The above specimen was selected because in it the readings were all taken by another and noted down without divulging them till the whole five sets were completed. The following is the calculation for V: 2d, 3d, 1st set. and 4th sets. 5th set. log c′ = 51607 51607 51607 " T = 99832 99832 99832 " d = 05131 05119 05123 ------- ------- ------- 56570 56558 56562 " r = 44958 44958 44958 ------- ------- ------- " tan φ = 11612 11600 11604 φ = 2694″.7 2694″.1 2694″.3 " c = 49670 49670 49670 " n = 41066 41066 41066 ------- ------- ------- 90736 90736 90736 " φ = 43052 43042 43046 ------- ------- ------- " V = 47684 47694 47690 V = 299800 299880 299850 In the following table, the numbers in the column headed "Distinctness of Image" are thus translated: 3, good; 2, fair; 1, poor. These numbers do not, however, show the relative weights of the observations. The numbers contained in the columns headed "Position of Deflected Image," "Position of Slit," and displacement of image in divisions were obtained as described in the paragraph headed "Micrometer," page 120. The column headed "B" contains the number of "beats" per second between the electric Vt₂ fork and the standard Vt₃ as explained in the paragraph headed "Measurement of the Speed of Rotation." The column headed "Cor." contains the correction of the rate of the standard fork for the difference in temperature of experiment and 65° Fahr., for which temperature the rate was found. The numbers in the column headed "Number of revolutions per second" were found by applying the corrections in the two preceding columns to the rate of the standard, as explained in the same paragraph. The "radius of measurement" is the distance between the front face of the revolving mirror and the cross-hair of the micrometer. The numbers in the column headed "Value of one turn of the screw" were taken from the table, page 127.