1878.] 703 
[|Chase, 
the system, and with a mean radius vector = VU, + 2/, (34.4845), the 
orbital period of Neptune would be 73966 days. Two successive subsi- 
dences (34,4845 -- n*) would bring the solar nucleal surface to about 2 of 
3, or 54.53 solar radii. The angular acceleration of rotation, due to sub- 
sequent nucleal contraction, would Therefore, when the Sun had 
pe 
contracted to its present limits, its rotation period would be 73966 —~ 54.53? 
- = 24.88 days.* 
If this were the only coincidence of its kind we might, perhaps, have 
some good grounds for looking upon it as merely curious and accidental. 
But the bond of connection, which we have already found between rota- 
tion and revolution, in the limiting formative undulations which are prop- 
agated with the velocity of light, may prepare us for accepting evidences 
of a similar bond in the phenomena of nebular subsidence. 
There are three other known systems of cosmical rotation, which may 
help us to judge as to the rightfulness of such an acceptance, viz.: that of 
the extra-asteroidal planets, with an estimated average period of about 10 
hours ; that of the intra-asteroidal planets, with an estimated period of 
about 24 hours, and that of the moon, with a synodic period of 29.5306 
days. If these periods are dependent upon the same subsidence which 
led to the early belt formations, we may reasonably look for evidence of 
that dependence of a character similar to that which we have found in the 
case of the sun. 
We have seen that the first subsidences from 2 VU and 2 2/, account for 
the orbital ruptures of Jupiter and the Earth ; secondary subsidences from 
points within the orbital belts, account for these three rotation periods. 
For 7, + n = 101.73 solar radiiand Jupiter’s orbital revolution (4332.585 
dy.) = 101. 73? = 10h.05 ; G, -+ m = 19.66 solar radii and Earth’s orbital 
revolution (366.256 dy.) - 19.66? = 24h.205; ), += 5.442 Earth’s 
radii and Earth’s rotation X 5.442? = 29.619 dy. In these accordances we 
have additional evidence of the equality of action and reaction. 
The normal character of rotation is still further traceable, even after the 
formation of the subordinate planets in the two principal planetary belts. 
If we seek the point of incipient condensation, which would lead to such 
rotation periods as have been generally assigned by astronomers to the 
different planets, we readily find that Gummere’s criterion, Newton’s third 
fe eee ee 
law, and the law of equal areas, lead to the formula 7 ( ; N eae in 
J 
‘ 
=These relations may have an important bearing on Croll’s hypothesis of 
the origin of solar radiation. In the stellar-solar paraboloid, of which traces still 
exist between Sun and «@ Centauri, there must have been frequent collisions. 
Some of Croll’s critics have shown strange misapprehensions as to the possible 
velocity of collision. The limit of possible relative velocity, from the simple 
cravitation of two equal meeting masses, is 2 VY 2gr. This would be equivalent, 
taking the values of g and7 at Sun’s apparent surface, to .017747, or more than 
750 miles per second. If projection were added to gravitation, or if the two 
masses had small solid nuclei of great density, while the greater part of their 
volume was gaseous, or if there were a large number of equal masses, the limit 
of possible velocity might be largely increased. 
