15G LESSONS ON TIMBER-PRESERVING. [Jult 



jected to attacks of the Teredo navalis or the Limnoria terebrans, 

 should have a very liberal dose of the liquid, is extremely 

 difficult to treat in this manner. All previous artificial processes of 

 drying, whether by currents of heated air, or by stoves in closed 

 chambers, or by superheated steam in closed chambers, are subject 

 to very grave objections. Mr, Boulton believes that timber cannot 

 be heated beyond 230" F, with safety ; as at a temperature much 

 exceeding 250' F. the woody fibre begins to be decomposed, and 

 the pyroligneous acids are distilled from it ; while warping and 

 twisting, as well as brittleness, are known to have been exhibited 

 on timber stoved before creosoting, Mr. Boulton was led by 

 numerous experiments to his new process, which is based on 

 the great difference betwixt the boiling-points of water and of 

 creosote ; the temperature at which water begins to distil being 

 212'' F., that of heavy oil of tar, commonly called creosote, ranging 

 from 350^ to 750' F. 



Our author details his method : — 



" The ordinary method of creosoting timber is familiar to all 

 -engineers. The timber is placed in a closed cylindrical vessel, an 

 air-pump is set at work, which produces a vacuum in the cylinder, 

 opens the pores of the timber, and serves to some extent (but by no 

 means completely) to draw out the moisture therefrom. The 

 creosote is then introduced into the cylinder, heated ordinarily to 

 100/120° F., -when the action of the air-pump is discontinued, and 

 the pressure-pumps are employed to force the creosote into the wood. 

 This is the method of injectiug antiseptic fluids, which was first used 

 by Breant, and adopted and improved by John Bethell and Henry 

 Potter Burt, This process is perfect when the timber is dry, but if 

 the timber be wet, it fails of its complete and adequate results, 



" In my improved process I introduce the creosote at a heat 

 slightly exceeding 212" F,, and I continnc the action of the air-jpump 

 after the creosote is introduced into the cylinder, the air-pump being 

 made to communicate with a dome which is fitted on the top of that 

 vessel. It will be readily seen that as the timber is thus subjected 

 to a temperature above the boiling-point of water, any ivatery 

 moisture contained within the pores of the wood must inevitably be turned 

 into vcqjour, and this vapour is dravm off by the action of the air-'pump) 

 through an ordinary condensing worm, the condensed moisture being 

 received in a tank. On the other hand, the temperature of the 

 creosote being much below that of its point of ebullition, that liquid 

 is not turned into vapour. By this means, however much the timber 

 may be soaked with water, it can be at once introduced into the 

 creosoting cylinder, the heat for the expulsion of the water in the 

 form of steam being supplied by the creosote." 



