210 THE POPULAR SCIENCE MONTHLY. 



the remaining irresolvability was purely optical, a sufficient amount 

 of negative evidence would probably have always existed to create 

 more than a doubt in the minds of many astronomers. On the dis- 

 covery of spectrum analysis, observers rallied around it, in the hope 

 of finding an escape from the dilemma ; and this new hope has not 

 been disappointed. The continuous spectra of some nebulse prove 

 them to be suns, enveloped in more or less of atmosphere. The 

 broken spectra of other nebulse show that they are in the condition 

 of an incandescent gas. The classification which the spectroscope 

 makes of the nebulae corresponds so well with their telescopic appear- 

 ance as to justify the confidence which one class of astronomers had 

 in their way of deciding on the truth of the nebular hypothesis. 

 While the spectroscope has manifested varieties of material, color, 

 temperature, and consolidation in nebulas and stars, both single and 

 composite, beyond any thing which the perfected telescope could ever 

 have revealed, it has at the same time found enough of earth in all of 

 them to make man feel at home anywhere in the visible universe. 

 The fact that certain well-known substances on this planet pass cur- 

 rent everywhere in Nature, leads irresistibly to the conclusion that all 

 the specimens came originally from the same mint. It is the legiti- 

 mate office of science to reduce the more complex to the simple ; to 

 explain, if possible, the existing state of matter by an anterior state. 

 The nebular hypothesis, which attempts to do this, no longer starts 

 from a conjecture but a reality, viz., the existence of diffused incan- 

 descent vapor ; and science will hold on to it, until a better theory of 

 mechanical development is found. 



An interesting question, which has waited thousands of years even 

 to be asked, and may wait still longer for an all-sufficient answer, re- 

 lates to the motion of what were once called the fixed stars. If num- 

 bers count for any thing, this is the grandest problem which can be 

 presented to the mind of the astronomer. The argument from prob- 

 abilities, which reposes on a substantial mathematical foundation, is 

 loud in affirming some kind of motion, and repudiates the notion of 

 absolute rest. We must place the stars outside the pale of science, 

 and where no process of reasoning can reach them, or we must sup- 

 pose that they subscribe to the universal law of all matter which we 

 know, and exert attractive or repulsive forces upon each other. There 

 may be one solitary body, or more probably an ideal point of space, 

 the centre of gravity of the material universe, around which there is 

 equilibrium, but everywhere else there must be motion. Though 

 distance may reduce the effect of each one of the forces to a minimum, 

 in the aggregate their influence will not be insignificant. The sun 

 must share the common lot of the stars unless we repeat the folly of 

 ancestral science, at which we now smile, and transfer the throne of 

 the heaven of matter from the earth to the centre of our own little 

 system. If the sun move, a new order of parallactic motion springs 



