[387 ] . . 
I have made this computation to great exaiftnefs, 
for the cafe of / = o, / — 4. #, and /= o, 
866 a. = a co f. 30° 3 the refult, 
10 If /= o. 
for 4 float-boards, the arith. mean = 0.33 c 
(»-e- n 13 a. aw). 
It may be obferved in this firft cafe, that there is 
fome advantage in taking 6 float-boards inftead of 4 
fhewn by the table j the effedt will be increafed in 
the ratio of 100 to 1 18, and yet will be more than 
about of the greateft effedt above calculated for 
a Angle vertical float-board } fo that the found di- 
menfions muft be a fmall matter altered, and the 
quantity ( 3 a ci increafed by- 1 -. 
for 6 =0,396 (&c, 
= °> 33 6 (^* 
= 0,323 (&V. 
= 0,295 (&c. 
= 0,214 (Off. 
0,277 (&v» 
0,281 
0,285 (&V* 
0,284 (&V. 
0,276 (&c. 
0,238 (£fc. 
In this fecond cafe 9 float-boards are to be taken 
inflead of 6 fliewn by the table, though the differ- 
ence will be but very fmalb and we fliall have 
an effedt which will be T 8 _ 0 %i of that of a ver- 
tical float-board, and in that ratio that the quan- 
tity / 3 ct a found by the above formulas, muft be in- 
creafed. * 
3° if 
9 
32 
lS 
an infinite number 
2 ° If f = 4 
for 6 flo. 
7 
w 9 
12 
1 8 
an infinite number 
D d d 2 
