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Page:Proceedings of the Royal Society of London Vol 59.djvu/180

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166
[Dec. 12,
Indices of Refraction for the Electric Ray.

It will be observed that the final results obtained from the two sets are freed from many of the unavoidable errors.

I give below the results of two sets of experiments each extending through eleven observations. The receiver was in an unusually good condition for nearly an hour, and during that time I took six observations with P to the front and six more with Q in the same position. As the receiver continued to remain in a fairly responsive condition I took five more for each set. As I have said already, greater weight should be given to the first two sets of six readings, as being taken under the most favourable conditions.

In the first two lines are given ten successive differences of the mean readings, taken with the cylinders P and Q.

P .... 71 70 70·5 70·5 70·5 70 69·5 69·5 69·5 70 = 701
Q .... 70 70 71 71 70 71 71 70 70 69·5 = 703·5
Mean .... 702·25

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The following are the readings in degrees for the first six sets of observations with P or Q.

P.
a. b. Mean. Difference.
1.......... 216 144 188  
71
2.......... 144 74 109
70
3.......... 74 4 39
70 .5
4.......... (360 )+4 293 328 ·5
70 ·5
5.......... 293 223 258
70 ·5
6.......... 223 152 187 ·5
352 ·5 .... A.
 
Q.
c. d. Mean. Difference.
1.......... 308 360 +18 343
70
2.......... 18 88 53
70
3.......... 88 158 123
71
4.......... 158 230 194
71
5.......... 230 300 265
70
6.......... 300 360 +10 335
352 ·0 .... B.
 

Mean of A–B = 352·25.

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