The American Library of Useful Knowledge, Volume 2 (Google eBook)

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Stimpson, 1831
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Page 194 - A float or large hollow metal ball is placed upon the surface of the water in the cistern. This ball is connected with a lever acting upon some part of the machinery, which controls the power or regulates the amount of resistance, as already explained in the case of the governor. When the level of the water rises, the buoyancy of the ball causes it to rise also with a force equal to the difference between its own weight and the weight of as much water as it displaces. By enlarging...
Page 182 - This is the case when pins, bolts, or nails, are used for binding the parts of structures together ; in which case, were it not for the friction, they would recoil from their places, and fail to produce the desired effect. Even when the wedge is used as a mechanical engine, the presence of friction is absolutely indispensable to its practical utility. The power, as has already been stated, generally acts by successive blows, and is therefore subject to constant intermission, and, but for the friction,...
Page 1 - Thus the organs of sense are instruments by which the mind is enabled to determine the existence and the qualities of external things. The effects which these objects produce upon the mind through the organs, are called sensations, and these sensations are the immediate elements of all human knowledge. MATTER is the general name which has been given to that substance, which, under forms infinitely various, affects the senses. Metaphysicians have differed in defining this principle. Some have even...
Page 38 - Every body must persevere in its state of rest, or of uniform motion in a straight line, unless it be compelled to change that state by forces impressed upon it.
Page 246 - The weights I use are one globule of gold, which weighs one grain ; and two or three others which weigh one-tenth of a grain each ; and also a number of small rings of fine brass wire made in the manner first mentioned by Mr. Lewis, by appending a weight to the wire, and coiling it with the tension of that weight round a thicker brass wire in a close spiral, after which the extremity of the spiral being tied hard with waxed thread, I put the covered wire in a vice, and applying a sharp knife which...
Page 246 - ... a grain. For if the thing to be weighed weighs one grain, it will, when placed on one extremity of the beam, counterpoise the large gold weight at the other extremity.
Page 235 - The arms of the lever being equal, it follows that if equal weights be put into the scales no effect will be produced on the position of the balance, and the beam will remain horizontal. If a small addition be made to the weight in one of the scales, the horizontality of the beam will be disturbed ; and after oscillating for some time, it will, on attaining a state of rest, form an angle with the horizon, the extent of which is a measure of the delicacy or sensibility of the balance. As...
Page 210 - This may be accomplished by a wheel bearing on its edge curved teeth, called wipers. The stamper is furnished with a projecting arm or peg, beneath which the wipers are successively brought by the revolution of the wheel. As the wheel revolves, the wiper raises the stamper, until its extremity passes the extremity of the projecting arm of the stamper, when the latter immediately falls by its own weight. It is then taken up by the next wiper, and so the process is continued. A similar effect is produced...
Page 10 - Animalcules have been discovered, whose magnitude is such, that a million of them does not exceed the bulk of a grain of sand ; and yet each of these creatures is composed of members as curiously...
Page 141 - Levers are commonly divided into three kinds, according to the relative positions of the power, the weight, and the fulcrum. In a lever of the first kind, as in Jig. 78., the fulcrum is between the power and weight. In a lever of the second kind, as in fig.

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