I 
{46) 
and having been fince frequently employed in making 
Experiments thereof, and Improvements thereon, I take 
Leave to add what follows as a Supplement tO’thofe 
Difcourfes on this Invention, which I am humbly 
of Opinion may, in Time, prove of great Ufe in 
thofe extenfive Branches of our foreign Commerce, 
wherein fo many of his Maiefty's Subjeds are con» 
cerned. 
At my publickly fetting out on this Invention, I 
had his late Majefty’s Leave feveral Times to have a 
Boat on the Canal in St. James\ Parky where the 
Shallownefs of the Water was fuch, that it would 
not admit of my ufing the Iron Fork, the Weight of 
which may be about four Pounds, and which I have 
defcribed in the franfa^ions afore-mentioned ; and 
therefore I was obliged to fall on fome Expedient to 
anfwer my Purpofe in fuch a Depth of Water. Va- 
rious were my Defigns to this End ; however at 
length I fixed fuch a Machine to my Boat, as had an 
equal Number of Revolutions in a meafured Diflance 
of a 000 Feet, even though the Boat went fwift or 
flow ; of which the Reverend Dr. DefaguUerSy and 
fome other Mathematician?, at Times, were Witnefs. 
As I did not defcribe this Inftrument in the former 
Account of my Machine, where it feems to Tie blend- 
ed with that of the Fork, I fhall give a Defcription 
of it here in the following Figures, 
In 
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