358 MR, A. E. TUTTON ON A COMPENSATED INTERFERENCE DILATOMETER. 



After these duplicate determinations with the same screw-length, an independent 

 series was taken on another day with a different setting of the screws. 

 Following are the results obtained : 



Expansion of Aluminium. 

 SERIES 1. 



Thickness of aluminium block, L^ = 12'188. 

 Length of screws above table points, I = 12'400. 

 Thickness of air-layer, d = 0'212. 

 Temperatures, t } = 10'l, t 2 = 68'9, t 3 = 123'4. 



t 3 t! = 58'8. t 3 ti = 113-3. 

 Pressures, 6, = 754, & 2 = 754'8, 6 3 = 756 millims. 

 Number of transited bands, /, = 30'35, f 3 = 60'32. 

 Correction for air refraction, 0"04, O'OG'. 

 Corrected number of bands, / 2 ' = 30'31, /,' = GO'26. 



Wave-length of light employed (C hydrogen), X = 0'0006562. |X = 0'0003281. 

 Diminution of thickness of air-layer, /' X = 0'0099449. /,' i X = 0'019772. 

 Elongation of tripod screws = measured length of screws X (a + 2fo for tripod 

 alloy) X temperature interval, 



I 



10- 9 (8600 + 4-56 -^y 

 10- (8600 -1- 4'56 ~ 



(t 2 ,) = 0-0064074. 

 (, - <,) = 0-012510. 



\ 



Expansion of aluminium block = diminution of thickness of air-layer + elongation 

 of screws, 



Lf 2 Lti = 0-0099449 + 0'0064074 = 0'0163523. 

 L, - L! = 0-019772 +0-012510 = 0'032282. 

 8 = O'OOO 268 23. <j> = O'OOO 000 125 31. 

 L = 12-1853. 

 a = 0-000022013. b = O'OOO 000 010 284. 



SERIES 2. 



Thickness of aluminium block, L, = 12'188. 

 Length of screws above table points, I = 12'400. 

 Thickness of air-layer, d = 212. 

 Temperatures, , = 8 '0, tz = 70'0, < 3 = 120 0> 6. 



t^ t l = 62-0. 3 ti = 112-6. 



Pressures, 6, = 755'1, & 2 = 7537, 6 3 = 752'7 millims. 

 Number of transited bands, / 2 = 32'20, f t = 60 '22. 



