296 



Dr. W. Miller on a 



In fig. 5 the curves giving the course of the beam are 

 shown, with an enlargement which indicates the " micro- 



scopic" form of the rajs in the neighbourhood of the point 

 r 2 / ri = 4/3, 0=tt/2. 



XXIV, A Constant Pressure Gas Thermometer. By 

 William Miller, M.A., JD.Sc, Ph.D., Senior Science 

 Master, Dollar Institution *. 



THE difficulties of construction of a satisfactory gas 

 thermometer, either for laboratory practice or for 

 refined measurements, are well known. A correction is 

 always necessary for that part of the gas which occupies the 

 stem of the instrument, unless the bulb and all that part of 

 the stem occupied by the gas are immersed in the same bath. 

 The importance of this correction increases as the temperature 

 rises, and as more and more gas is expelled from the bulb 

 into the stem, so that the mass of gas contained in the stem 

 becomes comparable with that enclosed by the bulb. 



In colleges and schools the direct verification of Charles's 



* Communicated by the Author. 



