64 THE WATER 



ment, the ship must be anchored bow and stern, as 

 even her yawing round a single cable will seriously affect 

 the record. The Pillsbury meter, as improved by the 

 British Hydrographic Office, is a beautiful machine, 

 but costly, and rather cumbrous to work. It could 

 probably be somewhat simplified and lightened. A 

 most interesting and practically untouched field lies 

 open to any yachtsman of ingenuity, who will attack 

 the problem of mid-water currents, which the ordinary 

 ship, whether naval or mercantile, has no time even 

 to consider. 



As to the daily movements of ocean water, the 

 subject of the theory of tides is rather for the astrono- 

 mer and mathematician than for the oceanographer. 

 It will be enough to say here that if a stay of any length 

 be made in an out-of-the-way port or harbour, daily 

 accurate measurements of tidal movement would be 

 found useful to the naval authorities, and of real value. 



A tide-pole, well guyed, marked in feet and decimals, 

 will do all that is necessary. A board carrying a light 

 scale-rod, floating freely in a square tube of four planks 

 knocked together, with holes in the bottom to admit 

 the water, will be found easier to read, as avoiding the 

 wash of the waves. Both these require frequent read- 

 ing, if the observations are to be of real value ; but 

 regular tide-gauges can be purchased, which record 

 the rise and fall automatically by curves on squared 

 paper. 



