THEIR ARRANGEMENTS AND FORMATION. 11 



exist among the constituents of our system, and further 

 tcking advantage of the light afforded by the ascertained 

 laws of matter, modern astronomers have suggested the 

 follovfllng hypothesis of the formation of that system. 



Of nebulous matter in its original state we know too 

 little to enable us to suggest how nuclei should be estab- 

 lished in it. But supposing that from a peculiarity in its 

 constitution, nuclei are formed, we know very well how, 

 by virtue of the law of gravitation, the process of an ag- 

 gregation of the neighbouring matter to those nuclei 

 should proceed, until masses more or less solid should 

 become detached from the rest. It is a well known law 

 in physics that, when fluid matter collects towards or 

 meets in a centre, it establishes a rotary motion. See 

 minor results of this law in the whirlwind and the whirl- 

 pool — nay, on so humble a scale as the water sinking 

 through the aperture of a funnel. It thus becomes cer- 

 tain that when we arrive at the stage of a nebulous star, 

 we have a rotation on an axis commenced. 



Now, mechanical philosophy informs us that the in- 

 stant a mass begins to rotate, there is generated a tendency 

 to fling off its outer portions — in other words, the law of 

 centrifugal force begins to operate. There are, then, two 

 forces acting in opposition to each other, the one attract- 

 ing to, the other throwing from, the centre. While these 

 remain exactly counterpoised, the mass necessarily con- 

 tinues entire; but the least excess of the centrifugal over 

 the attractive force would be attended with the effect of 

 separating the mass and its outer parts. These outer 

 parts would then be left as a ring round the central body, 

 which ring would continue to revolve with the velocity 

 possessed by the central mass at the moment of separation, 

 but not necessarily participating in any changes after- 

 wards undergone by that body. This is a process which 

 might be repeated as soon as a new excess arose in the 

 centrifugal over the attractive forces working in the pa- 

 rent mass. It might, indeed, continue to be repeated, 

 until the mass attained the ultimate limits of the conden- 

 sation which its constitution imposed upon it. From what 

 cause might arise the periodical occurrence of an excess 

 of the centrifugal force ? If we suppose the agglomera- 

 tion of a nebulous mass to be a process attended by refri- 

 geration or cooling, which many facts render likely, we 

 can easily understand why the outer parts, hardening 



