182 PHILOSOPHICAL TRANSACTIONS. [^ANNO 1787. 



westward, returning to the east in the evening ; a very small breeze. A little be- 

 fore 2 o'clock p. M. observed as follows. There was a very large circle or halo 

 round the sun, within which the sky was thick and dusky, the rest of the hemi- 

 sphere being clear ; and, a little more than 4- way from the horizon to the zenith, 

 was a beautifully enlightened circle, parallel to the horizon, which went quite 

 round, till the two ends of it terminated in the circle that surrounded the sun j 

 where, at the points of intersection, they each formed a luminous appearance 

 about the size of the sun, and so like him when seen through a thick hazy sky, 

 that they might very easily have been taken for him. Directly opposite to the sun 

 was a luminous cross, in the shape of a St. Andrew's Cross, cutting at the point 

 of intersection the horizontal circle, where was formed another mock sun, like 

 the other two mentioned above. The two lower limbs of the cross appeared but 

 faintly a little way below the circle, the two higher reached a good way above the 

 circle towards the zenith very clear and bright. In this horizontal circle, directly 

 half-way between the sun of the cross and those at the ends of the same circle, 

 were other two mock suns, of the same kind and size, one on each side ; so 

 that in this horizontal circle were 5 mock suns, at equal distances from each 

 other, and in the same line the real sun, all at equal heights from the horizon. 

 Besides these meteors, there was, very near the zenith, but a little more towards 

 the circle of the real sun, a rainbow of very bright and beautiful colours, not an 

 entire semi-circle, with the middle of the convex side turned towards the sun, 

 which lowered as the sun descended. This phenomenon continued in all its 

 beauty and lustre till about half after 2. The cross went gradually off first ; then 

 the horizontal circle began to disappear in parts, while in others it was visible ; 

 then the 3 mock suns farthest from the sun, the 2 in the sun's circle continuing 

 longest ; the rainbow began to decrease after these ; and last of all the sun's 

 circle, but it was observable at 3 o'clock, or after it." 



IX. Observations of the Transit of Mercury, May 4, 1786, at Dresden, By 

 M. Kohler, Inspector of the Mathematical Repository of the Elector of 

 Saxony, p. 47. 



Apparent time. 



Qh 21™ 54^ beginning of the planet's egress, doubtful. 



9 25 23 complete egress, or last contact, very certain. 



The telescope with which Mr. Kohler observed, was a Q-feet refractor of 

 Dollond's, magnifying 104 times. He made a comparison of his observation 

 with that of Alexander Aubert, Esq. from which he inferred the longitude of 

 Dresden to be 54™ SO'.Q east of Greenwich. 



