Vital Physics. 39 



tized iron lay, twenty to sixty feet below the surface of the 

 earth, over a considerable extent of area, in such case tht 

 pendulum (if composed, in parts, of steel), would give a 

 greater result than the exact amount of matter justified. 

 But if it were composed in part of gold, and some large 

 mass of matter of a diamagnetic character were placed in 

 like manner, another source of error would come into play, 

 though not to so great an extent as would arise from 

 magnetized iron acting upon a steel pendulum. 



The fact that greater density of matter over a given area 

 is admitted, as affecting the pendulum in its oscillations, 

 also leads to the examination of another source, not of 

 error, but of misunderstanding, about which the most 

 perfect accord is supposed to exist. Ask two men, perfectly 

 conversant with the subject, " What do you understand by 

 every particle of matter in the universe attracting every 

 other particle, with a force varying inversely, as the 

 square of their mutual distances, and directly as the mass 

 of the attracting particles ?"* 



The answer given is one of the two following : Either that 

 matter in one mass, which is the greater, attracts the 

 matter in the smaller mass, not in relation to the amount of 

 matter in the greater, but in the less mass of matter, 

 because it is equal and mutual (in relation to distance), and 

 the greater mass only attracts in proportion to the amount 

 of atoms contained in the less, and no more, because, to 

 repeat, it is equal and mutual. t Or the following : That it 

 is inversely as the distance and directly as the mass ; and 

 that the smaller mass is, therefore, drawn towards the larger 

 mass, not in proportion to the amount of matter which the 

 smaller mass contains, but according to the plus of matter the 

 larger mass represents over that of the smaller, and so the less 



* Grant's " History of Physical Astronomy," page 26. 

 f See Airy, quoted at page 51. 



