io8 



LECTURES AND ESS A YS 



the column ought to sink, for the less 

 will be the weight of the air over head. 

 He caused a friend to ascend the Puy 

 de Dome, carrying with him a barometric 

 column; and it was found that during 

 the ascent the column sank, and that 

 during the subsequent descent the column 

 rose. 



Between the time here referred to and 

 the present, millions of experiments have 

 been made upon this subject. Every 

 village pump is an apparatus for such 

 experiments. In thousands of instances, 

 moreover, pumps have refused to work ; 

 but on examination it has infallibly been 

 found that the well was dry, that the 

 pump required priming, or that some 

 other defect in the apparatus accounted 

 for the anomalous action. In every case 

 of the kind the skill of the pump-maker 

 has been found to be the true remedy. 

 In no case has the pressure of the 

 atmosphere ceased ; constancy, as re- 

 gards the lifting of pump-water, has been 

 hitherto the demonstrated rule of nature. 

 So also as regards Pascal's experiment. 

 His experience has been the universal 

 -experience ever since. Men have climbed 

 mountains, and gone up in balloons ; 

 but no deviation from Pascal's result has 

 ever been observed. Barometers, like 

 pumps, have refused to act ; but instead 

 of indicating any suspension of the 

 operations of nature, or any interference 

 on the part of its author with atmospheric 

 pressure, examination has in every in- 

 stance fixed the anomaly upon the 

 instruments themselves. It is this weld- 

 ing, then, of rigid logic to verifying fact 

 that Mr. Mozley refers to an " unreasoning 

 impulse." 



Let us now briefly consider the case 

 of Newton. Before his time men had 

 occupied themselves with the problem of 

 the solar system. Kepler had deduced, 

 from a vast mass of observations, those 

 general expressions of planetary motion 

 known as " Kepler's laws." It had 

 been observed that a magnet attracts 

 iron ; and by one of those flashes of 

 inspiration which reveal to the human 

 mind the vast in the minute, the general 



in the particular, it had been inferred 

 that the force by which bodies fall to 

 the earth might also be an attraction. 

 Newton pondered all these things. He 

 looked, as was his wont, into the dark- 

 ness until it became entirely luminous. 

 How this light arises we cannot explain ; 

 but, as a matter of fact, it does arise. 

 Let me remark here, that this kind of 

 pondering is a process with which the 

 ancients could have been but imperfectly 

 acquainted. They, for the most part, 

 found the exercise of fantasy more 

 pleasant than careful observation and 

 subsequent brooding over facts. Hence 

 it is that, when those whose education 

 has been derived from the ancients speak 

 of " the reason of man," they are apt to 

 omit from their conception of reason one 

 of its most important factors. Well, 

 Newton slowly marshalled his thoughts, 

 or, rather, they came to him while he 

 " intended his mind," rising like a series 

 of intellectual births out of chaos. He 

 made this idea of attraction his own. 

 But, to apply the idea to the solar system, 

 it was necessary to know the magnitude 

 of the attraction, and the law of its 

 variation with the distance. His con- 

 ceptions first of all passed from the 

 action of the earth as a whole to that of 

 its constituent particles. And persistent 

 thought brought more and more clearly 

 out the .final conclusion, that every par- 

 ticle of matter attracts every other particle 

 with a force varying inversely as the 

 square of the distance between the 

 particles. 



Here we have the flower and outcome 

 of Newton's induction ; and how to 

 verify it, or to disprove it, was the next 

 question. The first step of the philo- 

 sopher in this direction was to prove, 

 mathematically, that if this law of attrac- 

 tion be the true one, if the earth be con- 

 stituted of particles which obey this law, 

 then the action of a sphere equal to the 

 earth in size on a body outside of it is 

 the same as that which would be exerted 

 if the whole mass of the sphere were 

 contracted to a point at its centre. Prac- 

 tically speaking, then, the centre of the 



