Conditions in Streams 



79 



afford to their plant and animal inhabitants that 

 interest us here; and these have been little studied. 

 Most has been done on the Illinois River, at the floating 

 laboratory of the Illinois State Laboratory of Natural 

 History (see page 50). A more recently established 

 river laboratory, more limited in its scope (being 

 primarily concerned with the propagation of river 

 mussels) is that of the U. S. Fish Commission at Fair- 

 port, Iowa, on the Mis- 

 sissippi River. 



In large streams, espec- 

 ially in their deeper and 

 more quiet portions, the 

 conditions of life are most 

 like those in lakes. In les- 

 ser streams life is subject 

 to far greater vicissitudes. 

 The accompanying figure 

 shows comparative sum- 

 mer and winter tempera- 

 tures in air and in water of 

 Fall Creek at Ithaca. This 

 creek (see the figure on 

 page 24), being much 

 broken by waterfalls and 

 very shallow, shows hardly 

 any difference between sur- 

 face and bottom tempera- 

 tures. The summer tem- 

 peratures of air and water 

 (fig. 22) are seen to main- 

 tain a sort of correspond- 

 ence, in spite of the thermal 

 conservatism of water, due to its greater specific heat. 

 This approximation is due to conditions in the creek 

 which make for rapid heating or cooling of the water. 



Fig. 22. Diagram showing summer 

 and winter conditions in Fall Creek 

 at Ithaca, N. Y. Data on air 

 temperatures furnished by Dr. W.M. 

 Wilson of the U. S. Weather Bureau. 

 Data on water temperatures by Pro- 

 fessor E. M. Chamot. 



