relating to the Construction of the Heavens. 301 
with respect to their figure. These observations will esta- 
blish the former conclusions by an additional number of 
objects, and by the decisive argument of their brightness, 
which points out a seat of attraction. 
In the following four assortments are one hundred and 
fifty nebula?, which all agree in being a little brighter in the 
middle. This increase of brightness must be understood to 
be always very gradual from the outside towards the middle 
of the nebula, whatever be its figure ; and although this cir- 
cumstance, for want of time, has often been left unnoticed in 
the observation, I am very sure that had the gradation of 
brightness been otherwise, it would certainly not have been 
overlooked.* 
III. 853 is “ A very faint small nebula ; it is very gradually 
“ a little brighter in the middle.” 
III. 4,88 is “ A very faint extended nebula, near 3' long, 
* See Thirty two nebulae, the particular figure of which has not been ascertained, 
gradually a little brighter in the middle. II. 201, 401, 424, 444, 457, 528, 532, 6i6 p 
617, 648, 673, 677, 736, 904. III. 90, 106, 148, 331, 436, 472, 489, 519, 596, 633, 
654, 655, 6 56, 686, 853, 860, 896, 978. 
Twenty-four extended nebulae, gradually a little brighter in the middle. II. 184, 
192, 252, 285, 412, 478, 480, 565, 621, 688, 906. III. 14I, 233, 449, 461, 468, 
488, 532, 577, 736, 890. V. 8, 40, 50. 
Twenty nebulae of an irregular figure, gradually a little brighter in the middle. 
II- 357 ’ 4 ° 3 ’ 47 1 ’ 4 8 7 ’ 49 1 ’ 5 2 4 ’ 533 ’ 594 ’ 7 * 7 » 7 2 9 - IH - 2 7 2 ’ 4 28 ’ 434 ’ 6z6 ’ 
690, 857, 903, 947. V. 29. 
Seventy-four round or nearly round nebulae, gradually a little brighter in the mid- 
dle. II. 7, 40, 102, 129, 131, 162, 190, 249, 258, 267, 276, 286, 290, 308, 320, 338, 
428, 459, 474, 476, 477, 509, 516, 526, 602, 637, 699, 726, 737, 770, 780, 797, 81 1, 
8l2. III. 62, 63, 94, I05, 121, 122, I23, I33, l62, £63, 252, 292, 296, 298, 330, 
388, 409, 448, 466, 497, 522, 597,608,665,680, 746, 75O, 753, 8l8, 822, 823, 82,j-, 
858, 867, 889, 89I, 908, 917, 918, 923. 
