Where timber is exposed to heat and moisture, the albumen or gelatinous matter in the sap-wood speedily putrefies and decomposes, causing what is called rot. The rot in timber is commonly divided into two kinds, the _wet_ and the _dry_, but the chief difference between them is, that where the timber is exposed to the air, the gaseous products are freely evaporated; whilst, in a confined situation, they combine in a new form, viz. the dry-rot fungus, which, deriving its nourishment from the decaying timber, often grows to a length of many feet, spreading in every direction, and insinuating its delicate fibres even through the joints of brick walls. In addition to the sources of decay above mentioned, timber placed in sea water is very liable to be completely destroyed by the perforations of the worm, unless protected by copper sheathing, the expense of which causes it to be seldom used for this purpose. In modern houses the labours of the Builder, the Mason, and the Plasterer, would be of little use unless they were accompanied by that of the Carpenter, since a very large proportion of every building consists of the woodwork of which its interior structure is greatly composed. As it is one of the most useful, so the Carpenter’s may be considered the most ancient of trades, for nearly all other handicrafts require the preparation or manufacture of the materials, but the Carpenter originally found his materials in the forest, and at once set to work to construct various articles from the trunks and stems of the trees best suited for the purpose. We can only imagine one trade older than that of the Carpenter, and that is the Tool Maker, and as the earliest tools, or at all events some portion of them, were probably made of hard wood, the Tool Maker may in some sense be said to have been a Carpenter also. [Illustration: Axe. Adze.] [Illustration: Saw. Compasses. Plumb Rule. Hammer. Square. Mallet.]