248 



Mr. A. Le Sueur on the Spectra of 



[Mar. 3, 



guration and character of the nebula in its proximate neighbourhood. 

 (The trapezium of Orion, as will be seen from observations to be presently 

 recorded, is a case in point.) 



The spectroscope has, however, decided that rj in no way influences the 

 configuration as now seen ; the star is not only apparently but really on a 

 background, if not completely dark, at least free from nebulosity at all 

 comparable to the brighter parts ; moreover the nebulosity at s. end of 

 lemniscate (the shape there is occasionally made out, showing that nebula 

 does exist) is of a similar faint character. 



With this evidence that the eye-view with the 4-feet approaches the 

 actual facts, and a due consideration of those facts, it seems difficult to 

 imagine any conditions of aperture, definition, or other disturbing causes 

 which could produce a view at all approaching to that seen by Sir John 

 Herschel. 



We have therefore evidence of much weight that enormous changes have 

 taken place in this wonderful region. Is not the presence of nitrogen and 

 hydrogen in the star 77 a significant fact in connexion with these changes, 

 which appear to be nothing less than a destruction of nebula specially in 

 its neighbourhood ? 



Orion has been examined with a new and interesting result ; the spectro- 

 scope proves that in and about the trapezium nebula exists comparable 

 with the bright surrounding nebula. 



This observation is rendered easy by the large separation of the stars 

 consequent on great focal length of telescope ; indeed the whole separation 

 of the original image is not required, the observation being made more 

 crucial by a condension of between two and three times; with this arrange- 

 ment the separation is still sufficient, and the advantage is gained of view- 

 ing at the same time the bright surrounding nebula. 



The stars, sharply focused to give a linear spectrum, being threaded on 

 the slit singly or in pairs, or cautiously removed out of the field, it is seen 

 that the bright lines cross the trapezium with little if at all diminished 

 brilliancy. 



The ordinary telescopic view is therefore an erroneous one, produced by 

 the disturbing effect of the bright group. 



Jupiter has been examined (generally on moonlight nights) ; with this 

 object the orginal Cassegrain image is too faint for good work, but by in- 

 terposition of a suitable lens the image is condensed at pleasure within cer- 

 tain limits ; with the light thus increased the Fraunhofer lines G, F, b, E, D 

 are always easily seen, C also easily on a clear night ; the lines to which 

 special attention has been directed are the telluric lines 914 and P38 (for 

 convenience of reference I use throughout the numbers in Mr. Huggins's 



