ICO

HISTORICAL VIEW OP THE

to their senses, and contended that a mass of ten poundsmust, and does, f|ll in one tenth of the time occupiedby the falling of one pound: and, as Galileo had madethem fall in the same time, the only result was an in-veterate hostility against him. About the same timedon Giovanni de’ Medici had projected a scheme forcleansing the port of Leghorn, on which Galileo , beingconsulted, gave an unfavourable opinion, which wasafterwards fully justified by the failure of the plan.

■ This, however, excited violent hatred and machinationsagainst him on the part of the projector, which, in con-junction with the odium already called forth among thescholastics, determined Galileo in quitting Pisa , andtaking a similar situation, just then offered him, atPadua (1592), under the patronage of the state ofVenice.

In this appointment his writings and discoveries mul-tiplied fast ; and, with the prodigality of genius, heallowed many of his researches to get circulated amonghis friends, and even to be published surreptitiously, andclaimed by others as their own, without notice.

In the same year, 1592, Galileo published a treatise“ Della Scienza Mecanica,” in which, after examiningthe theory of the mechanical powers, he lays down thegeneral proposition, that all the advantage given by themis simply this: they make a small force equivalent to agreat one, by causing the former to move over a propor-tionally greater space in the same time. And, in fol-lowing out this principle, he further shows, that if theeffect of a force be estimated by the weight it can raiseto a given height, in a given time, this effect can neverbe increased by any mechanical contrivance whatsoever.He proceeded also to the theory of the oblique leverand tlie inclined plane, though upon principles morepurely mathematical than those of Stevin.

In the theory of motion he had, as we have seen,investigated some of the laws of falling bodies; he ex-tended this enquiry by first assuming that they receiveequal increments of velocity in equal times ; and thence