Correspondence. 33 1 
the first time, the igneous character of the rock was shown. The in- 
vestigators, mentioned thus far, all studied the rock as it occurs at tlie 
Crcen street exposure, wliere it was first observed by Vanuxem. 
Since the publication of Wiiiiiams's paper in 1887, serpentine has 
.liso been observed to occur in several placjs somcvvhal to the north- 
wtsl of the Green street l(x:ality. In igoi, during the construction of 
the large Butternut street trunk sewer, serpentine was encountered be 
lw(cn lultcrnut and Highland streets, about 150 to 200 feet north of 
IvTrmcr street. The cut through the serpentine extended for several 
hundred feel. It was found to occur also for a considerable distance 
in Highland street. P. F. Schneider* described this second occurrence 
in 1902, and C. H. Smyth, Jr.,f investigated the rock as to its petro- 
graphical characters. 
The rock at the "'Butternut and Highland" locality agrees, mega- 
scopically, with that of the original (Green street) locality, which is 
about five-eights of a mile distant. This agreement in the structure 
and mineral composition of the rocks of these two localities led Schnei- 
der to suggest that there may be some connection between them. He 
says: "The proximity of these dikesj to those at Green street, which is 
less than a mile away, suggests some underground connection, and in- 
asmuch as their general direction is the same they may be merely a 
continuation of those dikes The intervening space has frequently been 
trenched, and at such times the excavations have been carefully watched 
foi evidences of the dikes without revealing any trace of them." 
During the past few months a branch sewer to the Butternut street 
trunk sewer has been constructed in Griffiths street, about one-fourth 
of a mile to the northwest of the "Butternut and Highland" locality. 
Mr. H. B Brewster of the City Engineer's office, who had supervision 
of the construction of the sewer, called my attention to the character 
of the rock being thrown out, which on examination proved to be ser- 
pentine. The rock was encountered about 100. feet west of Butternut 
street. The cut through the serpentine is about 70 to 75 feet. It was 
found at a depth of 5 feet and is covered with drift. Between Butternut 
street and the serpentine the cut passed through about 30 to 40 feet of 
Salina shale. 
The rock at this new locality is like that from the other two local- 
ities, mentioned above, of a dark green color, sometimes almost black, 
distinctly porphyritic, showing phenocrj'sts of olivine, weathers easily 
on exposure to a dark green or yellowish green earth, and in some 
places has many inclusions. Judging from a megascopic examination 
of the rock at this Griffiths street exposure, it agrees exactly with that 
from the other exposures in Highland and Green streets. A detailed 
report on the microscopic characters will be made later. 
As already indicated, Schneider suggested that the "Butternut and 
Highland" locality might be connected with the exposure in Green 
street. From the fact that the rocks in these three localities are of 
• American Journal of Science, toI. xiv, (4), pp. 24-25, 1902. 
t " " " vol. xiv, (4-). pp. 26-30, 1902. 
t SCHNBIDBR thinks there are two dikes in the vicinitv of the "Butternat 
and Highland" locality. 
