BicKEETON. — On the Birth of Nebidce. 197 



and see, Phcenix-like, new suns arise from those cold masses of ashes, and 

 as he watches the amazing flash of the collision, he may see flights of 

 comets and meteors emerge from the flames and start on their long journey. 

 Travelling on, he may see worlds absorb their enveloping nebular curtains, 

 see others solidifying. In some, witness the garment of organized life 

 gradually extending itself and clothing the surface with vitality ; and should 

 he stay to take a detailed look, he would probably sometimes see forms of 

 life so strange, so weird, that the animated engines of Erewhon would be 

 commonplace compared to them. Is it possible that in some white hot 

 body he would see viscous silicon building itself into complex protoplasmic 

 molecular skeletons, developing organ after organ, and breathing forth its 

 halogen breath ? Perchance he might watch a silicon monster tenderly 

 waiting on a sickly friend, and feeding it with delicately-flavoured molten 

 flint broth. But methinks I hear someone whisper, "I thought so. Un- 

 doubtedly he is mad." So, remembering the fate of Solomon de Cans, and 

 being desirous of retaining my liberty, I conclude by thanking you for the 

 attention with which you have listened to me. 



Akt. XVI.— 071 the Birth of NebidcB. By Prof. A. W. Bickeeton, F.C.S., 

 President of the Philosophical Institute of Canterbmy. 

 [Read before the Philosophical Institute of Canterbury, 3rd July, 1879.] 

 In the following paper I propose to discuss the generic methods by which 

 nebulffi may be produced ; and also attempt to show how the various kinds 

 of nebulae, of definite structm-e, may have had theu' special form given 

 them. 



The word " nebulae," in this paper, will not apply to all gaseous bodies. 

 Thus the Sun is not improbably gaseous, but of such density as to give a 

 spectrum broken only by dark lines. On the other hand, I have shown it 

 is extremely probable, that all space is filled with more or less diffused gas, 

 not dense enough to be considered a nebula. I shall apply the term to 

 bodies rare enough to give a bright line spectrum, and dense enough to be 

 visible in the telescope, or to be associated by gravitation. 



Nebulffi may be formed by the aggregation of very diffused gas, by the 

 volatihzation and diffusion of dense masses, and by dense masses passing 

 into diffused gases, being there volatilized and attractmg gas towards them. 



The conversion of dense bodies into nebulae is probably chiefly effected 

 by impact, as already suggested by Croll and others, but I shaU attempt to 

 show that the ordinary idea of complete impact cannot play such an im- 

 portant part as " partial impact." I have already shown, that the partial 



