34 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



will be carried far from its normal position in one direction or the other, and thus 

 mask the true position of the main body of one or the other of these currents to a 

 very considerable extent. 



Lower portion. — It might be expected that in this position only the general causes 

 which produce and modify the currents iu the oceans could bring about any change 

 in either their vehjcity or thcrirdirection. But there is no doubt that the cumulative 

 effect of long-continued impulses, as described above, resulting in each case iu a gain 

 in one or the other of these directions, will ultimately be felt, and the result will be 

 seen iu a change of position of the main mass of the current. When these chauges 

 are brought about, they are of such a character as to evade detection, unless the 

 averages of many observatious are carefully studied, when the change in the posi- 

 tion of the resultant becomes manifest. The contrast between these two portions of 

 the current are seen in the apparently more flexible character of the upper portion 

 as compared with the lower, the former being characterized by rather rapid changes 

 in position, the latter by much slower motions. 



The 50'^ line indicates very clearly the changes which take place in the relations 

 of these currents. During the time when we were engaged upon this study its pre- 

 dominant shape was that of an inverted letter S, the lower part of the inverted 

 letter representing the main body or lower portion of the Gulf Stream. Neither the 

 40- line nor the 60" line shows any great deflections under any circumstances, thus 

 apparently indicating that they are well within the boundaries of each of the main 

 bodies of their respective currents. 



A study of the temperature proflles obtained in 1891 showed that the general 

 relations of the currents had remained the same, but it was noticed that during the 

 greater part of the time the curved bend of the lower part of the 50^ line touched 

 the edge of the continental platform, covering it completely from the depth of 70 

 fathoms to that of 120 fathoms in difl'erent places. This had occurred once or twice 

 in 1890, but it was then believed to be rather an accidental feature than otherwise. 



A comparison of the profiles of the three years revealed the fact that there had 

 been a progressive motion during that period toward the shore. In 1889 the lower 

 portion of the curve did not touch the edge of the continental platform at any point 

 within the area we were studying. In 1890 this portion of the curve touched the 

 continental edge both at Block Island and off Nantucket Island in the latter part 

 of the season, and in 1891, as has been said, it touched along the whole edge of this 

 portion of the jjlatform during the greater part of the summer. The change which 

 was thus produced in the temperature at the bottom along this edge of the conti- 

 nental platform was in the neighborhood of 10"^', an item of considerable importance. 



The effect produced by this change in temperature and its relations to the work 

 of the Fish Commission can be seen to best advantage by reference to a very inter- 

 esting problem iu biology with which it has a direct connection. At a conference 

 held in Washington with the Commissioner of Fisheries the results obtained were 

 carefully discussed. We saw very plainly that if the same rate of motion held good 

 during this year the whole of the continental edge, or at least that portion of it 

 with which wo were most directly concerned, would be covered with this warmer 

 water. Tlie idea was then suggested that if such were the case the conditions for 

 the reappearance of the tilefish would be established if environment meant any- 

 thing in the problem. In the years 1880 and 1881 this recently discovered fish had 

 been found in considerable numbers upon the area we were studying, and had 

 attracted so much attention among lishermen that preparations were made to take 

 it upon a commercial scale for the New York and Boston markets during the ensuing 

 season. Unfortunately, however, in the spring of 1882 the water from Cape May to 

 Nantucket became covered with countless millions of this fish in a dead or dying 

 condition. From that time the tilefish {Lopholatilus rhamaleoniiceps) disa])peared 

 from this area entirt^y, and all attempts to find it since then have been unsuccessful. 

 The cause of its disappearance became a sort of biological puzzle. 



