Leaving out the rate 23 as doubtful, the phonographic note made, at the beginning of the first reproduction of Series I, one beat per second with the fork; and toward the end, 1.6 beats. The variation here amounted then to .6 of a vibration, and according to the above table covered an interval of 4c, or the fiftieth part of a tone. In the second reproduction it was .8 of a vibration, or 5c; in the third, 1.1, or 7c; and in the fourth, .5, or 3c. The lowest rate of beating counted at any time during the ten minutes was 8, the highest 20, in ten seconds; the total span of the variation noted in the ten minutes being accordingly 1.2 vibration, or 8c, that is, one twenty-fifth of a tempered tone. During the ten second spaces the beats were not entirely regular, a certain momentary hurrying and slackening of them being occasionally noticeable.