58 POPULAR LECTURES AND ADDRESSES, 



sailing directions always add to the descriptions 

 of the two objects which are to be seen in line 

 for a clearing mark, a statement of their compass 

 bearings when so seen ; also information regard- 

 ing soundings when needed, or when available 

 as an aid. 



40. I cannot better illustrate the subject, and 

 particularly the kind of difficulties which the 

 stranger must grapple with, if, aided only by 

 sailing directions, he acts as his own pilot, than by 

 reading to you from the Admiralty Book of 

 Sailing Directions for the West Coasts of France, 

 Spain, and Portugal, some extracts regarding the 

 entrance to the Tagus over the bar of Lisbon. 

 I must premise that " turning through a channel " 

 is a technical expression for sailing through the 

 channel by a zig-zag course against the wind. 

 Directions for turning through a channel neces- 

 sarily specify, by proper landmarks, the extreme 

 limit to which a ship may safely go on either 

 side, from mid-channel, before turning to windward 

 for her next tack. 



" Opposite Lisbon, on the south shore, is 



