66 
LOED OXMANTOWN ON THE GEEAT NEBULA IN OEION. 
great discrepancies exist in almost every part, but these are probably to be attributed 
in a great measure to the difference of power in the instruments used and the amount 
of labour expended on the drawings, as no continuous change seems to be shown by 
them. In the case of the spiral nebula round 108, Bond’s, Lassell’s, and Hunter’s draw- 
ings appear to agree tolerably well, allowance being made for the difference of size of the 
instruments, but when we go back to Herschel’s drawing of 1837 we find a considerable 
discrepancy. Herschel’s drawing of 1825, however, as far as it goes, is in this place 
more like the latter drawings. With regard to the following extremity of the Huyge- 
nian region, all the former drawings, with the exception of Liapounov’s, represent the 
“ Frons” as curving round to meet the proboscis major, which latter also curves round to 
meet the former ; whereas Mr. Hunter represents both these parts as curving slightly in 
the opposite direction. This I am satisfied is their present appearance. If, however, 
the night is not good, they acquire very much the appearance of the other drawings, the 
light of the brighter portions being scattered, to a certain extent, over the intervening 
space. With regard to the shape of the preceding edge of the proboscis, the drawings of 
Herschel (1825), Bond, and Liapounov represent it as of a uniform curve throughout 
the greater part of its length, one elbow only at star 126 being shown in those drawings, 
which extend far enough south ; whereas in the case of the other drawings, more 
powerful means bring out more irregularity of outline. In the case of the Huygenian 
region, Herschel’s drawing (1837) agrees much more nearly with Mr. Hunter’s than 
any of the others, although the interval (30 years) is so much longer than in the case 
of Mr. Bond’s and Mr. Lassell’s drawings (15 and 9 years respectively). 
With reference to the relative brightness of the various parts, I find recorded by Mr. 
Hunter, Feb. 22nd, 1861, “ In bright moonlight the degrees of brightness are — 
“1. The Huygenian region. 
“ 2. The nebulosity immediately south preceding it. 
“3. The Mairian region. 
“ 4. The subnebulous region. 
“ 5. The south Messierian branch, and the nebulosity immediately 
north of the Huygenian region.” 
And again, “ The Observation of February 22nd, 1861, gives very different degrees of 
brightness for the various regions from what they had this season (1863-64). 
“ 1. The Huygenian region. 
“2. The nebulosity immediately south preceding it. 
“ 3. The nebulosity immediately north of it. 
“ 4. Subnebulous region. 
“ 5. The south Messierian branch and the Mairian region nearly equal.” 
Mr. Hunter on two occasions estimated, as nearly as he could, the relative brightness 
of the various masses of nebulosity of the Huygenian region. The following are his 
estimations (see diagram)*. 
* To these estimates we may attach much importance, as Mr. Huntek had the advantage of a considerable 
amount of training as an artist. 
