554 Transactions. — Miscellaneous. 



73. Gaseous adhesion and many other agencies are at work 

 to cause apsides to rotate. Consequently the larger nebular 

 planets would gradually pick up all matter within the limits 

 of their orbits, thus giving the rough order to the distance of 

 the planets that is commonly known as Bode's law. 



74. In a rotary nebula I have shown that much matter 

 will tend to become meteoric. The absorption by a planet of 

 every meteorite will tend to cause the planet to rotate in the 

 common direction of the nebula, and will cause the axis to 

 tend to become upright on the axial plane. This action will 

 tell most with planets near the centre of the series, such as 

 Jupiter and Saturn, because they will be largely gaseous and 

 in the thick of the meteoric matter. The outer planets will 

 necessarily be almost beyond the region of such influence, 

 while the near ones will have but slight entrapping atmo- 

 spheres, as explained hereafter. 



75. All this exactly accords with the actual inclinations 

 of the axes of the respective planets. 



76. It is probable that the orbits of the planets were ori- 

 ginally much smaller ; but much of the potential energy of 

 dimension would, as they shrank, be converted into energy of 

 rotation, and this, by tidal action, into increased distance 

 from the sun. The same may also be true of the moons. 



77. As the volume of the nebula diminished its tempera- 

 ture would increase. An increased temperature would produce 

 molecular exchanges between the planets and the nebula, and 

 this would most affect the nearer bodies. Thus the near 

 planets would lose all their light atoms by their escape into 

 the surrounding nebula ; whilst, on the other hand, the low 

 velocity of the heavy molecules of the nebula would allow 

 these molecules to be picked up by the planets. 



78. Hence the near or inner planets would be small and 

 dense, as we find them in our solar system, and the outer 

 planets large and less dense, as in reality they are. 



79. The heat of the contracting nebula will tend to increase 

 the temperature of the planets, which would consequently ex- 

 pand. This would lessen their hold upon their light matter in 

 two ways : (1) by the lessened attraction produced by expan- 

 sion, and (2) by the increased velocity of the molecules them- 

 selves. The near planets would consequently be composed 

 almost wholly of the heavy metals. The smaller and hotter 

 any planets were the greater would be their chance of being 

 without atmosphere. The absence of this and the small 

 volume of the planets would lessen their trapping action. 

 Consequently they would not be so upright in their orbital 

 planes as the middle planets. 



80. The distant planets, being almost out of the nebula, 

 would not collect an appreciable quantity of matter ; hence 



