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lowed conically to receive the extremity of the cyh'nder D, made 

 to fit it ; and this raifing the upper work on which the axis now 

 refts, lifts the inftrument off its fupports, which is then readily 

 turned round on the cylinder D, working in the cone C and 

 female cylinder F, F ; and may be then, in its reverfed pofition, 

 fmoothly and gently lowered down again to its fupports. 



