80 THE NEBULA IN ANDROMEDA. 



spicuous features were the sudden condensation of light at the 

 centre into an almost starlike nucleus ; the vast number of stars, 

 of every gradation of brilliancy, scattered over its surface, which 

 yet had the undefinable, but still convincing, aspect of not being 

 its components ; and, lastly, what appeared to be a sudden ter- 

 mination of the light on the side of the nebula preceding in right 

 ascension. 



But it was not until the beginning of the autumn that a careful 

 examination was commenced of the regions of the nebula remote 

 from the nucleus. On the 14th of September, a favorable oppor- 

 tunity offered for further investigation. By directing the attention 

 to the preceding portion of the nebula, as it passed the centre 

 of the field of view, it was evident that what had hitherto been 

 regarded as its boundary in that direction was rather a sudden 

 interruption of light, appearing like a narrow, dark band, in which 

 the eye could detect no deviation from perfect straightness, stretch- 

 ing, in the direction of the axis of the nebula, entirely across the 

 field of vision ; exterior to this, with respect to the axis, was 

 another band or canal, closely resembling the former, but some- 

 what less distinct, of equal regularity, and so nearly parallel with 

 it as to make it difficult to decide, by simple inspection, whether 

 they were not perfectly so. What particularly commands admira- 

 tion here is the regularity of structure displayed, — the uniform 

 influence, made manifest to the senses, of the same law over 

 an immensity of space of which the mind can form no adequate 

 conception ; since the distance at which Sir William Herschel 

 places this nebula requires that the length of the interior canal 

 should not be estimated at less than twenty times the distance of 

 Sirius from our system. 



As a groundwork for the delineation of the principal features 



