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REMARKS UPON THE PRESERVATION OF TIMBER. 



The perishable nature of timber when used in the construction of 

 edifices, and the most effectual and expeditious means of preventing 

 its decay, has been a subject of vast interest and importance to the 

 architect. The processes hitherto used of steaming or boiling to 

 create a speedy evaporation of ihe watery part, — " impair the 

 strength and elasticity of the timber," is tedious and attended with 

 much expense, and does not counteract the action of those causes of 

 decay which are inherent in wood and all organized bodies. 



Decay in timber arises from various causes ; if it commence while 

 the tree is standing, it is indicated by the death of some of the upper 

 branches ; by cracks and openings in the trunk, probably from the 

 infiltration of water into the interior ; and often by an unsound root. 

 This kind of decay, which extends from the heart outwards, continues 

 slowly in operation after the tree is cut down. But though this 

 decay is of importance, as there exists an effectual remedy, viz. of 

 cutting down the tree before it has reached its maturity, it is unne- 

 cessary to speak further of it. 



Decay may commence in sound timber from alternate exposure to 

 changes in the weather — to heat and cold — to moisture and dryness. 

 In this case, the process commences outwardly ; and painting or 

 covering the exposed parts with a coating of tar, &c. in some in- 

 stances has prevented, for a time, the progress of this decay, which 

 is termed the common rot. 



As in the common rot, the causes of decay are extrinsic, and are 

 principally brought into action in those parts which are exposed to 

 the vicissitudes of the weather ; widely different are they from those 

 which produce what is commonly termed the dry-rot. The causes 

 which produce this malady are the action of natural properties dis- 

 persed in the outer layers or vegetable parts of the wood, whose 

 decomposing operations soon proceed to the internal layers until the 

 whole structure becomes involved. 



The primary cause producing this disease is the heat accompanying 

 the fermentation of the albumen rousing into action the germs of 

 the fungi ; this vegetable structure, from its nutritious principles being 

 afterwards hollowed out by insects, permits the access of air and 

 moisture into the interstices, and produces what is properly termed 

 the sap-rot, since its elements chiefly abound in the outer layers of 

 the wood. 



