PROGRESS IN BIOLOGICAL INQUIRIES, 19 2 7 243 



use as laboratories and to set up the apparatus. The first observations of the 

 season were made on June 24 and the last on August 28. In this interval 

 observations were made on 233 lakes situated in Vilas and Oneida Counties. Ten 

 lakes were visited twice and one lake three times. Of the 233 lakes, 79 had been 

 examined in 1925 or 1926, or in both years ; 154 were visited for the first time 

 in 1927 ; and 5 lakes that were examined in 1926 were omitted this year. 



The field party consisted of E. A. Bir.ce and Chancey Juday, biologists ; Rex J. 

 Robinson, Henry M. Stark (to August 1), and F. H. L. Taylor, chemists; Lloyd 

 Setter (also a chemist) and Mrs. F. H. L. Taylor (during August), general 

 utility members. Another chemist, B. L. Browning, remained at Madison, giv- 

 ing full time to the determination of organic carbon in the dry residues from 

 lake water. In addition, work on the fish of the lakes was carried on directly 

 by the Bureau of Fisheries through Stillman Wright, aided by an assistant, 

 C. E. Juday. Mr. Wright will make direct report of his work to the bureau. 



The limnological work was along lines followed in 1926 and reported in that 

 year. Only one important new line of observation was started in 1927. The 

 University of Wisconsin provided the party with a motor-driven Sharpies super- 

 centrifuge, and with this 38 relatively large samples of plankton were obtained 

 from 24 different lakes, using from 30 to lOO liters of water for each sample. 

 These samples are to be analyzed by the chemists. 



The regular observations on each lake included the following : 



(1) On the lake, the temperature and transparency of the water. 



(2) In the laboratory, (a) two physical items — the color and conductivity 

 {total electrolytes) of the water; (6) 12 chemical items — hydrogen-ion concen- 

 tration, free and fixed carbon dioxide, oxygen, four forms of nitrogen (free 

 ammonia, nitrite, nitrate, and organic), soluble and organic phosphorus, silica, 

 and chlorides; and (c) one biological item — the amount of dry organic matter 

 in the centrifuge plankton. 



(3) Also in the laboratory, the securing and preserving of material for future 

 study, including (a) tow-net catches of plankton Crustacea, (b) quantitative 

 catches of net plankton wherever a series of samples was taken, (c) specimens 

 of the centrifuge plankton in all cases where the organic matter was deter- 

 mined, and (d) the dry residue from samples of water evaporated on the sand 

 bath at a temperature of about 75°. 



During the summer about 500 determinations of the hydrogen-ion concentra- 

 tion were made, representing all of the lakes examined and several depths in 

 many of them. About 400 determinations of organic matter were made in the 

 centrifuge plankton. The determinations of oxygen and carbon dioxide are 

 about as numerous as those of hydrogen-ion, and those of nitrogen, phosphorus, 

 silica, and chlorides are comparable with those of plankton. There are 408 

 samples of dry residue for chemical analysis, each representing ordinarily from 

 2.5 to 4 liters of water. A number of larger samples also were evaporated for 

 use in mineral analyses, and from six lakes large amounts of water were sent 

 to the university at Madison for evaporation in a vacuum pan. These were 

 from the lakes that had the smallest quantity of inorganic matter, and each was 

 about 115 liters of water. 



During 1926 the main attention of the field party was directed to gathering 

 series of samples from different levels in the deeper lakes, or at least samples 

 from surface and bottom in the case of shallower lakes. Eighty-nine such series 

 were obtained from 46 different lakes in 1925 and 1926. During the past sum- 

 mer 43 series were taken from 41 different lakes, including 11 lakes not so 

 examined before. Altogether, 57 lakes have been examined in this way, and 

 there are 132 sets of observations of this kind. The lakes include most of the 

 deeper lakes within 20 miles of Trout Lake. 



In 1927 the main attention of the party was given to securing data from as 

 many as possible of the larger lakes that could be reached from the labora- 

 tories. The practical limit of distance was 20 to 30 miles, as work had to be 

 carried on continuously. The lake must be reached, the work done on it, and 

 samples of water must be obtained and brought back to the laboratory in time 

 for the completion of the chemical and biological work during the day, or at 

 latest before the new samples of water came in the next day. 



Almost all of the larger lakes have been visited in an area of roughly 1,000 

 square miles, extending from the Michigan boundary to the north line of Town 

 XXXVII and lying between the Wisconsin River on the east and the Flambeau 

 on the west. A small number of lakes have been examined to the east of the 

 Wisconsin. The work of 1927 included about one-third of the area of the north- 

 eastern lake disti-ict and about the same proportion of its lakes, if the very 



