54 MINERALOGY AND LITHOLOGY. 
potash or soda, making a silicate, which is called soluble glass. This 
substance is a valuable cement. Wood, when coated with it, is fire- 
proof; and eggs, after being dipped in it, will remain fresh. It is, be- 
side, a great purifying agent, and nothing else put in the water will 
give that pure whiteness to linen that can be obtained by the use 
of this substance. There are many deposits in this state, which are too 
small to be of commercial value, but which might be much more gener- 
ally utilized by the people of the neighborhood. The substance has 
been latterly employed as the basis of dynamite.* It is a bad conductor 
of heat, and serves as a good protection for boilers and steam-pipes. 
A detailed list of localities for this substance in this state is given in the 
report above alluded to, by Dr. Edwards. 
These deposits are still being accumulated. If the material at the 
bottom of any stagnant pool of long standing is carefully examined with 
the aid of the microscope, these minute plants will be found in immense 
numbers. 
Dr. Jackson obtained seven and one half per cent. of phosphates of 
lime and magnesia from a specimen from Hooksett.{ Any such material 
would make an excellent fertilizer for fields near at hand. I have myself 
seen no such phosphatic infusorial earth, and attribute the presence of 
such an amount as indicated by Dr. Jackson’s analysis to some acci- 
dental cause. i 
39. HyprersTHENE [(Mg, Fe) Si O,]. 
This mineral is distinguished from other minerals related in compo- 
sition to pyroxene by its orthorhombic crystallization. It occurs in the 
gabbro of Waterville. It is a constituent not often visible to the naked 
eye, but is easily recognized by its optical properties observable in micro- 
scopic sections, and by the: circumstance that it possesses the same 
peculiar interpositions that make it so noticeable elsewhere. 
The most remarkable occurrences of hypersthene in America are at 
St. Paul’s. island, Labrador, and at one or two points in Canada. As 
there observed, it has a deep brown color, and easy cleavage parallel to 
the brachypinnacoid, and. the microscopic sections show that, inlaid in 
* See Ann. Rep., G. H. Cook, State Geologist of N. J., 1874. 
+ Geology of New Hampshire. Hitchcock. Vol. I, p. 502. 
t Geology of New Hampshire. Jackson, p. 185. 
