56— Geology of Massachusetts. 
of ponds. The interval between one dredging and another, was so 
variously stated to me, that I suspect it differs greatly in different 
places. I presume, however, that it ought never to be less than twen- 
ty years. But the fact, that there will be a renewal of the deposit 
after a certain time is interesting; because it shows that this mineral 
can never be entirely exhausted. 
Gen. Shepard Leach, of Easton, is the most extensively engaged 
in the iron manufactory of any man in the Commonwealth. He 
owns one blast and three air furnaces in Easton; one blast furnace 
in Foxborough, and another in Walpole; and one blast furnace and 
four air furnaces, in Chelmsford. In these he employs not far from 
five hundred men. He generally mixes the different sorts of ore, 
or at least, two or three of them together for smelting. Extensive 
iron works are also carried on in Wareham. Several furnaces exist 
in Berkshire, and a few in Worcester county. 
The preceding view of our deposits of iron, demonstrates that we 
abound in this useful metal, and that the demand, for centuries to 
come, cannot exhaust it. 
Ochres, &¢c. used as paints. 
There are two kinds of ochre, the red and the yellow, which 
are merely pulverulent varieties of the red and brown oxide of iron. 
The yellow ochre is abundant with our hematite and argillaceous 
ores, and is frequently employed asa pigment. According to Mr. 
C. T. Jackson, red ochre occurs in Boylston in a bed four or five 
inches thick, mixed with clay. It has already been mentioned, that 
the earthy phosphate of iron in Hopkinton, is employed as a blue 
paint. Prof. Dewey mentions that a yellow earth is found in Williams- 
town, from which great quantities of yellow ochre are obtamed by 
washing. Dr. J. Porter states, that yellow earth occurs in Monroe, 
which, when purified, affords a “pale red paint.” The process of 
preparing it he says is now suspended for want of a demand. 
Lead. 
Several ores of this metal.are enumerated by mineralogists, as oc- 
curring in Massachusetts; but none is found in sufficient quantity to 
render it of any statistical interest, except the sulphuret, commonly 
called galena; and all the important veins of this species are con- 
fined to the vicinity of Connecticut river. No fewer than thirteen of 
these occur in that region of sufficient importance to deserve notice. 
