Principles of the Nebular Theory. 



263 



given a gaseous diffusion of all matter through all space, and 

 a slow contraction from whatever cause, then there must result 

 an infinite number of separate nebulous masses ; and like the 

 clouds in our atmosphere, they must be irregular in shape, 

 different in size, and at unsymmetrical distances apart. Then, 

 by the action of gravity, those which were near must have 

 fallen into each other, until the resulting masses became so far 

 apart as to be beyond each other's sensible gravitation. But 

 when one nebula fell into another it could never fall in the 

 direction of the centre of gravity, because it must have been 

 at the same time under the gravitating influence of other 

 neighbouring nebulae drawing it from a direct line and causing 

 it to strike obliquely. If we strike a suspended ball in the 

 direction of the centre, it will fly straight onward ; but strike 

 it obliquely, and it will spin round. In like manner, from the 

 oblique falls of the nebulae every resulting mass would rotate. 



A small nebula striking a large one very obliquely would 

 cause a rotation only on the surface. Moreover clouds have 

 high prominences, long projecting arms, and extended out- 

 liers ; all these in falling to the level of rotundity would also 

 be under the influence of other neighbouring nebulae; and 

 therefore they would fall obliquely and cause surface-currents. 

 These surface-currents, by the composition of forces, would 

 unite in one current ; and this one resulting surface-current 

 would be the rotation of the globe. But all surface-currents 

 would be retarded by friction on the next interior layers ; 

 still the momentum of rotation would not be lost. What was 

 lost by the exterior would be gained by the interior, until the 

 resulting mass rotated, however slowly. 



Secondly. However slowly rotation might begin, the force of 

 gravity would hasten its velocity until on the equatorial zone the 

 centrifugal would equal the centripetal force. — In consequence 

 of the contraction of the nebulous globe, and of a very slow 

 rotation, a particle at A (fig. 1) would move in the direction 



from A to C. It would there- 

 fore move in the direction of 

 an inclined plane, and gra- 

 vity would increase its velo- 

 city downwards. All the 

 other particles on the surface 

 represented by dots on the 

 outer circle would also move 

 down in the inclined plane 

 directions toward the centre; 

 and all would be hastened 

 alike by the same force of 

 gravity. There would be no 

 actual inclined planes, for 



Fig. 1. 



