Lake Maxinkuckee, Physical and Biological Survey 197 



Serial water temperatures : — In addition to the observations on 

 the temperature of the surface of the lake, many serial tempera- 

 tures were taken. On July 18, 1899, a regular observation station 

 was established at the deepest place in the lake, known as the 

 Deep Hole, where the water is 89 feet deep at the ordinary stage 

 of water. A buoy was placed to mark the station. Readings 

 were taken daily i'rom July 18 to September 30, 1899, and from 

 July 17, 1900, to June 28, 1901, not daily but usually two to three 

 times a week. Readings were taken at the surface and usually at 

 5-foot intervals from the surface to the bottom. Usually the 

 temperature of the air also was recorded, and the condition of the 

 sky and direction of the wind noted. 



From July 18 to August 14, 1899, a self-registering Negretti- 

 Zambra deep-sea thermometer was used. From August 15 to Sep- 

 tember 21, a Ritchie thermophone was used, with not wholly satis- 

 factory results, after which the deep-sea thermometer was again 

 used. 



A similar serial-temperature observation station was estab- 

 lished July 30, 1899, at the Kettlehole, in the southwest corner of 

 the lake, in which the maximum depth is 40 feet. Seven sets of 

 records, at 5-foot intervals, were made there in July, August and 

 September, 1899, and 12 sets in July, August and September, 1900. 

 More than 150 water-temperatures were recorded at the Kettle- 

 hole, and over 4,200 at the Deep Hole. The total number of water- 

 temperatures taken and recorded is therefore about 10,000. Most 

 of the surface temperatures are given in the tables on the preceding 

 pages and the serial temperatures will be found in the following 

 tables. 



Temperatures at the Deep Hole: — Many serial temperature 

 records were made at the Deep -Hole. These are set forth in the 

 tables on the following pages. An examination of these vari- 

 ous tables reveals some very interesting facts, particularly with 

 reference to the position of the thermocline, that is, the line or 

 depth of most rapid change in temperature. 



During the winter months, when the lake is covered with ice, 

 the temperature of the water from top to bottom is quite uniform, 

 the variation sometimes being nil, and usually not more than 2 or 

 3 degrees. When the ice goes off in the spring, the sun's rays 

 begin to affect the upper strata of the water to gradually increasing 

 depths. From a mean surface temperature of 33.1^ in February, 

 it rose in March to 34.8°, in April to 45.8 \ in May to 62% and so 

 on, until in August it reached 80.1°. By INIay the water had 



