518 AUXILIARY FOREST INDUSTRIES. 



[Boulton* says that the presence of water in timber at the 

 time of creosoting is most prejudicial to successful injection, 

 and that railway-sleepers and other timber should be stacked 

 and dried for several months before injection. This pre- 

 caution can be secured easily in the case of railway-sleepers 

 or telegraph-poles, but when timber is sawn from logs kept 

 in timber-ponds in the docks, it is difficult to afford a proper 

 time for stacking and drying it before creosoting. Owing, 

 however, to the injury done to timber by drying it artificially 

 at temperatures up to 250 F., the action of stoves in closed 

 chambers, or of superheated steam, is very prejudicial ; he 

 therefore considers 230 F. as the limit of safety for heating 

 timber intended for engineering purposes. Boulton has there- 

 fore patented a process depending on the different boiling 

 points of water (212 F.) and of heavy tar-oils (350 F. to 

 700 F.) ; the creosote is admitted at a temperature slightly 

 over 212 F. and the action of the air-pump continued, so 

 that any water in the logs is converted into steam and drawn 

 off by the air-pump through a condensing worm in a dome 

 on the top of the injecting cylinder. The creosote is still 

 liquid at 212 F. and replaces the water in the log, which is 

 not then subject to any excessive heat, and consequently its 

 tissues are uninjured. Boulton also maintains that in the 

 case of railway-sleepers to be used in India and other hot 

 countries, this injecting at a temperature of 212 F. fills all 

 cracks in the wood with creosote ; as in India therefore the 

 sleepers will not be subjected to such a heat in the ballast, 

 they will not crack any further there, which is not the case 

 with sleepers injected at a heat less than that they may 

 experience in Indian ballast. Tr.] 



When heavy tar-oil is used for injecting purposes, the wood 

 is coloured dark black ; the hard, pitchy components of the 

 tar form a crust almost as hard as stone on the surface and 

 fill all the crevices of the wood. [In England about 50 gallons 

 of heavy tar-oil are used per load of 50 cubic feet, the oil 

 weighing 11 Ibs. per gallon. Tr.] 



F. Lowenfeld has designed a portable apparatus for injecting 



* S. 1'.. lioultoi), An improvement in the process o!' Creosoting Timber." 



