and when so used in decks, flooring, &c., rendering it dangerous to walk upon.
In the transverse section of a tree will be found a number of lines radiating from the centre and presenting a star-like appearance. These are the medullary rays of the botanists, but are best known to carpenters as the silver grain, or felt (a, Fig. 3 ). This peculiarity of appearance is due to thin plates of compressed cellular tissues, which usually run continuously from the pith to the bark. Although, as a general rule, this
FIG. 3.
is the case, yet in some species a secondary series is found, overlapping or scarfing by, but very seldom touching, the primary rays (b, Fig. 3) If, therefore, we carefully examine the smooth surface of a transverse section of the stems of most trees, we can generally trace these thin plates or rays. They can be seen to great advantage in the Beech, and, more or less, in all the varieties of Oak; but they are far less distinct in the Lime, Yew, and Chestnut, and in the Firs and Pines they cannot be traced, although botanists believe them to be present.
Before converting or employing most kinds of woods, particularly in dealing with unseasoned timber, it will be
