xri 



THE I'UOGRESS OF 



In cases where an experiinentuni rrucis cannot 

 be resorted to, there is often a great want of 

 conclusive evidence. This is tin- cast; in agri- 

 rulture, in medicine, in political economy, &c. 

 To make one experiment similar to another in 

 all respects but one, is what tho czperimentttm 

 crucis, and the principle of induction, in general, 

 requires. But this, in the sciences just named, 

 can seldom be accomplished. Hence the great 

 difficulty of separating the causes, and allotting 

 to each its due proportion of the effect. Men 

 deceive themselves in consequence of this con- 

 tinually, and think they are reasoning from fact 

 and experience, when, in reality, they are draw- 

 ing their conclusions from a mixture of truth 

 and falsehood. Facts so incorrectly apprehended 

 only serve to render error more incorrigible. 



Of the twenty-seven classes into which instantia 

 are arranged by Bacon, fifteen address them- 

 selves immediately to the understanding; five 

 serve to correct or inform the senses ; and seven 

 to direct the hand in raising the superstructure 

 of art on the foundation of science. The examples 

 which we have selected, are from the first of these 

 divisions. The other two arc of inferior importance, 

 and may be omitted in this imperfect summary. 



Such are the rules laid down by Baron for 

 prosecuting the sciences by induction. The 

 effects which were ultimately produced by the 

 Novum Organum must have been very great. It 

 may be questioned, indeed, whether those who 

 have contributed most effectually to the advance- 

 ment of the sciences, have ever rigidly adhered 

 to Bacon's rules. And, in general, such a rigid 

 adherence is unnecessary ; because so much 

 assistance can, in general, be derived from what 

 knowledge has been already acquired, that a 

 rigid natural historical detail of all the pheno- 

 mena becomes unnecessary. It was only in the 

 infancy of science that such details were requisite. 

 Boyle often draws them up in his inquiries into 

 the cause of various phenomena, and his in- 

 vestigations were of considerable use in forward- 

 ing those branches of science which he cultivated. 

 Bacon also was mistaken in conceiving that, by 

 investigation, mankind may become acquainted 

 with the essences of the powers and qualities 

 residing in bodies. So far as science has hitherto 

 advanced, no one essence has been discovered, 

 either as to matter or as to any of its more 

 extensive modifications. Thus we are still in 

 doubt whether heat and electricity be qualities or 

 substances. Yet we have discovered many im- 

 portant properties or laws, by means, of which 

 heat and electricity, whether properties or sub- 

 stances, are regulated. And from this know- 

 ledge, probably, we derive as much advantage as 

 could be obtained from a complete knowledge of 

 their essence. 



Such are the two methods of advancing science. 

 By experiment or observation all the new facts 

 in every science are acquired. By the applica- 

 tion of mathematical reasoning to these facts 

 they are reduced to the requisite simplicity, and 

 the general principles which regulate every par- 

 ticular science determined. Let ns now en- 

 deavour to trace the progress which has been 

 made in the different physical sciences since 

 these two powerful means of advancement were 

 fairly applied to them. 



I. MECHANICS. 



Stevinus, an engineer in the Low Countries, is 

 the first person who passed beyond the point at 

 which the ancients had stopped, by determining 

 accurately the force necessary to sustain a body 

 on a plane inclined at any angle to the horizon. 

 This knowledge he seems to have deduced from 

 the fact, that a chain laid on an inclined plane, 

 with a part of it hanging over at top in a per. 

 pendicular line, will be in equilibrio if the two 

 ends of the chain reach down exactly to the 

 same level. The first appearance of Stevinus's 

 solution of this problem was in the year 1585. 

 His works, as we now have them, were collected 

 after his death by his countryman, Albert Gerard, 

 and published at Leyden in 1634. 



But the man to whom mechanics is indebted 

 for the first great steps which it made in advance 

 is Galileo, who was born at Pisa in the year 

 1564, and who is, perhaps, the most remarkable 

 man that appeared in that age, so prolific in men 

 of first-rate genius. In 1592 he published a 

 treatise, Delia Scienza Mechanica, in which he 

 has given the theory not only of the lever, but 

 also of the Inclined plane and screw, and in 

 which he laid down this general proposition, 

 that small weights are able to move large ones 

 only by a great increase of velocity, or that 

 weights are in equilibrio when the weight of 

 each multiplied into its velocity is the same. 



While a student at Pisa, he had made experi- 

 ments on falling bodies, and discovered the fact 

 that light and heavy bodies fall to the ground in 

 the same time, making allowance for the resist- 

 ance of the air. From observing the vibrations 

 of the lamps in the cathedral he had come to 

 this very important conclusion, that great and 

 small vibrations of the pendulum are performed 

 in the same time, and that this time depends 

 only on the length of the pendulum. 



These experiments drew upon him the dis- 

 pleasure of his masters, who were offended that 

 he should consult nature and experiment instead 

 of Aristotle, and their commentaries on the 

 dogmas of the Grecian sage. This was the origin 

 of those persecutions, proceeding from a mixture 



