1836.] 



Notice of Books. 



165 



mounted as ail Equatorial after a plan proposed 1 believe by Smeaton: 

 the telescope was supported upon a brick tablet surmounted by a 

 slab of granite, into which I had introduced three pieces of brass, one 

 having a conical hole, another a slit, and the third being a plane ; these 

 were " run in" with boiling lead, and with the tablet were as secure 

 as could be desired: — the power employed was 60, and the obsei nation 

 consisted in noting the time by the transit clock when the Comet or 

 Star occupied the centre of the field of the telescope (as pointed out 

 by a neatly defined diaphraghm placed in the focus of the eye piece) ; 

 when the declination and hour angle were read off— the former which 

 is read off from a circle of 7 inches diameter (graduated to every 30' 

 but reading off to single minutes) can be depended upon to 1 or 2 mi- 

 nutes ; whereas the latter (which is read off from a circle of 3| inches 

 diameter graduated to every 4 minutes but reading off to every 20 se- 

 conds of time corresponding to 5' of a great circle) cannot I fear be 

 depended upon to 3' or 4'. The observations on the meridian with the 

 transit instrument were made by observing the time of disappear- 

 ance behind the edge of a piece of paper pasted upon the second glass 

 of the eye-piece ; the paper thus pasted was seen very distinctly, and 

 could with great accuracy be made to coincide with the centre wire. 



" Notes and Remarks.— August 30. I had adjusted the instrument 

 approximately only for the purpose of sweeping — on finding the Comet 

 a further adjustment was made which (twilight approaching) only left 

 time for two observations. 



" August 31. Clouds prevented further observation. 



H September 19. Continued cloudy weather every morning since 

 the 31st. 



" 20. The instrument very accurately adjusted — the sky particu- 

 larly clear, and the Comet well defined, but not visible to the unassist- 

 ed eye. 



" October 17. Tail about 5 ° long — directed towards Lyras. 

 " 18. Rather hazy — tail 4° or 5° long. 



" 19. Very clear, tail 15° or 20° long to my short sight, but one of 

 the assistants with a sextant measured it 30° long. 



" 22. The Comet appears better defined than I have yet seen it,— 

 tail 15° long. 



'* November 5. The telescopic appearance has improved, but by 

 reason of moonlight the appearance to the unassisted eye, is that of a 

 nebulosity as bright as a star of the 4th magnitude. 



" 6. The nucleus neatly defined— to the unassisted eye the tail ap- 

 peared 7° long. 



" 7. The tail appears very well defined, and certainly brighter than 

 I have yet seen it ;— -in the telescope, its appearance is brighter in the 



