130 
but the central part is of more uniform character. In general, 
however, the nucleus is globular, and remarkable from the 
comparative smallness of its diameter, and its very condensed 
appearance. Either the stars which compose it are few in 
number, or more closely compacted than is usual. 1132, 
M. 98, is a good example: ‘ the long ray is resolved, except 
at the very extremities, with 560 ; the globular nucleus is seen 
with 1280 to consist of very close stars.” 1148, described as 
**a nucleus with two branches, a star north following,” ap- 
peared to Dr. R. as “an irregular ring of stars round a 
brighter group, but having an appendage like that of M. 51, 
in which is the bright star seen by H.” 1357, fig. 37, isa 
similar object, both ‘‘ the ray and appendage being full of 
stars, but the nucleus requires a higher power to resolve it 
than the night will bear.” In 1466, fig. 84, the nucleus pro- 
jects on each side of the ray, so that its diameter must be 
greater than the thickness of the exterior stratum. 
He could not leave this part of his subject without calling 
attention to the fact that no REAL nebula seemed to exist 
among so many of these objects chosen without any bias: all 
appeared to be clusters of stars, and every additional one which 
shall be resolved will be an additional argument against the 
existence of any such. There must always be a very great 
number of clusters, which from mere distance will be irresol- 
vable in any instrument; and if it prove to be the case that all 
the brighter nebulz yield to this telescope, it appears unphi- 
losophical not to make universal Sir J. Herschel’s proposi- 
tion, that “a nebula, at least in the generality of cases, is 
nothing more than a cluster of discrete stars.” 
These observations will suffice to show how much may be 
hoped from this telescope; but they are far from being a fair 
measure of its powers, being made at very low temperatures. 
Almost always the thermometer was at 22° or 20° when they 
ceased working; and on one occasion it was as low as 17° 
the lowest he remembered in Ireland. In such circumstances 
