45, COENHILL, B.C., AND 122, REGENT STREET, W., LONDON. 471 



FlG. 2850. FIG. 2868. FIG. 2872. FIG. 2869. FIG. 2852. 



2848 Tate's Double-Action Air Pump, with large cylinder, and very firm and 



strong metal mountings, complete (fig. 2848) . . . . 990 



2849 Sprengel's Air Pump, constructed on the principle of converting the space 



to be [exhausted into a Torricellian Vacuum ; it may thus briefly be 

 described : If a small hole be made in the top of a barometer tube, the 

 mercury sinks and draws in air ; if the experiment be so arranged as 

 to allow air to enter along with mercury, and the supply of air is limited, 

 while that of the mercury is unlimited, the air will be carried away, and a 

 vacuum produced. The apparatus is chiefly composed of glass tubes, and 

 is of such a nature that it can hardly be offered for sale, but must be 

 arranged to meet the requirements of the operator. It has been much 

 used in preparing G-eissler's Vacuum Tubes, and will be found fully 

 described in Ganot's Work on Physical Science. Supplied to Order. 



2850 Exhausting Syringes (fig. 2850) 8 6 10 6 



2851 Condensing Syringes 086 0106 



2852 Condensing and Exhausting Syringes, both in one 



instrument (fig. 2852) 16 



2853 Condensing and Exhausting Syringes, of large size . 1 10 

 2954 Condensing Pumps, large, with Metal Valves . .440 660 



2855 Single Transferor (fig. 2855) 16 



2856 Double Transferrer (fig. 2856) 220 



2857 Vacuum or Pressure Gauge, small, for attaching to 



Pneumatic Apparatus (fig. 2857). See also Gauges, 



page 196) 056 076 



2858 Flat Brass Plate, ground for open receivers, with collar 



of leather and sliding wire (fig. 2858) . . . 15 150 



2859 Brass Syringe or Pocket Condenser, for producing Heat 



and Light by rapid compression of air within the 



Brass Cylinder (fig. 2859) 056 086 



2860 Syringe and Lead Weight, with ground glass plate for 



open receiver . . . . . . . . 10 6 15 



2861 Glass Globe and Stop -cock (very light), for proving the 



density or weight of air and gases (fig. 2861) . . 12 6 15 



2862 Copper Bottle, Scale Beam and Stand, with balance 



weight, for weighing air (fig. 2862) .... 330 



