CHAr. VII.] GRAVITATION AND INERTION. 87 



The string certainly holds the stone in its course as 

 long as the motion lasts, but there the analogy ends. 

 And as regards the centrifugal forces there is no 

 analogy in the two cases, excepting the fact of both 

 tending to carry the revolving body frpm the centre 

 round which it revolves. In the case of the stone, 

 the centrifugal force gives the stone a tendency to fly 

 off at a tangent from the circle in which it is revolved, 

 in the direction of its motion. But, as regards astral 

 gravitation, considered as the centrifugal force which 

 opposes the centripetal force of the earth's gravita- 

 tion : if the moon were not acted on by the revolv- 

 ing force of the earth's gravitation, but only by 

 the direct force, then astral gravitation would tend 

 to carry the moon directly from the earth, not at a 

 tangent to any part of its orl)it : and when in 

 motion, astral gravitation tends to carry the moon 

 off at a tangent from its orbit certamly, but in 

 the opposite direction to that of its motio7i. The cen- 

 trifugal force endeavours to place the moon at c in 

 the higher orbit, c d e, instead of at b ; to which 

 latter it is carried by the revolving force along its 

 orbit from a.^ (Fig. 19, p. 88.) 



^ The reader will observe that the theory of counter-attraction, 

 or astral gravitation, need not be considered to supplant the New- 

 tonian theory of centripetal and centrifugal foi'ces, but rather to 

 define the nature of the latter force ; showing that it is similar to 

 the former : both beiaig gravitation caused by vis-inerti?e, which is 

 just as much the primary cause of the centripetal as of the centri- 

 fugal force. 



The effects are matters of observation, so that the point at 



