86 



STRENGTH OF CONIFEROUS WOOD. 



Pine, Silver Fir and Cembra Pine ; and among the strongest American 

 species are the Douglas Fir, the southern Pitch Pine (Pinus palustris), 

 the Yellow Pine (P. ponderosa), the Noble Fir (Abies nobilis) and 

 Lawson's Cypress. 



The transverse strength of coniferous wood is ascertained by 

 experiment. The results given in the 'following table were obtained by 

 the Timber Inspector to the British Admiralty. Lengths of the wood 

 to be tested were cut seven feet long and two inches square, and 

 placed on supports six feet apart ; water was then poured into a 

 vessel suspended from the middle until the piece broke. English Oak 

 was taken as the standard and valued at I'OOO. 



-M 



Fig. 48. Transverse section of a stem of I'imix l.<ir'-i<>, sho\vii 



A, the end of a year's growth ; B, the beginning of new 



growth ; M, medullary rays ; R, resin-duct, x 150. 



Pitch Pine (Pinus palustris) 

 Dantzic Fir (Pinus sylvestris) . 

 Kauri Pine (Ac/athis australis) . 

 Canada Spruce (Picea niyra) 

 Canada Red-pine (Pinus resinosa) 

 Russian Larch (Larix sibirica) . 



P>y Elasticity is understood the change which the minute Sparta 

 may undergo in shape without fracture of the wood when an 

 external force is exerted upon it. The elasticity of coniferous wood 

 appears to depend in a great measure on what is called " even 

 grain," or uniformity in the size and arrangement of the wood fibre 

 which is greatly dependent on the rate of growth, and this, of 



