i8q2.J 
505 
[Crosby. 
GENERALIZED VERTICAL SECTION OF THE ROCKS OF HINGHAM. 
Gray slate 
500 to 
1000 
feet. 
Sandstone and conglomerate, alternating 
200 
300 
“ 
Red slate 
50 “ 
75 
t 4 
Conglomerate 
75 “ 
100 
Red slate 
20 “ 
30 
Conglomerate 
40 “ 
50 
Red slate 
20 
40 
“ 
- Conglomerate 
30 “ 
50 
“ 
Gray and red slate 
90 “ 
130 
“ 
Conglomerate, sandstone and slate, alternating 
100 11 
170 
“ 
Gray slate 
40 “ 
60 
“ 
Fine conglomerate and sandstone, alternating 
120 “ 
200 
Melaphvr 
120 “ 
240 
Conglomerate, thickness undetermined. 
Granite (diorite, granite, and felsite). 
Dikes of diabase intersecting the bedded rocks, owing chiefly, 
it is probable, to the less continuous outcrops, but partly, no 
doubt, to the fewer faults, are much less conspicuous in Hing- 
ham than in Nantasket. They probably agree with the Nantasket 
dikes in dating from the plication and faulting of the strata. The 
most important distinction is that between the great masses of 
coarsely crystalline diabase scores or hundreds of feet in breadth 
and very irregular in outline, and the ordinary, narrow, wall-like 
dikes of finely crystalline diabase. The latter, at least, belong 
chiefly to the east-west systems of Xantasket. Xo clear intersec- 
tions have been observed ; and no dikes which could be referred 
with certainty to the youngest or north-south system of Nantasket. 
STRATIGRAPHIC DETAILS. 
The actual observations are, to a very large extent, recorded on 
the maps, which, it will be noted, not only show, in the colors, 
the probable distribution and relations of the rocks, but also, by 
appropriate characters printed in black, the position and extent of 
every outcrop, with the dip and strike of the bedded rocks, etc. 
By this device, the verbal descriptions are greatly abbreviated; 
and the combination of fact and theory — the interpretation in 
each case being, as it were, superimposed upon the facts them- 
selves — enables the reader to judge more readily as to how well the 
one fits the other. A few only of the more interesting points in 
