held together? By the tenacity, or force of cohesion, of the fibres: which is one of the forces in nature, and which we can measure exactly against other mechanical forces, and ascertain how much of any of them it suffices to neutralize or counterbalance.
If we examine any other case of what is called the action of man upon nature, we shall find in like manner that the powers of nature, or in other words the properties of matter, do all the work, when once objects are put into the right position. This one operation, of putting things into fit places for being acted upon by their own internal forces, and by those residing in other natural objects, is all that man does, or can do, with matter. He only moves one thing to or from another. He moves a seed into the ground; and the natural forces of vegetation produce in succession a root, a stem, leaves, flowers, and fruit. He moves an axe through a tree, and it falls by the natural force of gravitation; he moves a saw through it, in a particular manner, and the physical properties by which a softer substance gives way before a harder, make it separate into planks, which he arranges in certain positions, with nails driven through them, or adhesive matter between them, and produces a table, or a house. He moves a spark to fuel, and it ignites, and by the force generated in combustion it cooks the food, melts or softens the iron, converts into beer or sugar the malt or canejuice, which he has previously moved to the spot. He has no other means of acting on matter than by moving it. Motion, and resistance to motion, are the only things which his muscles are constructed for. By muscular contraction he can create a pressure on an outward object, which, if sufficiently powerful, will set it in motion, or if it be already moving, will check or modify or altogether arrest its motion, and he can do no more. But this is enough to have given all the command which mankind have acquired over natural forces immeasurably more powerful than themselves; a command which, great as it is already, is without doubt destined to become indefi-
