18, 5 Valencia: Commercial Philippine Timbers 491 
marines, Albay, Samar, Leyte, Samal, Agusan, Zamboanga; 
but there is reason to believe, from commercial specimens, that 
it is more widely distributed than botanical collections made up 
to date would indicate. The amount of yakal in the Islands is 
estimated by Foxworthy ° at 3 per cent of the total volume of the 
commercial forests; of this amount, gisok undoubtedly forms 
a very considerable share. 
The sapwood of gisok is about 8 centimeters thick, light yel- 
low when fresh, often staining in seasoning to a light yellowish 
gray; the heartwood when fresh is only slightly darker, grad- 
ually turning on exposure to a deep yellowish brown; it is very 
hard, very heavy, tough, and almost impossible to split in a 
radial direction, being strongly cross-grained. For a hard wood, 
it is not difficult to work, except that the crossed grain makes 
it difficult to plane radial sections. It is very durable, even 
when exposed to the weather or in contact with the ground, 
being destroyed very slowly by fungi and rarely attacked even 
by termites, but is poor in salt water, as teredos riddle it in a 
short time. 
Structure.—Pith rays fine, numerous, distinct, light yellow, 
showing clearly against the background of brownish wood tis- 
sue; pores fairly numerous, scattered singly, rarely in groups 
of two or three, frequently with a tendency to form curved 
or oblique lines; soft tissue in rather thin rings about pores, 
sometimes confluent about groups or lines of pores but never 
forming continuous tangential bands; wood tissue very dense and 
homogeneous in appearance, occupying a very large proportion 
of the total area of the cross section and taking a glossy cut 
. under a sharp tool. : 
Gisok (invariably sold and used under the name yakal) is 
used for all kinds of construction where great strength and 
durability are required, except for salt-water piling; for ax, 
peavey, and cant-hook handles, capstan bars, levers of all kinds; 
railroad ties; paving blocks. 
RELATION OF PROPERTIES TO USES ° 
The most important strength values are: For large beams, 
modulus of rupture, modulus of elasticity, and shear ; for long 
columns, modulus of elasticity and crushing strength in compres- 
*Philip. Journ. Sci. § C 13 (1918) 166. 
‘For a more complete discussion see Bull. U. S. Dept. Agr. 556 (1917) 
6, 7. 
