SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 8 = 



ments above referred to, and velocities (given in feet per minute) 

 determined as before with the Hill katathermometer. Before drawing 

 conclusions from the data in Table i it appeared advisable to obtain 

 more comparisons with other thicknesses of diaphragm. Pieces of 

 rubber of the 0.18 and 0.36 mm. thickness were stretched for several 

 days and then cemented into the calorimeter holes previously filled by 

 0.18 and 0.36 diaphragms. The new thicknesses measured 0.12 and 

 0.27 mm. A series of comparisons with these new diaphragms is sum- 

 marized in Table 2. 



Table I. 



From Tables i and 2, preliminary plots were made of the differences 

 calorimeter temperature minus room temperature and calorimeter 

 temperature minus thermoelement temperature, for each thickness of 

 diaphragm, and for the four conditions of air velocity, viz, o, 80, 180, 

 and 280 feet per minute. As would be expected, the difference 

 between the calorimeter temperature and the surface temperature 

 determined by the thermoelement appeared to be a linear function 

 of the difference between the calorimeter temperature and the sur- 

 rounding room temperature. For each of the plots the best straight 

 line was drawn through the points and the origin. From each of the 

 plots values of the calorimeter temperature minus thermoelement 

 temperature were read off at two places, 5° and 10° calorimeter tem- 

 perature minus room temperature. These values were then replotted 



