PRESERVATION OF TIMBER. 



Disease, Cause and Effects. 



The decay of timber is caused by the 

 growth and activities of fungi. The minute 

 spores of one of these fungi, germinating 

 on a piece of wood, send out fine threads, 

 which enter the wood cells and soon give 

 off a complex compound called a ferment 

 or enzyme, which dissolves certain parts of 

 the wood fibre. The dissolved fibre serves 

 as food for the fungus. The threads throw 

 out branches and sub-branches, and soon 

 the timber is permeated by a mass of such 

 threads, the growing parts of which give 

 off ferment. The action of the ferment 

 changes the chemical and physical properties 

 of the wood, rendering it, in some cases, 

 like brown charcoal, in others white, soft 

 and stringy, and the wood is said to be rotten 

 or decayed. Eventually some of the threads 

 grow out from the surface of the timber, and 

 form toadstools and other excrescences. 

 Under these are found cavities containing 

 thousands of spores, which, when ripe, are 

 blown off into the air and settle upon other 

 timbers, where the precess is repeated. 

 Moisture and heat are favorable to the 

 growth of the fungi, as are also the starches, 

 sugars and oils found in the cells of the sap- 

 wood but wanting in the heart wood. If 

 protected from the action of these fungi, 

 wood will last indefinitely. Hence the 

 accumulation of dead wood should be avoided. 

 If air is excluded, as when timber is kept 

 constantly and entirely immersed in salt or 

 fresh water, the fungi cannot thrive. Sap 

 confined in timber with air, ferments, pro- 

 ducing dry rot; as where beams are enclosed 

 air-tight in brick work. etc.. and where 

 green timber is painted or varnished, or 

 treated with creosote, etc. The sap then 

 not noly prevents the thorough penetration 

 of the oil, etc., but may cause the greater 

 part of the wood to rot although its firm 

 outer shell gives it a deceptive appearance 



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