[ '00 ] 



flone or any thing almoft will ferve as an occafional weight, as 

 alfo any veffel to hold water, in which cafe nothing is wanting 

 to it that may not be every where fupplied; and as the 

 inftrument, with the hook or arm K which fupports it, might be 

 made of a fize not much greater than in fig. 2. fo it may, when 

 conftruded in this form and fize, be, as a concomitant to a 

 fmall Hadley's fextant, an ufeful acquifition to a traveller who 

 would equip himfelf expeditely : with this view, and for fecurity 

 againft accidents, the mirror and the whole frame might be 

 made of polifhed fteel : and when it is conftruded upon this 

 fmaller fcale, the ftem may with advantage be made a little 

 longer than in proportion to the figure, becaufe its length has 

 relation not fo much to the dimenfions of the other parts, as 

 to the length of the firing, and quantity of the weight ap- 

 pended ; both which may remain unaltered. 



I WOULD not have propofed the inftrument here defcribed, 

 if I imagined that the level mentioned by Mr. Vince (in his 

 Pradical Aftronomy, page 33), or any other one, were equally 

 cafy in its conftrudion and ufe, and capable like this of 

 being every where fabricated : that defcribed by him is (as I 



underftand 



of the inftrument of double fize will be to that of the other one in a ratio com- 

 pounded of both, i. e. of 4 X 8, (or of 32) to 1, which will be reduced to the 

 ratio of 16 to i; becaufe when the length of the ftem is doubled, the power of 

 the weight to fupprefs the tremors is doubled : from whence appears the neceflity 

 of making it as fmall and light as poflible, becaufe the appended weight cannot be 

 conveniently enlarged. 



