1881 .] 
197 
[Dodge. 
probable clew to the interior composition and structure of the 
earth. 
This examination may serve as an illustration of the aid micro- 
scopical lithology may be to the practical side of life ; since now, 
for the first time since this rock has been worked, can the iron 
master who wishes to use it, approach understandingly the metal- 
lurgical problems it presents, whether he desires to use the entire 
rock or only the sejiarated magnetite. 
For the original paper the reader is referred to the Bulletin of 
the Museum of Comparative Zoology, Geological Series, Vol. I, 
pp. 183-187. 
NOTES ON THE GEOLOGY OF EASTERN MASSACHUSETTS. 
BY W. W. DODGE. 
This paper 1 presents some details in relation to certain portions 
of the group of stratified rocks in the vicinity of Boston, a gen- 
eral view of the local distribution of which was given in a previ- 
ous series of notes published in the Proceedings in 1875. 
Slates underlying the city peninsula of Boston. It is well 
understood that the northern part of the city of Boston, includ- 
ing Charlestown and East Boston, and that portion of the harbor 
marked by extensive flats adjoining Bird Island, are underlaid by 
stratified rocks. These are chiefly slate so far as is at present 
known, but the extent, position and character of the underlying 
ledges, and their relation to the rocks of the neighboring cities 
and towns, have never been sufficiently ascertained, nor have the 
scattering observations made possible from time to time by 
excavations been satisfactorily put upon public and per- 
manent record. It was stated in 1872 that a well at Squire’s 
pork-packing establishment in East Cambridge reached rock at 
130 feet. In at least one part of the city peninsula the ledges 
rise to a considerable height above high-water mark. 
1 Acknowledgment is gladly made of the assistance and information received from 
the gentlemen connected with the offices of the Sewer Department, City Engineer, and 
Improved Sewerage Company and from private sources. 
