40 Vital Physics. 



is compelled by the greater in proportion to its mass. This 

 latter is, no doubt, the correct interpretation of the facts 

 observed in relation to the oscillations of the pendulum 

 when tried at the base of large mountain masses. 



But it still remains to be asked, Is the Vllth Proposition 

 and its Vllth Theorem, in the third Book of the " Principia," 

 correct according to the advanced state of experimental 

 science or practical chemistry, which runs as follows : 

 " Gravitatem in corpora universa eamque fieri proportion- 

 alem esse quantitati materise in singulis" ?* 



If towards the earth's centre is alone meant, then it may 

 be safely granted that all particles of matter, when removed 

 a given distance from each other, have, or may have, an 

 equal attraction for each other, though this cannot be 

 positively proved as yet. But the mean of the whole will 

 certainly be in the centre, whichever view is correct ; 

 and, for astronomical purposes, the centre is the point in 

 distance from which all objects ought to be calculated. 



But when mutual attraction is insisted upon at any 

 distance, then nothing can be more false than the doctrine 

 of equal attraction ; for the entire science of chemistry rests 

 upon the unequal attraction which given elements have for 

 each other, from the repellent condition in which electric 

 currents, or caloric, places different material substances or 

 atoms towards each other. 



Boyle's experiment, so often cited, of a feather and a 

 sovereign falling simultaneously to the bottom of an ex- 

 hausted tube, connected with an air-pump, appears to settle 

 the whole matter at once, and proves that every particle 

 of matter is equally attracted towards the earth's centre^ 

 Such might do to settle men's minds pleased with toys. 

 But remove all resistance to falling bodies, and the inherent 



Newton's " Principia," third edition, page 403. 



