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the glafs tube is fufpended in it, 

 B B, the brafs fcaie of three Paris 

 inches divided into an hundred parts, 

 C C C C, the glafs tube or great 

 meafure ? whofe lower and open ex^ 

 tfemity is fecured by a brafs ferrule^ 

 D, the magnifier for the more ac- 

 curate obfervation. 



Fig. II. The fmall tube or mea- 

 fure fixed in its brafs focket. #, is 

 an elafblc piece of brafs, having a 

 pin pairing through a hole in the 

 under part of the focket, which 

 pin is pufhed upwards by the elaf- 

 ticity of the piece <2, and enters in, 

 a cavity on the under fide of the 

 Clider, made on purpofe to flop it, 

 and to prevent the bended fleel 

 fpring from forcing the Aider en- 

 tirely out of the focket. N.B. Ithink 

 that this machine may do very well 



without 



