and on the Condition of the Sun's Surface. 9S 



bear no relation to the burning of the carbon, but to the disen- 

 gagement of the nitrogen they must be attributed. 



In other cases dark lines are replaced by bright ones, as in 

 the well-known instance of the electric spark between metallic 

 surfaces. The occurrence of lines, whether bright or dark, is 

 hence connected with the chemical nature of the substance pro- 

 ducing the flame. For this reason they merit a much more 

 critical examination than has been yet given to them, for by 

 their aid we may be able to ascertain points of great interest in 

 other departments of science. Thus if we are ever able to acquire 

 certain knowledge I'especting the physical state of the sun and 

 other stars, it will be by an examination of the light they emit. 

 Even at present, by the aid of the few facts before us, we can 

 see our way pretty clearly to certain conclusions respecting the 

 sun. For since substances which are incandescent, or in the 

 ignited state through the accumulation of heat in them, show no 

 fixed lines, their prismatic spectrum being uninterrupted from 

 end to end, it would appear to follow that the luminous condition 

 of our sun, whose light contains fixed lines, cannot be referred 

 to such incandescence or ignition. At various times those who 

 have studied this subject have offered different hypotheses : one 

 regarding the sun as a solid or perhaps liquid mass in a con- 

 dition of ignition ; another considering the light to be electrical ; 

 a third supposing him to be the seat of a fierce combustion. 

 Of such hypotheses we have given reason for declining the first. 

 Prismatic analysis, which demonstrates no resemblance between 

 the light of the sun and that of any form of electric discharges 

 with which we are familiar, enables us in like manner to reject 

 the second; and upon the whole, facts seem most strongly to 

 prepossess us in favour of the third, in artificial combustions 

 similar fixed lines being observed. If sach is to be regarded 

 as the physical condition of the sun, we can no longer contem- 

 plate him as an immense mass slowly and tranquilly cooling in 

 the lapse of countless centuries by radiation into space, as so 

 many considerations drawn from other branches of science have 

 hitherto led us to suppose, but he must be regarded as the seat 

 of chemical changes going on upon a prodigious scale, and with 

 inconceivable energy. 



If the law designated above, that the more energetical the 

 chemical action in combustion the more refrangible the emitted 

 light, be translated into the conceptions of the uudulatory theory, 

 it not only puts us in possession of a distinct idea of the manner 

 in which the combustive union of bodies is accomplished, the 

 quickness of vibration increasing with the chemical energy, but 

 it also enables us to transfer for the use of chemistry some of the 

 most interesting numerical determinations of optics. 



University, New York, Dec. 10, 1857. 



