18 Fishery Board for Scotland. 



ing from the south-west of Ireland southwards along the Spanish and 

 African coasts, we see the isotherms all gently bending to the south- 

 ward. The water near to, and for some distance from, the continental 

 coast is cooler than at corresponding latitudes in mid-ocean : this 

 being the simple consequence of that southward set of the great 

 eddy, which here, on the eastern side of the ocean, draws down waters 

 from the northward to take the place, and to follow in the track, of 

 those which had been carried westward by the great Equatorial Cur- 

 rent. In sliort, it is possible throughout to interpret this Temperature 

 Chart of ours in terms of the current-system which controls the 

 motions of all the waters of the Atlantic. 



In Fig. 2 we have another chart, which shows, this time, the 

 annual range, or total rise and fall between winter and summer, of 

 the Atlantic temperatures. For an important part of the ocean, 

 especially to the north-west, in the Greenland Seas and in Davis 

 Straits, we have all too little information for the construction of 

 such a map ; but we can see, more or less, how the lines are bound 

 to run. In Dr. Schott's Geographic des Atlantischen Oceans, the 

 reader will find a similar map (on a smaller scale), which agrees in 

 the main, but differs in part, from the general picture which I have 

 given of the phenomena. 



Looking at this chart as a whole, we at once see that it is in the 

 open ocean (as we might expect) that there is least seasonal change 

 of temperature. The great mass of ocean water acquires and loses 

 heat slowly, while in the shallower waters, and in the neighbourhood 

 of land, the seasons show a much more marked effect. In mid-ocean, 

 from the southern border of our map to the neighbourhood of 

 Iceland, the seasonal fluctuation only varies between about 4° and 

 7° 0. Doubtless it is much greater close to the Icelandic coast, but 

 on this point we have at present no definite information. 



In the British area the variations in temperature-range are very 

 simple and diagrammatic. A short distance from our western and 

 northern coasts we have everywhere the typical oceanic condition 

 of a small seasonal fluctuation, somewhere about 6° C, but as we 

 pass into the narrow seas the range rapidly increases. Off the west 

 of Scotland and in the Irish sea the increase of range is not great, 

 for there is free and open contact with the ocean. But as we pass 

 up the English Channel the range steadily increases; and within 

 the North Sea, as we pass from the Shetland region to the German 

 Bight, we see the annual range gradually increasing from about 6° 

 to at least 14° C. 



On the other side of the ocean, from Newfoundland to the 

 American coast, we have a still more marked increase of seasonal 

 range. In the neighbourhood of the peninsula of Gaspe our chart 

 shows a range of about 16" C, but it may well be greater in these 

 shallower waters, to which our sources of information do not extend. 

 The steady increase of temperature-range in this part of the ocean, 

 just where in our former map we saw the close-packed isotherms 

 of mean temperature, is doubtless connected with a tendency for 

 the two opposing currents, cold and hot, to vary in magnitude or 

 force with the seasons of the year, and more or less to shift their 

 relative positions accordingly. In short, we are probably here 

 observing a somewhat mixed phenomenon, consisting in part of a 



