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Durand, Loyal, Jr. (ed.) / Transactions of the Wisconsin Academy of Sciences, Arts and Letters
volume XXXI (1938)

Whitney, Lester V.
Continuous solar radiation measurements in Wisconsin lakes,   pp. 175-200 PDF (7.7 MB)

Page 176

 176 Wisconsin Academy of Sciences, Arts, and Letters 
ords of solar energy both in air and in water at various depths. With such
records, the total solar energy delivered to the surface of the lakes, and
its transmission to various depths, could be found under all conditions normally
present in summer. The central part of the apparatus was a Cambridge Double
Recorder which measured continuously the solar energy received by several
thermopiles or Photox cells. In 1935 records were made on four lakes of different
color and transparency; these were Trout, Crystal, Boulder, and Muskellunge.
The records were checked and standardized with records of solar energy made
by an automatic Kipp Solarimeter with a Richard Recorder. The Kipp Solarimeter
in turn was calibrated in terms of the standard solarimeter used by the United
States Weather Bureau in Madison, Wisconsin. In 1936 the work was confined
to Trout Lake, 
- but Photox cells as well as thermopiles were used, continuous records being
taken at greater depths than before. 
 The apparatus was set up so that it could be readily moved from lake to
lake. The recorder itself was supported by a 
- strong wooden frame solidly bedded on the sandy shore of the lake. It was
covered by a tent, but for special protection a large wooden case covered
the recorder and its frame. The purpose of the case was to protect the recorder
if a wind storm should carry the tent away. Happily no such storm occurred;
the recorder functioned perfectly throughout both summers. 
 It should be added that the -recorder was received by the Survey in August
1934. The general arrangement of recorder and thermopiles was worked out
and the apparatus set up on Trout Lake at that time by Mr. Donald Kerst.
The instrument came at so late a date in August that records for only a few
days could be made. 
 The recorder itself consists essentially of two galvanometers so arranged
that a continuous record can be made on a rotating drum by arms which extend
out from the galvanometers. Below the ends of these arms and just above the
drum is an inked thread. A chopper bar descends once a minute, pressing the
arms and thread against the paper, leaving dots on the record. The galvanometer
swings freely between readings. Just after the dots are made, automatic switches
are thrown, connecting the galvanometers to other thermopiles or Photox cells.
At the same time a different colored thread is moved under the chopper 

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