Observations of Nebule and Clusters of Stars. 5 
Thus, with a less expenditure of time and labour, the various details of the process 
were recalled to mind. 
A six-foot speculum was then polished, and if a careful mspection of the surtace 
with the unassisted eye, together with a general impression that the process had 
proceeded in the same manner as had just given good results with the three-fvot, 
rendered it probable that its performance would be good, it was removed from the 
machine to the tube, which was the only place where it could be properly tested, 
there having been for some years no arrangement for testing it in the workshop, and 
even afterwards no sufficiently convenient and expeditious plan. Thus, sometimes 
a speculum would stand every test on occasions when there was exceptionally good 
definition ; at other times after waiting for, say a fortnight, for a test night, it was 
found manifestly inferior to that which had been in use, but which, having become 
somewhat tarnished by exposure, it was not in every instance thought desirable to 
replace in the tube until after some delay it had been repolished. It is not, there- 
fore, surprising that conflicting impressions as to the performance of the six-foot 
reflector should have been formed by persons who had, on one occasion only, an 
opportunity of looking through the instrument. 
ABBREVIATIONS USED IN THE DESCRIPTIONS OF THE NEBULAE AND CLUSTERS. 
alm. almost. | aia irregular figure. 
am. among. I little (adv.) long (adj.) 
app. appended. L large. 
att. attached. m. much. 
b. brighter. M. middle (or in the middle.) 
bet. between. M Messier. 
biN. binuclear. n north. 
B. bright. neb nebula. 
153, 1D), Bonner Durchmusterung. | neby. nebulosity. 
13, Wo Bessel-Weisse. np. north preceding. 
C. considerably. nf. north following. 
com. cometic. nr. near. 
C. compressed. N. nucleus (or to a nucleus. ) 
Cl. cluster. p- preceding. 
dist. distance. p- pretty (before F, B, L, 8, &c.) 
dif. diffused. pg. pretty gradually. 
diffic. difficult. pm. pretty much. 
D. double. ps. pretty suddenly. 
dA. @ Arrest. 12 poor. 
def. defined. | IP, Philosophical Transactions. 
e. extremely. Yr. resolvable (mottled.) 
ee. excessively. rr. partially resolved. 
er. easily resolvable. rrr. well resolved. 
E. elongated (or elongation.) R. round. 
fe following. R. nova. New nebula found at Birr Castle. 
F. faint. Ri. rich. 
g. gradually. s. suddenly. 
g. group (on the diagrams.) s. south. 
CAC: General Catalogue. sp. south preceding. 
H. Sir W. Herschel. sf. south following. 
h. Sir. J. Herschel. SC. scattered. 
inv. involved. st. stars. 
irr. irregular. | sev. several. 
