120 OF WOOD IN GENEEAL 



As to seasoning, since tinaber loses from f to | or, wlien per- 

 fectly dried, ^ of its weight in the process, and strength and the 

 co-efacient of elasticity vary directly with density, its effect is 



obvious. 



Unfortunately, the systems employed for stating the results of 

 experiments vary almost as much as the dimensions of the speci- 

 mens tested, so that it is a matter of considerable calculation to 

 compare the records of different experimenters. Mr. Sharpies, 

 for instance, defines the co-efficient of elasticity, or rather of longi- 

 tudinal extensibiUty, as the weight in kilograms sufficient to 

 elongate a stick 1 centimetre square to double its original length, 

 were that possible, and states results ranging from 25,699 in Mcus 

 aurea to 165,810 in the Western Tamarack {Ldrix occidmtdlis). 

 To translate his results into the tons per square inch usual in 

 England it is necessary to divide them by 151-1. (See footnote 

 on p. 115.) 



So too while Professor Thurston defines the modulus of rupture 

 as " th^ quantity which represents the stress upon a unit of area 

 of cross-section ... at the instant of breaking under the transverse 

 stress," and Mr. Sharpies expresses this hreahing-weight, as it is 

 generally termed, in kilograms per square centimetre, English 

 writers here also use tons or pounds per square inch. So too 

 Mr. Sharpies gives the resistance to longitudinal pressure, or ultimate 

 weight which a stick will support, in the number of kilograms re- 

 quired to crush a stick one centimetre square by such pressure, 

 while Mr. Laslett terms this vertical strength, and states it in the 

 number of pounds of vertical force required to crush 1 square inch 

 of base. Mr. Sharpies also gives the resistance to indentation or 

 number of kilograms required to sink a punch 1 centimetre 

 square to the depth of 1*27 millimetres perpendicularly to the 

 fibres. 



It is well-nigh impossible to reduce all the results of 

 different experimenters. They will, therefore, be here stated 

 mainly in the form and with the terminology of their respective 

 authors. 



The following symbols will be employed : 



S.G. = Specific gravity, compared to water as 1000. 



W= Weight of a cubic foot in pounds. 



E= Co-efficient of elasticity, stated in tons or pounds per square 

 inch, or in kilograms per square centimetre. 



e'= Elasticity compared to Oak as 1-00. 



^= Transverse strength in pounds per square inch. 



3?'= Transverse strength compared to Oak as 1-00. 



/= Co-efficient of bending strength in tons per square inch. 



