CHAPTER XXXIV. 



HOW LATITUDE IS RECKONED. 



All those who have been to sea have looked on, more or less mystified, 

 while one of the ship's officers takes his observations to find out just where 

 the ship is. If the average landlubber is asked to tell just what happens on 

 such occasions he will confine his explanations, as a rule, to stating that the 

 instrument involved is a sextant, and that the sun plays an important part in 

 the affair. After that — unless he is an exceptionally well-informed land- 

 lubber — he will trail off into vague remarks about latitude and longitude, and 

 then, ten to one, change the subject. 



But the sextant suddenly jumped into the limelight with the discovery of 

 the pole; for, besides being indispensable to the seafarer, it is equally so to 

 polar explorers. It is by its use alone that Peary and Cook were able to de- 

 termine their whereabouts while on their weary marches through the frozen 

 north. In fact, if they had not had the useful little instrument among their 

 paraphernalia they would have been absolutely unable to tell whether they 

 were at the coveted goal or hundreds of miles away from it. 



Hence, this query is now more pertinent than ever: What is a sextant 

 and what does it do ? 



The sextant is an instrument for measuring angles between distant objects. 

 It consists of a frame in the form of a sector, embracing somewhat more 

 than one-sixth (usually about one-fourth) of the whole circle; two mirrors, 

 one wholly silvered and one silvered over half its surface, a movable arm 

 pivoted at the center of the sector and carrying the fully silvered mirror, and a 

 vernier, or measuring scale; an arc along the circumference of the sector 

 , graduated into degrees, minutes and seconds and an eye-piece. Its name is 

 derived from the Latin word sextans, signifying the sixth of a circle. 



People are often puzzled to know why the sextant should be so called, 

 when it can measure angles up to 129 degrees, or the third of a circle. But, as 

 Lecky points out in his well-known "Wrinkles in Practical Navigation." if the 

 possessor of a sextant will look at the arc, he will find out that by his eve alon^ 



325 



