SOIL STERILIZATION 95 
lift the pan at all four corners, transferring the weight to the car 
wheels. The whole apparatus is then rolled along, the width of the 
pan, and if the worm gear is well oiled, a sharp throw of the crank 
will cause it to spin in lively fashion, lowering the pan to its new 
position. The gear is intended for raising short lines of light venti- 
lators, but fills this purpose admirably. Steam is delivered in the 
center of the pan by means of a hose from a temporary steam line 
into a pipe running lengthwise beneath with a few holes drilled 
through to spread the steam.” 
Perforated pipe—The perforated pipe system is 
popular and highly satisfactory. There are many 
modifications in its installment, but the general plan is to 
provide gangs or sets of perforated iron pipe. These may 
Fig. 31.—Peg or rake steam sterilizer used by some growers at Toledo, Ohio. 
be 25 to 90 feet long, depending upon the supply of steam, 
size of house and number of men available to move them. 
Fifty-foot lengths are convenient to handle. The number 
of pipes in each set is variable, although five is a common 
number. The perforated pipes are usually 1'4 inches in 
size, although 114-inch pipe is used in some of the largest 
greenhouses where the gangs are very long. The holes 
are 4 or 4% of an inch in size, sometimes larger, and 
about a foot apart. The pipes are laid 16 to 18 inches 
apart and connected with a 2-inch header. 
A successful grower at Irondequoit, N. Y., uses a 2- 
