DURABILITY OF WOOD. 75 



hollow cap connected with a force pump is placed over one 

 end and the liquid forced through the cup into the wood which 

 results in forcing- out the sap at the opposite end and replac- 

 ing it with the antiseptic. All the antiseptics mentioned have 

 been used to some extent for this purpose, but for various rea- 

 sons chloride of zinc is now most generally used. Railroad 

 ties properly treated with this material are reported to last 

 twice as long as those not so treated but owing to the abund- 

 ance of cheap timber in this section the necessity for the 

 practice of such economy is not yet apparent here although 

 commonly adopted in Europe. 



In the following table is shown approximately the time 

 fence posts will last in Minnesota. This table is based on 

 practical experience in this state: 



TABLE SHOWING RANGE OF DURABILITY OF FENCE POSTS IN 



MINNESOTA. (Air dry.) 



Red Cedar 30 years. 



White Cedar (quartered 6 in. face) 10-15 " 



White Oak (6 in. round) 8 " 



Red and Black Oak 4 " 



Tamarack (Red wood ) 9 " 



Elm , 6-7 " 



Ash, Beech, Maple 4 " 



Black Walnut 7-10 " 



FUEL VALUE OF WOODS.* 



"The relative fuel values here given are obtained by de- 

 ducting the percentage of ash from the specific gravity, and 

 are based on the hypothesis that the real value of the combus- 

 tible material in all woods is the same. 



"It appears from Mr. Sharpies' experiments that resinous 

 woods give upwards of 12 per cent, more heat from equal 

 weights burned than non-resinous woods; the heat produced 

 by burning a kilogram of dry non-resinous wood being about 

 4000 units, while the heat produced by burning a kilogram of 

 dry resinous wood is about 4,500 units, a unit being the 

 quantity of heat required to raise one kilogram of water one 

 degree centigrade. 



*This article on the fuel value of woods is taken from the "Report 

 of the Tenth Census," by Prof. C. S. Sargent. 



