Relation of Specific Gravity to Rings-Per-Inch in Cottonwood Construction Lumber

Nine hundred paired measurements of specific gravity and rings-per-inch were made on Populus deltoides Bartr. from 15 sawmills scattered over Illinois. Specific gravity was determined by immersion and rings-per-inch counted on the end grain surface of each piece. The data were analyzed statistically. For two rings-per-inch the average specific gravity is 0.412 and for eight rings-per-inch 0.466. Thus the gravity increases as the number of rings-per-inch increase. About 8 percent of the total variation in specific gravity is related to rings-per-inch.

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