424 A. L. Day and J. K. Clement — Gas Thermometer. 



moelements and of the pressure within the bulb. Between 

 each two pressure readings a reading of the barometer was 

 made by the observer at the gas thermometer, the barometer 

 having been arranged in a conveniently accessible position for 

 that purpose. All the readings were arranged in symmetrical 

 groups in such a way that the time rate of change of temper- 

 ature, if any, would fall out in the arithmetical mean of the 

 pressures and temperatures at the beginning and end of the 

 series. At the close of this set of observations, readings were 

 made of the three thermometers which gave the temperature 

 of the mercury column of the manometer. The temperature 

 of the unheated space requires no separate determination in 

 view of the fact that a change of 5° in the room temperature 

 does not affect it by an appreciable amount. The average 

 room temperature was therefore sufficiently accurate to deter- 

 mine the correction for the unheated space. 



Following such a series, the temperature was increased by 

 the desired interval and the same operation gone through with 

 again. Constant attention was of course required in the mean- 

 while to see that, in increasing the temperature of the furnace, 

 and therefore of the bulb, the pressures inside and outside 

 the bulb did not get too far apart. The same was true of the 

 cooling at the close of the series. 



Before the bulb was connected up with the manometer for 

 the final filling, readings were made of the position of the 

 fixed point which defines the constant volume upon the scale. 

 This was done by letting in mercury with both tubes open 

 and reading the mercury level in the long tube when the men- 

 iscus in the short tube was raised so as to be just tangent to 

 the fixed point. The following readings were obtained : 





Position of 



"Fixed 



POIXT " ON THE 



May \ 



Scale. 

 1 1906 









Temperature of Scale 





Scale reading 





Lower end 



Upper end 





em 



Thermometer No. 15 



Thermometer No. 11 





69-049 





22*4° 



22-8° 





■050 





22-5 



23-0 





■051 





22-5 



23'1 





•053 





22-7 



23-4 





•054 





22-6 



23-6 





•055 





22-6 



23-7 





•054 





22-6 



23-7 



Mean 



69-0523 



2 5 "5 6 



23-33 



Correction — •001 





— 0-3 

 22-26 



— 0-45 





69-051 



22-88 





69-051 





22-57° 



