6l4 PHILOSOPHICAL TRANSACTIONS. [ANNO ]784. 



of which, to my present knowledge, have been seen before by any person; most 

 of them indeed are not within the reach of the best common telescopes now in 

 use. In all probability many more are still in reserve; and as I am pursuing this 

 track, I shall make them up into separate catalogues, of about 1 or 300 at a 

 time, and have the honour of presenting them in that form to the r. s. 



A very remarkable circumstance attending the nebulae and clusters of stars is, 

 that they are arranged into strata, which seem to run on to a great length; and 

 some of them I have already been able to pursue, so as to guess pretty well at 

 their form and direction. It is probable enough, that they may surround the 

 whole apparent sphere of the heavens, not unlike the milky way, which undoubt- 

 edly is nothing but a stratum of fixed stars. And as this latter immense starry 

 bed is not of equal breadth or lustre in every part, nor runs on in one straight 

 direction, but is curved and even divided into 2 streams along a very considerable 

 portion of it; we may likewise expect the greatest variety in the strata of the 

 clusters of stars and nebulae. One of these nebulous beds is so rich, that in 

 passing through a section of it, in the time of only 36 minutes, I detected no 

 less than 31 nebulae, all distinctly visible on a fine blue sky. Their situation 

 and shape, as well as condition, seems to denote the greatest variety imaginable. 

 In another stratum, or perhaps a different branch of the former, I have seen 

 double and treble nebulae, variously arranged; large ones with small, seeming 

 attendants; narrow but much extended, lucid nebulae or bright dashes; some of 

 the shape of a fan, resembling an electric brush, issuing from a lucid point ; 

 others of the cometic shape, with a seeming nucleus in the centre; or like cloudy 

 stars, surrounded with a nebulous atmosphere; a different sort again contain a 

 nebulosity of the milky kind, like that wonderful, inexplicable phenomenon 

 about G Ononis; while others shine with a fainter, mottled kind of light, which 

 denotes their being resolvable into stars. See fig. 4, &c. 



It is very probable, that the great stratum, called the milky way, is that in 

 which the sun is placed, though perhaps not in the very centre of its thickness. 

 We gather this from the appearance of the galaxy, which seems to encompass 

 the whole heavens, as it certainly must do if the sun is within the same. For, 

 suppose a number of stars arranged between two parallel planes, indefinitely ex- 

 tended every way, but at a given considerable distance from each other; and, 

 calling this a sidereal stratum, an eye placed somewhere within it will see all the 

 stars in the direction of the planes of the stratum projected into a great circle, 

 which will appear lucid on account of the accumulation of the stars; while the 

 rest of the heavens, at the sides, will only seem to be scattered over with con- 

 stellations, more or less crouded, according to the distance of the planes or 

 number of stars contained in the thickness or sides of the stratum. 



Thus, in fig. 5, an eye at s within the stratum ab, will see the stars in the 



