62 



PROCEEDINGS OP THE AMERICAN ACADEMY 



From the preceding table it is seen that the ether thermometer 

 cannot be used to measure temperatures accurately. The coefficient 

 of expansion of ether is by no means constant, and besides the ether 

 adheres to the sides of the thermometer tube. The real value of the 

 coefficient cannot be obtained from these results, as only the bulb of the 

 thermometer was subjected to the low temperature ; but as the bulb 

 was very large in proportion to the bore of the tube, an approximate 

 value may be obtained. 



When the temperature, as given by the air thermometer, was 



— 60° .2 C the ether thermometer stood at — 42° .3 C; the reading 



42.3 

 of the ether thermometer was — -^ of what it should have been if it 



dO.2 



contracted regularly. Thus temperatures in the neighborhood of 



— 42° C, as given by the ether thermometer, can be corrected, and 



60.2 

 more approximate results obtained, by multiplying by jy-o = 1.42. 



It should be remembered that the temperatures thus obtained are 

 by no means accurate ; they are only rough approximations. 



Applying this correction to the temperatures given by the ether 

 thermometer, we have : — 



If now the values of d X E from all the preceding tables are mul- 

 tiplied by the constants necessary to obtain the absolute values of the 

 electromotive forces, the preceding results may be summed up in 

 the following table. The first column gives the temperatures of one 

 junction of the copper and nickel ; the other junction was always 

 at 0°. The second column gives the absolute values of the corre- 

 sponding electromotive forces, in the C. G. S. system of units. The 

 third column gives the differences between the alternate electromotive 

 forces. And the fourth the differences between the corresponding 

 temperatures. 



