3C)3 PHILOSOPHICAL TRANSACTIONS. [ANNO J 783. 



focus, 6.2 inches aperture, and power 227. It extended to all the stars in 

 Harris's maps, and the telescopic ones near them, as far as the 8th magnitude. 

 The catalogue of double stars, which he communicated to the k. s., and the dis- 

 covery of the Georgium Sidus, were the result of that review. His 3d review 

 was with the same instrument and aperture, but with a very distinct power of 

 400, which he had experienced to be much superior to 227, in detecting exces- 

 sively small stars, and such as are very close to large ones. At the same time he 

 had ready at hand smaller powers to be used occasionally after any particularity 

 had been observed with the higher powers, in order to see the different effects of 

 the several degrees of magnifying such objects. He had also 18 higher magni- 

 fiers, which gave a gradual variety of powers from 460 to upwards of 6000, in 

 order to pursue particular objects to the full extent of the telescope, whenever a 

 favourable interval of remarkable fine weather presented a proper opportunity for 

 making use of them. This review extended to all the stars in Flamsteed's cata- 

 logue, with every small star about them, as far as the 10th, 1 1th, or 12th mag- 

 nitudes, and occasionally much farther, to the amount of a great many thousands 

 of stars. To show the practicability of what is here advanced, Mr. H. men- 

 tions, that the convenient apparatus of his telescope is such, that he had many 

 a night, in the course of 1 1 or 12 hours of observation, carefully and singly ex- 

 amined not less than 400 celestial objects, besides taking measures of angles and 

 positions of some of them with proper micrometers, and sometimes viewing a 

 particular star for half an hour together, with all the various powers of his tele- 

 scope. The particularities he attended to in this last review were, 1, the exist- 

 ence of the star itself, such as it is given in the British catalogue. 2. To observe 

 well whether it was double or single, well defined or hazy. 3. To view and 

 mark down its particular colour, whenever the altitude and situation of the star 

 would permit it to be done with certainty. 4. To examine all the small stars in 

 the neighbourhood, as far at least as the 12 magnitude, and note the same par- 

 ticulars concerning them, except the colours, which would have taken up too 

 much time in committing to paper, and be of no very material use. The result 

 of these observations he collects under a few general heads in the following 

 articles. 



1. Stars lliat are lost, or have undergone some capital change, since Flam- 

 steed's time. — In the British catalogue we find 2 remarkable stars of the 4th mag- 

 nitude in the constellation of Hercules, viz. the 80th and 81st. But these are 

 no more to be seen, though often and diligently sought for. — In the northern 

 claw of Cancer Flamsteed has placed 3 stars of the 6th magnitude; they are the 

 53d, 55th, and 5t)th of his catalogue. The latter of them is vanished. We 

 find a very small telescopic star near the place where the 50th should be: this 

 may possibly be the remains of that vanishing star; but that may be ascertained 



