Tin Dunihility (ind Preservation of Woods 253 



are secured if an even temperature can be maintained. 

 This is better accomplished by steam, which, however, is 

 not always to be had. The less surface the liquid has, the 

 less oil will he lost by volatilization; hence the tank 

 should not be of too large diameter. 



The Forest Service recommend- surrounding the metal 

 tank with a plank framework inclosing a space 4 inches 

 wide between the tank and the boards. This space should 

 be packed with sawdust. This packing is especially 

 beneficial in cold climates. It prevents the too rapid 

 solidifying of the creoeote. The erection of such a plant 

 will cost from $30 to $45. 



For this treatment the seasoned peeled posts are placed 

 in the tank of creosote, either wholly submerged or only 

 the butts under as i- de>ired. and kept there from J to 6 

 hours. The temperature of the creosote should be kept 

 as nearly as possible between 200 and 210. The expan- 

 sion caused by the heat forces out much of the water and 

 air from the wood cells. 



The fires are then drawn and the po>N left in the cool- 



lution for \ 14 hours. The cooling causes a 



vacuum in the cell- from which the water and air were 



driven by the heat, and the creosote is forced into the>e 



vacuums by the pressure of the atmosphere. Mr. Weiss of 



vice thinks that a short hot bath and a long 



cool bath probably will give the most economical re>ults. 



If there are a large number of posts to be treated and it 

 i> desirable to hurry the work, two tanks may be used, one 

 for the hot bath and the other for the cool. The posts 

 may then be tran-ferred directly from one tank to the 

 other and the hot tank immediately refilled. This U an 



