310 HENRY B. WARD! 



Zacharias (94g). The technical station of the Boston water 

 works is well described by Whipple (9Tb) who sets forth clearly 

 the importance of such an enterprise in its relation to the 

 water supply of a great city. 



Last year the United States Fish Commission made a pre- 

 liminary survey of the region about Put-in-Bay, Lake Erie, 

 with reference to the fitness of this point for an experiment 

 station in connection with the government fish hatchery. The 

 work will be continued the coming summer (H. M. Smith, 98.) 

 The necessity for an aquacultural experiment station, the 

 right of such a foundation to governmental support, its proper 

 location and function and allied questions are discussed by 

 Ward (98a). Zacharias (95g) believes that a wandering lacus- 

 trine station is of secondary importance; some evidence to the 

 contrary could be found in the work of Fric and Vavra (94, 

 97), Reighard (94), Ward (96b). 



The temperature conditions of freshwater lakes were dis- 

 cussed by Fitz Gerald (95). In temperate climates, deep lakes 

 show a winter curve running from 0° Cat the surface to 4° C 

 at the bottom, while the summer curve is reversed, extending 

 from 24° C at the top to 7° -10° C at the bottom. Whipple 

 (95a) shows that a temperature difference of 3° C prevents wind 

 from maintaining circulation and the lower region remains 

 stagnant until the fall overturning mixes the water of the lake. 

 Birge (97a) made a most careful study of the temperature con- 

 ditions and variations in Lake Mendota. The warming of the 

 water in the spring is gradual and uniform until the difference 

 between top and bottom is 7°-8 c C. Then gentle winds with high 

 temperature lead to the formation of a mass of warm water 

 on the surface so thick that however the wind may blow there is 

 always a warm stratum floating on the colder water. Immediately 

 below the warm water is a layer a meter or less in thickness in 

 which the temperature falls very rapidly; this layer Birge 

 names the thermocline. Below it the temperature falls gradu- 

 ally to the bottom of the lake. Once formed, late in June, at 

 about eight meters of depth, it moves downward slowly and 



