making evinced and was the result of the instinct and experi- 
ence of a stratigrapher. 
It is impossible to read the dignified reports of the first, 
second, third, and fourth districts, strong and copious contri- 
butions to geology at a period in our scientific life when, except 
for differential or sporadic work at the hands of Eaton, McClure, 
and Featherstonhaugh, and more consecutive efforts from Jack- 
son, Hitchcock, Troost, Percival, and Owen, nothing had been 
done in geology of commanding excellence — except the great 
work of the Professors Rogers — it is impossible to read these 
productions without being struck with the literary smoothness 
and the mental solidity of the Report on the Fourth District. 
Here the pervading skill of presentation admirably expresses 
the geological simplicity of the facts. But the care and beauty 
of demonstration are happily united with suggestion. At one 
point we are invited to consider the varying rates of deposition 
for fine or heavy sediments, at another the character of shore 
and off-shore deposits, here the mechanics of river erosion are 
discussed, and there the alternating velocity and slowness of 
tides. We ponder on the changing colors of strata and what 
they mean, or are made to feel by some analogy how real those 
ancient beaches and ocean beds were. We are carried across 
Lake Ontario, and shown the Laurentian base of our system 
upon which in shelving order the later formations lie, appearing 
on the southern borders of the lake as the Upper Silurian ; and 
the realization of this is made distinct and memorable. 
Hall’s relation to American geology is that of the 2//usmt- 
nator. He presented a broad, intelligible proposition, and on its 
basis a mass of evidence fell into discrete symmetry. Such 
was the succession of overlapping strata, their encircling lines 
