114 CLASSICS OF MODERN SCIENCE 

 were connected together. Without entering into any kind of cal- 

 culation, it is evident that a certain degree of light within a very small 

 space, joined to the particular shape this object presents to us, which 

 is nearly round, and even in its deviation consistent with regularity, 

 being a little elliptical, ought naturally to give us the idea of a con- 

 junction in the things that produce it. And a considerable addition 

 to this argument may be derived from a repetition of the same 

 phenomenon, in nine or ten more of a similar construction. 



When Dr. H. examined the cluster of stars, following the head of 

 the Great Dog, he found on March 19, 1786, that there was within 

 this cluster a round, resolvable nebula, of about 2' in diameter, and 

 nearly an equal degree of light throughout. Here, considering that 

 the cluster was free from nebulosity in other parts, and that many 

 such clusters, as well as such nebulae, exist in divers parts of the 

 heavens, it seemed very probable that the nebula was unconnected 

 with the cluster; and that a similar reason would as easily account 

 for this appearance as it had resolved the phenomenon of the double 

 star near e Bootis ; that is, a casual situation of our sun and the two 

 other objects nearly in a line. And though it may be rather more 

 remarkable, that this should happen with two compound systems, 

 which are not by far so numerous as single stars, we have, to make 

 up for this singularity, a much larger space in which it may take 

 place, the cluster being of a very considerable extent. 



On February 15, 1786, Dr. H. discovered that one of his planetary 

 nebulae had a spot in the centre, which was more luminous than the 

 rest, and with long attention, a very bright, round, well-defined centre 

 became visible. He remained not a single moment in doubt, but 

 that the bright centre was connected with the rest of the apparent 

 disc. October 6, 1785, he found a very bright, round nebula, of 

 about 1%' in diameter. It has a large, bright nucleus in the middle, 

 which is undoubtedly connected with the luminous parts about it. 

 And though we must confess, that if this phenomenon, and many 

 more of the same nature, recorded in the catalogues of nebulae, 

 consist of clustering stars, we find ourselves involved in some diffi- 

 culty to account for the extraordinary condensation of them about 

 the centre; yet the idea of a connection between the outward parts 

 and these very condensed ones within, is by no means lessened on 

 that account. 



