4)28 Description of Crow's Seaman's Octant 



nevertheless, of a nature to be very useful at times. Also for 

 such purposes, and for containing fuel, there is a spacious 

 cellar under the lecture-room and laboratory. 



LIX. Description of Crovv-'s Seaman's Octant and Traverse 

 Worker*. 



[With a Plate.] 

 TTPON introducing the Seaman's Trigonometrical Octant 

 ^ and Traverse Worker to the notice of that numerous and 

 enterprising class of men who form the chief glory and sup- 

 port of the British nation, it may safely be said, without fear 

 of contradiction, that of all the various instruments which 

 have hitherto been invented for performing the practical rules 

 in navigation without the help of tables, the one now proposed 

 is not only the easiest for general practice, but will be found 

 more expeditious and correct. 



This instrument is, of all others hitherto produced for the 

 purposes of navigation, so extremely simple in its use, that it 

 is presumed a very few examples will make the whole suffi- 

 ciendy plain to the meanest capacity. 



It has often been suggested by experienced navigators, that 

 if an instrument could be so contrived as to answer satis- 

 factorily all the purposes required in keeping a ship's dead 

 reckoning, very few seamen, if any, would perplex themselves 

 with tables. An eminent author, in speaking of a table of 

 natural sines, tangents, &c. says : " There are few tables printed 

 perfectly correct : besides the trouble of taking out the loga- 

 rithms, adding them together and subtracting, the difficulty 

 there is in finding the required number answering the loga- 

 rithm at last." Now expedition requires that one should not 

 be encumbered with unnecessary figures; and it is also certain 

 that the greater the number of figures employed, so in pro- 

 portion is the chance of error. 



The Seaman's Octant and Traverse Worker is deduced 

 from and constructed upon principles combining geometry and 

 trigonometry, whence alone rest the entire foundation of all 

 the various sailings ; and as we know that the sine, tangent, and 

 secant of an angle, is called the sine, tangent, and secant 

 of the arch which measures that angle ; and the sides are in 

 the same proportion one to another as the sines of the opposite 

 angles ;— hence it must be evident to any intelligent seaman, 

 that the results given by the Seaman's Octant will at all times 



• From a pamphlet published by the Inventor. 



be 



