26 CALORIMETERS FOR STUDYING RESPIRATORY EXCHANGE, ETC. 



THERMOMETERS. 



In connection with the calorimeter and the accessories, mercurial and 

 electric-resistance thermometers are employed. For measuring the tem- 

 perature of the water as it enters and leaves the chamber through horizontal 

 tubes, mercurial thermometers are used, and these are supplemented by 

 electric-resistance thermometers which are connected with a special form of 

 recording instrument for permanently recording the temperature differ- 

 ences. For the measurement of the temperatures inside of the calorimeter, 

 two sets of electric-resistance thermometers are used, one of which is a 

 series of open coils of wire suspended in the air of the chamber so as to 

 take up quickly the temperature of the air. The other set consists of resist- 

 ance coils encased in copper boxes soldered to the copper wall and are 

 designed to indicate the temperature of the copper wall rather than that 

 of the air. 



MERCURIAL THERMOMETERS. 



The mercurial thermometers used for measuring the temperature differ- 

 ences of the water-current are of special construction and have been cali- 

 brated with the greatest accuracy. As the water enters the respiration 

 chamber through a horizontal tube, the thermometers are so constructed 

 and so placed in the horizontal tubes through which the water passes that 

 the bulbs of the thermometers lie about in a plane with the copper wall, 

 thus taking the temperature of the water immediately as it enters and as it 

 leaves the chamber. For convenience in reading, the stem of the ther- 

 mometer is bent at right angles and the graduations are placed on the 

 upright part. 



The thermometers are graduated from to 12 C. or from 8 to 20 C. 

 and each degree is divided into fiftieths. Without the use of a lens it is 

 possible to read accurately to the hundredth of a degree. For calibrating 

 these thermometers a special arrangement is necessary. The standards used 

 consist of well-constructed metastatic thermometers of the Beckmann type, 

 made by C. Eichter, of Berlin, and calibrated by the Physikalische Tech- 

 nische Eeichsanstalt. Furthermore, a standard thermometer, graduated 

 from 14 to 24 C., also made by Eichter and standardized by the Physi- 

 kalische Technische Eeichsanstalt, serves as a basis for securing the absolute 

 temperature. Since, however, on the mercurial thermometers used in the 

 water-current, differences in temperature are required rather than absolute 

 temperatures, it is unnecessary, except in an approximate way, to stand- 

 ardize the thermometers on the basis of absolute temperature. For cali- 

 brating the thermometers, an ordinary wooden water-pail is provided with 

 several holes in the side near the bottom. One-hole rubber stoppers are 

 inserted in these holes and through these are placed the bulbs and stems of 

 the different thermometers which are to be calibrated. The upright por- 



