Processes for Wood-preservation. 191 



might prove very effectual. It is even recommended for stakes 

 and posts, which -without preparation would speedily decay. The 

 wood should be peeled before boiling. 



756. Immersion in Water, or placing in Soils permanently Wet. It 

 is well known that piles driven into the soil, or timbers laid in the 

 water, or under a wall where it is always damp, and where access 

 to the air is wholly prevented, will last for an immense period. 

 Wrecks of vessels will thus remain for centuries, aud sometimes 

 vessels are sunk to preserve them from decay, as was done with the 

 fleet captured by Commodore Perry on Lake Erie, in 1814. It 

 remained under water in the harbor at Erie, Pa., for many 

 years. Timber is sometimes thus preserved till wanted, or it is 

 immersed at certain seasons to protect it from insects that infest 

 ship-yards. 



757. Wood that has been long buried or immersed, finally becomes 

 black and dense, but it retains its texture. Foundations laid upon 

 piles or timbers should of course never be drained, nor should air 

 be ever admitted to them from sewers or otherwise. Washing and 

 immersion in sea-water have been recommended. 



758. Penetration of Liquids, and of Solid Suhdance-s in Solution., 

 This may be secured in a variety of ways, as from simple capillarity 

 by immersion in a cold liquid, or by boiling, or by compression at 

 one end of a piece of timber still covered with its bark, or by first 

 exhausting the air from the pores, and afterwards admitting liquid 

 substances under pressure, or by exposure to antiseptic agents in 

 the form of vapor, generally under pressure, or by absorption in the 

 living trees, by placing liquid substances where they may be taken 

 up as the sap is taken up in the vital process of vegetation. 



759. As penetration under pressure after exhaustion of the air, 

 first proposed by Brfeant, is employed in many processes, the method 

 may be briefly described, as nearly alike in all. A strong and large 

 iron cylinder is constructed, one end of which may be fully opened, 

 or strongly closed, at will. The wood usually first wrought into 

 shape for use, is placed upon a frame, usually running upon wheels, 

 so that it may be easily run into the cylinder and withdrawn with- 

 out displacing the wood piled or fastened upon it. The pressure is 

 generally supplied- by steam, but sometimes by pumps, and its 

 amount is shown by a gauge. The exhaustion is sometimes obtained 



