[ Ir 4 ] 
race, to which the float being adapted, the water 
cannot otherwife efcape than by moving along with 
the wheel. It is obfervable, that a wheel working 
in this manner, as foon as the water meets the float, 
receiving a fudden check, it rifes up againfl: the float, 
like a wave againfl: a fixed objecfl: j infomuch that 
when the fheet of water is not a quarter of an inch 
thick before it meets the float, yet this flieet will 
a£t upon the whole furface of a float, whofe height 
is 3 inches ; and confequently was the float no higher 
than the thicknefs of the flieet of water, as the the- 
ory alfo fuppofes, a great part of the force would have 
been loft, by the water’s dafliing over the float *. 
In further confirmation of what is already deli- 
vered, I have adjoined the following table, contain- 
ing the refult of 27 fetts of experiments, made and 
reduced in the manner above fpecified. What re- 
mains of the theory of underfliot wheels, will natu- 
rally follow from a comparifon of the different ex- 
periments together. 
* Since the above was wrote, I rind that Profefl'or Euler, in the 
Eerlin A<fts for the year 1748, in a memoire intitled, Maxims pour 
ar anger le plus avantageufment les machines dejlin'ees a elever de I’eau 
par le moyen de pomp es^ page 192. § 9. has the following paflage ; 
which feems to be the more remarkable, as I don’t find he has 
given any demonftration of the principle therein contained, either 
from theory or experiment; or has made any ufe thereof in his 
calculations on this fubjebt. “ Cependant dans ce cas puifque 
“ l’eau eft reflechie, & qu’elle decoule fur les aubes vers les cotes, 
“ elle y exerce encore une force particuliere, dont 1’efFet dc l’im- 
“ pulrion fera augmente ; & experience jointe a la theorie a fait 
“ voir que dans ce cas, la force eft prefque double : de forte 
“ qu’il faut prendre le double de le fe&ion du fil d’eau pour ce 
“ qui repond dans ce cas a le furface des aubes, pourvu qu’elles 
“ foient afiez larges pour recevoir ce fupplement de force. Car ft 
“ les aubes netoient plus larges que le fil, on trait d’eau on ne 
“ devroit prendre que ne fimple fe&ion, tout comme dans lc pre- 
" mier cas, on l’aube toute entire eft pappee par l’cau.” 
TABLE 
