Intelligence and Miscellaneous Articles. 235 



of temperature resulting from this last cause can be represented by 



m 



_ r i-233 ? m being a constant dependent only on the elasticity of the 



air, and r the observed excess. We should have, then, in vacuo 

 with the two thermometers the two equal excesses 



12-51 +gl2-51 1 -* 33 : 



10 + — —10 1 ' 233 , whence m- 



S'D 



:2'24. 



Let us take in the same way the observations of 3 h 45 m , 4 h , and 

 4 h 20 m , all three made with the same diaphragm, but different from 

 the preceding one ; they conduct to the equation 



9-77+ ^-9-77 1,233 : 



O'D 



12-15+ g 12-15 1 ' 233 , whence m==2-09. 



Let us adopt for the value of the coefficient of cooling m the mean 

 of the two values thus obtained, m=2*15 ; with the aid of this co- 

 efficient we can draw up the following Table of the temperatures 

 which would have been observed in vacuo : — 



Time. 



Temperature of 

 the enceinte. 



Temperature of the 

 large thermometer. 



Temperature of the 

 small thermometer. 



h m 

 2 40 



2 55 



3 10 

 3 30 



3 45 



4 

 4 20 

 4 35 



1410 

 1405 

 14 05 

 14-00 

 13-95 

 1390 

 13-85 

 13-80 



o 



35*40 (diaphragm a) 

 34*64 (diaphragm b) 



o 



34-54 (diaphragm b) 

 33 - 6'5 (diaphragm c) 

 34-20 (diaphragm a) 



33 50 (diaphragm a) 

 33-10 (diaphragm a) 







33-83 (diaphragm a) 







On tracing the curve representing the course of the thermometer 

 for one and the same admission-aperture, it is readily recognized 

 that the relative temperatures at the different periods all combine 

 with perfect regularity, whether they come from the large or the 

 small thermometer. 



Let us now consider two experiments made with different dia- 

 phragms • and as the small thermometer is that which approximates 

 most nearly to the theoretical conditions (especially for small ad- 

 mission-apertures), let us take the three experiments relative to 

 3 h 10 m , 3 h 30 m , and 3 h 45 m . Making use of the curve of the tem- 

 peratures for the diaphragm «, and reducing all to one and the 

 same temperature, 14°, of the enceinte, we have for the tempera- 

 tures at one and the same period: — 



o 



Diaphragm a 34*45 



Diaphragm b 34-0S 



Diaphragm c 33*70 



Applying to these data the equation I established in my previous 



