( 281 ) 



On (he Glaciers and Climate of Iceland. By W. Sartorius 

 VON Waltershausen. 



(^Continued from page 140.) 



By means of the rules of navigation, the displacement 

 of a ship by currents is inferred by the comparison of the 

 position of the ship, deduced from asti'onomical observation, 

 with that given by the dead reckoning. At the same time, I 

 believe I may say from experience, that such observations 

 are, for the most part, subject to considerable errors, which 

 are to be attributed partly to faults in the astronomical ob- 

 servations, and partly to the steering of the vessel. To de- 

 duce in this manner, with sufficient precision, the direction 

 and velocity of a current is, in all cases, very difficult ; and 

 to do so for certain points of the sea at least, it would be 

 necessary to combine, in a systematic way, a much greater 

 number of observations than have hitherto been employed. 

 The observations of this kind, made in ordinary trading ves- 

 sels are entirely untrustworthy, and the errors in the deter- 

 mination of the positions of vessels, which are the necessary 

 consequence of the ignorance of the observers and the defec- 

 tiveness of the instruments, are too often ascribed to oceanic 

 currents. 



These matters are somewhat more favourably arranged in 

 ships of war, where good sextants and excellent chronometers 

 are provided ; but even in those vessels much is still to be 

 desired, and the results obtained regarding the currents are 

 often so contradictory, that it is impossible to combine them 

 with one another. 



Floating bodies, on the other hand, such as bottles thrown 

 out for the express purpose of giving information respecting 

 currents, and also trunks of trees, fruits, and seeds of many 

 plants, which are borne through the wide ocean from one side 

 of the world to the opposite, or from one country to another, 

 although they frequently afford no indication as to the velo- 

 cities of the currents, yet often yield important results regard- 

 ing their general courses. From many observations and ex- 

 periments, it can no longer be doubted that the Gulf Sti'eam, 



