12 



BULLETIN 604, IT. S. DEPARTMENT OF AGRICULTURE. 



Table 9. — -Results of strength tests on incense cedar and associated species as 

 compared with longleaf pine. 



Species. 1 



Specific 

 gravity 

 (based 



on 

 volume 

 when 

 green). 



Bending. 



Modulus of 

 rupture. 



Pounds 



per 

 square 

 inch. 



Per 



cent. 



Modulus of 

 elasticity. 



Thou- 

 sands 



of 

 pounds 



per 

 square 

 inch. 



Per 



cent. 



Maximum 

 crushing 

 strength (par- 

 allel to grain). 



Pounds 



per 

 square 

 inch. 



Per 

 cent. 



Longleaf pine 2 (Pinus palustris) 



Douglas fir (Pseudotsuga tarifolia) 



Incense cedar (Libocedrus decurrens) 



White fir (Abies concolor) 



Sugar pine (Pinus lambertiann) 



Western yellow pine (Pinus ponderosa) . 



0.528 

 .418 

 .363 

 .350 

 .360 

 .377 



9,070 

 8,280 

 6,040 

 5,970 

 5,270 

 5,180 



100.0 

 91.4 

 66.6 

 65.8 

 58. 1 

 57.1 



1,540 

 1,597 



754 

 1,131 



966 

 1,111 



100.0 

 103.7 

 48.9 

 73.4 

 62.7 

 72.1 



4,400 

 4,030 

 3,030 

 2,800 

 2,600 

 2,400 



100.0 

 91.7 

 6S.9 

 63.6 

 59.1 

 55.0 



1 Tests made on green specimens 2 by 2 inches and free from all defects. 



s The data on longleaf pine and Douglas fir are from Forest Service Bulletin No. 108; the data on cedar, 

 white fix, sugar pine, and western yellow pine, from Forest Service Circular No. 213. 



Tests on strength in relation to moisture, also made on small pieces, 

 showed that thoroughly dry sapwood and heartwood are each 2.50 

 times as strong as green wood. In these tests the sapwood proved to 

 be slightly stronger than the heartwood at all stages of seasoning. 

 It was not always possible, however, to take the heart and sap speci- 

 mens from immediately adjacent sections of the tree, which might 

 explain this slight difference. 



The average shrinkage in cross section in the above tests, in passing 

 from the green to the thoroughly dry condition, was 9 per cent for 

 the sapwood and 6 per cent for the heartwood. 



DURABILITY. 



Incense cedar is known to be one of the most durable timbers on 

 the Pacific slope. The life of a split heart-cedar fence post is reputed 

 to be from 20 to 30 years, and of rails from 30 to 40, and numerous 

 instances have been cited where they have lasted longer. Sap-cedar 

 posts, on the other hand, are said to last but 5 or 6 years. 



THE TREE. 



GENERAL DESCRIPTION. 



Incense cedar is one of the most characteristic trees of the California 

 forests, its shreddy, deeply furrowed, yellowish-brown or cinnamon 

 colored bark, rapidly tapering bole, and dark-green foliage distin- 

 guishing it at once. It resembles somewhat eastern arbor vitas (the 

 white cedar of the north woods) in its flat sprays of scalelike leaves. 



