188 HYDROGRAPHK'AL SURVEYING [chap. vii. 



used for the smaller detail, where sufficient angles to fix cannot 

 be obtained. It is especially useful in delineating the shores of 

 islands, or of small bays which have no fixed point in them. 



For instance, in Fig. 54, let us suppose the two points, 

 marked Ash and Lime, are fixed, but in between them is the 

 small bay shown. 



At Ash we obtain the angle between Lime and A, the next 

 point visible, and also the distance by our ten-foot pole. If 



Scufe of lards. 



we can make out that B is a point, and can see any prominent 

 spot on it, we shall get an angle to that also. 



We then go to A, sketching in between on the way. At A 

 we become aware of the little bay, and v/e send the pole over 

 to C, pointing out to the man with it where to stand, and telling 

 him to put a stick or stone there, when he is signalled to go on 

 toB. 



At A we get all we can, angles from Lime as zero, to Ash, 

 B, C, tangent of bay on towards D, and anything prominent, 

 and the distance to C by the pole. 



Leaving a little mark at our station at A, we go to Lime, 

 and take angles from Ash to A, B, and distance to B by the 

 pole now there. 



We then go back to B, and send the pole over to D, and 

 again get all angles we can, and distance to D. 



We now sit down and plot our data. We have two angles 

 to A from Ash and Lime, and a distance to A from Ash. These 

 ought to agree, and we prick in A. We have the line to B 

 from Lime, and perhaps from Ash as well, but we will suppose 

 not, and will plot B by the distance from Lime. Then, placing 

 our protractor on B, lay off the angle observed there to Ash, 

 which ought to go through, and make a check for B. 



