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the Y is hauled through the water by a rope, fattened 
to the ttem or tail thereof, it may turn round, and, 
of confequence, endeavour to turn the rope round. 
The other end of the rope, being fattened to the end 
of a fpindle capable of moving freely round, will be 
made to do fo by the rotations of the Y, communi- 
cated to the rope. A motion being thus communi- 
cated to a fpindle within the flhip, this fpindle may 
be made to drive a fett of wheel- work, which will 
regifter the turns of the Y ; and the value of a cer- 
tain number of thefe turns being once found, by pro- 
per experiments, they are eafily reducible into leagues 
and degrees, csV. The only difficulty then is, whe 1 - 
ther this Y will make the fame number of rotations 
in going the fame fpace, when it is carried through 
the water faft, as when it is carried flow. Upon 
this head Mr. de Saumarez, as well in the paper above- 
cited, as in a fublequent one publifhed in Philo f 
tfranf N° 408. for March 1729. has given an ac- 
count of feveral trials, which he has made of it, from 
which it appears, that this machine, in part, anfwers 
the end propofed ; and is, in part, defective : The 
errors of which he fuppofes to proceed from the fink- 
ing down of the Y into the water, upon a flow mo- 
tion ; the axis of its rotation being then more oblique 
to the horizon than in a quick one. 
In a machine, conftrudted like this, it is evident, 
that the end of the fpindle, to which the rope is fatt- 
ened, mutt; be of fufficient ftrength and thicknefs, 
not only to bear the force or ftrefs, that the hauling of 
the Y through the water will lay upon it, in the 
greateft motion of a fhip; but alfo to bear the acci- 
dental jerks, that the waves will fuperadd thereto. 
The 
