70 INTRODUCTION* 



anchor, the constant turnings and changes of place 

 which it experiences, admit of no accurate observ- 

 ation with the lead. But the more do these risings 

 of the sea deserve to be carefully observed upon 

 the coasts. The simplest mode is, to fix up, at a 

 part of the coast, where the water is as quiet as 

 possible, and no surf, an upright pole, divided (best 

 painted) into feet and inches, so that the foot of it 

 may never be dry, even when the water is at the 

 lowest. Sometimes it may be so placed, that the 

 height of the water may be seen from the ship by 

 means of a telescope. With respect to the observ- 

 ations themselves, it is not easy to make too many, 

 particularly at the beginning. (During the high 

 tides in Japan, they were sometimes noted down 

 every ten minutes, and oftener.*) Let the true time 

 be observed, with the force of the prevailing wind, 

 and, as much as possible, the direction of the ebb 

 and flood tides. The observations at the time of 

 new and full moon deserve especial attention. The 

 assertion, often controverted, and partly confirmed, 

 of a decrease, or progressive increase of the mean 

 elevation of the sea, in different parts of the earth, 

 is so very remarkable a fact, that the navigator is 

 lU'gently requested to pay particular attention to 

 any observations, which may serve to confirm the 

 one or the other assertion. 



The second great motion of the sea, viz. the 

 currents, has a most important influence on navi- 



* Krusenstern'is Voyage, vol. iii. 



