REPORT OF COMMISSIONER OF FISH AND FISHERIES. LXXYII 
PHYSICAL INQUIRIES. 
Physical inquiries of one kind or another form a part of nearly all 
the held work that is carried on, and reference to them has been made 
under several other headings. Temperature and density observations 
are taken frequently by all the vessels in connection with their dredg- 
ing and sounding operations at sea, principally at the surface and 
bottom, but to some extent also at intermediate depths. The arrange- 
ments made a number of years ago with the Light-House Board and 
Signal Service for continuous temperature records at certain of their 
stations still continue with satisfactory results, but the number of sta- 
tions used for that purpose is much smaller now than formerly. Through 
the courtesy of the Southern Pacific Railroad Company similar obser- 
vations are also taken at the railroad crossings of several of the large 
western rivers. The number of permanent stations in operation has 
proved totally inadequate, however, to accomplish what is most de- 
sired, namely, to determine the precise relations of temperature to the 
movements of migratory fishes, the isotherms corresponding with the 
advance schools. This subject has been partly worked up with respect 
to the shad, mackerel, and menhaden, but further data are required 
before definite conclusions can he reached. In case the laws which gov- 
ern their movements can be fully demonstrated, it is rational to suppose 
that the arrival of any pelagic or anadromous fishes upon the sea-coast 
or along a river course may to some extent be anticipated and the fish- 
ermen be given warning of their near approach. The difficulties in the 
way of such a fortunate solution of this problem may be insurmount- 
able, but as yet the matter has not been fairly tested, and it is only 
recently that the proper course to be pursued has been thoroughly com- 
prehended. 
The temperature stations of the Light-House Board, the Signal Serv- 
ice, and the Southern Pacific Company furnish continuous series of 
observations, which are taken twice daily at the light stations, and once 
a day at the others, the reports being submitted monthly. The light 
stations are chiefly in more or less exposed positions ; those of the 
Signal Service in harbors, and those of the Southern Pacific Company 
at river crossings, as before explained. The names and locations of the 
stations which furnished information during the year are as follows : 
TEMPERATURE STATIONS ON THE ATLANTIC COAST. 
Stations of the Liyht-House Service: 
Coast of Maine: Petit Manan Island, Mount Desert Rock, Natinicus Rock, 
Seguin Island, Boon Island. 
Coast of Massachusetts: Race Point, Pollock Rip light-ship, Nantucket New 
South Shoal light-ship, Cross Rip light-ship, Vineyard Sound light-ship. 
Coast of Rhode Island: Brenton Reef light-ship, Block Island southeast light. 
Long Island Sound: Bartlett Reef light-ship, Stratford Shoals light-ship. 
Coast of New r York: Sandy Hook light-ship. 
Coast of New Jersey: Absecon Inlet, Five Fathom Bank light-sliip. 
