468 



NEGEETTI AND ZAMBEA, HOLBOEN VIADUCT, E.G., 



FIG. 2832. 



PNEUMATICS, HYDRAULICS, AND 

 HYDROSTATICS. 



PNEUMATIC APPARATUS, 



2832 



Improved Double-Barrel Air Pump, as No 2832, combined with a Third 

 Cylinder on Tate's principle for obtaining the most perfect exhaustion 

 possible, the large vertical cylinders being used for rapidly exhausting 

 any receiver, and the horizontal cylinder for completing the exhaustion 



to the most extreme point . 17 10 



Our engraving (fig. 2832) at the head of this section represents the most 

 improved arrangement of Air Pump yet constructed. With this instrument very 

 large receivers are rapidly exhausted in the usual manner, until the mercury in the 

 gauge falls to -inch of the scale, when further exhaustion is obtained by using the 

 Tate's pump placed at the side of the larger cylinders. At a temperature of 60 

 degrees of Fahrenheit an exhaustion as low as ^th of an inch may be produced, 

 and when the pump is in very perfect action, and the temperature very low, greater 

 exhaustion may be obtained. 



2833 Largest Size Double-Barrel Air Pump, on strong 

 Mahogany Stool Stand, barometer gauge and cistern, 

 with graduated scale divided to inches and tenths, 

 Gun Metal ground receiver plate, or ground Plate 

 Glass, 23-inches diameter, key and lever . . . 36 



