jg NEW METHOD OF MEASURING A SHIPS VELOCITY. 



cording to the ship's velocity. By a few comparisons of the 

 quantity of weight raised from the deck with the rate of 

 sailing, a scale may be marked. 

 or a spring and In an improved state, of the experiment, instead of using 

 - weights or a pulley, the inner end of the line (coming direct 

 from the water) can be fastened to a spring, and communi- 

 cate with an index that shall express the rate of sailing. 



This machine (if so plain a contrivance deserve that 

 name) may be put on constant duty, or dropped occasionally 

 to ascertain the rate. 



Objections which occur, are, 

 Objections, & 1st* The line being liable to contraction or expansion as 

 answers to ^} ie temperature of the water varies. But it is scarcely to 

 be supposed, that the greatest contraction or expansion of 

 line from its mean state (after it has been properly stretched 

 and seasoned) wilt occasion an alteration of a hundredth part 

 in the force of the pull. 



2d. That in a fresh wind the part of the line between the 

 ship and the surface of the water, will be liable to some ad- 

 ditional pull from being exposed to the wind. To this in- 

 convenience, the log line in the common 'way of heaving 

 the log is likewise exposed when the wind is much aft. In 

 either case, when the ship is not right before the wind, the 

 remedy is the same: which is, to throw the log or the line 

 over from before the lee gangway, and to give a few fathoms 

 more of stray line ; for which however, in the new method 

 proposed, it would be necessary to apply a correction, the 

 quantity of which may be accurately ascertained. 



3d. The motion of a ship in pitching. But this is not to 

 be regarded as an objection; for the rate of sailing is to be 

 estimated only by what the experiment shows when the ship 

 is going steadily; in the same manner as in taking bearings, 

 if the compass swings, we wait till it is quiet. Whenever 

 the ship goes steadily for ten seconds together, or even five 

 seconds, the pull of the line will be regulated to the average 

 rate of sailing. 



XI. 



