[wheeler] CUBICAL EXPANSION OF VITREOUS QUARTZ 149 



Soon after, there appeared an article by N. Eumorfopoulos 1 in 

 which he took the view with Scheel and Heuse that the values of 

 Callender and Moss for the expansion of mercury were too low, 

 especially below 100°C. He had determined the cubical expansion of 

 the bulb of a fused silica weight thermometer. His results for the 

 cubical expansion, which were obtained from the apparent 

 expansion observed and the values of the absolute expansion of mer- 

 cury as given by various observers, are shown in Fig. III. (which is 

 taken from Eumorfopoulos' paper), curves I. -II I. Eumorfopoulos 

 concludes that Callendar and Moss's values for the expansion of mer- 

 cury lead to inadmissable values for cubical expansion of fused silica 

 at low temperatures. 



Curves IV, and V, obtained from Scheel's value for the linear 

 expansion of two different specimens of fused quartz, led Eumorfo- 

 poulos to conclude that for accurate work it was unsafe to apply 

 results obtained from one specimen of silica to another. While this 

 discrepancy between the values for the cubical expansion of mercury 

 corresponds to a difference of 50% or more between the axial and 

 radial expansions of silica, it would be explained, as Callendar 2 points 

 out in his reply to the criticism of Scheel and Heuse, by a difference 

 of only 2% in the case of verre dur. In a paper which soon appeared, 

 Callendar 3 described an experiment in which the axial and radial 

 expansions of a quartz tube, obtained from the Silica Syndicate who 

 had supplied the bulbs used by Harlow and Eumorfopoulos, were 

 directly compared by the interference method. The axial coefficient 

 between 0° and 100°C. was found to exceed the radial by -20 x 10- 6 . 

 Assuming, as Callendar did, -465 x 10- 6 as the axial coefficient, the 

 cubical coefficient comes out to be -995 x 10- 6 , — a result in entire 

 agreement with Harlow's experimental value. 



Thus, to quote from Callendar, "The principal objection advanced 

 by Eumorfopoulos against the results of Callendar and Moss, at low 

 temperatures where the observations are admittedly more difficult, 

 appears to be that, according to his weight thermometer, the cubical 

 expansion of silica would vanish between 0° and 15°C. This apparently 

 impossible result is confirmed by the observations with the ring and tri- 

 pod, which show that the difference between the axial and radial 

 coefficients increases, while the axial coefficient diminishes more 

 rapidly at low temperatures." 



Had the matter ended here, we might have been content to 

 accept Harlow's lower value for the cubical expansion of fused quartz 



1 Phil. Mag. (6) 23, pp. 653-655, 1912. 



2 Phil. Mag. (6) 23, pp. 679-683, 1912. 



3 Phil. Mag. (6) 23, pp. 998-1000, 1912; ZS. f. Instrkde 32, pp. 19-1-195, 1912. 



