52 Vital Physics. 



Let a different mode of illustration be given, that a 

 clear view may be obtained as to what directly as the mass 

 signifies. 



If instead of using the words directly as the mass, it be 

 enunciated that the less of two unequal masses represents 

 the degree of attractive force in operation by the two 

 bodies mutually attracting each other, then a better concep- 

 tion might be obtained ; for the greater mass only attracts 

 the lesser in proportion to the amount of matter the smaller 

 of the two bodies contains, and the attractive force of the 

 greater is only equal to the amount of atoms contained in 

 the less, yet where the sun and moon and earth are in 

 conjunction, as in the spring tides, their mutual attractions 

 are greater than either alone; but this arises from there 

 being two independent centres, both pulling and being 

 pulled one way, combined with the relation of distance, and 

 not from the direct increase of matter represented by the 

 moon, added to that of the earth, simultaneously acting in 

 one direction. 



It need scarcely be added, that directly as the mass and in- 

 versely as the square of the distance only applies to large 

 bodies, when removed beyond a certain and, as yet, unknown 

 distance from each other ; for the action of the pendulum is not 

 only affected by large mountain masses within a given radius 

 from the point of observation, but also by the density of 

 masses beneath the earth's surface, whereby the motion of 

 the pendulum is much affected, in areas no great distance 

 from each other. A very important analysis of this subject 

 has been given by Archdeacon Pratt, of Calcutta, on the 

 deflection of the plumb line in India, caused by the attrac- 

 tion of the Himalaya mountains, and of the elevated 

 regions beyond, and its modification by the compensating 

 effect of a deficiency of matter below the mountain 

 mass. 



