J2 TRANSIT OF MERCURY. 



(13.) March 9, 1783. It is very foggy; yet in the tele- 

 fcope I fee the ftars without aberration, and they are very 

 bright. A Serpentarii is without a fingle ray. 



(1+.) April 6, 1783. A very thick fog fettles upon all my 

 glades; but the fpecula, even the 20-feet, which has fo large a 

 lurface, remained untouched. I fee perfedtly well. 



Froft. 



Whether froft (15.) Nov. 15, 1780; five o'clock in the morning. An 



be an impcdi- excellent fpeculum, No. 2, will not a6t properly; the frofty 



ment to diftina . ^ , ,, r , . ^ . . "U 



vifioii by tele- morning probably occanons an aiteratron in its ngure. An-- 



fcoj>eB. other fpeculum. No. 1, a6ts but indifferently, though I have 



known it to Ihew very well formerly in a very hard froft : for 



inftance, November 23, 1779, I faw with the fame mirror, 



and a power of 460, the vacancy between the two flars of the 



double liar Caftor, without the leafi: aberration. 



(16.) Oa. 22, 1781. Froft feems to be no hindrance to 

 perfeft vifion. The tube of my 7-feet telefcope is covered 

 with ice ; yet I fee very well. 



(17.) Nov. 19, 1781. It freezes very hard, and the ftars, 

 even thofe which are 50° high, are very tremulous. I fufpecl 

 their apparent diameters to be diminifhed ; and, if I recoiled 

 right, this is not the firft time that fuch a fufpicion has occurred 

 to me. 



(18.) Jan. 1 0, 1782. My telefcope would not a6t well, even 

 at an altitude of 70 or 80 degrees. There is a ftrong froft. 



(19.) Jan. 31, 1782. I cannot fee with a power of 460, 

 the ftars feem to dance fo unaccountably, and yet the air is 

 perfectly calm : even at 60 or 70 degrees of altitude, vifion is 

 impaired. 



(20.) Feb. 9, 1782. That froft is no hindrance to feeing 

 well is evident; for, not only my breath freezes upon the fide 

 of the tube, but more than once have I found my feet fattened 

 to the ground, when I have looked long at the fame ftar. 



(21.,) Oa. 4, 1782. It froze very feverely this night. At 

 firft, when the froft came on, I faw very badly, every object 

 being tremulous ; bu<, after fome time, and at proper altitudes, 

 I faw as well as ever. Between five and fix o'clock in the 

 morning, obje£ls began to be tremulous again ; occafioned, I 

 fappofe, by the coming on of a thaw. 



(22.) Jan, 



