WEIGHTS AND MODULI. It seems best thus early to introduce the two series of weights and moduli to be employed in the tabu lar descriptions of species that form part of succeeding chapters. Further descriptions and the reasons for preferring these par ticular series of figures will be given later. The figures referred to are as follows: First. Results of experiments conducted by the National Forest Service. These figures occupy the leading spaces in the descrip tions of species (Chapters V, VI, VII, and VIII) under the titles of "Weight," "Modulus of Elasticity," and "Modulus of Rupture." Results have not yet been obtained for all of the species thus de scribed so that some of the spaces set apart for the figures reported for the National Forest Service are vacant.
Second. Results of experiments conducted by the Watertown Arsenal for the Tenth United States Census. These figures appear in the spaces immediately following those occupied by, or set apart for, the National Forest Service figures.
Weights are given in pounds, and coefficients in pounds per square inch. Fractions of pounds and lower figures in coefficients have been omitted as superfluous.' The trunks from which banded woods are obtained grow in thickness from the outside. The new layers of wood are deposited upon the outside of others that were formed before. Practically all of the woods that are used in construction are of this type. The forest sources are widely distributed, and the numerous species present an almost infinite range of possibilities.