( 4 11 ) 
After Variety of Experiments, I was at laft fo hap- 
py as to anfwer my Purpofe in fome Meafure j and as 
m Guernfey we are at a Lofs for curious Workmen, 
in the Year 1715. I came to London , and furniihed 
my felf with a Boat, and all the Materials neceftary 
for my D.fign. Daily was I on the River Thames 
making Experiments, and was frequently honoured 
with the Company of feveral of the Literati , who 
were greatly pleafed with my Invention ; but, not 
being fully fatisfied of the Certainty thereof, they ad- 
vifed me to try it on a Standing- Water. According 
to their Defire I did fo, for I obtained a Liberty 
feveral Times of having a Boat on the Canal in St. 
James's Park , where 1 demonftrated, to fuch curious 
Perfons as favoured me with their Company, the Ufe- 
fulnefs of feveral Inftruments *, for we there fixed two 
Poles for Marks, and notwithftanding I many Times 
alter’d theMotion of myBoat,by fometimes rowing fa ft, 
and at other Times flow, yet had my Machine under 
Water the fame Number of Revolutions between the 
Marks. It may, perhaps, be ask’d, how I came to be 
allured that the Revolutions of the Engine under 
Water are regular, let the Motion be fwift or flow, 
and that they anfwer the fame Diftance > I will not 
yet fay, that this admits of fo clear a mathematical 
Proof, as any Propofition in Euclid , however, I have 
mechanically found it fo in a great Variety of Expe- 
riments- and that every Turn or Revolution of the 
Engine under Water juft meafures 10 Feet, which I 
call the decimal hydraulical Circumference thereof. 
The Primum Mobile , or Soul of this Machine, is 
in the Form of the Letter Y, and is made in Iron, or 
any other Metal: At each End of the Lines, which 
conftitute the Angle, or upper Part of that Letter, 
are two Pallets not much unlike the figure of the 
Log ; 
