CAUSES which affca the ACCURACY 



and (3 = , fo that *(3 = ^ , half the hyperbolic logarithm 



of which, or that of 5 . , is = 1.0782, and this multiplied 



o \/o 



into , fuppofing .0015, gives -I- .0016 to be multiplied 

 into A, or the height as already approximated. The correction 



here is, therefore, about 6 of A. In other cafes, it will ex- 



ceed this proportion as b$ diminifhes, but (becaufe |3 will rare- 



25 \ i 



ly be greater than - ) . its minimum will be about - . In 



144 770 



the meafurement of great heights, therefore, this equation may 

 deferve to be confidered. 



3 1 . WE come now to find the correction which muft be made 

 on the ordinary rule, on account of the diminution of gravity 

 as we afcend from the furface of the earth. By 27. we have, 



f 



H ~ r 



22 A r 2Z hr 



(im) +______ (i /) . an jjj^g we 



(im) +______ (i /) \ . 



ready, that z = - R _ r -- - nearly, if we fub- 

 (i ;) (i m) 



ftitute this value of js, or rather that which was before derived 



from 



