38 Geology of Massachusetts. 
believe that from the Vineyard to be of this description. At any rate 
the alum which the Salem company produce, is of a good quality, and 
is made in large quantities. They formerly obtained their clay from 
Gay Head; but they now procure it of a better quality from the west 
side of the island, in Chilmark. 
Clay as a Manure. 
Writers on agriculture, speak of clay as next in value to marl, for 
manuring light and sandy lands; and I cannot but think that our far- 
mers have yet something to learn on this subject. Marl, they cannot 
procure, but at a great expense ; but clay is usually at hand—and we 
have very much of the land which it will help. Yet I am not aware 
that in any instance the experiment has been thoroughly made. 
Marl. 
Marl for our farmers, scarcely exists in the State, except in a few 
places in Berkshire county, where it is of little use, because the 
soil already contains so much calcareous matter. It is said to have 
been found in Lancaster, but whether in large or small quantities, is 
not stated. Judging from the nature of the surrounding country, I - 
venture to predict that it will not be found there in abundance. In 
Duxbury also, it occurs in considerable quantity. In Pittsfield, is 
abed of earthy marl, but not extensive. It is found more abundant- 
ly, it is said, in Lenox; and it exists also in Williamstown. 
Peat. 
This useful substance must be regarded as alluvial in its character, 
since the process of its formation is now going on. It results chiefly 
from mosses and other plants, more or less decayed. In the eastern 
part of the State, it is found in great quantities. West of Worcester, 
it has scarcely been sought after, on account of the comparative abun- 
dance of wood. It will probably, however, never be found so abun- 
dantly in the western part of the State, asin the eastern. I have 
ascertained the existence of peat in the following towns, and do not 
doubt that it occurs in many others. ‘There are two varieties; the 
fibrous and the compact. In the former, the moss, turf, and roots 
out of which peat is formed, have not lost their fibrous structure : 
but in the latter, they are converted into a compact and nearly ho- 
mogeneous mass. 
The fibrous and compact varieties, probably exist at nearly every 
locality. Iam sure of their occurrence in Cambridge, Newton, and 
