. The crustacea of the plankton, July, 1894-Dec., 1896 . nts employed until July 27th, 1896, after which date a ther-mophone was used. The latter instrument has proved extremelyuseful and accurate. A full description of the instrument maybe found in Science, Vol. II. of 1895, page 639. As constructedfor my work, the instrument ranges from minus 5 to plus 30degrees C, each degree being graduated into fifths. There isno difficulty in reading the instrument to less than degreeC, and its readings are exceedingly accurate, agreeing exactlywith those of a standard thermometer with which it has b
. The crustacea of the plankton, July, 1894-Dec., 1896 . nts employed until July 27th, 1896, after which date a ther-mophone was used. The latter instrument has proved extremelyuseful and accurate. A full description of the instrument maybe found in Science, Vol. II. of 1895, page 639. As constructedfor my work, the instrument ranges from minus 5 to plus 30degrees C, each degree being graduated into fifths. There isno difficulty in reading the instrument to less than degreeC, and its readings are exceedingly accurate, agreeing exactlywith those of a standard thermometer with which it has beenconstantly compared. Observations can be made very rapidly,the time of a single reading varying from one to one and a halfminutes, according to the amount of change of temperature-from the last reading. Tha temperature bottle contained about 1^ litres and had asmall neck. It was lowered to the desired depth; allowed to re-main from one to three minutes for the glass to acquire the tem-perature of the water; was then uncorked by a sudden jerk on the*. 00 «D 00 «D Temperatures. 287 line, and allowed to fill. It was then drawn rapidly to the sur-face and the temperature read by means^of a long-stemmed ther-mometer graduated to one-fifth of a degree. The time of rais-ing the bottle from the bottom of the lake was ordinarily aboutten seconds; and the small size of the opening prevented mix-ture of the upper water with that in the bottle. The tempera-ture of the water in the center of the bottle, which was meas-ured by the thermometer, did not change perceptibly during thetime required for the thermometer to set. The water from thelower part of the lake, however, was somewhat warmed by con-tact with the glass and the air in the bottle. This error wascarefully determined by comparison with the thermophone, andis about one-fifth of a degree C, when the difference betweensurface and bottom is about 10 degrees. Errors much more considerable than this occur with the useof the tempera
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