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



the table, and connecting with the base of the pump barrel, 

 which is perforated, and the channel terminated by a valve 

 opening upwards. The piston and cap of the pump barrel 

 also have valves opening upwards ; the one on the cap hav- 

 ing a bent pipe ground into the cover of the valve, for con- 

 veying the oil driven over by the action of the pump into an 

 oil box which is attached under the frame, and may be 

 slided out to empty of oil. On the connecting pipe between 

 the cylinder and socket, there is a projection, with aperture, 

 having a screw the same size as that of the receiver plate, 

 and having a large milled-head screw to close it, and where 

 occasionally connexion may be made with the gauge, appa- 

 ratus, &c. There is from the under part of the receiver 

 plate, and running lengthwise on the top of the frame nearly 

 to the end, a brass pipe terminating in a brass cap, with 

 screw, to which a large stop-cock is attached, supporting a 

 mercury gauge. The gauge consists of a glass tube bent in 

 an U form, hermetically sealed at one end, which tube, and 

 a small portion of the bottom of the other, is filled with 

 mercury ; the tube is attached to a silver scale, graduated 

 to inches, and tenths thereof, and is about eight or nine 

 inches long. The scale and tube are secured within a stout 

 glass shade, which is cemented by a brass cap fitting the 

 large stop-cock as above. 



A long barometer gauge sometimes accompanies the pump, 

 consisting of a strong tube, 33 inches in length, open at both 

 ends, having a reservoir of mercury at the bottom, and at- 

 tached above to the under side of the cap supporting the 

 short gauge. The scale is divided into inches and tenths. 

 This gauge, owing to the great length of the tube, requires 

 great care in using, as, by an accident, the mercury may be 

 drawn into the pump, materially injuring it thereby. On 

 this account it is most usually dispensed with. The stop- 

 cock in the connecting pipe is to close the communication 

 between the receiver and pump-barrels, and that beneath 

 the gauge, to close the communication between the gauge and 

 the receiver. The length of the cylinder is nearly one foot, 

 the diameter 3 inches, the plate 10 inches. Oil should be 

 occasionally supplied by pouring that which is perfectly 

 clean into the aperture in the receiver-plate, and also into the 

 cup over the packing-box, through which the piston moves. 

 The plate and receivers are ground true, and require but a 

 little tallow or oil to prevent the scratching of the two sur- 



