MR. A. E. TUTTON ON A COMPENSATED INTERFERENCE DILATOMETER. 355 



SERIES 4. 



Length of screws above table, L^ = 12'369 = thickness of air-layer, d. 

 Temperatures, x = 10'8, t, = 707, *, = 121'l. 



t 2 , = 59-9. t a ti = 110-3. 

 Pressures, &, = 761 '5, Z> 2 = 76 TO, & 3 = 7597 millims. 

 Number of transited bands, f z = 21-61, f s = 4078. 

 Correction, -f 2'26, + 3'65. 



Corrected number of bands, / 2 ' = 23'87, f 3 ' 44'43. 

 Wave-length of light employed, X = 0'000546. X = 0'000273. 

 Elongation of screws, L 2 L^ = 0'0065164. Lt a L^ = 0'012129. 

 ^=0-00010688. (j> = O'OOO 000 023 394. 

 L = 12-3678. 

 a = O'OOO 008 642 1. & = O'OOO 000 001 891 5. 



SERIES 5. 



Length of screws above table, L<i 12'369 thickness of air-layer, d. 

 Temperatures, *, = 10'3, t, 68 '1, t 3 = 118 0> 8. 



, <! = 57-8. t 3 ti = 108-5. 

 Pressures, ^ = 765'3, 6 2 = 766'0, b 3 = 766'8 millims. 

 Number of transited bands, / 2 = 20'78, / 3 = 40'14. 

 Correction, + 2'19, -f 3'58. 



Corrected number of bands, // = 22*97, f 3 ' = 4372. 

 Wave-length of light employed, X = "000546. |X = "000273. 

 Elongation of screws, Lt 2 L, = Q-0062708. ~Lt 3 Lt r = 0"011935. 

 = 0-000 106 15. <jt = O'OOO 000 029 846. 

 L = 12-3678. 

 a = O'OOO 008 582 8. b = O'OOO 000 002 413 2. 



The results dei'ived from the five series are compared in the following table, and 

 the mean values for a and b extracted : 



