C 296 ] 



Fig, IV. The brafs fcale with its 

 tinder-piece to be fcrewed to it, and 

 ferving to embrace clofely, by its 

 fpring, the glafs tube, fo as to be 

 fufpended by it upon the brafs gingle, 

 expreiTed in Fig. V. The iniide of 

 this under-piece ought to be lined 

 with a piece of fponge, on purpofe 

 to prefs foftly againft the glafs, 

 and to prevent its being fcratched 

 by Hiding the glafs tube up and 

 0o wn againft the brafs. 



Fig. V. The gingle, or the two 

 brafs rings, fuch as are ufed in 

 common fea-compaffes, whofe move- 

 able axes act contrary to one ano- 

 ther, to give the body fufpended 

 upon them every poiiible motion, 

 and thus to keep it in a perpendi- 

 cular line, 



N. B, 



