Analysis of a course of lectures on natural and experimental philosophy : viz. 1. Properties of matter, 2. Mechanics, 3. Chemistry, 4 and 5. Pneumatics, 6. Hydrostatics, 7. Electricity, 8. Electricity [sic], 9. Optics, 10. Use of the globes, &c., 11 and 12. Astronomy / by A. Walker.

  • Walker, A. (Adam), 1730 or 1731-1821.
Date:
[1795?]
Catalogue details

Licence: Public Domain Mark

Credit: Analysis of a course of lectures on natural and experimental philosophy : viz. 1. Properties of matter, 2. Mechanics, 3. Chemistry, 4 and 5. Pneumatics, 6. Hydrostatics, 7. Electricity, 8. Electricity [sic], 9. Optics, 10. Use of the globes, &c., 11 and 12. Astronomy / by A. Walker. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    C t .-; ] ]>olfed by 4lb. if it be hung on a balance at twice tlie diftance from the fulcrum. Hence the force, or power, of any machine, whether fimple or compound, is eafily computed ; for when two bodies are fufpended upon any machine, fo as to aft agairift one another, if the perpen- dicular afcent of one body, be to the perpendicular defcent of the other in the inverfe ratio of their weights, they will balance one another; and therefore fo much quicker as the power moves than the weight, fo much is the advan- tage gained by the machine, and gives this mechanical anxiom, “ That what is gained in power, by any ma- chine, is loft in time of working it. Sir Ifaac New~ tons. All kinds of mechanical engines confift, more or lefs, of thefe Jlx powers. Viz. the lever, the wheel and axle, the fyjlem of pulleys, the inclined plane, the wedge, and the fcrew. The lever is a bar of wood, or metal, turning upon a prop, or centfe, (commonly called the fulcrum) and is ufed either to raife weights or overcome refiftances. There are three kinds of levers, and in each of them, the velocity of each point is direftly as its diftance from the prop. When this prop is between the weight and the power, ’tis called a lever of the firf kind: and fo much as the power is further from the prop than the weight, (or its center of gravity) fo much is the advantage gained by the power over the weight. Iron crows, fcijfars, pincers, rudders offlips, isic. are levers of the firf kind. A lever of the fecond kind, is when the weight, or rejiflance, is between the prop and the power, as in doors turning on hinges, knives that turn on a centre at the point; oars, fs’e. A lever of the third kind, is when the power is applied between the weight and the prop, ns in rearing a ladder againft a wall; moving our legs and arms by the power of the mufcles, &c. The bended lever differs in nothing from one of the firf kind, but in form, it is like a hammer drawing a nail. In each of thefe levers, fo much as the power moves farther, or ffiorter than the weight, fo is