vegetable tissue compressed into a given space, in the first construction of the tree, but also on the quantity and quality of the secretions ultimately lodged in it. The same species of tree will present a difference in this respect, according to the country or situation where it grew, and also according to the character of the seasons during the time it flourished. According to the nature of the tree, if placed in favourable circumstances in reference to soil and weather, it invariably prepares and lodges in the stem those principles which it was designed to elaborate--the oak preparing tannin--the sugar-maple preparing its saccharine juice. That the primary object of these was some advantage to the tree itself can scarcely be doubted, but the secondary applications of which they are capable, give reason to suppose that these also were contemplated in their formation. The consideration of the means by which they are formed, and the direct consequences of their formation on the air, by abstracting certain elements from it, and supplying others, belong to the subject of leaves; it is the object of the present paper to view them as formed, and to show their amazing utility. The mechanical properties of the stems of trees, both exogenous and endogenous, render them extremely serviceable to mankind. The uses to which a single species of plant may be put are numerous and important, of which the reed (arundo phragmites) is an example, for after the root has assisted in binding and consolidating the soil, the stem is susceptible of the most varied applications[A].