[ 3 ® ° ] 
(§IV.) > ^ 
fhall have c 
4 vz u 3 
3 « 
•/ 3 
■r 
-V A *2. 
** -f ff 
a,cc 
— o, we 
= v-VAvv- 4- zz. 
«« + ff 
oc ct 
If/— O, we have ss = 0,2881; w and c = 0,345-j 
f=^* zz — Oyigovv c — 0,3361; 
j — ct zz = fvv c = fv. 
fo that whatever be the relation of f to a, the velocity 
c is ever nearly — 4 v, and the more exactly fo, as 
f is greater. Wherefore we may always aflume _l_. 
n@.vv. (aa —ff) — d 7r for the effect of the flream 
upon a float-board whofe plunged part is u — f; this 
etfed will be increafed in the ratio of 4 to 9, when 
the wheel has no motion, for making c — o, we 
find it — n@vv. (a cl — ff). 
§ VII. Hitherto we have all along fuppofed, that 
the float-board did through its whole plunged part 
receive the perpendicular impulfe of the flream ; but 
it is eafily underflood, that the wheel coming to turn, 
prefents to the flream the plane of the float- board 
under an angle which is continually varying, which 
diminifhes its eflfedt every inflant, as it removes from 
the vertical : This inconvenience may be remedied by 
multiplying the number of the float-boards, fo that 
when the firfl is removed from the vertical as far as a 
certain point, the next may occupy that advantageous 
place, to he in its turn replaced ibme time after by 
a third, and fo on. Now our third inquiry is, to 
aflign the angle contained between two float-boards, 
or, which comes to the fame, the number of float- 
boards the wheel fftould confifl of, that its eftebt may 
he the greateft poflible, being of no lefs importance than 
the preceding ones. To begin then with the molt 
Ample 
