DECAY OF STRUCTURAL TIMBER. 67 



for too long a period, because, so far as known up to this time, the 

 only safe method for avoiding the chance of getting sap-rotted pieces, 

 such as shown in figure 11, is to chemically treat the wood before the 

 fungus has had an opportunity of getting a foothold. 



Where large timbers are used, it is always well to lessen the chances 

 of internal decay, or so-called dry-rot, by building composite timbers. 

 Some recent striking instances were noted in a large building where 

 12 by 12 inch oak timbers were used for posts and beams. One of the 

 wood-destroying fungi had gained entrance through the lower ends of 

 some of these vertical posts, had grown up through them without any 

 signs on the outside, and had infected the horizontal beams. The 

 decay had proceeded from the cellar to the tenth story of the large 

 factory building. The discovery of the decayed condition was made 

 when a hole was bored into one of the timbers for the purpose of in- 

 serting a screw; the timbers were then removed, and it was found 

 that they had entirely decayed with the exception of a shell of about an 

 inch in thickness on the outside. In reconstructing this building oak 

 timbers were used, but instead of using 12 by 12 inch pieces for posts 

 they were made of four 3 by 12 inch pieces bolted together. The 

 chances for internal decay of such posts will be much lessened. The 

 most efficient method for preventing the decay of timber consists in 

 chemical treatment. References to tins subject will be found in the 

 bibliography appended hereto (12, 13, 14, 15, 28, 29, 64, 81, 85, 86, 

 90, 91, 103, 108). 



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