[ 5+4 ] 
fink fatter than the' other, and endeavour to give it a 
direction down into the water *. 
I had intended ‘to have made trial of the effed of 
thefe alterations, but have been prevented, partly 
by want of opportunity, and partly from the indif- 
ference, with which I found fuch a contrivance as this, 
even if brought to perfection, was likely to be re- 
ceived by feamen ; who, in general, do not feein to be 
over- fond of making trial of new inftruments, efpe- 
cially if propofed by landmen, as, in deritton, they are 
pleated to call us. 
Indeed it may be objected, that, could we meafure 
the way of a fliip thro’ the water ever fo exaCtly, 
unlefs fome method were found out, of afcertaining 
the currents, c 5 k.; a fhip’s courfe, with refp^Ct to the 
globe, could not hereby be determined. But then it 
may be replied, with equal juftice, that it is for want 
of a means of meafuring the way of a fliip thro' the 
water (and this compared with other check obferva- 
tions), that the drift and velocities of the principal 
currents have not already been determined. 
Mr. de Saumarez, in his fecond paper, of March 
1729. makes mention of another machine for this 
purpofe, which he himfelf acknowleges to be inferior 
to his former, efpecially in rough weather at fea. But 
as fcveral others have fallen upon, and propofed, a ma- 
chine fimilar to this ; it may not be amifs to add the 
following remarks upon it. The firtt mover, in this, 
is compofed of four arms, fixed to the bottom of a 
pcrpen- 
* Mr.. RufTel’s plate was joined to a thank, who never found it 
to jump out of the water, at any time, when he made ufe of it. 
