VOL. LXXIV.] PHILOSOPHICAL TRANSACTIONS. Q\"J 



assumed point, and cut off by the bounds of the stratum. Thus, in fig. 7, let 

 s be the place of an observer ; srrr, srrr, lines in the planes rsr, rsr, drawn from 

 s within the stratum to one of the boundaries, here represented by the plane ab. 

 Then, since neither the situation of s, nor the form of the limiting surface ab, 

 is given, we are to assume a point, and apply to it lines proportional to the 

 several gages that have been obtained, and at such angles from each other as 

 they may point out ; then will the termination of these lines delineate the boun- 

 dary of the stratum, and consequently manifest the situation of the sun within 

 the same. But to proceed. 



If the sun should be placed in the great sidereal stratum of the milky way, 

 and, as we have surmised above, not far from the branching out of a secondary 

 stratum, it will very naturally lead us to guess at the cause of the probable mo- 

 tion of the solar system : for the very bright, great node of the Via Lactis, or 

 union of the two strata about Cepheus and Cassiopeia, and the Scorpion and 

 Sagittarius, points out a conflux of stars manifestly quite sufficient to occasion 

 a tendency towards that node in any star situated at no very great distance ; and 

 the secondary branch of the Galaxy, not being much less than a semi-circle, 

 seems to indicate such a situation of our solar system in the great undivided 

 stratum as the most probable. 



What has been said in a former paper on the subject of the solar motion, 

 seems also to support this supposed situation of the sun ; for the apex there as- 

 signed lies nearly in the direction of a motion of the sun towards the node of 

 the strata. Besides, the joining stratum making a pretty large angle at the 

 junction with the primary one, it may easily be admitted that the motion of a 

 star in the great stratum, especially if situated considerably towards the side far- 

 thest from the small stratum, will be turned sufficiently out of the straight di- 

 rection of the great stratum towards the secondary one. But I find myself in- 

 sensibly led to say more on this subject than I am as yet authorized to do ; I 

 will therefore return to those observations which have suggested the idea of ce- 

 lestial strata. 



In my late observations on nebulae 1 soon found, that I generally detected 

 them in certain directions rather than in others ; that the spaces preceding them 

 were generally quite deprived of their stars, so as often to afford many fields 

 without a single star in them ; that the nebulae generally appeared some time after 

 among stars of a certain considerable size, and but seldom among very small 

 stars ; that when I came to one nebula, I generally found several more in the 

 neighbourhood ; that afterwards a considerable time passed before I came to 

 another parcel ; and these events being often repeated in different altitudes of 

 my instrument, and some of them at a considerable distance from each other, 

 it occurred to me, that the intermediate spaces between the sweeps might also 



VOL. XV. 4 K 



