Descartes, Rene Mechanics 1665 London Thomas Salusbury en desca_mecha_071_en_1665.xml 071.xml

DISCOURSES OF THE MECHANICKS: A MANVSCRIPT of Mon&longs;ieur Des-Cartes.

The Explication.

Of Engines, by help of which we may rai&longs;e a very great weight with &longs;mall &longs;trength.

The Invention of all the&longs;e Engines de­pends upon one &longs;ole Principle, which is, That the &longs;ame Force that can lift up a Weight, for example, of 100 pounds to the height of one foot, can life up one of 200 pounds to the height of half a foot, or one of 400 pounds to the height of a fourth part of a foot, and &longs;o of the re&longs;t, be there never &longs;o much applyed to it: and this Principle cannot be denied if we con&longs;ider, that the Effect ought to be proportioned to the Action that is nece&longs;&longs;ary for the production of it; &longs;o that, if it be nece&longs;&longs;ary to employ an Action by which we may rai&longs;e a Weight of 100 pounds to the height of two foot, for to rai&longs;e one &longs;uch to the height of one foot only this &longs;ame ought to weigh 200 pounds: for its the &longs;ame thing to rai&longs;e 100 pounds to the height of one foot, and again yet another 100 pounds to the height of one foot, as to rai&longs;e one of 200 pounds to the height of one foot, and the &longs;ame, al&longs;o, as to rai&longs;e 100 pounds to the height of two feet.

Now, the Engines which &longs;erve to make this Application of a Force which acteth at a great Space upon a Weight which it cau­&longs;eth to be rai&longs;ed by a le&longs;&longs;er, are the Pulley, the Inclined Plane, the Wedg, the Cap&longs;ten, or Wheel, the Screw, the Leaver, and &longs;ome others, for if we will not apply or compare them one to another, we cannot well number more, and if we will apply them we need not in&longs;tance in &longs;o many.

The PVLLEY, Trochlea.

Let A B C be a Chord put about the Pulley D, to which let the Weight E be fa&longs;tned; and fir&longs;t, &longs;uppo&longs;ing that two men &longs;u&longs;tain or pull up equally each of them one of the