1881. 67 EG RUSH VR VAG Scz. 
apparently perfect. However, the antenne of the crickets were remark- 
ably long, and seemed to guide them more than their eyes. He related 
observations made by Prof. Putnam on the crickets, and also on the 
crawfish from the Cave, shut up in an aquarium, which seem to indicate 
that they judge of their food more by touch than by sight. © 
Dr. NEWBERRY had observed in an old Spanish mine in New Mex- 
ico, millions of bats clinging to the rock, many of them with their 
young, at a point several hundred yards from the entrance. In all 
cases such denizens of caves find ready access to the exterior atmos- 
phere through the crevices and galleries. 
Mr. STEVENS had observed bats at the saine distance from the 
entrance as noted by Dr. Trimble. In regard to the absence of fatigue 
in traveling underground, he had found a walk of thirty miles had 
caused no more exhaustion than one of ten miles on the surface; this 
was probably due to the purity, coolness and dryness of the atmos- 
phere. 
Mr. BRITTON stated that a M\Vatural Sczence Association had 
recently been formed on Staten Island, having for its particular object 
the collection and diffusion of information on all subjects relating to the 
Natural History of the Island, and the formation of a cabinet illustra- 
tive of its natural products. The meetings are held at New Brighton 
on the second Saturday of each month. The officers of the Associa- 
tion are: 
Bresiden tt aegis acgatig yaa nee - «eit apne Sanderson Smith. 
Gorresponding Secretary, to. esi) +. kis wstee Arthur Hollick. 
BCOLMING SECLELAPY). 2-1 (1/s-c)o ss . > + arate 6 Charles W. Leng. 
COT aye ct teh Dyekees Dyess sinters - apeceeeiens William T. Davis. 
The address of the Corresponding Secretary is at Port Richmond. 
December 109, 1881. 
SECTION OF PHYSICS. 
Vice-president, Dr. B. N. Martin, in the Chair. 
Thirty persons present. 
A specimen of acicular hornblende in quartz was exhibited by 
Mr. W. L. CHAMBERLAIN. 
The following paper was read by Prof. W. P. TROWBRIDGE: 
ON THE DETERMINATION OF THE HEATING SURFACE REQUIRED IN 
STEAM PIPES EMPLOYED TO PRODUCE ANY REQUIRED DIS- 
CHARGE OF AIR THROUGH VENTILATING CHIMNEYS., 
To ventilate a room properly requires the frequent removal of vitiated 
air and the introduction of fresh or pure air, the quantity, by weight, 
of the air introduced and rejected being equal in a given time, 
