The volume of the nebula after the separation of the ring for the system of Jupiter having been 1,347,380,629,180^{15} cubic miles, this volume has to be condensed into the volume of the Asteroidal nebula of 744,000,000 miles in diameter and consequently of volume of 215,634,925,373,133,820^{9} cubic miles. Then if we divide the first of these volumes by the second, we find the density to have been increased 6·2484 fold, as used above for the average thickness of Jupiter's ring. But the density of the Jovian nebula was 2,794,417,420 times less than water, dividing which by 6·2484 makes the Asteroidal nebula to have been 447,218,905 times less dense than water. This again divided by 773·395 makes it 578,254 times less dense than air, which will give us 0·00047384° as its absolute temperature--or the same as -273·99952616°. Next, from the Asteroidal nebula 774,000,000 miles in diameter, volume of 215,634,925,373,133,820^{9} cubic miles, and density 447,218,905 times less than water, we have to deduct the volume of the whole of the system which in Table No. II. we have supposed to have been 367,792,000,000 cubic miles at density of water. Multiplying this by 447,218,905 we get the volume to have been 164,482,717,200^{9} cubic miles for the ring at the same density as the nebula; so, deducting this quantity from 215,634,925,133,820^{9}, we get 215,634,760,890,416,620^{9} cubic miles as the volume to which the nebula had been reduced by the separation of the ring. For the dimensions of the ring we have the mean diameter of the orbit of the representative Asteroid as 520,600,000 miles, that is twice its distance from the centre of the nebula, which makes its circumference to be 1,635,516,960 miles in length. Dividing then the volume of the ring, which we found to have been 164,482,717,200^9 cubic miles by this length, the area of its cross-section must have been 100,569,251,938 square miles, which divided by the breadth of 171,000,000 miles--the difference between the radii of the Asteroidal and Martian nebula, namely 372,000,000 less 201,000,000--makes the thickness of the ring to have been 588 miles. But the inner having been 6·339 times more than the outer edge, as we shall see presently, the average thickness would be 185 miles. MARTIAN NEBULA.