208 



BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE. 



Fig. 203. Bladder and Weights. A pneumatic in- 



strument (Fig. 206) to show the elasticity of 

 atmospheric air. It is formed of a circular 

 base, hollowed out in the middle into a cup 

 shape, having three stout brass wires connect- 

 ing with the top, and between these wires, a 

 movable box, the bottom of which is hol- 

 lowed out as the base. A small bladder, with 

 a small quantity of air in it, is placed in the 

 cavity below the box, and the box filled with 

 shot, or any heavy weight. The weights and 

 cup slide easily up and down between the wires. When 

 this instrument is put under the receiver of an air-pump, 

 and the air exhausted from around it, the elasticity of the 

 air within the bladder will expand it so much as to raise up 

 the heavy weights above it, and thus show its rarefaction. 



Price, $1.75 and $2. 



Fig. 207. 



Weight Lifter by the Expansion of 

 Air. Fig. 207 consists of a cylin- 

 der of brass, having a closed bottom, 

 attached to a small frame by a flange 

 at the top of the cylinder, within 

 which a solid piston moves freely, to 

 the rod of which there is a small 

 stage, on which weights may be 

 placed. When the piston rod is 

 down, there is a space in the lower 

 part of the barrel containing air, the 

 expansion- of which, when placed 

 under a receiver and exhausted, will 

 raise a heavy weight. 



Price, $5.00. 



The Improved Weight Lifter, or Upward Pressure Appa- 

 ratus. (Fig. 208, page 210.) This apparatus consists of a 

 very stout brass cylinder, having a stout flange at the top, 

 set in a stand supported on three iron legs about thirty 

 inches in height. The piston is accurately fitted to the 

 bore of the tube, and a ring attached to the under side of 

 the piston, from which weights are attached by a stout leather 

 strap. The stop of the glass cylinder is ground perfectly 



