[wheeler] CUBICAL EXPANSION OF VITREOUS QUARTZ 153 



The recent work of C. B. James 1 at the Macdonald Physics 

 Building, McGill University, on the expansion of mercury at low 

 temperatures by the silica dilatometer method, is in accord with the 

 more recent view of Callendar that the cubical expansion of a fused 

 silica bulb may be calculated from the linear expansion and cannot 

 be neglected at low temperatures. 



IV. 



THE MOST PROBABLE MEAN VALUE OF THE 

 LINEAR EXPANSION. 



Since it appears that the cubical expansion of fused silica may 

 be calculated very approximately from the linear, an accurate knowl- 

 edge of the latter is of interest to those using dilatometers and other 

 forms of apparatus constructed of fused silica. Accordingly, the 

 averages of what appear to be the most accurate determinations have 

 been arranged in convenient form for reference. 



Following the method adopted by Mr. Kaye in 1910, the values 

 of (l t — 1 ) /1 , (where l t is the length at t°C. and 1 that at 0°C.) 

 obtained from the results of various observers, have been arranged 

 in Tables III, IV, and V. In the tables, the means of the values 

 given appear in the last column. 



In addition to results already referred to, those of Scheel and 

 Heuse 2 published in January, 1914, are included. The values which 

 they obtained between — 253° and 100°C. are represented by the 

 formula : — 



l t = 1 [1 + -362 t + -001813 t 2 - -00000340 t 3 ] 10- fi . 



Table III. 



1 Trans. Roy. Soc. of Canada, Sec. Ill (3) 8, pp . 51-58. 1914. 



2 Verh. d. D. Phys. Ges. 16, pp. 1-3, 1914. 



Sec. Ill, 1914—11 



