18 



A MANUAL - OF THE CONIFERS. 



" The specimens experimented on were carefully selected from the 

 best description of wood, and free from all defects. Each wood had 

 two trials, and the figures give a mean result. 



" It will thus be seen that none of the Firs experimented on approached 

 in strength either the Douglas Fir or the Pitch Pine, it having required 

 a weight of 280 lbs. to break a small bar of their wood no more than 

 an inch and a quarter square; 168 lbs. broke a piece of British Larch 

 of the same scantling ; moreover, .between the Douglas Fir and the 

 Pitch Pine, whose strength was equal, there was this great difference, 

 that while the latter snapped short under a strain of 280 lbs., the 

 Douglas Fir yielded unwillingly with a rough and long rend." 



The elasticity of Coniferous wood is very considerable. It was 

 observed centuries ago in the Yew, which led to the wood of that tree 

 being employed in making bows for archery. The woods of the common 

 Spruce, Bed and Pitch Pines, and several of the Cypress tribe, are all 

 more or less elastic, which materially enhances their utility in the various 

 purposes of carpentry to which they are applied. The property is, 

 however, most decisively demonstrated by the readiness with which the 

 molecules of the wood receive and transmit the vibrations of sound ; 

 this is especially the case in the Fir and Pine tribe. Professor Tyndall,§ in 

 giving the results obtained by the experiments of Wertheim and Chevandier 

 to determine the velocity of sound through different kinds of wood, 

 shows that the velocity along the fibre of Fir wood is fourteen times 

 the velocity in air; in other words, that whereas sound travels under 

 ordinary circumstances through air whose temperature is 60° Fahr. at 

 the rate of 1,120 feet per second, it travels through Fir wood at the 

 rate of 15,218 feet in the same period of time. Also along the fibre 

 of Pine wood it is ten times the velocity in air. He also further 

 proves the elasticity of Fir wood by a beautiful experiment, || by which 

 musical sounds generated in one apartment of a building were transmitted 

 through a long deal rod and perfectly reproduced in another. The high 

 degree of elasticity in the molecular structure of Fir and Pine wood 

 renders it a suitable material for the construction of certain parts of 



Pinus rigida. f Alies nigra. 



§ Lectures on Souiid, p. 41. 



J Pinus resinosa. 

 Idem, p. 80, 



