[ 555 3 
fpindle: Firft, as the preftfure upon it is Ieis ; and, fe- 
condly, as it allows the fpindle and fhoulder to be of 
a lefs diameter. To break the jerks of the waves ; 
next to the end of the fpindle I fixed a fpiral fpring 
of wire, to which the cord was fattened ; which, by 
this means, was capable of playing backwards and 
forwards, and giving way to the irregularities of the 
fea : and, left: the plate fhould lay faft hold of any 
thing, or any extraordinary jerk fhould damage the 
fpindle or fpring, a knob, or button, was fattened 
upon the cord, at a fmall diftance from the fpring, 
which flopped upon a hole in a piece of wood, and 
prevented the fpring from being pulled out to above 
a certain length 5 fo that all addition of force, beyond 
this, could only tend to break the cord, and carry 
away the plate. The fpindle, being thus guarded 
from accidents, will allow of a ttill further diminu- 
tion of its fize ; fo that, at laft, I ventured to make 
the fpindle-pivot no more than one-twentieth of an 
inch diameter, and that of the fhoulder one-eighth ; 
being of tempered tteel, and fufficiently fmooth. 
The hole, in which the pivot, and againft which the 
fhoulder worked, was of agate likewife, well po- 
liihed. 
Being thus provided, in May 17 fi- I procured a 
boat, upon the ferpentine river in Hyde-park, to try 
how far the turns of the machine would be confittent 
with themfelves, when the fame fpace was meafured 
over with the fame, and with different velocities. 
The courfe was determined at each end, by obferving 
the coincidence of two trees, in a line nearly at right 
angles to the river. We, however, rowed beyond the 
5 mark. 
