THE CURKENTS. 295 



Bhowed the phenomena for the months of February, May, August, and 

 November, being the middle month of each seasonal quarter. 



The discussion and integration of Current observations involve a great 

 amount of tedious labour, and there is no question but that the data used 

 by Rennell and others required much revision, as each succeeding and 

 better estimate gives a lower rate of progress to the movement of the 

 surface waters, though previous discussions as to their nature have been 

 confirmed. In the remarks on the Meteorological Office Current Charts, 

 Mr. E. H. Scott, the Director, says : — The number of observations em- 

 ployed in the construction of the General Chart exceeded 7,500, each of 

 which took 24 hours to make, so that some idea may be formed of the 

 length of time required to accumulate them, and the great difficulty which 

 is experienced in collecting information about Currents. 



(240.) In this book, limited as it necessarily is to generalities, space 

 could not be afforded to give the introduction of these Monthly Charts, 

 but in the subsequent descriptions of each branch of Ocean Circulation in 

 the North Atlantic we shall add the notes which elucidate the Current 

 Charts, and which were also drawn up by Mr. E. Strachan. 



In pursuing these calculations, it was found that in many localities the 

 Currents were represented as most devious and erratic, frequently of great 

 strength, and yet, on a mean, showing that there was no continued set of 

 the waters in any special direction. The diagrams of the direction of the 

 Wind at the Liverpool Observatory (page 203), in their more complicated 

 parts, give a good notion of their motions, as their paths, when traced, 

 resemble each other much. In other parts, as in the great Equatorial 

 Current, the motion, as estimated, is remarkably uniform, and this demon- 

 strates that these observations generally are entitled to confidence. 



(241.) In founding any theories of circulation or movement of the ocean 

 waters upon the basis of the (acknowledged to be) imperfect observations 

 used by Major Eennell, it may be objected that many of them are now old, 

 and therefore still less trustworthy. To this it may be replied, that they 

 were mostly taken in wooden ships (with very little iron in them to affect 

 the compasses) by careful navigators, in an age when great pains were taken 

 with the dead-reckoning. A doubt may very fairly be expressed whether 

 the observations of an equal number of modern ships would give as trust- 

 worthy results; their greater speed, and less attention to D.E., more refined 

 astronomy superseding it ; and errors in the compass owing to the iron 

 used in the construction or cargo of the modern ship, all tend to give con- 

 fidence in these old observations. 



(242.) There is one general result in discussing any lai'ge number or 

 collection of Current observations. They show that the surface water 

 moves at a much lower velocity than has been attributed to Current motion 

 generally. Perhaps this may in some degree arise from the fact that only 

 those of remarkable strength have been selected, without properly taking 

 into account the greater number of observations which would give a much 

 more moderate rate. 



(243.) Bottles. — It has been a well-known practice for many years to 

 send these floating messengers as indicators of Currents. In 1843, Captain 

 A. B. Becher, R.N., drew up a very interesting chart of the North Atlantic 



