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CONCLUSION. 



IN concluding the uranological part of the physical description 

 , of the universe, in taking a retrospect of what I have attempted 

 (I do not say accomplished), after the execution of so difficult 

 an undertaking, I think it necessary once more to call to mind 

 that this execution could have been effected only under those 

 conditions which have been indicated in the Introduction to 

 the third volume of Cosmos. The attempt to carry out such 

 a cosmical treatment of the subject is limited to the repre- 

 sentation of space and its material contents, whether aggre- 

 gated into spheres or not. The character of the present 

 work differs therefore essentially from the more comprehensive 

 and excellent elementary works on astronomy which the various 

 literatures of modern times possess. Astronomy, as a science, 

 the triumph of mathematical reasoning, based upon the sure 

 foundation of the doctrine of gravitation and the perfection of 

 the higher analysis (a mental instrument of investigation), 

 treats of phenomena of motion measured according to space and 

 time ; locality (position) of the cosmical bodies in their mutual 

 and perpetually- varying relations to each other ; change of form, 

 as in the tailed comets ; change of light, as the sudden appear- 

 ance or total extinction of the light of distant suns. The 

 quantity of matter present in the universe remains always the 

 same ; but from what has already been discovered in the 

 telluric sphere of physical laws of nature, we see working in 

 the eternal round of material phenomena an ever-unsatisfied 

 change, presenting itself in numberless and nameless combina- 

 tions. Such an exercise of force by matter is called forth by 



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