1887. | NEW YORK ACADEMY OF SCIENCES. 35 
its rapid drying afterward. A determination of the total ab- 
sorption of water gave for its ratio 0.148, in percentage of the 
weight of the stone, and for the proportion of empty spaces in 
its interstices, or ‘‘ voids,” 0.422, in percentage of its volume. 
The tenacity of the stone was determined by various tests on 
a series of sawn cubes, two inches onaside. The average re- 
sistance to quick compression, per square inch, was found to lie 
at 16,118 pounds, between wooden plates; and at 20,208 pounds, 
between cast-iron plates. The amount of condensation of such 
a cube, under compression between cast-iron plates, reached 
50 ten-thousandths of an inch at a pressure of 40,000 pounds, 
and 90 ten thousandths at 60,000 pounds, the cube finally ex- 
ploding at a pressure of 80,000 pounds within a quarter of an 
hour. In the fracture of a bar of the stone, 6 inches long by 
2 inches square, by rapid application of sufficient pressure at 
its middle, while supported on steel faces for a distance of 4 inch 
from each end, the breaking load, calculated to a 1-inch span, 
was found to be 1,346 pounds for the stone on its present ‘‘ bed” 
surface, and 1,144 pounds on its side, the lamination of the stone 
running with the axis of the bar. The amount of deflection in 
the middle of such a bar, with the pressure slowly applied in the 
position ‘‘on bed,” reached 38 ten-thousandths of an inch at a 
pressure of 1,000 pounds, 61 at 2,000, and 90 at 2,250; on the 
side, 30 at 1,000, and 42 at 1,500 pounds. 
To determine the durability of the stone, wet cubes were ex- 
posed during a winter in the open air to a series of 42 successive 
freezings, with alternate thaws, and a loss was found of 0.009 per 
cent of the weight of the stone, per square inch of surface ex- 
posed. 
Microscopic EHxamination of the Dolomyte. 
When a natural surface of the dolomyte is examined under 
a low magnifying power, it is found to consist entirely of crystal- 
line grains, so closely compacted together as to be indistinguish- 
able except by slight differences in their shades of color. Most 
of the grains consist of grayish-white to dark smoky-gray dolo- 
mite, but particles of brass-yellow pyrite, grayish-white quartz, 
and yellow scales of magnesian mica or phlogopite, can be also 
easily recognized. In a thin section, the following complete 
series of the constituent minerals was distinguished. Dolomite, 
in compact grains, often with a fine lining, which indicates the 
twinning structure. These grains varied in sizefrom 1 to 5 mm. 
Calcite, in occasional compact colorless grains of similar size. 
Phlogopite, in minute irregular scales, blades, and fibrous grains, 
either colorless or salmon-yellow. Pyrite, in brass-yellow, bright 
grains and crystals in the form of modified cubes and octahedra, 
