190 HYDROGRAPHICAL SURVEYING [chap. vii. 



Swamps near the coast should be sketched in as far as 

 necessary, and a look-out kept for evidences of any extension 

 of their area in winter. Information on these points can be 

 picked up from passing inhabitants. 



Angles should be got also to any conspicuous objects farther 

 inland, as they will be very useful when the topography is 

 sketched, and the surveyor should always look ahead, and 

 seize any opportunity of the kind for helping on other parts 

 of the work than those he may be immediately engaged in. 



Roads near the coast should be walked back to, and fixed 

 here and there, sketching in between. 



Rocks above water, or breaking, should be fixed. Though 



these come into the province of the sounding, it is often 



useful to have them down first ; and in the case of a break 



only, it may be very much so indeed, as it may be an 



isolated head, which a boat sounding near high water may 



n.iss. 



Low- Though it is the high-water line that the coast-liner is more 



Water immediately concerned with, he should mark at low water 



Shore- "^ 



line. the position of the dry line, especially where this runs off a 



long way at points, etc. 



In a detailed survey on a large scale, it will be necessary 



to send some one round the water-hne at low tide to get it 



accurately, but on small scales this is more usually obtained 



by the soundings, for by reducing these to the low-water level 



of springs, a series of points will be obtained, where each line 



of soundings crosses the low-water line, which can then be 



drawn in as a hne passing through these points. 



As the tide rises or falls, the time should be noted at which 



rocks and various parts of the shore cover or uncover. Reference 



to the tidal register will show their heights above low-water, or 



the amount they uncover, which should be expressed on the 



chart. 



Every part of the survey should be seen at least once at 



low-water, and rocky heads that dry, with their heights stated 



against them, must not be omitted from the chart. 



Eieva- Angles of elevation for heights of the hills should be taken 



tions of when getting the angles for fixing the points of the chart, 



from main and secondary stations, or any well-fixed points ; 



but if the coast-hner gets some more elevations from marks 



