66 POPULAR LECTURES AND ADDRESSES. 



part of the North Cachopo nearer than a quarter 

 of a mile ; but the southern turning mark carries 

 a vessel within ij half cables of the South Cachopo 

 and as the tides here are uncertain, the shoal 

 should be approached with caution. It is by no 

 means desirable to have a tree for a clearing mark, 

 which may be down at any moment ; but the 

 mariner in this case, in standing towards the latter 

 bank need go but little beyond the line of the 

 central leading mark. In places, both the North 

 and South Cachopo are steep-to." 



41. The process of "taking angles" by the 

 sextant is found useful for finding the ship's place 

 when in sight of land. It consists of measuring 

 by the sextant, held horizontally, the differences of 

 azimuth as seen from the ship (s) of three known 

 objects or landmarks (A, B, c). Open the three 

 rulers of the station pointer to the measured 

 angles ASB, BSC, and then lay it down on your 

 working chart, and slip it about till the edges 

 of the three rulers pass through the positions 

 of A, B, C, as shown on the chart. The centre, or 

 pointer of the instrument then shows the place 



