Prof. D. Kirkwood on the Nebular Hypothesis. 1638 
collect into several masses, having orbits nearly identical. “‘ These 
Masses should assume a dpkeeoiaal 
would be 
bj If it be said that the small eccentricities of the planetary or- 
i the approximate coineidence of their planes with that of the 
Solar equator, and the uniformity of direction 1n which the plan- 
ts move, are ultimate facts that the final cause of these arrange- 
* Harte’s Translation of Laplace’s System of the World, ¥ol. ii, note vii, 
