TECHNICAL QUALITIES OF THE TREES 



109 



(b) Remedies against destruction are:- Impregnation; painting; charring the part imbedded in the 

 soil; winter cutting; change of species when replacing ties; l<iln drying, steaming and smoking; raising 

 buildings high above ground. 



VIII. Heating power. Heating power or fuel value bears a direct ratio to specific gravity air-dry. All 

 wood fibre having the specific gravity r56, equal weights air-dry of our common species furnish equal 

 heat. On the other hand, light weight means greater inflammability and a quicker heat, which naturally 

 lasts for a short time only. The heating power of hard coal is to that of lignite and to that of wood as 

 5'2:4"3:1. In other words :- 1 pound of hard coal yields as much heat as do r21 pounds of lignite 

 or 52 pounds of wood. 



(a) Influencing factors are found in the following conditions :- 



1. Presence of rosin increases the heating power by about 12 per cent. 



2. A cord of wood containing 45 per cent moisture has, after German experiments, the heating power 

 of half a cord of air dried wood. After Sargent, the discrepancy is not so great. One cord 

 of green wood contains 250 gallons of water, and the calories of heat required to convert this 

 large amount of water into steam are lost to heating purposes. 



3. Unsound wood has a reduced heating power, the cell walls being decayed. 



4. Chestnut, and to a certain extent larch and spruce, are despised in open fires owing to crackling 

 and emission of sparks. Black gum is despised because it is difficult to split and therefore 

 difficult to season. Hornbeam, birch, and alder are said to furnish a particularly quiet flame. 



(b) Schedule of the heating power of wood:- 



(c) Conversion of fuel wood, to serve in the production of energy, into "Wood Producer Gas," 

 is being recommended. A gas engine generator is the means to the end. One cord of pine or Douglas 

 fir wood is said to yield 150,000 cubic feet of wood gas, equal to ri55 kw. hours. 



The cost of a "Wood Producer" gas plant is given as .yl30 per kw. The heat liberated in cooling 

 the gas from r200 down to 70 degrees is said to be sufficient, in addition, to drive the pumps and other 

 equipment connected with the plant. 



IX. Miscellaneous technical qualities of wood. 



(a) Adaptability to planing, molding, and lock cornering; varnishing and polishing; painting and 

 gluing; mortising (bad in rock birch used for hubs, good in oak or beech). 



