“Give it string--give it string--gently, gently--now stop; there is no occasion for your running any farther but let out the cord, as long as the kite carries it off vigorously, and keeps it fully stretched; but wind it up the moment its tension is relaxed.” “It is rising very fast,” cried the breathless boy, “but the string burns my hand as it passes through it; I shall not be able to endure the heat.” “Be patient, and let it pass more slowly; put on your glove,” said his father. “Ay, ay; put on your glove,” repeated the vicar; “even Xenophon himself, who declaimed so warmly against the effeminacy of the Persians, for wearing gloves, would scarcely have refused his consent to their use on such an occasion.” “What is it that produces so much heat?” enquired Louisa. “The friction of the string,” replied her father. “Do you not know that carriages frequently catch fire from the friction of their wheels, unless it be prevented by the application of grease?” “Yes,” said Tom; “and I have heard that the natives of some countries kindle their fires by rubbing pieces of wood together.” “The original inhabitants of the new world,” observed his father, “throughout the whole extent from Patagonia to Greenland, procured fire by rubbing pieces of hard and dry wood against each other, until they emitted sparks, or burst into flame; some of the people to the north of California produced the same effect by inserting a kind of pivot in the hole of a very thick plank, and causing it to revolve with extreme rapidity: the same principle will explain how immense forests can have been consumed; for it is evident, that the violent friction of the branches against each other, from the agitation of the wind, would be fully adequate to the production of such an effect.” “You have also an excellent example of the effect of friction in producing heat,” said the vicar, “in the history of the whale fishery; for, in harpooning the fish, unless the sailors observe the greatest caution in letting out the rope, its friction upon the side of their boat will be sure to set it on fire.” “And how do they manage it?” asked Louisa. “As soon as the whale dives,(35) after having been wounded, it draws out the line or cord of the harpoon, which is coiled up in the boat, with very considerable velocity. In order, therefore, to prevent any accident from the violence of this motion, one man is stationed with an axe to cut it asunder, if it should become entangled; while another, with a mop, is constantly cooling with water the channel through which it passes.” “The kite is now at a considerable height,” observed Tom; “but look at the string, how bent it is! I have repeatedly endeavoured to pull it straight, but without success.” “How could you have expected to succeed in the attempt? Consider the weight of such a long line of string.” “Then it is not the pressure of the atmosphere which gives it that curved form?”