WEIGHTS OF WOODS. 41 



quick-growing species, greater in heartwood than in sapwood. 

 Moisture is so far more variable in amount in the same wood, 

 according to the extent to which it has been naturally or 

 artificially seasoned, that no comparison of the weights of different 

 woods can be of any value unless the samples have been kiln- 

 dried, and even by this method it is difficult to secure a uniform 

 elimination of moisture. Many tables have been published giving 

 the density or specific gravity of various woods, their weight, 

 that is, as compared to that of water, to three or even four 

 places of decimals. A more useful form of statement, however, 

 is perhaps the weight of a standard cube, either that of a cubic 

 foot in pounds or that of a cubic decimetre in grams. 1 Thus, 

 while water weighs 62 '321 Ibs. per cubic foot, timbers range from 

 13 to 85 Ibs. per cubic foot. 



They may be grouped from this point of view in the following 

 six grades : 



Approximate weight 



of 1 cubic foot Specific 



in pounds. gravity. 



1. Very Light, - - - not exceeding 24 '26 *4 



Spruce, Willow and most Poplar. 



2. Light, 2430 '4 -5 



Northern Pine, Hemlock Spruce, Linden. Chestnut. 



3. Medium, - ... - - - 3036 '5 '6 



Pitch-pine, Douglas Spruce, Sycamore. 



4. Heavy, 3642 '6 '7 



Most Birch, Beech and Walnut. 



5. Very heavy, 42-48 '7 '8 



Hornbeam, Hickory and good Ash and Elm. 



6. Heaviest, - Above 48 Above -8 



Some Oak, most Teak, Mahogauy, Jarrah, Mora and Greenheart. 



Whilst such kiln-dried weights as those employed here range 

 from a specific gravity of -26 in Ficus aurea, or 13 Ibs. to the 

 cubic foot in Eryihrina suberosa, to 1-3 in Black Iron- wood 

 (Conddlia ferrea), or 85 Ibs. to the cubic foot, as in Anjan 

 (Hardurickia bindta), none of the native woods of temperate 



1 To facilitate the conversion of one measure into the other it may be 

 noted that 1 cubic foot = nearly 28^ (28'315) cubic decimetres, and 1 pound 

 avoirdupois = 453 (453 '592) grams. 



