WITH A FOURTEEN FEET REFLECTOR. 169 



speculum near it, although it did not prevent a very perfect definition of the 

 discs of large stars, was yet apt to throw around them flitting rays and burrs 

 of light, sometimes hiding very close or faint companions. By a skilful appli- 

 cation of diaphragms, these might be so far annihilated as to afford a good 

 separation of such stars as a Coronse Borealis, ^ Orionis, fi" Bootis, y Virginis, 

 ;i Ophinchi, and others of less than 1" in distance, but the loss of light by this 

 mode of proceeding was a serious inconvenience. On objects as ill-defined as 

 nebulae, however, the full light of the telescope could be employed to the ut- 

 most advantage. It was not long before a strict scrutiny revealed to us many 

 particulars concerning the nebulsB of the elder and younger Herschels, which 

 it was obvious that they had not noticed, and in some instances spaces of nebu- 

 lous matter of great extent, connected with well known nebulae, but altogether 

 overlooked by former observers. These considerations decided the application 

 of the instrumental power we had obtained to this interesting field of inquiry. 



6. The nebulae which are the subjects of the present paper are 1991, 2008, 

 2092 and 2093 of Sir J. F. W. Herschel's large catalogue, (Phil. Trans. 1833.) 

 These are, in reality, but three, since 2092 and 2093, as will be shown' in this 

 paper, are but parts of one very extensive nebula, united by a long, irregular 

 band of very faint nebulous matter. These three nebulae are among the most 

 interesting objects in the heavens; perhaps, with the exception of Nebula 

 Orionis and Nebula Andromedae, the most so. They are represented in Plates 

 IV., VI., and VII., with the stars in and near them, visible in the fourteen feet 

 telescope. The number of objects examined is small, in order that the utmost 

 accuracy in the delineation of the peculiar features and minutiae of these ne- 

 bulae, attainable by protracted scrutiny, might be aimed at. This must still 

 be limited by the unavoidable errors of judgment and the power of the tele- 

 scope. It is hoped, however, that by this means something has been done to 

 supply, in the examination of these nebulae, the place of measurement in that 

 of double stars, and to put in our possession data by which future changes, if 

 there be any, can be recognised and detected in at least a few of these wonder- 

 ful sidereal systems. 



7. The first intention was to intrust entirely to careful estimation the copy- 

 ing of the stars which were to form the ground-work of the nebula, since no 

 means of measurement were then at hand. The following is a sketch of the 

 course of procedure adopted in pursuance of this plan. The limits of the 



VII. — 2 s 



