270 Physical Principles of the Nebular Theory. 



Cor. 3. — A nebula with a still smaller amount of primitive 

 rotation through its interior would abandon a still smaller 

 amount of its materials toward its circumference, and a larger 

 amount in the neighbourhood of its centre, and would form a 

 sidereal system with very many stars located closely together 

 near the centre. When seen by us obliquely it would be called 

 an elliptical nebula. 



Cor. 4. — A nebula with only a shallow surface-rotation, and 

 no rotation through its vast interior, in the beginning, might 

 collect the most of its materials in one large body at the centre. 

 Its abandoned rings might indeed form millions of stars ; but 

 from a vast distance they would appear as a nebulous haze 

 around the great central body. Such a sidereal system we 

 should call a nebulous star. 



Scholium. — All sidereal systems formed by the action of 

 gravity on slowly contracting nebulous masses must not ne- 

 cessarily have regular forms, either round or elliptical. Thus 

 millions of individual suns may revolve around their common 

 centre of gravity, but be irregularly situated — -just as our own 

 solar system must appear from a distance as a very irregular 

 cluster. 



Cor. 5. — We know of but two forces at work in forming 

 the sidereal, the solar, and the planetary systems — the force 

 causing the condensations, and the force causing the rotations. 

 The condensations were caused by the chemical force, the 

 same as when oxygen and. hydrogen combine and condense 

 into water. The nebular condensations could not have been 

 caused by the radiation of heat ; for when all matter was ex- 

 panded through all space the heat could not radiate away, 

 for there was no other space where it could go. Else- 

 where I have endeavoured to prove that the ancient nebulae 

 were great chemical laboratories, evolving those modifications 

 of matter which we call simple elements, and evolving now 

 the light and heat of the sun and the other stars. 



Cor. 6. — The centrifugal force in astronomy arose from the 

 conversion and conservation of the force of gravity. Faraday, 

 with all the simplicity and directness of great genius, says that 

 " inertia is always a pure case of the conservation of force." 

 Among the stars the centrifugal force, or inertia, sprang from 

 the rapid revolutions ; and the rapid revolutions sprang from 

 gravity. Therefore the centrifugal and the centripetal forces, 

 whose actions are in opposite directions and antagonistic, have 

 the same origin. Among all the cases of the conversion of 

 the physical forces, this is the only one where we can under- 

 stand how it is done. 



Scholia. — The nebular theory, as here expounded, is a very 



