108 C. T. Jackson on minerals from the Emery mine of Chester. 
was made by my son, John C. Jackson. I was’ in hopes 
would have had time to repeat the work and determine the 
which contain microscopic erystals of Brookite. nearly, 
scratching quartz distinctly but feebly. G. = 3:39. a ae 
ac Tn - . - . * 147 5 iss 
. [80°75] 83-0 
Oxyds eidsaiioa aint - 4:50 
Sesquioxyd of iron ik ome titanium, - 30 
10000 = 100°8 
The diaspore occurs in both the North and South Mountains, 
associated with emery a chloritoid. It exists both in bladed 
striated ws and in small prisms of considerable length, 
sometim: inch or shisha long. Only the microscopic crystals 
gins wevtectly defined forms. 
hloritoid.—Ten grains of the chloritoid were selected for the 
analysis, as pure as possible, but it still con cae capi 
ye a 
Water, - - - - - 11:00 11:00 
Silica, - . - - - 22:50 22°50 
Alumin - - - - ~ 28°50 28°50 
rotoxyd of iron, - ‘i - 18:00 
a of eke - - - 41°50 20°25 
. - 18 — 
100-80 05 
analysis of masonite: (From ated made in 1839 and pub- 
lished in 1840; Geol. of R. I., page 88, Prov., R. L., 1840. ie 
analysis was repeated several times, and this is a mean of a num 
ber of ey dads ate analyacs 24 so koa on 25 end 50 grain lots ) 
Water, 4-000 
Silica | - - - > * - 33-200 
Alumina, - - > - - - 29000 
agnesia, - - - - - 0 240 
Protoxyd of iron, - . - - - 25924 
Oxyd of manganese, - = See 6000 
99374 
Boston, March, 1866. 
