CHAPTER D 



NANSEN BOTTLES AND REVERSING THERMOMETERS 



D-1 General Remarks. — Sea water samples 

 are collected from various depths in the ocean 

 by means of specially adapted water sampling 

 bottles. The first bottle was invented by Hooke 

 in 1611. Since then, more than 50 types have 

 been developed and used by different oceano- 

 graphic institutions throughout the world, how- 

 ever, the types of bottles in general use have 

 been reduced to a few of simple but rugged 

 design. This is so because only a few are de- 

 signed to withstand the rigorous working con- 

 ditions and have specific or desirable features. 

 The type used by the Oceanographic Office is 

 a modification of the one developed by the Nor- 

 wegian arctic explorer and oceanographer, 

 Fridtjof Nansen, in the latter part of the 19th 

 century. This type is known as the Nansen 

 bottle. 



Water temperatures at various depths are ob- 

 tained with deep sea reversing thermometers. 

 These special thermometers are attached to the 

 exterior of the Nansen bottle. Re\ersing ther- 

 mometers were first developed by the firm of 

 Negretti and Zambra, of London, in 1874. Pres- 

 ently used deep sea reversing thermometers are 

 precision instruments and have changed very 

 little since first developed. 



D-2 Deep Sea Reversing Thermometers. — 



Deep sea reversing thermometers are delicate, 

 highly accurate, mercurial thermometers spe- 

 cially designed for determining in sifu water 

 temperatures. There are two types of reversing 

 thermometers : Protected and unprotected. The 

 temjierature scale is Celsius (centigrade) and 

 is carefully etched on the glass stem. Each ther- 

 mometer is calibrated by tne manufacturer, and 

 all thermometers used by the Oceanographic 

 Office also are calibrated by the U.S. Naval 

 Oceanographic Instrumentation Center before 

 they are used at sea. In addition, thermometers 

 are recalibrated at periodic intervals throughout 

 their life. The scale is read with a thermometer 

 reader or viewer. Each thermometer actually 

 consists of two instruments : One, the reversing 

 thermometer which is called the mairi ther- 

 niomefer; the other, an ordinary thermometer 

 which is called the auxiliary tlxermometer. 



D-3 The Main Thermometer.— The main 

 thermometer is essentially a double-ended ther- 



mometer (fig. D-1). In the upright or lowering 

 position, it has a large reservoir of mercury at 

 the lower end connected by means of a fine 

 capillary to a small bulb at the upper end. The 

 capillary is constricted and branched just above 

 the reservoir. This branching point is called the 

 appendix dead arm. The function of the appen- 

 dix is to pi'ovide a means of separating the mer- 

 cury in the stem from the mercury in the reser- 

 voir. Above the appendix, the thermometer is 

 bent in a 360° loop, called the pigtail, from 

 which it continues straight and terminates with 

 the bulb at the upper end. The thermometer is 

 so constructed that in the upright or lowering 

 position mercury fills the reservoir, the capillary 

 (pigtail and stem), and sometimes part of the 

 bulb, depending upon the temperature. When 

 the thermometer reverses, the mercury column 

 breaks at the appendix and descends into the 

 bulb, filling it and part of the stem, thus indi- 

 cating the temperature at the depth of reversal. 

 The mercury remains at this reading until the 

 thermometer is returned to the upright position 

 when the mercury drains from the bulb and 

 back into the reservoir. 



D-4 The Auxiliary Thermometer. — The aux- 

 iliary thermometer is a small, ordinary mercu- 

 rial thermometer that is mounted alongside the 

 main thermometer (fig. D-1). It is used to ob- 

 tain the air temperature at the time the main 

 thermometer is read. The auxiliary temperature 

 is needed as corrections must be applied to the 

 main thermometer reading to compensate for 

 the change in volume of the mercury in the 

 main stem. This volume of mercury changes ow- 

 ing to the difference between the m situ water 

 temperature and the air temperature. 



D-5i Protected Reversing Thermometers. — 



The main and auxiliary thermometers of pro- 

 tected reversing thermometers are enclosed in 

 a heavy glass jacket (fig. D-1). The jacket is 

 sealed at both ends and the air within is partial- 

 ly evacuated. The space surrounding the reser- 

 voir of the main thermometer is filled with 

 mercury. This mercury serves as a thermal con- 

 ductor and gives the instrument greater sensi- 

 tivity to temperature change. The sealed jacket 

 protects the thermometer from hydrostatic 

 pressure thereby giving a true reading of the 



D-1 



