84 fHE WORLtK 



the horizon, as the index had been moved, and as shown at a, it 



would appear in the quadrant, as in the figure preceding,brought 

 to the line of the horizon. Now just before noon, on ship-board, 

 the sailor sets the index of his quadrant to about the altitude of 

 the sun, and defending the eye by a set of dark glasses, shown at 

 G, page 82 he looks through the eye -hole D, and the unsilvered 

 portion of the horizon glass, and sees a distinct image of the sun, 

 almost touching the horizon, thus : 



It is true, he cannot see the horizon in the silvered portion of the 

 horizon glass, but he can bring the image close to the line where the 

 silvering is removed from the glass, and then by inclining his qua- 

 drant a little, as in figure 2, page 83, he can make the sun, appa- 

 rently, describe the dotted arc c d, just touching the horizon. We 

 will suppose he is looking just before noon, i. e. before the sun 

 comes to the meridian, or reaches his highest altitude in the 

 heavens, and that an assistant stands near, ready to note the time 

 when this highest point is reached. As he looks through his 

 quadrant, the image of the sun, which a moment before described 

 the arc c d, and appeared to touch the horizon in its course, will 

 seem to rise a little, he therefore moves the index, and brings it 

 down again, all the time sweeping backward and forwards ; if it 

 rises a little more, he again brings it down, very soon he perceives 



