ANTISEPTIC TREATMENT OF WOOD. 519 



wood, which is hased on the principle of first steaming the 

 wood and then injecting it hy forcing-pumps in chambers 

 deprived of air. There are six of these chambers, which can 

 be connected successively with the steam-generator, and in 

 which the process of injecting is carried on continuously, the 

 sixth chamber being removed and charged with wood, the 

 first chamber steamed, and so on. 



In Blythe's system (according to Gayer) the wood is dried 

 artificially and then placed in boilers, where it is subjected 

 to a high pressure of steam containing heavy oil of creosote 

 in suspension. The wood is subjected to injection during 

 6 to 20 hours ; it is injected completely, and assumes a dark 

 colour like that of several tropical woods. The softened wood 

 is rolled and pressed till it is reduced in thickness by 

 10 % or even 40 %. The effect of the injection is increased 

 by compressing the wood, and thus a very superior kind of 

 furniture-wood is produced (Exner). It is preferable to use 

 freshly felled wood, and Exner states that beechwood thus 

 injected and compressed gains up to 19 % in strength. 



III. Steeping Converted. Wood in Antiseptic Liquids.* 



This method is employed chiefly for kyanising stakes and 

 small pieces of wood. Large wooden troughs like cooling- 

 troughs are partly filled with a solution of 1 part of corrosive 

 sublimate to 150 parts water; railway-sleepers, telegraph- 

 poles, etc., are placed in them, weighted to make them sink, 

 and kept from 8 to 10 days immersed. The solution pene- 

 trates only 2 mm. into the wood, which cannot be altered in 

 shape after immersion. 



[Boulton says that small pieces of wood, hop-poles, fencing- 

 slabs, stakes, etc., may be placed in an open trough with 

 heavy tar-oil, which is heated by a fire under the trough, care 

 being taken not to raise the temperature of the creosote above 

 230 F. Tr.] 



Other methods by immersion give inferior results. Formerly 



* ('/'. K. Henry. " Preservation ties Bois centre la Pourriture." Berger 

 Leviault et Cie., Nancy. 1907. 



