FURTHER LIMNOLOGICAL OBSERVATIONS ON THE FINGER 



LAKES OF NEW YORK. 



By EDWARD A. BIRGE and CHANCEY JUDAY, 

 Wisconsin Geological and Natural History Survey, Madison, Wis. 



INTRODUCTION. 



In 1 910 and 191 1 the U. S. Bureau of Fisheries enabled the authors of the present 

 paper to spend some weeks in the study of the Finger Lakes of New York. The results 

 of this work were published in the Bulletin of this Bureau for 1912 (Birge and Juday, 

 19 14). In this expedition there were applied to the study of the New York lakes 

 methods that had already been tried on the lakes of Wisconsin, which are much 

 smaller and shallower than those of New York. The resulting report dealt with the 

 hydrography of the lakes, their temperatures and heat budgets, their content of dis- 

 solved gases, and their net plankton. Since that study was made, the Wisconsin 

 survey has increased the scope of its observations on lakes. In particular there has 

 been devised and used extensively a new instrument, the pyrlimnometer, designed for 

 measuring the transmission of the sun's radiation through the water of a lake; numer- 

 ous determinations of the weight of the individual members of the net plankton have 

 been made; an elaborate study of the nannoplankton, both numerical and quantitative, 

 has been completed; and it is now possible to make a rough correlation between count 

 and weight of both net plankton and nannoplankton. 



The Bureau of Fisheries authorized a second expedition to the New York lakes 

 in July and August of 191 8, in order to apply these newer methods to them. The 

 following paper reports the results of the observations. 



The authors are indebted to Hobart College, Geneva, for the free use of its labora- 

 tories during their stay on the lakes, and to Prof. E. H. Eaton, of the same college, for 

 unwearied assistance in their work. Much of the success which was reached was due 

 to this aid. All recorded series of temperatures between 1911 and 191 8 were taken 

 by Prof. Eaton, as also were those taken after August i, 1918. 



This report comes from both of its authors, as was the case with their former paper 

 on the same subject. Mr. Juday, however, has prepared the part which deals with 

 the plankton and Mr. Birge that which relates to temperatures and transmission of 

 radiation. 



TEMPERATURES AND HEAT BUDGETS. 



The temperatures of the Finger Lakes were discussed in our former paper (Birge and 

 Juday, 1914, pp. 546-575), and it is unnecessary to repeat what was said there. Addi- 

 tional observations have been made and the discussion can be enlarged, therefore, at 

 certain points. 



