July 4, 1879. 1 0.1 2552.0 2 255.3 2551.7 3 510.5 2551.9 4 765.6 2551.9 5 1020.7 2552.1 6 1275.7 2552.0 7 1530.7 2551.8 8 1786.5 2551.4 9 2041.6 2551.7 10 2297.0 2551.5 ------- 11 2552.1 255.180 = mean ÷ 10. 12 2807.0 + .699 = reduction for mean time. 13 3062.4 + .003 = correction for rate. 14 3317.5 + .187 = correction for temperature. ------- 15 3572.8 256.069 = number of vibrations per second at 65° Fahr. 16 3827.7 17 4082.5 18 4335.9 19 4593.3 20 4848.5 The correction for temperature was found by Professor Mayer by counting the sound-beats between the standard and another Ut₃ fork, at different temperatures. His result is +.012 vibrations per second for a diminution of 1° Fahr. Using the same method, I arrived at the result +.0125. Adopted +.012. _Résumé of determinations made at Naval Academy._ In the following table the first column gives the date, the second gives the total number of seconds, the third gives the result uncorrected for temperature, the fourth gives the temperature (centigrade), the fifth gives the final result, and the sixth the difference between the greatest and least values obtained in the several determinations for intervals of ten seconds: July 4 20 255.882 27.0 256.069 0.07 5 19 255.915 26.4 256.089 0.05 5 18 255.911 26.0 256.077 0.02 6 21 255.874 24.7 256.012 0.13 6 9 255.948 24.8 256.087 0.24 7 22 255.938 24.6 256.074 0.05 7 21 255.911 25.3 256.061 0.04 8 20 255.921 26.6 256.100 0.02 8 20 255.905 26.6 256.084 0.06 8 20 255.887 26.6 256.066 0.03 ------- Mean = 256.072 In one of the preceding experiments, I compared the two Vt₃ forks while the standard was tracing its record on the cylinder, and also when it was in position as for use in the observations. The difference, if any, was less than .01 vibration per second. _Second determination_. (Joint work with Professor A.M. Mayer, Stevens Institute, Hoboken.) The fork was wedged into a wooden support, and the platinum tip allowed to rest on lampblacked paper, wound about a metal cylinder, which was rotated by hand Time was given by a break-circuit clock, the rate of which was ascertained, by comparisons with Western Union time-ball, to be 9.87 seconds. The spark from secondary coil of the inductorium passed from the platinum tip, piercing the paper. The size of the spark was regulated by resistances in primary circuit. The following is a specimen determination: