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cifely of equal diameters. I then contrived that the bar fliould 

 not hook on the pivots, but be preffed upwards by a fpring 

 againft their under parts. Fig. VI. (hews the principle of this 

 adjuftment. A is the extremity of the pivot of the axis ; c the 

 fpring, which is attached to the notched piece n, n, refling on 

 the pivot, and forcing the piece T, T upwards, which raifes 

 the whole adjufting tool, and keeps the notch 1, 1, bearing 

 againft the lower part of the pivot ; 1, 1, m, m is a piece 

 flmilar to the vertical bar of a level feen in profile; o, o is 

 the profile of the perpendicular bar which ftrengthens the hori- 

 zontal bar ; to the middle of this is attached the vertical bar 

 y, y, with two fine points, one being moveable; befide this hangs 

 the plumb-line x, x, with the plummet P fwinging in water. 



Although this adjuftment was independent of all inequality 

 in the pivots, yet it was objedionable, becaufe during the adjuft- 

 ment there was the weight of the tool on the axis, from v^hich 

 it was difengaged in the ad of obfervation ; whence the inftru- 

 ment w"as proved and applied in diflimilar circumftances. But 

 whilft I had this tool actually in hands, the following elegant and 

 unobjedlionable mode was devifed by Mr. Ramfden, which 

 immediately made me lay afide all thoughts of the former ; and 

 in fadt I know of no late invention that feems to promife more 

 towards the improvement of all aftronomical inftruments where 

 plumb-lines are applied. 



In one fide of the tube of the telefcopc, and twelve inches 

 from each end of it, he makes a fmall hole, and inferts a very 

 ihin femipellucid bit of ivory, with a black dot in the centre; 



in 



