180 Mr. J. Croll on the Physical Cause of Ocean- currents. 



proof that those winds are the cause of the ocean -currents than 

 this general agreemeatof thetwo systems as indicated by the chart. 

 Take, for example, the North Atlantic. The Gulf-stream follows 

 exactly the path of the prevailing winds. The Gulf-stream bifur- 

 cates in mid Atlantic; so does the wind. The left branch of the 

 stream passes north-eastwards into the Arctic regions, and the 

 right branch south-eastwards by the Azores; so does the wind. 

 The south-eastern branch of the stream, after passing the Cana- 

 ries^ reenters the equatorial current and flows into the Gulf of 

 Mexico; the same, it will be observed, holds true of the wind. 

 A like remarkable agreement exists in reference to all the other 

 leading currents of the ocean. This is particularly seen in the 

 case of the great Antarctic current between long, 140° W. and 

 160° W. This current, flowing northwards from the Antarctic 

 regions, instead of bending to the left under the influence of ro- 

 tation, turns to the right when it enters the regions of the 

 westerly winds, and flows eastwards towards the South-American 

 shores. In fact all the currents in this region of strong westerly 

 winds flow in an easterly or north-easterly direction. 



Taking into account the effects resulting from the conforma- 

 tion of sea and land, the system of ocean-currents agrees pre- 

 cisely with the system of the winds. All the principal currents of 

 the globe are in fact moving in the exact direction in which they 

 ought to move, assuming the winds to be the sole impelling 

 cause. In short, so perfect is the agreement between the two 

 systems, that, given the system of winds and the conformation 

 of sea and land, and the direction of all the currents of the ocean, 

 or more properly the system of oceanic circulation, might be 

 determined a priori. Or given the system of the ocean-currents 

 together with the conformation of sea and land, and the direc- 

 tion of the prevailing winds could also be determined a priori. 

 Or, thirdly, given the system of winds and the system of currents, 

 and the conformation of sea and land might be roughly deter- 

 mined. For example, it can be shown by this means that the 

 Antarctic regions are probably occupied by a continent and not 

 by a number of separate islands, nor by sea. 



While holding that the currents of the ocean form one system 

 of circulation, we must not be supposed to mean that the various 

 currents are connected end to end, having the same water flow- 

 ing through them all in succession like that in a heating-appa- 

 ratus. All that is maintained is simply this, that the currents 

 are so mutually related that any great change in one would 

 modify the conditions of all the others. For example, a great 

 increase or decrease in the easterly flow of Antarctic water in the 

 Southern Ocean would decrease or increase, as the case might 

 be, the strength of the West- Australian current ; and this change 



