64 PROTECTION OF PLA>^TS, 1920-21 



their side, i. e. completely submerged, is the best to use for the cold liquid. The 

 foot, or lower part of the post, which has been charred or slightly burnt in the 

 fire, will absorb a large quantit}^ of creosote, while the upper part will al)sorb 

 sufficient to prevent rapid decay. This is a good method of treatment for the 

 more perishable kinds of wood, such as the willow, the poplar and the maple. 

 The same results maybe obtained by placing the foot of the post in a tub filled 

 with creosote and, by means of a brush, apply two or three coatings of creosote 

 on the upper part. 



The "open tub" method is quite satisfactory when only a small quantity 

 of posts are to be treated, but with a larger quantity it is desirable to have a 

 permanent plant installed. The wooden vessel must be replaced by one made of 

 galvanised iron, in order to avoid the possibility that the formet- maj^ not always 

 be watertight. The kind of fire described as used with the "open tub" method 

 results in a loss of heat, while, with an iron vessel, the fire can be placed immed- 

 iately beneath arid a chimnby of stonfe or brick constructed. If one prefers 

 to use steam heat, a coiled pipe inside the galvanised iron vessel will prove satis- 

 factory. This prevents allidanger of fire and allows the creosote to be kept 

 always at the same temperature with the minimum of evaporation. The piping 

 in the "cold" vessel affords opportu^iitj^ of again heating the creosote if any 

 risk of solidification exists. 



Cost of Treatment 



From the following figures, given by Mr. Weiss, ("The Preservation of 

 Structural Timber," page 178), the cost of treatment by the Brush Method, 

 the Dipping Method and by Impregnation can be calculated : 



In 1915 the price of creosote was 2c per lb. 



" " zinc chloride was 5c " " 



" " mercuric chloride was 70c " " 



" " sulphate of copper.. 5c " " 



In the case, therefore, of a post seven feet long and six inches thick at the 

 top, the cost by different methods would be : 



The Brush Treatment __ _ 4c to 6c. 



The Dipping Method .^. : 5c to 7c. 



Method of injection with Sulphate of Copper, Zinc Chlor- 

 ide or Mercuric Chloride 3c to 7c. 



Injection with Creosote.. _ 12c to 20c. 



If the whole post was "injected," the cost of this method would be doubled. 

 The following table shows the results of treatment bj^ the different methods 

 in preserving the posts : 



Length of Life Cost per Post, 



of Posts in after Treatment 



Years. and Placing in 



Position. 



Non-treated posts. 5 years 20c.. 



Brush treatment 9 " 25c.. 



Dipping method 11 " 26c 



Injection with Chloride of Zinc, or 



Mercury, or Copper Sulphate 12 " 25c.. 



Injection with Creosote.... 21 " 40c.. 



