It is not necessary that the substance should be very hard; a cord rubbed backwards and forwards swiftly against a post or a tree will take fire; a stick of wood pressed against another which is turned swiftly about in a lathe, will soon make it turn black and emit smoke. Even the palms of your hands, if you rub them briskly together, when they are dry, will smell as if they were scorched. The method of exciting fire by rubbing two sticks of wood together, was anciently practised by country people, and is still retained in some parts of the world. The manner is exactly described in Captain Cook’s voyage. The inhabitants of New-Holland are there said to produce fire with great facility, and spread it in a wonderful manner. To produce it, they take two pieces of _soft_ dry wood; one is a stick about eight or nine inches long, the other piece is flat. The stick they shape into an obtuse point at one end, and pressing it upon the other, turn it nimbly by holding it between both their hands, as we do a chocolate mill, often shifting their hands up and down, and then moving them down upon it to increase the pressure as much as possible. By this method they get fire in less than two minutes, and from the smallest spark they increase it with speed and dexterity. The matter of fire is attracted more or less by all bodies. When any heated body comes in contact with a cold one, the former loses a part of its heat, and both of them become equally warm. If heated iron is laid upon a stone, its heat will flow into the stone; if thrown into the water, the heat will be diffused through the water. If a number of different substances, as metals, wood, wool, &c, are brought together into a place where there is not a fire, if they are of different temperatures, that is of different degrees of heat, the fire will be attracted from the hottest to those that are colder, till a perfect equilibrium is produced, or till they have all acquired the same temperature, as may be proved by applying the thermometer successively to each of them.