12 Geology of Massachusetts. 
Hornblende Slate, Geiss. 
Gneiss, which differs from granite only in having a slaty structure, 
occupies more of the surface of the State than any other rock. It 
sometimes takes into its composition the black mineral called horn- 
blende ; even losing its common ingredients; and then it.is denomi- 
nated Hornblende Slate. Sometimes the quartz so greatly predom- 
inates over the other ingredients, that itis properly called quartz rock. 
The soil resulting from the decomposition of gneiss is so well mark- 
ed, as not to be easily mistaken by an experienced eye. Its pre- 
dominant ingredient is a rather fine whitish sand; and sometimes 
beds of extremely pure sand are found in it; as in Pelham and 
Shutesbury. Indeed, the appearance of the soil from gneiss, indi- 
cates uncommon poverty and sterility. But facts do not correspond 
to this anticipation ; for in no part of the State do we find finer look- 
ing farms, or the appearance of more thrift and independence among 
their occupants, than in the region where gneiss prevails: I refer 
chiefly to Worcester County, most of which is based on this rock. 
The western part of the range, however, embracing the eastern part 
of Franklin, Hampshire and Hampden Counties, is in general char- 
acterized by a rather barren soil. But this region is more elevated 
than the surface farther east. Where it isnot so high, as in Monson 
and Brimfield, we find the same appearance of fertility as in the towns 
farther to the east. It is a question worthy of attention, however, how 
far the soil from our gneiss-rock may owe its agricultural character 
to the iron that so generally accompanies this rock. Certainly the 
jron gives it an appearance of sterility which does not belong to it. 
Greenstone. 
This is one of the varieties of rock embraced under the general 
term trap rock. 'The variety most common in Europe is basalt: 
and the soil produced by its decomposition is said to be of a supe- 
rior quality. The greenstone of Massachusetts, however, except 
some of its rarer varieties, is but little acted upon by ordinary decom- 
posing and disintegrating agents; and is proverbially one of our 
hardest and most indestructible rocks. Hence the soil that covers 
itis generally quite scanty. Itis, however, very peculiar; and we 
find upon our greenstone ridges, quite a number of plants, shrubs, and 
trees, that are not found, except rarely, upon the other formations. 
The eastern part of the County of Essex is in a great measure com- 
posed of greenstone ; and its superior agricultural character, in gene- 
