438 MR. J. E. H. GORDON ON MEASUREMENTS OF ELECTRICAL CONSTANTS. 
Name of dielectric. 
Glass—- 
Doable extra-dense flint 
Extra-dense flint . 
Dense flint. 
Light flint. 
Hard crown . 
Common plate, two spe¬ 
ctra ens— 
No. 1. 
Halbweisses g’lass 
White mnrren. 
Common flint . 
Ebonite, four slabs— 
No. 1. 
o 
99 .. 
„ 3. 
)> 4 . 
Best quality gntta percha 
Chattebton’s compound . 
India-rubber— 
Black. 
Grey vulcanized . 
Solid paraffin, specific 
gravity at 11° C. = '9109, 
melting point 68° C. Six 
slabs cut in planing ma¬ 
chine; results corrected 
for cavities— 
No. 1. 
2 
9 9 .. 
„ 3. 
„ 4. 
„ 5. 
„ 6. 
Paraffin, clear, quickly 
cooled. 
Slow cooled, white. 
Shellac ... 
Sulphur .... 
Bisulphide of carbon 
K as determined by 
present experiments. 
3164* 
3-054* 
3-013* 
3-108.* 
3-258 
3-228 
mean 3 - 243 
2-2697D 
2 I 097 > m ean 2'284< 
2-3077 J 
2-462. 
2-547. 
2-220 
2-497 
1-9940 4 
1-9784 
1- 9969 
2- 0126 
1- 9654 
2- 0143 
1-9936 
2-74 
2-58 
1-81. 
K as determined by 
experimenters 
mentioned in next 
column. 
10-1 . 
7-4 . 
6-85 . 
6-10 . 
2-96 
mean 3’31 
3-66 
5-83 . 
Greater than L76 
2" 76. 
3-15. 
2-21 . 
2-56. 
2-12 to 2-34 . 
2'69 to 2-94 . 
2-32 . 
1-96 . 
1-977 
Previous 
experimenters 
Hopkinson 
Hopkinson . 
Hopkinson . 
WijLLNER 
Schiller. 
Schiller 
Faraday . 
Siemens. 
Boltzmann 
Schiller. 
Whllner 
Schiller 
Schiller 
Boltzmann . 
WijLLNER . 
Gibson and 
Barclay 
References. 
‘ Proc. Roy. Soc.,’ 1877, p. 298, 
vol. xxvii. 
‘ Sitzb. Konigl. bayer. Akad.,’ 
March, 1877. 
Pogg. Ann., vol. clii., p. 535,1874 
‘ Exp. Res.’ 
‘Weiner Sitzb.,’ Jan. 9, 1873. 
‘ Sitzb. Konigl. bayer. Akad.,’ 
March, 1877. 
Pogg. Ann., vol. clii., p. 535, 
1874. 
Carl’s ‘ Repertorium,’ vol. x., 
pp. 92, 165. 
‘ Sitzb. Konigl. bayer. Akad.,’ 
March, 1877. 
Phil. Trans., 1871, p. 573. 
Specific gravity at 11° C., calculated from data in Messrs. Gibson 
and Barclay’s paper, ='9080. Multiplying Messrs. Gibson and 
Barclay’s value of K by ratio of specific gravities, we have 1-9833 
for my paraffin by Gibson and Barclay’s method. 
1-68 . 
1 - 
1 - 
2-00 . 
2"95 to 3"73 
IS } 1 ' 85 
2-88 to 3-21 
2- 24 . . . 
3- 84 . . . 
Schiller. 
Schiller. 
Faraday . 
Whllner 
WijLLNER 
Faraday . 
Boltzmann 
‘ Exp. Res.,’ 1270. 
‘ Sitzb. Konigl. bayer. Akad.,’ 
March, 1877. 
‘ Exp. Res.,’ 1266. 
Carl’s 1 Repertorium,’ vol. x., 
pp. 92, 165. 
* Note added September 25, 1879.—At tlie time (Christmas, 1877) when these experiments were made the glasses were newly 
cast. On repeating the experiments in August, 1879, it was found that the specific inductive capacities of all the optical glasses had 
considerably increased in the course of eighteen months, the new values being: D.E.D.F., 3'838 ; E.D.F., 3 621; L.F., 3-443; 
II.C., 3"310. For full details of these experiments see ‘ Report of the British Association,’ 1879, p. 250. 
