. Bulletin. Forests and forestry -- United States. EFFECT OF AGE. 17 Logs from the top cau usually be roeosiiizod by the hiiger pereeiitage of sapwood and the sinaller i)rop()itioii and more regular outlines of the bands of sumnierwood, which are more or less wavy in the butt k)gs. Both weight and streugth vary in the different parts of the same eross section from eeuter to periph- ery, aud though the variations appear frequently irregular in single individuals, a detinite law of rela- tion is nevertheless discernible in large averages, and once detern)ined is readily observable in every tree.
. Bulletin. Forests and forestry -- United States. EFFECT OF AGE. 17 Logs from the top cau usually be roeosiiizod by the hiiger pereeiitage of sapwood and the sinaller i)rop()itioii and more regular outlines of the bands of sumnierwood, which are more or less wavy in the butt k)gs. Both weight and streugth vary in the different parts of the same eross section from eeuter to periph- ery, aud though the variations appear frequently irregular in single individuals, a detinite law of rela- tion is nevertheless discernible in large averages, and once detern)ined is readily observable in every tree. A separate inquiry, avoiding the many variables which enter into the mechanical tests, permits the fol- lowing deductions for the wood of these pines, and especially for Longleaf; the data I'eferriiig to weight, but by inference also to strength : 1. The \ariation is greatest in the butt log (the heaviest part) and least in the top logs. •2. The variation in weight, hence also in strength, from center to periphery depends on the rate of growth, the heavier, stronger wood being formed dur- ing the period of most rapid growth, lighter and weaker wood in old age. 3. Aberrations from the normal growth, due to unusual seasons aud other disturbing causes, cloud the uniformity of the law of variation, thus occasion- ally leading to tlie foiiuation of heavier, broad ringed '"^^' wood in old, and lighter narrow-ringed wood in young- trees. 4. Slow-growing trees (witli narrow rings) do not make less heavy, nor heavier wood than thriftily grown trees (with wide rings) of the same age. (See tig. 2.) EFFECT OF AGE. The interior of the butt log, representing the young sapling of less than fifteen or twenty years of age, and the central portion of all logs containing the pith and two to live rings adjoining, is always light and weak. The heaviest wood in Longleaf and Cuban Pine is formed between the ages of fifteen and one hundred and twenty years, with a specific weight of over 0.(50
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