THE K.EAPPEARANCE OF THE TILEFISH. 
325 
in the U. S. Fish ('oininission Bulletin, vol. ix. This aeeount eoutaiiis a record of over 
temperature observations, and tlie general results were of such importance that 
Commissioner McDonald continued the work during the summer of 1890, at which time 
the United States Coast Survey steamer Blake was detailed to act in cooperation with 
the Granqnis. 
During the summer of 1891 the Grampus was placed again at the disposal of 
Professor Libbey, and the work was continued along the same lines as during the two 
previous years. Unfortunately, the results of these investigations, perhaps the most 
complete ever conducted over a tract of the ocean of equal extent, have never been 
published, although they yielded extremely important data relative to the physical 
changes affecting the sea and the sea bottom. Professor Libbey found that a compari- 
son of the temperature records as shown by the temperature cross-sections constructed 
upon the basis of the observations made in this body of water for the three years 
1889, 1890, and 1891, demonstrated that there had been a progressive movement of 
the warm water, of 50° temperature, toward the shore. 
In a communication addressed to Commissioner McDonald in 1892, Professor 
Libbey wrote : 
III 1889 the lower portion of the curve did not touch the edge of the coutiueutal platform at .any 
point within the area we were studying. In 1890 this portion of the curve touched the continental 
edge hoth at Block Island and off Nantucket Island in the latter jiart of the season; and in 1891, as has 
been said, it touched along the whole edge of this iiortion of the platform during the greater part of the 
summer. The change which was thus produced in the lemperatnre at the bottom along this edge of the 
continental platform was in the neighborhood of 10^, an item of considerable importance. — (Report 
II. S. Fish Commission, 189.3, p. 34. ) 
Pi ofessor Libbey, in a conference with Commissioner McDonald, showed that if the 
movement of the warm band toward the shore continued during the summer of 1892, 
the whole of the continental edge, or that part of it upon which the tilefish had once 
flourished, would present environmental conditions favorable to the return of the fish. 
The importance of these presentations was recognized by Commissioner McDonald, 
and though other work had been laid out for the Grampus, she was ordered to prepare 
for further explorations of the Gulf Stream and the bottom fauna off the southern iSTew 
England coast. Professor Libbey writes: 
In .July the Commissioner and myself went out in tbe schooner Oranqms, south of Martha’s 
Vineyard, to the area which seemed to promise a reward for our labors. IVe found the temperature 
conditions right, set the cod trawls, and caught the tilelish. During the remaining portion of the 
summer I spent considerable time tracing out the limits of the area over which the temperature of 
50° and above could be found, using the. trawl lines at the same time to ascertain if the tish were 
there. We found them all the way to the Delaware capes, and were satisfied that, though they were 
not numerous, they had taken advantage of the changed conditions to occupy the area. 
It is thus seen that whereas Professor Verrill in 1882 had given reasons for the 
disappearance of the fish, and had stated that, “It is probable that iu a few years 
theyyvill occupy these grounds by migrating northward, even if there be not enough 
left here to replenish their race,” and although an indiscriminate search of ten years 
had failed to find any trace of the lost fish, the results of Professor Libbey’s tempera- 
ture investigations enabled him to show that the physical conditions of the sea bottom 
were variable, to prove that there was a definite movement of warm water toward the 
area earlier occupied by the tilefish, and to predict that if this movement continued 
the tilefish would be found again iu its old habitat. 
