191 



Procedure, Series I. — For this series of measurements the tube A was 

 kept at steam temperature, while the tube B was paclied in melting ice. 

 The tubes were first carefully cleanecT, washed with acid and alkali solu- 

 tions, rinsed and dried, then mounted in place as in Fig. 2. Dry air free 

 from CO» was drawn through them for some time, meanwhile gently 

 warming them with bunsen burners. A small amount of the quartz powder, 

 previously heated and cooled in a dessicator, was introduced, and the dry 

 air suction continued for some time. The apparatus was iheu racked and 

 tilted as described above in order to effect a proper distribution of the 

 powder, steam was admitted about A and the ice bath placed about B. 

 After a period ranging from one to two hours, with both tubes open to 

 the atmosphere through the drying train, the glass rod was rubbed, the 

 temperatures and atmospheric pressure were observed and the steam and 

 ice baths were withdrawn. After some hours the figures were measured 

 in the manner above described. The thermometers used were frequently 

 compared with standards, and the temperature in the steam jacket was 

 constantly checked from standard barometer readings. One complete set 

 of average wave length measurements is given in table I, and the data for 



eight such experiments, together with calculated values of " are 



"'I 00 



given in table II. 



Tube A, in 



Stearti. 





Ti'be B, in 



Melting Ic 





55.43 





A 



63.73 





/., 



93.50 





38.07 



96.47 





32.74 



132.13 





38.63 



129.23 





32.76 



170.37 





38.24 



162.03 





32.80 



20880 





38.43 



194.50 





32.47 



246.80 





.38.00 



227.60 





33.10 



285.13 





38.33 



260.80 





33.20 



323.47 





38.34 



293.77 





32.97 



361.60 





38.13 



326.03 





32.26 



399.95 





38.35 



358.97 





32.94 



438.17 





38.22 



391.63 





32.66 



476.23 





.38.06 



424.93 





32.30 



514.33 





38.10 



457.87 





32.94 



553.10 





38.77 ' 



490.50 





32.63 



591.20 





38.10 



523,10 

 556.00 

 589.17 





32.60 



32.90 

 33.17 



Most probabl 



s value of 



Most probable value of 



A = 38.262 mm. d 



- 0.01, 





/ = 32.838 mm. 



± 0.01, 





e — 0.225 mm. 







e = 0.279. 







Table 1. 



