294 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



object is to dry wood rapidly by this jH-ocess, the treatment is 

 effected simply with water. 



Superficial carbonisation, belonging to the third group, is suitable 

 to hard woods which cannot be impregnated with antiseptic 

 substances. This treatment is of more lasting efficacy. The 

 charring is produced by a flaming jet, which in the current of 

 compressed air forms a kind of blow-pipe and causes a strong 

 disengagement of heat. The flame draws out the water contained 

 in the superficial layers, dries the fermentable portions, car- 

 bonising the external part completely, and it produces a torrefied 

 surface about half a millimetre (^V of an inch) thick, almost 

 distilled and impregnated with the products of this distillation, 

 which are empyreumatic creosoted substances. 



Di-ying with smoke is effected in a chamber of masonry heated 

 by the combustion of moist sawdust, which yields a thick smoke, 

 but renders the wood useless for many industries, on account of 

 its disagreeable odour and the slight i^esistance of its fibres, which 

 have undergone some change. 



None of these processes, except that of Nodon and Bretonneau, 

 solves in an entirely satisfactory manner the problem of the rapid 

 drying of wood or the complete penetration of antiseptic or fire- 

 proofing products. They have succeeded in utilising electricity 

 for modifying the constituents of the sap. 



The working of this process is quite simple. The apparatus 

 consists of vats of cement or wood, which are tilled with the 

 solution employed for the treatment of the wood. This may be 

 antiseptic, or formed of salts for rendering the wood uninflam- 

 mable. That in use at Aubervilliers is a solution of crystallised 

 magnesium sulphate (80 parts water, 20 magnesium sulphate) 

 heated to 35° C. (95° Fahr.), in which the wood is immersed. This 

 bath may be used indefinitely, provided it is regenerated with 

 ma^^nesium sulphate. About every month the bath is brought to 

 the boiling point in order to coagulate and readily separate the 

 organic matters proceeding from the wood. 



Before the solution of magnesium sulphate was employed, other 

 baths were experimented with, which were abandoned on account 

 of practical objections, such as the deposit of resinous matter on 

 the surface of the wood, which had to be removed by scraping and 

 washin", or on the fibre itself, which quickly blunted the tools 

 employed in working the wood. 



In the treatment with the magnesium sulphate the continuous 



