GROWING BACTERIOLOGICAL!. Y STERILE POTATO PLANTS H 
FILLING THE CANS WITH SOIL 
The cans were filled with approximately 115 kilograms (253.53 
pounds) of soil. A lesser quantity would collapse somewhat under 
steaming or watering, and a greater weight would bulge in heating or 
fail to transmit the water properly. The soil was added a little at a 
time and tamped with a small post or pointed stick. Within a few 
inches of the top a galvanized-iron water shield was put in place. 
This shield was made of a strip 6 inches wide and long enough to 
make a hoop 14 inches in diameter. At the side adjacent to the 
joint of the top rim of the can a semicircular fold was made to fit 
around the pipe extending through the cover. The shield was jointed 
loosely by folding the end edges back and catching one into the 
other. The shield was raised 1 inch above the rim, which brought 
the soil against the cover when it was in place. A block of wood 4J/9 
inches long by 1J^ inches square, the ends cut at an angle of 30°, was 
put into the soil so that the lower end came directly under the center 
hole in the cover and the upper end at the edge of the large hexagonal 
opening. No soil remained outside the water shield, but inside it 
was well packed and left no space between the cover and soil when 
the cover was in place. After these details were completed a 5^-inch 
iron rod was inserted anywhere near the rim of the can, pushed to 
the bottom, and withdrawn. 
Figure 5 shows the diagram of the top view of a filled can, also a 
cross section of it on the line A-B. When the cover is placed on the 
can, the line A-B of the cover shown in Figure 1 coincides with the 
line A-B of Figure 5. 
TILLING THE KETTLE 
After the cans were filled with soil they were ready to be sterilized. 
The kettle held six cans and covers and the accessories used in steri- 
lization. Three cans were placed in the bottom, the cans so turned 
that the bail eyes were immediately accessible for attaching the 
hoisting device. The covers, turned on edge, were deposited beside 
the cans. Over each of the three bottom cans a large piece of sheet 
iron was placed at an angle to carry off the water of condensation 
which dripped from above. After the bottom cans were arranged a 
tripod made of iron pipe was put in, and on this the three top cans 
rested, care being taken that no can in the upper tier rested against 
another can. The covers were conveniently placed edgewise beside 
the cans. The thermometer bulb was inserted in the soil of one can, 
the wires passed through the rim, and the union joined. The lid was 
clamped down and the 11 clamps strongly tightened, using a short 
pipe for a lever. The contents of the kettle were now ready for 
sterilization. 
STERILIZATION 
The pet cocks and all escape valves on the kettle were opened wide 
and the steam turned on slowly. As the air began to be displaced 
more steam was admitted, and after a few minutes the valves were 
closed and finally the pet cocks also. The steam could then be ad- 
mitted as fast as the pressure in the boiler would allow. The boiler 
pressure was kept at the highest point possible, in order to have the 
steam carry the greatest degree of heat. Low-pressure steam quickly 
condensed on striking the cold kettle and cans. 
