JO June, 1910. J 



Stcrilizatioi/ of Soils. 



367 



compartments by a single-brick partition. Each of these compartments 

 has a capacity of two tons, only one bemg used at a time, so that whilst 

 one lot of soil is being sterilized the other one is being filled. 



The method adopted for the production of the necessary heat is a 

 simple one. Steam is supplied by means of a small portable boiler worked 

 at a pressure of between 25-30 lbs. ; |-inch piping is led from the boiler 

 to the floor of each pit. where it is joined to a T-piece, and from the 

 T-piece in each of the pits six pipes are let into spaces between the brick- 

 work on the floor, somewhat resembling the prongs of a large fork. The 

 pipes m the spaces of the brickwork are lightly covered with sand. They 

 are 8 Inches apart, are plugged at the ends furthest from the boiler, have 

 a fall of I inch, and are perforated along one side by 3-i6ths inch holes 

 3 inches apart. To carry off the condensed steam a drain is provided of 

 ordinary tiles. It runs along the whole length of the pits close to the 

 plugged ends of the steam pipes, is buried in cinders an inch below the 

 surface, and has a fall of two or three inches. Two valve taps enable 

 the operator to turn the steam into the desired compartment. 



SOIL STERILIZATION BY STEAM. 



The soil or other substance to be sterilized is placed in one of the pits. 

 It 'is then covered with sacking and the steam turned on for a period of 

 about two hours. The sacking prevents the too rapid e.scape of the steam 

 from the surface and raises the whole mass to a higher temperature and in 

 a shorter time than it would otherwise attain were it left uncovered. When 

 the upper layers reach a temperature of 212 deg. F. it is allowed to 

 steam for 30 minutes, the whole of)eration occupying a period of two and 

 a half hours. The second compartment having been prepared during the 

 sterilization of the first one, the steam is cut off from the latter and turned 

 on to No. 2, and in this manner the sterilization of the ."^oil proceeds with- 

 out interruption. 



As .soon as the .soil taken from the sterilizer is sufficiently cool it is 

 ready as a seed bed. When it is necessary to sterilize cow or stable manure 

 for the purpose of killing weeds, &c.. it is treated in like manner, but on 

 removal from the pit it is desirable to spread it out in a layer of 4 inches 

 to drv it somewhat. 



