From the text: 'The insulating properties of the bark influence the relative resistance of various species of trees. Within a species the tree with the thickest bark is afforded the best protection. Other factors such as bark character and structure are also of significance. Measurements of bark thickness made at 6 inches above ground indicate that chestnut oak and yellow poplar have the thickest bark, scarlet and black oaks are intermediate, and white oak has the thinnest bark. Yellow poplar has an extremely thick layer of moist inner bark which makes for good insulation. White oak bark is soft and flaky, whereas black and chestnut oak bark is hard and firm. The bark of scarlet oak is comparatively smooth, and, although equal in thickness to that of more resistant species, apparently is a better conductor of heat. In addition to growth rate, form, and value of the wood, the relative resistance to basal injury should at present be considered in judging the desirability of a species for timber production in the southern Appalachian Mountains.'