[ 493 ] 
1736, and the latter in 1 73 p, the refult of Mr. La- 
belye’s computations was given : but neither the in- 
veftigation of the problem, nor any rules, were at 
that time exhibited to the public. 
In the year 1742 was publifhed Gardiner’s edition 
of Vlacq’s Tables j in which, among the examples 
there prefixed to fhew fome of the ufes of thofe 
tables drawn up by the late William Jones, Efq; 
there are two examples, one fhewing how to com- 
pute the fall of water at London-bridge, and the 
other applied to Weftminfter-bridge : but that ex- 
cellent mathematician’s inveftigation of the rule, by 
which thofe examples we-e wrought, was not printed,, 
altho’ he communicated to feveral of his friends copies 
thereQf. Since that time, it feems as if the problem 
had in general been forgot, as it has not made its ap- 
pearance, to, my knowlege, in any of the fubfequent 
publications. As it is a problem fomewhat curious* 
tho’ not difficult, and its folution not generally known 
(having feen four different foliations, one of them 
very imperfeft, extracted from the private books of 
an office in one of the departments of engineering in 
a neighbouring nation), I thought it might give fome 
entertainment to the curious in thefe matters, if the 
whole procefs were publifhed. In the following in- 
veftigation, much the fame with Mr. Jones s, as the 
demonftrations of the principles therein ufed appeared 
to be wanting, they are here attempted to be fup- 
plied. 
Principles. 
I. A heavy body , that in the firft fecond of time has 
fallen the height of feet, has acquired fiich a ve- 
locity , 
