43 
attached the valves, v, working in a cylinder attached to the lower 
end of the reservoir. A handle is attached to the upper end of the 
piston, and the lower end is pointed and works closely 
in the lower small cylinder only at the point opposite g. 
The reservoir is filled through the opening at e , which 
is protected by a screw cap. In B, the instrument is 
ready for insertion in the soil. At A, is shown a sect. on 
of the lower portion of the instrument, nearly one-half 
natural size, and this view represents the position of the 
valves, v, when the instrument is being withdrawn from 
tlies til. It operates very simply. When the piston is 
pulled up it is stopped at the proper point by the metal 
pi a through the piston near p, in B. This brings the 
upper valve into the reservoir, r, and the liquid im- 
mediately fill ; the chamber between the two valves ; this 
is the measuring chamber, and its size can be easily 
regulated to li Id a teaspoonful, or more or less, by 
simply screwing the valves either way or by winding* 
cloth around the piston between the valves. Before in- 
serting in the soil, the piston is pushed down and is 
slopped by the lower valve striking against the bottom 
of its cylinder. The valves are then in the position 
shown in B. As the lower portion of this valve cylinder 
is cut out larger, the liquid escapes into this lower cham- 
ber, /. c.. and some runs down around the lower part of 
the piston but is prevented from escaping by the 
arrangement near the point, at g, by which the piston 
here fits very closely. The pulling up of the piston 
again, of course, lets the charge of liquid run out, and 
at the same time the measuring 
chamber is again filled, thus secur- 
ing an automatic action. It was found 
necessary to have an opening in the 
lower chamber, /. r.,iu order to allow 
air to take the place of the liquid so 
it could freely run into the soil. This 
opening, o, also supplies the measur- 
ing chamber with air which is drawn 
up into the reservoir and then dis- 
places the liquid and allows it to 
freely enter the measuring chamber. 
All parts of the instrument are made 
of brass, except the small discs or 
leather in the valves, and the wooden 
handle on the piston ; the reservoir 
may be made of tin. All parts must 
Fig. 17.— The McGoweu Injector. 
