OD fF Pits ew AY, I6r 
way vifible on the graduated arch. The fpring L always 
counteracting the preflure upon the palate, and bringing 
back the index on any relaxation of the force imprefled. 
A fhip going through the fea opens a paflage for her- 
felf, making a hole in the water equal to her immerged 
bulk. As fhe pafles on, this vacancy is filled up by the 
tumbling in of the waters from each fide, and from un- 
derneath, at the ftern, with great violence. So that there 
is a fair current of water from her bow to her ftern, paf- 
fing under the bottom and along fide; the force of which 
current is in direct proportion to the velocity of the fhip’s 
progreflive motion. ‘This machine is, therefore, advan- 
tageoully placed at the bow of the fhip, where the current 
firft begins, and acts fairly upon the palate; in preference 
to the ftern, where the tumultuous clofing of the waters. 
eaufes a wake, vilible to a great diftance. ‘The palate D is 
funk nearly as low as the keel, that it may not be influ- 
enced by the heaping up of the water, and the dafhing of | 
the waves at and near the water-line. The arch K is to 
afcertain how many knots or miles {he would run in one 
hour, at her then rate of failing. But the graduations on 
this arch muft be unequal ; becaufe the refiftance of the 
fpring L will encreafe as it becomes more bent; fo that 
the index will travel over a greater {pace from one to five 
miles (which I fuppofe to be a medium) than from five to 
twelve. Laftly, the palate, rod, {pring and all the metallic 
parts of the inftrument fhould be covered with a ftrong 
varnifh, to prevent ruft from the corrolive quality of the 
falt water and fea air. 
IMPROVEMENT orf tuts MACHINE. 
Let the rod or fpear AB Fig. 1, be a round rod of iron 
or fteel ; and inftead of moving on the fulcrum or joint as 
at C, let it pafs through and turn freely in a focket, to 
which focket the moveable joint muft be annexed as, re- 
prefented: 
