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study. It seeks to avail itself of the perfect astronomy 

 of the solar system to comprehend that of the whole 

 starry firmament, and, from the known dimensions of 

 the one, to measure the unknown dimensions of the 

 other, in the same manner as from the dimensions of 

 the terrestrial globe those of the solar system were dis- 

 covered. The researches on the parallax of the fixed 

 stars, which leads to a knowledge of their distance with 

 regard to us ; the measure of their own movements, and 

 especially that of the motions of the solar sytem ; the 

 system of double and groups of stars, the mutual rela- 

 tions of which would seem to afford evidence of the 

 existence of other solar systems; the study of nebulae ; 

 the changes which certain stars experience in the quan- 

 tity of light which emanates from them; why stars, 

 perfectly known and described in the astronomical cata- 

 logues, have disappeared from their places and been no 

 more seen, while others have appeared in other parts 

 of the heavens, where, if they had existed before, they 

 could not fail to have been discovered ; finally, what is 

 the physical constitution of the universe, and what the 

 universal law which governs it, are the mighty subjects 

 now undergoing investigation investigations which 

 can be rendered successful, only by constant and precise 

 observation of the phenomena of the heavens by means 

 of the most powerful and exact instruments, aided by 

 and kept on a level with the general progress of science 

 and the arts, so that astronomical observations, profiting 

 by an enlightened theory, may reach the highest pos- 

 sible degree of exactness. 



The least civilized Governments have understood the 

 necessity of prosecuting these investigations. Observa- 



