ANTISEPTIC TREATMENT OF WOOD. 528 



The greater durability of beech is due to the fact, that it 

 absorbs more creosote than oak, but its injection is necessarily 

 more costly. 



Thus with creosote : 



Cost. 



-v. ,/. 



An oak sleeper absorbs . 22 Ibs. 1 3 



A Scots-pine sleeper . 79 24 



A beech sleeper ,, . 79 ,, 24 



So that including the cost of the wood, oak sleepers cost 4s. 

 8<L and beech sleepers 4s. 5<l. each. 



Injection with copper sulphate increases three-fold the 

 durability of spruce and silver-fir. 



The Nodon-Bretonneau method of seasoning wood by 

 electricity was tried in London several years ago, but did not 

 give satisfactory financial results. The system consists in 

 placing the timber to bo seasoned in a large tank and immers- 

 ing all but an inch or two in a solution containing ten per cent, 

 of borax, five of resin, and three-quarter percent, of carbonate 

 of soda. The lead plate upon which it rests is connected with 

 the positive pole of a dynamo, the negative pole being attached 

 to a similar plate, arranged on its upper surface so as to give 

 good electrical contact, and the circuit is completed through 

 the wood. It is stated that under the influence of the current 

 the sap appears to rise to the surface of the bath, while the 

 aseptic borax and resin solution takes its place in the pores of 

 the wood. Tin's part of the process requires from five to eight 

 hours for its completion, and then the wood is removed and 

 dried either by artificial or natural means. In the latter case 

 about a fortnight's exposure in summer weather will complete 

 the process. 



SECTION III. 



ALTERING THE COMBUSTIBILITY OF WOOD, ETC. 



The combustibility of wood is increased always by drying 

 it. Absolutely dry wood has the greatest heating-value. 



