Chase.] i)'-4: [Sept. 17, 



locities of rotation and revolution being the same, we may i-egard her dis- 

 tance as a rotation-unit ; and the distance of Venus's orbit from Earth's, 

 measured in Earth's radii, corresponds with Neptune's distance from Sun, 

 measured in Sun's radii, (6453 at mean distance, 6518 at mean aphelion). 

 Venus's mean distance from Earth being .27667 of Earth's mean radius 

 vector, San's distance is found by dividing Venus's distance by .27667. 



392 X Moon's distance — 93,155,000 miles. 



6453 X Earth's radius -- .27667 = 92,470,000 " 

 6518 X " " ^ -37667 = 93,395,000 " 



Before any physical phenomenon can take place, there must be a physi- 

 cal force to which it can be traced. The first step in creative develop- 

 ment should therefore be the creation of force. The potential energy of 

 a body represents the difference between its present, or actual energy, 

 and the greatest energy of which it is capable. In gravitation it is often 

 referred to the results of a possible fall from the present position to the 

 centre of attraction. If such reference were strictly true, the potential 

 energy would always be infinite ; if it is not true, it is desirable to find 

 at what point increase of energy must cease, and all the energy must 

 become actual. Various essays towards this determination have been 

 made in Electricity and Chemistry ; if all force is unitary in its origin, 

 the most encouraging field for investigation would seem to be the one in 

 which force is manifested on the largest scale — the astronomical field. 



The energy which acts with reference to the Sun as a centre, is shown 

 in two prominent ways ; in planetary revolution, the velocity of which 

 in a circular orbit I will represent by v and in solar rotation or retarded 



a, 



revolution, « Let v be the velocity towards which they both tend, 



and to which they would both be equal if all the potential energy of revo- 

 lution, rotation, and internal resistance could be changed into actual 

 energy, v varies inversely as the square root of radius, while v ^ varies 



inversely as radius, so that if the potential is expressed in units of the 

 radius at which the velocities would become equal, v r, = V'~v~ v ^o 



always being a mean proportional between v^ and Vy This, however, is 

 not the limit of possible energy, for the velocity communicated by infinite 

 fall = ^2 v and a body approaching the centre with that tangential 

 velocity would immediately recede, never to return. /2 v^* may there- 

 fore be called the velocity of dissociation. 



If we suppose a circular orbit to be flattened until it becomes a linear 

 ellipse with the solar focus at one end, the mean orbital velocity through 



2 

 twice the diameter = — ® . If shrinkage or fall continues after v .j^v 



the greater centrifugal force of rotation destroys rotation proper, giving 

 * The superscript line denoting the greatest velocity possible. 



