HEATING- POWER. 97 



Lanpreclit's investigations into the exceptional durability of 

 some beecbwood give some idea of the value of another method, 

 in which the tree is felled in full foliage and left with its crown 

 on till the wood is dry, and the wood then converted. He 

 reported that twenty houses are still standing at Lenterode in the 

 Harz Mountains which were built 150 to 200 years ago, and the 

 beech woodwork is still undecayed. The wood was felled whilst 

 the foliage was coming out, and the trees remained with their 

 crowns on till the foliage had developed and become completely 

 dry. The wood was then converted and air-dried. 



It may also be remarked that this wood was thoroughly 

 smoke-dried, for there were no chimneys to the houses, and the 

 smoke found its way out, as it could, through the roof. 



Similar results were obtained at Vienna in the case of park- 

 palings prepared from beech-trees felled whilst the foliage was 

 coming out, barked, and left lying till the next spring. They 

 lasted seven to eight years, whilst ordinary beech palings last 

 only about a year without decaying. 



Section XIII. — Heating -Power. 



By the term heating-power of wood, is meant the amount of 

 heat which a certain weight of wood will give out when burned 

 in ordinary stoves. Carbon and hydrogen are the elements of 

 wood which will burn, and when oxidised they pass into the 

 air as carbon dioxide and water, whilst the inorganic elements of 

 wood remain as the ash. 



Since the demands for wood-fuel for smelting ores in con- 

 tinental Europe and in the South of England, which were 

 formerly considerable, have been greatly reduced and forest man- 

 agement is therefore principally occupied in producing timber, 

 the heating-power of wood has only a small influence on its 

 value, though the question is still an interesting one. 



It is a fact that thoroughly lignified woody tissue has the 

 same heating-power for all species of trees, but the varying forms 

 of tissues found in the different species, the addition of resin 

 and other materials, and of water in varying quantity after 

 the wood has been air-dried, cause different woods to have 

 different heating-powers. The fact that the specific gravity of 



VOL. V. H 



