[July 19, 1872: 
y+ r==modulus of light+ ee 
There are, therefore, NINH principal planetary orbital divisions, deter- 
mined mainly by centres of explosive gyration ; NINE successive centres 
of linear oscillation between the modulus of light and the reciprocal of 
gravity ; NINE similar centres between the limit of the Sun’s possible at- 
mosphere and the Sun’s surface; and finally, NINE successive powers of 
NINE, that exert important centrifugal determinations. For we find : 
At 9“? the fulcrum of the solar system, if the planetary masses were 
concentrated in a point at 7. 
At 9 7 is the seat of an explosive oscillation, which would tend to de- 
tach a nebulous ring, with a mass 9 m, provided the centre of oscillation 
of the ring were at the present geometrical planetary mean, 9* 7. For, 
in order that the separation should begin, the velocity of nebular rota- 
tion at the surface of the central body should bear such proportion to 
the mean velocity of revolution in the ring as the radius of the central 
mass to the radius of the ring’s centre of oscillation, and as the velocity 
of virtual revolution at the central surface, to the like velocity at the seat 
of explosion, (1 + 812" ) 
At 917, a planetary mass which was in nebulous condition in the above 
ase, having acquired sufficient central condensation for the detachment 
of an interior planet, would have its fulcrum at the Sun’s surface, if its 
centre of gravity were at the distance of Mercury. The combined effect 
of these two primitive hypothetical breaks is perhaps recorded in the 
solar rotation, which occupies nearly, if not precisely, §X+<729, * the 
planetary orbital time at the Sun’s surface. 
At 9° 7 is the Sun’s surface, the probable seat of many of the explo- 
tions which have lately attracted so much attention. 
At NINE 7, is the first theoretical exterior limit of explosion, in which 
she Sun is central and its opposite surfaces are centres of alternate direct 
and reverse explosive oscillation. Here is, perhaps, the limit of an im- 
portant solar envelope. 
Near Nine times the first exterior limit, or 9’, is the orbit of Mercury. 
Near NINE times the second exterior limit, or 9’7, is the asteroidal 
limit. 
Near NINE times the third exterior limit, or 9'7, is the orbit of 
Neptune. 
Near NINE times the fourth exterior limit, or 9°7, is the centre of Sun- 
ward explosive oscillation which determines the reciprocal of gravity. 
Such considerations, conjoined with the observed increase of spotted 
surface on the side of the Sun next the Earth and most remote from 
other disturbing planets,* seem to furnish a clue to the seclution of the 
Sun-spot mystery. Even if all the planets were so arranged as to be 
either in mutual heliocentric conjunction or opposition, their combined. 
xT 
De La Rue, Stewart and Loewy. Proc. Roy. Soc., xx., 210, sqq. 
ie ss 
