The cost of timber, which enters so largely into the cost of a house, is in a great degree the cost of transport. In countries where there are great forests, timber-trees are worth nothing where they grow, except there are ready means of transport. In many parts of North America, the great difficulty which the people find is in clearing the land of the timber. The finest trees are not only worthless, but are a positive incumbrance, except when they are growing upon the banks of a great river; in which case the logs are thrown into the water, or formed into rafts, being floated several hundred miles at scarcely any expense. The same stream which carries them to a seaport turns a mill to saw the logs into planks; and when sawn into planks the timber is put on shipboard, and carried to distant countries where timber is wanted. Thus mechanical aid alone gives a value to the timber, and by so doing employs human labour. The stream that floats the tree, the sawing-mill that cuts it, the ship that carries it across the sea, enable men profitably to employ themselves in working it. Without the stream, the mill, and the ship, those men would have no labour, because none could afford to bring the timber to their own doors. [Illustration: Timber Rafts of the Tyrol.] What an infinite variety of machines, in combination with the human hand, is found in a carpenter's chest of tools! The skilful hand of the workman is the _power_ which sets these machines in motion; just as the wind or the water is the power of a mill, or the elastic force of vapour the power of a steam-engine. When Mr. Boulton, the partner of the great James Watt, waited upon George III. to explain one of the improvements of the steam-engine which they had effected, the king said to him, "What do you sell, Mr. Boulton?" and the honest engineer answered, "What kings, sire, are all fond of--_power_." There are people at Birmingham who let out _power_, that is, there are people who have steam-engines who will lend the use of them, by the day or the hour, to persons who require that saving of labour in their various trades; so that a person who wants the strength of a horse, or half a horse, to turn a wheel for grinding, or for setting a lathe in motion, hires a room, or part of a room, in a mill, and has just as much as he requires. The _power_ of a carpenter is in his hand, and the machines moved by that power are in his chest of tools. Every tool which he possesses has for its object to reduce labour, to save material, and to ensure accuracy--the objects of all machines. What a quantity of waste both of time and stuff is saved by his foot-rule! and when he chalks a bit of string and stretches it from one end of a plank to the other, to jerk off the chalk from the string, and thus produce an unerring line upon the face of the plank, he makes a little machine which saves him great labour. Every one of his hundreds of tools, capable of application to a vast variety of purposes,