BULLETIN 1465, U. S. DEPARTMENT OF AGRICULTURE 
cross section, made on the line A~B, shows the arrangement of the 
pipe in the tube and the tube in the cover. In the center the remnants 
of the handle project upward, with holes in the ends. 
The upper (threaded) end of the pipe projecting from the cover 
was fitted with a vent cap, consisting of a %-inch to J/g-inch reducer, 
two 3^8-inch elbows, and a 3^-ineh pipe 3 inches long, and connected in 
this order. A cross section of the vent cap assembly is shown in 
Figure 2. 
The interior of the elbows and the upper two-thirds of the pipe 
were closely packed with asbestos wool. As already noted, the pipe 
was deeply threaded. The interior of the cap was painted with oil and 
graphite, which permitted it to be 
screwed on fully and tightly and 
yet allowed its easy removal with 
freedom from excessive friction or 
binding after much steaming at 
indeterminate intervals. 
SOIL-STERILIZING KETTLE 
Fig. 2.— Cross section of the vent cap. It con- 
sists of a %-inch to H-inch reducer, into which 
fit successively two H-inch elbows and a H-inch 
pipe 3 inches long and open at the end. The 
elbows and upper two-thirds of the J^-inch pipe 
are closely packed with asbestos wool 
The kettle in which the cans of 
soil were sterilized was a high-pres- 
sure process kettle. The ordinary 
process kettles used in canning fac- 
tories are of comparatively light 
construction and endure a pressure 
of not to exceed 25 pounds to 
the square inch. Although that 
used in the experiments was iden- 
tical in design with the lighter kind, 
it was of much heavier construction, 
the hinged and counterpoised lid 
having an increased number of 
clamps (11) and the pressure ad- 
justment being 65 pounds. 
The kettle rested on beam sup- 
ports over a large pit and was pro- 
vided with four heavy lugs at 
the center, which held it upright. 
One-half of the kettle was below 
distance of some 3 feet which the 
The approximate inside 
the floor of the room, leaving a 
cans had to be raised to be put into it. 
dimensions of the kettle were 4J^ feet in diameter by 6 feet high, 
measuring from the perforated false floor in the bottom. The steam 
line entered near the bottom at one side. In the center of the con- 
vex bottom a drain of 2-inch pipe led off to one side and closed with 
a valve operated from above by a rod. From the rim at the top 
another 2-inch pipe led downward, closing with a gate valve. 
On the left side there was a steam-pressure gauge and thermometer, 
the latter being afterwards dispensed with as an unnecessary obstruc- 
tion. The safet3 r valve in the lid was set to release at 65 pounds 
pressure. In the upper rim were four %-inch holes threaded for 
pipe. These were all plugged except the extreme left one. This 
