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 1^-inch pipe is used in some of the largest 

 greenhouses where the gangs are very long. The holes 

 are */ 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- 



