300 



CONSTRUCTION OF PUMP 



A short metal collar, with a discharge-tube in the side, is 

 fixed with sealing-wax upon the upper end of the barrel, the apertur 

 for the discharge-tube having been made in the metal before it i 

 bent round to form the collar. The pump is screwed to a small board c 

 wood, which has a hole corresponding to the width of the suction 

 tube, and may be supplied with four legs, so that a vessel of wate 

 may be placed underneath, if the suction-tube is short ; or the boar< 



FIG. 199 



may be fixed by a screw-clamp to the edge of the table so as to pi 

 ject partly, a vessel of water is placed upon the floor, and a suctic 

 tube 70 or 80 cm long is allowed to dip into the water. 



The downward motion of the piston should be rather slow, It 

 the water forced between the piston and the sides be projected OA 

 the top of the barrel ; the piston should also be moistened beft 



