GKOWING BACTEEIOLOGICALLY STEEILE POTATO PLANTS 7 
tially of a supply tank, an air-pressure tank, and two measuring 
cylinders, all made portable by being mounted on a substantial hand 
truck. The machine is shown in Plate 2, A. 
The details of the supply and air-pressure tanks with their connec- 
tions are shown in Figure 3. 
The air tank was suspended beneath the truck, the water tank of 
66 gallons capacity being fastened above. The air-pressure tank 
opened to the air through the valve A and to the water tank through 
the valve B. Above valve B was a small cylinder at G tightly 
packed with asbestos wool. Above G was a check valve C and also 
a pipe H entering the convex end of the water tank, bending upward, 
the open end terminating as near the top as possible. At the point 
I a pipe led out above to an elbow, on top of which was valve D and 
at the side of which was a pipe provided with a valve (E) and ex- 
Fig. 3.— Diagrammatic cross section of the tanks and connections of the watering machine (except 
the cylinders) . The high-pressure air tank is reached by way of the valve A . Air escapes through 
valve B into the cylinder G packed with asbestos wool, through the check valve C and pipe H, 
to the top of the water tank. Water is drained and steam admitted to the water tank through 
the valve F. The tank is filled through the valve D and pipe at I. The valve E is used only 
at time of sterilization, being closed at other times. The water is forced up through the pipe J 
and out at L. At M is a pressure gauge and at N a pet cock 
tending toward the front of the tank. In the bottom of the tank was 
valve F. In the concave end of the water tank was a pressure gauge 
M and a pet cock N. A pipe J whose free end was close to the bot- 
tom of the tank led upward to the outside and into a tee at K, at 
which point the pipe from valve E was attached. The upper open- 
ing of the tee led into a pipe shown broken at the point L. 
This pipe led to the measuring and distributing cylinders, the 
details of one being shown diagrammatical^ in cross section in Fig- 
ure 4. 
The pipe L, broken at the bottom, is a continuation of the pipe L 
of Figured. The top of pipe L terminated in a three-way right- 
angle valve O, which served to direct the water into the pipe P, lead- 
ing to the right-hand cylinder, identical in every respect with the 
cylinder II (shown in fig. 4), to which the pipe Q leads. 
