724 PHILOSOPHICAL TRANSACTIONS. [aNNO 1 /Qfj,. 



all conclusions drawn from their action on the thermometer will apply to the in- 

 vestigation of the hrilliancy of the sun. And here the forms laid down by 

 Mr. Mayer, in his little treatise De Variationibus Thermometri accuratiiis de- 

 finiendis,* may be of considerable service to distinguish the regular causes of the 

 change of the thermometer from the adventitious ones, among which I place the 

 probable instability of the sun's lustre. 



Introductory Remarks and Explanations of the Arrangemeiit and Characters used 



in the Catalogue. 



This catalogue contains Q constellations, which are arranged in alphabetical 

 order. I have called the present collection the 1st catalogue. The rest of the 

 constellations, which are pretty far advanced, will be given in successive small 

 catalogues as soon as time will permit to complete them. Each page is divided 

 into 4 columns, the 1st of which gives the number of the stars in the British 

 catalogue of Flamsteed, as they stand arranged in the edition of 1/25. The 2d 

 column contains the letters which have been affixed to the stars. The 3d column 

 gives the magnitude assigned to the stars by Flamsteed in the British catalogue ; 

 and the 4th contains my determination of the comparative brightness of each 

 star, by a reference to proper standards. 



All numbers used in the 4th column refer to the stars of the same constella- 

 tion in which they occur, except when they are marked by tlie name of some 

 other constellation ; and in that case ftie alteration so mtroduced extends only to 

 the single number which is marked, and which then refers to the constellation 

 affixed to the number. To each star which I could not find in the heavens, and 

 which, on examining Flamsteed's observations, appeared never to have been seen 

 by him, I have set down " does not exist." To such as I could not find in the 

 heavens, but which however appeared to have been observed by Flamsteed, I have 

 set down " Lost." This is to be understood only to mean that the star in 

 question was not to be seen when I looked for it, but that possibly at some 

 future time, if it be a changeable or periodical star, it may come to be visible 

 again. 



Simple Characters, 



' The least perceptible difference less bright, 



. Equality. 



, The least perceptible difference more bright. 



— A very small difference more bright. 

 — , A small difference more briglit. 



— — A considerable difference more bright. 

 Any great difference more bright in general. 



* Tobiae Mayeri opera inedita, 1 .r— Orig. 



