Page:On the economy of machinery and manufactures - Babbage - 1846.djvu/312

278 distance below the surface of the sea, would, in many circumstances, be almost invaluable. Such a vessel, evidently, could not be propelled by any engine requiring the aid of fire. If, however, by condensing air into a liquid, and carrying it in that state, a propelling power could be procured sufficient for moving the vessel through a considerable space, the expense would scarcely render its occasional employment impossible.

(339.) Slide of Alpnach.Amongst the forests which flank many of the lofty mountains of Switzerland, some of the finest timber is found in positions almost inaccessible. The expense of roads, even if it were possible to make them in such situations, would prevent the inhabitants from deriving any advantages from these almost inexhaustible supplies. Placed by Nature at a considerable elevation above the spot at which they can be made use of, they are precisely in fit circumstances for the application of machinery to their removal; and the inhabitants avail themselves of the force of gravity to relieve them from some portion of this labour. The inclined planes which they have established in various forests, by which the timber has been sent down to the water-courses, have excited the admiration of every traveller; and in addition to the merit of simplicity, the construction of these slides requires scarcely anything beyond the material which grows upon the spot.

Of all these specimens of carpentry, the Slide of Alpnach was the most considerable, from its great