212 



NOTICES OF AUTHORS. 



strength will sometimes vary as much as 3, 2, 1; 

 that is, a beam, say 2 inches square, and 4 feet long, 

 taken from near the root, when horizontally placed, 

 and resting only at each end, will support three 

 times as much as a like beam in like position from 

 near the top of the tree, although both are equally 

 clear of knots or cross section of grain. This is par- 

 ticularly manifest in large fast-grown silver fir and 

 old ash, and the difference is always greatest in old 

 trees. He will also find that the position of the 

 beam, in respect to the layers being circular round 

 the heart, flat, on edge, or at an angle, has consider- 

 able influence, and, should he inquire farther, will 

 perhaps notice, that the timber from different sides 

 of the tree is not always alike strong ; that one speci- 

 men of timber will be superior to another, both being 

 moist, and inferior to it when both are dry, and that 

 also, as in No. 1, the tree at the same height on the 

 same side, will contain timber diff^ering in strength 

 fully one half, and not always diminishing in strength 

 from the heart outwards, even in hard wood. We 

 are well pleased with one gentleman of the Navy 

 Dock-yard, who naively admits, that he is incompe- 

 tent to decide on these subjects, having been alto- 

 gether devoted to the mathematical, in estimating 

 the strain and resistance timber suffers under dif- 



