Page:Popular Science Monthly Volume 45.djvu/336

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which obtains between the sap wood and the heartwood in this species.

The ash has certain peculiarities which separate it quickly from the papaw and most other woods. There is, in short, almost as much individuality in the woody tissues as in the foliage or flowers of many trees. Note, for example, the well-marked porous

PSM V45 D336 Radial section of pin oak.jpg
Fig. 6.—Radial Section of Pin Oak.

portions, each ring being made up of two quite distinct parts, namely, the open vascular inner part and the dense fibrous outer portion. This arrangement of substance is conducive to that elasticity so characteristic of the ash, and, together with its medium weight, fits it for very wide and extensive service in implements and other ways.

There is another feature of woods, and one of great value from the artistic as well as economic standpoint, that the solar print illustrates. It is shown in some of its beauty in Figs. 1 and 2, while it fails quite completely in the ash namely, the thin, radiating bands which connect the center of the ste with the periphery and are known to botanists as the medullary rays, and to the workers in wood as the "silver grain." Fig. 4 is here introduced as showing this element of structure in a remarkable manner. The section is of the pin oak, and the lower right-hand corner represents for our purpose the center of the stem. The rings of wood are wide, irregularly scalloped, and show the points of structure previously mentioned in a superior manner. But best of all are the lines shot through the whole timber like rays of light (in the negative. Fig. 5) from the center to the circumference. They introduce another element, which up to this time has been left