On page 150, Vol. iii, No. 2, November 20, 1920, line 18, for The resistance after, etc., read The resistance due to A and M after, etc.; line 20, of the same page, equation (4) should read as follows:

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page 151, line 11, equation (5) should read as follows:

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line 16, of the same page, for the value of O is 92.57 read the value of O is 82.57; lines 16 and 17, of the same page, for (92.57 – 10) ÷ (100 – 10) = 0.917 read (82.57) ÷ (90) = 0.917.