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.—lt might be expected that in this position only the general causes 
which produce and modify the currents in the oceans could bring about any change 
in either their velocity or their direction. But there is no doubt that the cumulative 
effect of long-continued impulses, as described above, resulting in each case in a gain 
in one or the other of these directions, will ultimately be felt, and the result will be 
seen in a change of position of the main mass of the current. When these changes 
are brought about, they are of such a character as to evade detection, unless the 
averages of many observations 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 profiles 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 different 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 whoie edge of this 
portion of the platform 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 in biology with which it has a direct connection. At a conference 
held in Washington with the Commissioner of Fisheries tle 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 we were most directly concerned, would be covered with this warmer 
water. The 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 fishermen 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 chameleonticeps) disappeared 
from this area entirely, and all attempts to find it since then have been unsuccessful. 
The cause of its disappearance became a sort of biological puzzle. 
