Figs. 8 and 9 show how a vessel with a leak at first fills very rapidly, so that the crew, finding they cannot gain on the water with the pumps, take to their boats. But if they would remain they would find after a while that the quantity entering would be less as the surfaces without and within became more nearly equal, and that the pumps would now be able to prevent it from rising higher. The water would also begin to reach light wooden work, empty chests, and water-casks, which would give buoyancy, and thus the ship could be kept afloat longer than the crew at first expected. In this connection he calls attention to the Chinese method of water-tight compartments which Mr. Le Roy had already adopted in his boat on the Seine. Fig. 12 is intended to show the loss of power in a paddle-wheel because the stroke from _A_ to _B_ is downward and from _D_ to _X_ upward, and the only effective stroke is from _B_ to _D_. A better method of propulsion, he thinks, is by pumping water out through the stern, as shown in Figs. 13 and 14. Figs. 15, 16, 17, 18, 19, 20, 21, and 22 illustrate methods of making floating sea anchors by which to lay a vessel to in a gale. Fig. 24 shows how a heavy boat may be drawn ashore by bending the rope from _C_ to _D_. Fig. 23 represents a new way of planking ships to secure greater strength, and Figs. 26 and 27 are soup-dishes which will not spill in a heavy sea. But this delightful letter is published in all of the editions of his works, and should be read in order to render his ingenious contrivances intelligible. Among the few of Franklin’s writings on scientific subjects which are not in the form of letters is an essay, entitled “Peopling of Countries,” supposed to have been written in 1751. It is in part intended to show that Great Britain was not injured by the immigration to America; the gap was soon filled up; and the colonies, by consuming British manufactures, increased the resources of the mother country. The essay is full of reflections on political economy, which had not then become a science, and the twenty-second section contains the statement that there is no bound to the productiveness of plants and animals other than that occasioned by their crowding and interfering with one another’s means of subsistence. This statement supplied Malthus with the foundation for his famous theory that the population of the earth increased in a geometrical ratio, while the means of subsistence increased only in an arithmetical ratio, and some of those who opposed this theory devoted themselves to showing error in Franklin’s twenty-second section rather than to disputing the conclusions of Malthus, which they believed would fall if Franklin could be shown to be in the wrong.