THIRTEENTH ANNUAL MEETING. 167 
The data upon which this conclusion is based are as follows: 
First—The shad make their appearance in the St. Johns 
river, Florida, as soon as the temperature of the river falls to 
60 degrees, or thereabouts, which takes place from the middle 
of November to the rst of December. At this time the river is 
colder than the ocean plateau outside, and the movements or 
migration is from warmer to cooler areas in the direction of the 
normal temperature of 60 degrees. 
Second—The shad which are spawned in the Potomac in 
April, May and June, remain in the river all summer. Schools 
of them may be frequently seen in the river in front of Washing- 
ton. They continue abundant until the latter part of October 
or 1st of November. When the temperature falls below 60 de- 
grees, they begin to drop down the river in their migrations 
seaward. In this case they are moving from cooler to warmer 
waters and toward the normal temperature of 60 degrees. 
Third—The beginning of the spring run of shad into the Po- 
tomac river is about coincident with the date when the river 
temperature rises above that of Chesapeake bay. In this case, 
too, the shad are moving from cooler to warmer waters, and in 
the direction of the normal temperature of 60 degrees, for the 
temperature of both bay and river is at the beginning of the 
season always below 60 degrees. 
It will be seen, therefore, that wherever we have been able to 
intercept the shad in its migrations and place it under observa- 
tion, it is always moving in the directiqn of the normal tempera- 
ture of 60 degrees. 
Assuming it to be true as a general fact that the shad in their 
ordinary migrations are ever traveling on temperature paths 
which lead to the normal temperature of 60 degrees, it becomes 
possible to determine the law, the rate, and the Jimit of their 
movements in a certain area, by tracing the shifting of the areas 
of congenial temperature under the influence of the seasons. 
The data for the discussion are furnished by the records of 
observations of water temperatures, made at the lighthouses by 
the direction of the Lighthouse Board, and at Washington by 
an employee of the United States Fish Commission. 
The three stations selected for comparison of ocean, bay and 
