21.-REP0RT UPON A PHYSICAL INVESTIGATION OF THE WATERS OFF 
THE SOUTHERN COAST OF NEW ENGLAND, MADE DURING THE 
SUMMER OF 1889 BY THE U. S. FISH COMMISSION 
SCHOONER GRAMPUS. 
BY WILLIAM LIBBEY, JR., SC. D. 
Professor of Physical Geography, College of New Jersey, Princeton. 
[Plates cxxiv-CLvm and one text figure.] 
PURPOSE AND PLAN OF THE INVESTIGATION. 
During a part of tlie summer of 1889 the Fish Commission schooner Grampiis was 
assigned to the investigation (under the direction of the writer) of certain problems 
relating to the waters lying off the coast of the New England and Middle States. 
The object of the expedition was to study the temperature relations between the cold 
wall of the Labrador current and the warm waters of the Gulf Stream, with the idea of 
establishing some connection between the changes in temperature in the waters and 
the migrations of the fish which inhabit them. That such a connection does exist has 
been shown by the researches of the Commissioner of Fisheries, Mr. M. McDonald, 
upon the shad, and of Prof. G. Brown Goode upon the menhaden. The attempt was 
now to be made to verify this upon a larger scale and in a systematic manner. 
It is believed that in the seasonal variations of the hydro-isothermal lines will be 
found the key to explain the migrations and the geographical distribution of our 
important food species as well as of the food upon which they subsist, as both depend 
upon the temperature variations which determine the changes that occur in their loca- 
tion. It may also happen that while the changes in position of these areas of equal 
temperature will differ in succeeding seasons, they will, however, stand in some essen- 
tial relation with the general meteorological conditions upon the land which are under 
constant observation and discussion. The data eventually obtained will undoubtedly 
lead to important generalizations bearing upon the questions of physical geography 
and biological physics, or the relation of marine species to their physical environment. 
Our plan of operations was to start at a point south of Nantucket Island, and 
then running due south, to make a series of soundings, accompanied by a set of obser- 
vations upon the temperature and specific gravity of the water at various depths. The 
observations were made by means of instruments attached to a steel-wire cable which 
was controlled upon the deck of the vessel. These serial-temperature and specific- 
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