68 
IOWA ACADEMY OF SCIENCES. 
and ponds.* It contains the Nissitisset river, Flint pond, 
Long pond, Parker’s pond, Pennichuck pond, Round pond 
and Spaulding’s pond, besides a large area of swamp. The 
southeastern part of the slate area is largely occupied by the 
present valley of the Nashua. • 
Within this area the hills of slate rise in ridges to a height 
of one hundred feet above the adjacent lowland. They do not 
form continuous ridges, nor does their general direction con- 
form to the direction of strike. This general direction is N. 
70® E., while the strike is on the average N. 57® E., though 
the strike varies a few degrees even in strata but a few feet 
apart, as the rock is much contorted. These hills are low in 
contrast with the hills in the gneiss and schist area adjoining. 
Prom the top of Long Hill, a hill of the Monadnock type just 
south of Nashua, these slate hills appear below the Cretaceous 
peneplain. 
The valleys between these hills, even the hills themselves, 
are mantled with drift, and the river valleys deeply covered 
with washed drift; but further reference to this important 
feature is here omitted as not a part of the problem under 
consideration. 
Description of the EocJcs. — The character of the rocks and the 
relation of them one to another is perhaps best seen along a 
line from Shattuck’s ledge, Nashua, northwestward. At Shat- 
tuck’s ledge, the rock is gneiss in part heavy, in part quite 
schistose. 
At the reservoir, three quarters of a mile west, occurs slate 
with bands of graphite. Northwest for three miles the rock is 
a slate very much crushed and crumpled, and in the northern 
part of this area, a shaly slate interbedded with gneiss. The 
dividing lines, then between the slate and the schist, and 
between the schist and the gneiss, are not definitely marked 
lines, but are intermediate places in a series of gradations. 
Similar gradations from slate through schist to gneiss are to 
be found in the southwestern part of the area near the conflu- 
ence of Gulf brook and Nissitisset river. Here, south of the 
Massachusetts line, the slate is both shaly and quartzose. 
Just north of the Massachusetts line quartz veins are very 
marked in a dark schistose rock. This same structure is found 
in a railroad cutting near by, revealing in an excellent manner 
^The contour lines of the accompanying map are as given on the New Hampshire 
state geological atlas. 
