Knowledge for the People, Or the Plain Why and Because, Volume 29

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General Books LLC, 2009 - History - 162 pages
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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1832. Excerpt: ... gance, where convenience is a main point, as in a vehicle for travelling. Why should a road up a very steep hill, be made to wind or zig-zag all the way? Because, to reach a given height, the ease of the pull is greater, exactly as the road is made longer. Why is it important to make roads as level as possible? Because, a horse drawing on a road where there is a rise of one foot in twenty, is really lifting one twentieth of the load, as well as overcoming the friction, and other resistance of the carriage.--Arnott. THE WEDGE. Why are cutting instruments, knives, razors, the axe, fyc. examples of the wedge? Because at the same time that we pull them lengthwise, we press them directly forward, against the object A saw, too, is a series of wedges. Why does a razor, (if drawn lightly over the hand) dart into the flesh, whereas, if pressed against the hand with considerable force, it will not enter? Because of the vibration of particles produced by the drawing action, which enables the razor to insinuate itself more easily. We witnessed an example, only a few days since, when a bon vivant, in a fit of mischievous ecstasy, seized a pointless table knife, and passed it very lightly down the back of his friend's coat. The injury was not immediately seen, but the cloth proved cut, from the collar to the waist; whereas, had the knife been heavily pressed against the cloth, the coat would have escaped injury, and the gay fellow the expense of his folly. Why is the wedge so important an agent in the arts and manufactures? Because it exerts enormous force through a very small space. Thus, it is resorted to for splitting masses of timber, or stones. Ships are raised in docks, by wedges driven under their keels. The wedge is the principal agent in the oil-mill. The seed...

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