REMEDIES AGAINST FOREST INSECTS. 
41 
inder b l and above the valve b the inner cylinder is closed as shown in 
the cut. Thus it represents a displacement cylinder and its capacity 
bears such a relation to the outer cylinder that on the downward stroke 
it displaces a body of water equal to that taken up by the upward 
stroke of the piston, thus producing a constant pressure in a simple 
single-barreled pump. 
The packing >d is held in place by a metal follower and fits snugly to 
the inner surface of the outer cylinder. The pipe, c, is of rubber hose and 
made of any length desired to suit the depth of cask or tank and with 
a fine wire strainer on the bottom. The head of the pump is of cast iron 
and bulged to allow room for a considerable head of water j iron flanges 
extend out from its lower part and furnish support by which it is bolted 
to the tank. All of the working parts are brass. The packing burr and 
follower around the upper end of the piston cylinder are the same style 
as ordinarily used with steam machinery so as to withstand any reason- 
able pressure. The head to which is attached the compensating bar 
screws into the top of the piston cylinder. The outlet is tapped through 
the bulged cast-iron head, and the pressure is much better if a good- 
sized air chamber is attached to the discharge pipe just outside of the 
pump head. 
The pump from which Fig. 7 was made has two discharge pipes, and 
one man easily supplies pressure for two ordinary streams of spray. 
Fig. 8.— Single-discharge pump. 
Fig. 8 shows a similar pump entire, fitted with a single discharge pipe. 
