1883.] Mineralogy. 1159 
The hygrometricity, or amount of moisture absorbed from the 
air, is obtained by heating the rock at 100° C. until the weight is 
constant, and reducing the result to decimals. In expressing the 
hygrometricity of basalt as 0.371, it is meant that 100 grammes 
of the dry rock weigh 100.371 after the expulsion of the humid 
air. The hygrometricity of limestone is 1.669 
The imbibition, or faculty of absorbing water, is measured b 
soaking the rock in water for some time under the bell glass of 
an air pump, and then weighing after it has been carefully wiped. 
It represents the maximum of water absorbed by 100 grammes 
of rock perfectly dried at 100° C. The imbibition of basalt is 
0.551, of limestone 1.981. 
The thermic resistance and coefficient of thermic conductibil- 
ity is obtatined by determining the time, in seconds, which it 
takes for an interval of temperature of 34° C., issuing from a fixed 
source of heat at 100° C. to traverse the thickness of one centi- 
meter of rock. The temperature of the rock at the beginning 
and end of the experiment is noted, as well as its weight, amount 
of surface, thickness, etc., much care being required for this de- 
termination. The thermic resistance is obtained graphically from 
these data. For basalt it is given as 83, and for limestone as 59. 
The specific heat is obtained by a method previously described 
by Lagarde and the author, and involves the immersion of the 
rock in alcohol whose volume, density and specific heat are pre- 
viously known. Thomson's galvanometer is used in the experi- 
ments, and the specific heat of basalt is determined as 0.2699, 
and of limestone as 0.253. 
The elasticity of rebounding, which is directly related to the 
molecular elasticity developed by either optical, thermic or me- 
chanical vibrations, is determined very simply, by counting the 
number of times that a ball of ivory rebounds from the rock. While 
quartz causes the ball to rebound 42.2 times, basalt causes it to 
rebound 25.9 times, and limestone 35.48 times. Taking the elas- 
ticity of quartz as the unit, the resilient elasticity of basalt is 
0.614, and of limestone 0.840. 
STIBNITE FROM JapaN.—The very beautiful crystals and groups 
of crystals of stibnite from Japan, are already well known to a 
number of mineralogists. The specimens, by their beauty, bril- 
‘ancy and size, will attract attention in any cabinet. They are 
‘aid to come from the Island of Jaegimeken Kannaizu, in South 
r ES, Dana, describing some remarkably fine specimens - 
“cently received by the sie Shere at Yale College, it is shown 
