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our heavens. That was but one instance, though a striking one, 

 of that mutability to which suns and planets are subject as well 

 as the rocks which form the earth or the weed which grows 

 in their crevices. This constant "becoming" and passing away 

 is the law of the existences which people the infinitude of space 

 above us, no less than of mortality. The question then may be 

 asked out of what do they arise, and into what do they pass ? 

 In what faint nebulous matter do suns have their birth, and into 

 what dust are they at last dissipated. 



Science, as yet, cannot answer this with precision, but there 

 are intimations that at no distant date the problem will be 

 solved. I have taken upon me, therefore, this evening to direct 

 your attention to the dust and gaseous matter of the universe, and 

 to the changes which it undergoes. These clouds of luminous 

 gas or more solid particles we will consider under two aspects, 

 moving and stationary. When in motion we term them comets, 

 when at rest nebulae. Occasionally the astronomer perceives in 

 the far away depths of the sky a small, faintly luminous spherical 

 body. He discovers that it is travelling comparatively slowly 

 towards the sun. As it nears that great controlling mass 

 its velocity is accelerated; at the same time it undergoes 

 extraordinary changes. Jets of luminous cloud are by some 

 unknown forces evolved from the nucleus and driven back like 

 jets of steam from a locomotive on its road. These form what we 

 term the tail. At last a luminous train, attaining perhaps a 

 length of one hundred millions of miles, blazes across the sky. 

 These long filaments of light do not always coalesce with the 

 main portion of the train. This was the case with the great 

 comet of 1858. Two successive appearances of that comet are 

 now on the screen. Those of you who remember it will see but 

 a faint adumbration of its splendour in the picture now before 

 you. All comets, however, do not evolve a tail ; nor are they 

 restricted to one. The comet of 1744 had six tails. Their forms 

 are as singular as manifold. Some have not even a bright nucleus, 

 though the generality of them are so distinguished. In some the 



