THE HOME PITWOOD SUPPLY. 3 



A very considerable difference of opinion appears to exist 

 as to (i) the number of cubic feet or lineal feet of pitwood 

 per ton, and (2) the number of lineal feet of pitwood per cubic 

 foot. 



In neither case is exact calculation possible, seeing that the 

 sizes given always refer to the diameter of the piece at the 

 small end. The cubical contents of the piece will vary according 

 to the form-factor or taper of the prop. Moreover, the average 

 diameter of a prop, say 3 inches at the small end and 3 feet 

 in length, will naturally be less than the average diameter of a 

 3-inch prop of 5 feet in length. It is estimated that for 2 inches 

 and 2^ inches pitwood, a 20 per cent, allowance should be 

 made on the quarter-girth at the small end, a 1 5 per cent, 

 allowance for 3 inches, and a 10 per cent, allowance above that 

 size. 



With regard to the number of cubic feet to a ton, there 

 is room for very wide variation according to the species of 

 timber, and its condition at the moment — whether it is newly 

 felled containing a large amount of water, or has been peeled 

 and dried for some months. It is possible to calculate with 

 fair accuracy the minimum and maximum of cubic feet per 

 ton, but it must be clearly kept in view that in actual practice 

 various intermediate quantities may be got. Figures quoted 

 from actual weighings and measurements, while no doubt 

 perfectly accurate for the particular consignment, cannot 

 necessarily be accepted as conclusive for average results. 



A cubic foot of water weighs 62J lbs., and assuming for 

 the purpose of calculation that timber has the same weight, 

 an addition of say 15 per cent, must be allowed for bark which 

 is not measurable. A further allowance must be made between 

 solid measurement and quarter-girth measurement, represented 

 by the proportion 77-9 : ioo-q. This gives 92-2 lbs. per. 

 cubic foot, quarter-girth measurement, for a specific gravity 

 of i-o, and assuming freshly felled coniferous timber to have 

 a S.G. of '9, the actual weight per cubic foot, quarter-girth, 

 would be 83 lbs. or 27 cubic feet per ton. In the case of peeled 

 timber no bark allowance is necessary, and assuming a S.G. 

 of -6 for fairly well dried pitwood, the weight per cubic foot, 

 quarter-girth, would be 48 lbs., or 46 cubic feet per ton. 



On the basis of these calculations the following table has 

 been prepared. The other figures given are merely a matter of 

 arithmetic. 



