SHIPS WAY. 163" 
always look full to the fouth-weft point of the horizon,. 
or towards the port of deftination ; and, confequently, will 
prefent only an oblique furface to the refifting medium—- 
more or lefs oblique as the fhip deviates more or lefs from 
the true courfe of her voyage. As, therefore, the refift- 
ance of the water will operate lefs upon the palate in an 
oblique than in a dire& pofition, in exact proportion to 
its obliquity, the Index H will not fhew how many knots 
the veflel runs.in her then courfe, but will (it is expected) 
indicate how many fhe gains in the direct line of her in- 
tended voyage. ‘Thus, in Fig. 5, if the fhip’s courfe lies 
in the direCtion of the line AB, but fhe can fail by the 
wind no nearer than AC; fuppofe then, her progreflive 
motion fuch as to perform AC, equal to five knots or miles 
in one hour; yet the index H will only point to four knots: 
on the graduated arch, becaufe fhe gains no more than at 
that rate on the true line of her voyage, viz. from A to B. 
Thus will the difference between her real motion and that: 
pointed out by the index be always in proportion to her’ 
deviation from the intended port, until fhe fails in a line 
at right angles therewith, as AD; in which cafe the palate 
would prefent only a thin fharp edge to the refifting me- 
dium; the preflure of which fhould not be fufficient to 
overcome the friction of the machine, and the bearing of. 
the {pring L. So that at whatever rate the fhip may {ail 
on that line yet the index will not be affe&ed: Shewing 
that fhe gains nothing on her true courfe. In this cafe, 
and alfo when the veffel is not under way, the action of 
the {pring L fhould caufe the index to point at 0; as repre- 
fented by the dotted lines in figure 1 and 4. 
As the truth of this inftrument muft depend on the 
equal preflure of the refifting medium upon the palate D 
according to the fhip’s velocity, and the proportionable 
action of the {pring L, there fhould be a pin or fcrew at 
the joints C and F, fo that the rod may be readily unfhip- 
ped and taken in, in order to clean the palate from any 
foulnefs ; 
