M* Arago on Utt Physical ConistituHon of the Sum 209' 



itself, non-luminous satellite^ circulates' round the star and-^. 

 eclipses it periodically. 



In accordance with one or other of these suppositions, the 

 light which is exhibited some time before the disappearance 

 or before the reappearance of the star has not issued from 

 all the points of the circumference. Hence, there can be no 

 doubt of the complete neutralisation of the tints of which we 

 have just spoken. 



If a changing star, when examined by a polarizing tele- 

 scope, remains perfectly white in all its phases, we may rest 

 assured that its light emanates from a substance similar to 

 our clouds, or our inflamed gas. Now, such is the result of 

 the few observations that have hitherto been made, and which 

 it >vill be highly useful to complete. This means of investi- 

 gation demands more care, but succeeds equally well, when 

 applied to those stars which experience only a partial varia- 

 tion in their brilliancy. 



The conclusion to which these observations conduct us, 

 and which we may, I think, without scruple generalise, may 

 be announced in these terms : Our sun is a star, and its 

 physical constitution is identical with that of the millions of 

 stars with which the firmament is strewed. 



I have thus endeavoured, according to the plan which was 

 previously assigned me, to give a sketch of all that we now 

 know relative to the volume, the distance, and the physical 

 constitution of the immense globe whence we derive our light. 

 This sketch, in its circumscribed limits, will suffice to unde- 

 ceive those who thought it a duty to call in question the im- 

 portance and the certainty of the results obtained by modern 

 observers. 



If candid, they will recognise, that, in the history of the 

 progress of our knowledge — a progress undoubtedly indefinite 

 — the labours of the astronomers of the nineteenth century 

 will not pass unnoticed. 



As to critics, who have not been inspired by a love of 

 truth, they do not merit a moment's attention from this 



t assembly ; and as for myself, I cannot but despise them. 

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