relating to the Construction of the Heavens . 297 
No. 177 in the third class is “ A very faint nebula of an 
u irregular round figure, about 2 or 3 minutes in diameter." 
See fig. 10. 
The appearance of an irregular round figure necessarily 
requires that the extent of two dimensions of the nebulous 
matter should be nearly equal in every direction at right 
angles to each other. The unseen dimensions may certainly 
be longer or shorter than the visible irregular diameter ; but 
then it must be absolutely extended centrally in the line of 
sight, which is a condition that has no probability in its favour; 
and the greater the number is, of such nebulae, the less is the 
probability that the form of the nebulous matter should be 
irregularly cylindrical, or conical. For, except an irregular 
cylinder or cone, placed in the particular required situation, 
no expansion of the nebulous matter but an irregular globular 
one can be the cause of the irregular round figure of the 
above-mentioned nebulae. Then since the irregular globular 
form has this advantage above the cylindrical and conical 
figure, that it will answer the required end in any situation 
whatsover, it is certainly that which ought to be admitted as 
the cause of the observed appearance. 
This method of reasoning upon the form of the nebulous 
matter from the observed figure of nebulae, will lead us a step 
farther than it might have been supposed. For granting it to 
231. II. 97, 191, 243, 254, 273, 336, 560, 758, 895, 896. hi. 208, 224, 311, 474, 
566, 600, 61 4, 621, 673, 674, 688, 728, 784, 813, 835, 931, 955. 
Twenty one nebula of an irregular round figure of various large sizes. I. 69, 108, 
1 61 . II. 197, 240, 494, 513, 537, 538, 552, 685, 727, 872, 890. III. 426, 447, 
558, 862, 876. V. 7. Connoiss. 70. 
Six nebula of an irregular round figure of a mean diameter from 5 to 5'. III. 1 3 la 
»77> 22 5> 261, 542, 6 ij. 
MDCCCXI. Q q 
