18 BULLETIN 1050, U. S. DEPARTMENT OF AGRICULTURE. 
Specific gravity. — The ratio of the weight of a piece of wood (or 
other substance), usually oven-dry, to the weight of an equal volume 
of water, with the latter considered as 1. (For most woods the 
specific gravity is less than 1, because they are lighter than water, 
which weighs nearly 62.5 pounds per cubic foot.) 
Storied rays. — Rays arranged in horizontal layers or stories in the 
tree, producing "ripple" marks on tangential faces. (See fig. 12.) 
Summerwood. — The outer, often darker and harder portion of 
each annual ring. 
Tangential. — Along a tangent, or at right angles to the radius. 
Tangential, surface. — A longitudinal surface cut approximately at 
right angles to the rays, equivalent to flat grain or plain-sawed 
surface. 
Tyloses. — Glistening, froth-like ingrowths in the pores of the 
heartwood, closing them up more or less. 
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