190 Processes for Wood-preservation. 



charring is the best method of preserving them. After they have 

 been used several years, they may be taken up, rasped off, burnt 

 over a second time, and again used. The same may be done with 

 beech and other woods, where they have not been thoroughly im- 

 pregnated. 



751. By a process invented by M. de Lapparent (1862) a blow- 

 pipe was devised for carbonizing the outside of railroad ties, under 

 a flame of common burning gas and air, supplied from separate 

 reservoirs, with pipes that unite just as they issue. This process has 

 been largely employed at Cherbourg in preparing wood to resist 

 decay in the French fleet, and a list of twenty-four vessels is given 

 in which this method was used. It has also been employed in Dantzic 

 and Pola. 



752. By an apparatus of more powerful construction, patented by 

 a French engineer, Hugon, in 1864, the flame is supplied from 

 coal-oil. This has been used by the Orleans Eailway Company, and 

 from four sets of apparatus 288 ties could be prepared in a day, at 

 a very low rate, and it is claimed with excellent result. It is also 

 used in preparing telegraph poles. It has been thought that the 

 preservative qualities obtained by partial charring are at least partly 

 due to the formation of creosote in the pores of the wood — a sub- 

 stance known to be one of the best of antiseptic agents. 



753. By painting well seasoned wood with boiled linseed oil 

 thickened with pulverized charcoal, it will last much longer in the 

 ground than without this application. The paint should be allowed 

 to dry before the posts are set. 



754. A coat of hot coal tar and sand may be applied to posts to 

 great advantage before setting them in the ground. The end of 

 the wood should especiallj' be well coated, and the covering should 

 extend a foot above the ground. It is claimed that this is particu- 

 larly valuable when applied to chestnut stakes and posts. 



754. Glauber, in 1657, recommended charring the surface of 

 wood, then covering witli tar, and immersing in pyroligneous acid. 

 He is said to have been the first to recommend the use of tar, which 

 in one form or another has since been employed in very many of 

 these methods for the preservation of timber. 



755. It is said that green Lombardy poplar absorbs boiling coal 

 tar very readily, and acquires thereby very durable properties. It 

 might be tried upon Cottonwood and willow, and for some uses it 



