C. H, Hitehcock— Helderberg Rocks in New Hampshire. 561 
composed the exploring party, and Mr. Huntington first de- 
tected the presence of the Pentamerus. Our attention was 
called to the spot by Mr. A. R. Burton of the village, who had 
seen limestone there. It is about fifty rods southerly from E. 
Fitch’s house, in an open pasture near the forest, and above an 
orchard. The first rock seen above Mr. Fitch’s is the dia- 
base,* running N. 65°-70° E., and containing a layer of white 
quartz. In the pasture the strike changes to nearly east and 
west, and this fact is made certain by the position there of the 
white quartz, which curves with the diabase, but may be a 
little nearer the Helderberg after the bend is passed than before. 
This is confirmed by examining the rocks east of the Helder- 
berg range. On fig. 4 below, there are thirty rods of chloritie 
rock east of the slate range, but on Fitch Hill, in consequence of 
the transverse course of the slate, it lies on the southeast of the 
diabase altogether, as shown in fig. 5. To the southwest there 
is another outcrop of this range of diabase, because the Helder- 
berg is cut off by it, but the fossiliferous seam again covers it 
when the low ground is reached, and the hard rock is seen no 
more. 
Furthermore, the contact between the Helderberg and diabase 
on Fitch Hill is not a direct succession or interstratification, 
since there has been a sliding of one rock over the other. The 
removal of the turf revealed a slickensides between the two. 
As expressed by Pres. W. B. Rogers, who examined the 
locality with us a few days later, it ‘“ looks as if the limestone 
had backed up on to the green rock” These facts are men- 
tioned to show our reasons for believing that the Helderberg 
rocks on Fitch Hill and the neighborhood overlie the Lisbon 
group unconformably. 
The order of the rocks from Fitch’s house to the very sum- 
mit of the hill is well shown in fig. 5. What I have called the 
top of the hill thus far signifies the highest part of the clea 
la This section reaches the very summit, which is wooded. 
Above the Lisbon series, or the diabase, come about fifty feet 
of Lower Helderberg limestone, holding the Pentamerus and a 
Gasteropod, with the others mentioned by Mr. Billings. This 
is followed by forty or fifty feet of coralline slate ; thirty or 
forty feet of friable conglomerate, white when weathered, like 
the Oriskany sandstone of New York, the quartz pebbles being 
of the size of kernels of Indian corn. Next is a bluish, some- 
what siliceous limestone of two sorts. Then follows considera- 
ble tough, massive hornblende rock, with no signs of stratifica- 
tion and a strange associate of the Pentamerus limestone. On 
the very apex of the hill is a sandstone weathering white, but 
* Prof. Hitchcock Isewhere that his “diabase” is not known to contain 
labradorite sel ners other rock; it is metamorphic.—v. p. p. 
