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OW ithe PL OUcG HH.. 21

meafure approaches this ftate, and does it the more, the higher it is cultivated, by being pulverifed and cleared of obftruétions. Now, it feems abundantly evident from theory, that, abftraGting from friction, the {um of the refiftance which different wedges, whofe backs are equally thick, meet with in {eparating the parts of any folid body to the fame diftance, muft be nearly the fame. Theory teaches what common. fenfe indeed dictates, that the longer wedge requires lefs force to move it through the fame fpace; but this is a conveniency, or an apparent advan- tage only, and no faving of force upon the whole. Becaufe the longer wedge, in mo- ving through the fame fpace, does not over- come an equal quantity of refiftence. In order to overcome the fame refiftence, the longer; wedge muft move through a fpace at leaft as much greater than the fhorter one, as the length of the former is greater than that of. the latter. So that the gain of force upon the whole will be nothing, as the longer wedge lofes as much one way as it faves another*, This * From the theory of the wedge, the power is to the refiftence as half the back to one of the fides;

confequently,

ee