#Or (2) by heightened response.#--The removal of sluggishness by vibration, resulting in increased molecular mobility, is in other instances attended by increase in the height of response, as will be seen from the two sets of records which follow (fig. 64). Cold, due to prevailing frosty weather, had made the wires in the cell somewhat lethargic. The records in (_a_) were the first taken on the day of the experiment. The amplitudes of vibration were 45 deg., 90 deg., and 135 deg.. In (_b_) are given the records of the next series, which are in every case greater than those of (_a_). This shows that previous vibration, by conferring increased mobility, had heightened the response. In this case, removal of molecular sluggishness is attended by greater intensity of response, without much change in the period of recovery. In connection with this it must be remembered that greater strain consequent on heightened response has a general tendency to a prolongation of the period of recovery. [Illustration: FIG. 64 (_a_) Three sets of responses for 45 deg., 90 deg., and 135 deg. vibration in a sluggish wire. (_b_) The next three sets of responses in the same wire; increased mobility conferred by previous vibration has heightened the response.] It is thus seen that when the wire is in a sluggish condition, successive vibrations confer increased molecular mobility, which finds expression in quickened recovery or heightened response. #Effect of temperature.#--Similar considerations lead us to expect that a moderate rise of temperature will be conducive to increase of response. This is exhibited in the next series of records. The wire at the low temperature of 5 deg. C. happened to be in a sluggish condition, and the responses to vibrations of 45 deg. to 90 deg. in amplitude were feeble. Tepid water at 30 deg. C. was now substituted for the cold water in the cell, and the responses underwent a remarkable enhancement. But the excessive molecular disturbance caused by the high temperature of 90 deg. C. produced a great diminution of response (fig. 65). [Illustration: FIG. 65.--RESPONSES OF A WIRE TO AMPLITUDES OF VIBRATION 45 deg. AND 90 deg. (_a_) Responses when the wire was in a sluggish condition at temperature of 5 deg. C. (_b_) Enhanced response at 30 deg. C. (_c_) Diminution of response at 90 deg. C.]