CELESTIAL CHEMISTRY. 227 



SPECTRUM OF THE NEBULA m ORION. 



At the meeting of the Royal Astronomical Society, March 10, 

 1865, Mr. Huggins observed that " the recent examination of the 

 great nebula in Orion shows that this large and wonderful object 

 belongs to the class of gaseous bodies. The light from this 

 nebula resolves itself, under the refractive power of the prism, 

 into the same three bright lines. With a narrow sUt they appear 

 exceedingly thin and well-defined. The intervals between them 

 are dark, and in the light from no part of this nebula was any 

 indication detected of a continuous spectrum, such as is charac- 

 teristic of incandescent solid or liquid matter. Different portions 

 of this great nebulous mass were brought successively upon the 

 slit, but the results of minute examination showed that the whole 

 nebula emits light, which indicates a constitution identical 

 throughout the body. The light from one part differs from that 

 of another in intensity alone. 



" The four bright stars of the trapezium, and other stars distrib- 

 uted over the nebula, gave a continuous spectrum. According 

 to Lord Rosse and Prof. Bond, the brighter parts near the tra- 

 pezium consist of clustering stars. If this be the true appearance 

 of the nebula under great telescopic power, then these discrete 

 points of light must indicate separate and probably denser por- 

 tions of the gas, and that the whole nebula is to be regarded 

 rather as a system of gaseous bodies than as an unbroken vapor- 

 ous mass. Since the usually received opinion of the enormous 

 distances of the nebulge has no longer any foundation to rest ujion, 

 in respect of the nebulae which give a gaseous spectrum, it is 

 much to be desired that proper motion should be sought for in 

 such of them as are suitable for this purpose. If the gaseous 

 matter of these objects represented the ' nebulous fluid,' out of 

 which,' according to the hypothesis of Sir William Herschel, stars 

 are to be elaborated, we should exj^ect a spectrum on which the 

 groups of bright lines wei-e as numerous as the dark lines due to 

 absorption found in the spectra of the stars. If the three bright 

 lines be supposed to indicate matter in its most primary forms, 

 still we should expect to find in some of the nebula, or in some 

 parts of them, indication by a more complex spectrum, of an 

 advance in the formation of the separate elementary bodies which 

 exist in the sun and in the stars. A progressive formation of 

 some kind is, however, suggested by the presence in many of the 

 nebulae of a nucleus, the spectrum of which indicates that it is 

 not pure gas, but contains solid or liquid matter. It may, there- 

 fore, be, that nebulas which have little indication of resolva- 

 bility, and yet give a continuous spectrum, such as the Great 

 Nebula in Andromeda, are not clusters of suns, but gaseous 

 nebulas, which, by the gradual loss of heat, or the influences of 

 other foi'ces, have become crowded with more condensed and 

 opaque portions. 



" So far as my observations extend at present, they suggest the 

 opinion that the nebulse which give a gaseous spectrum are sys- 



