102 ANNUAL OP SCIENTIFIC DISCOVERT. 



PRESERVING TIMBER. 



M. Lapparent, naval constructor in the French navy, in a recent 

 essay on the preservation of timber, advocates charring its surface as 

 the most effectual way of securing it from rot for a long period. He 

 says : " By charring timber the surface is subjected to a considera- 

 ble heat, the primary effect of which is to exhaust the sap of the 

 epidermis, and to dry up the fermenting principles; in the second 

 place, below the outside layer, completely carbonized, a scorched sur- 

 face is found, that is to say, partly distilled, and impregnated with the 

 products of that distillation, viz., creosote and empyreumatic oils, 

 the antiseptic properties of which are well known. A bench, the legs 

 of which had originally been charred to the depth of nineteen inches, 

 after remaining in the ground eighteen years, near a pond, was dug 

 up, and found to be in such good preservation that it was difficult to 

 get the point of a knife into the extreme end of one of the legs. On 

 the other hand, vine props of oak, driven into the dry soil close by, 

 were rotten in one year." M. Lapparent's method, which is now ap- 

 plied in the French dock-yards, consists in subjecting the timber to a 

 slight carbonization, by means of a jet of common coal-gas. A work- 

 man, says M. Lapparent, can, in an average day's work of ten hours, 

 carbonize a surface of four hundred and forty square feet. In ship- 

 building, gas-charring should be applied to every surface likely to be 

 in contact with moist or stagnant air. In house-building, it should be 

 applied to the beams and joists embedded in the walls or surrounded 

 with plaster ; to the joists of stables, cow-houses, and laundries, which 

 are affected by a warm, moist atmosphere ; and to the wainscotting 

 of ground-floors. For railway-sleepers, charred timber, when scraped, 

 can be painted any color. 



