688 PHILOSOPHICAL TRANSACTIONS. [ANNO 1785. 



remove all doubt on the subject, both by showing the stars in the continuation 

 of the stratum, and by exposing a very strong milky nebulosity beyond them, 

 that could no longer be mistaken for the dark ground of the heavens. 



To these arguments, which rest on the firm basis of a series of observation, 

 we may add the following considerations drawn from analogy. Among the great 

 number of nebulae which I have now already seen, amounting to more than QOO, 

 there are many which in all probability are equally extensive with that which we 

 inhabit; and yet they are all separated from each other by very considerable in- 

 tervals. Some indeed there are that seem to be double and treble; and though 

 with most of these "it may be that they are at a very great distance from each 

 other, yet we allow that some such conjunctions really are to be found; nor is 

 this what we mean to exclude. But then these compound or double nebulae, 

 which are those of the 3d and 4th forms, still make a detached link in the great 

 chain. It is also to be supposed, that there may still be some thinly scattered 

 solitary stars between the large interstices of nebulae, which, being situated so as 

 to be nearly equally attracted by the several clusters when they were forming, 

 remain unassociated. And though we cannot expect to see these stars, on ac- 

 count of their vast distance, yet we may well presume, that their number cannot 

 be very considerable in comparison with those that are already drawn into systems; 

 which conjecture is also abundantly confirmed in situations where the nebulae are 

 near enough to have their stars visible; for they are all insulated, and generally 

 to be seen on a very clear and pure ground, without any star near them that 

 might be supposed to belong to them. And though I have often seen them in 

 beds of stars, yet from the size of these latter we may be certain, that they 

 were much nearer to us than those nebulae, and doubtless belonged to our own 

 system. 



Use of the gages. — A delineation of the nebula, by an application of the 

 gages in the manner proposed in a former paper, may now be attemped, and a 

 table is calculated, and here given, for this purpose. It gives the length of the 

 visual ray for any number of stars in the field of view contained in the 3d column 

 of the former table of gages from -^ to 100000. If the number required be not 

 found in the 1st column of this table, a proportional mean may be taken be- 

 tween the two nearest rays in the 2d column, without any material error, except 

 in the few last numbers. The calculations of resolvable and milky nebulosity, 

 at the end of the table, are founded, the first, on a supposition of the stars 

 being so crouded as to have only a square second of space allowed them; the 

 next assigning them only half a second square. However, we should consider 

 that in all probability a very different accumulation of stars may take place in 

 different nebulae; by which means some of them may assume the milky appear- 

 ance, though not near so far removed from us; while clusters of stars also may 



