Page:Collected Physical Papers.djvu/178

158 responded, exhibiting almost its original sensibility. Observe how the subsequent portion of the curve is a repetition of the curve No. 28, and how the substance arrives at the second fatigued state b′. To observe the

effect of mechanical disturbance a gentle tap was given to the receiver, and at once there was produced an increase of resistance due to the transformation of B into A, the receiver regaining its sensitiveness by the transformation. The action of radiation was continued, and after a few reversals the substance once more arrived at the third fatigued state, b″. The process described above could be repeated any number of times.

Experiments similar to the above were carried out with an arsenic receiver. From the curve given below