ADMINISTRATION 111 



tween 60 and 70 per cent. As a result, many 

 manufacturers have remodeled their old kilns to 

 embody the new Forest Service methods. A new 

 method has also been developed for the rapid dry- 

 kilning of Eastern hemlock, which has great com- 

 mercial possibilities. 



Experiments in wood preservation have to do 

 with the kind of preservatives it is best to use, the 

 character of the wood to be treated, and the 

 methods of injection. Experiments have devel- 

 oped the best methods for treating railroad ties, 

 mine timbers, fence posts, wood paving blocks, 

 telephone and telegraph poles, and wharf piling. 

 Untreated mine timbers have been found to last 

 only from 1 to 2 years, while treated ones are 

 usually entirely sound at the end of 4 years. Un- 

 treated railroad ties last from 5 to 10 years, while 

 treated ones will last over 15. Such experi- 

 ments as these have shown the advisability of 

 treating all kinds of timbers with creosote or zinc 

 chloride, or some other preservative. Many new 

 preservatives are being proposed or marketed each 

 year by various companies or individuals. These 

 are all tested to determine their value to prevent 

 the growth of fungi in the wood. Their efficiency 



