During the past two months my attention has been directed to the telephone, chiefly as an instrument which illustrates in a remarkable way the delicacy of hearing. As some of these experiments are novel, and may possibly assist those who are investigating the physical phenomena of the instrument, I beg to give a short account of them to the Society. To save circumlocution in description, the term “proximal” will be applied to the telephone receiving the stimulus, and the term “distal” to the one at the other end of the arrangement. Thus, if A talks to B, A will use the proximal, and B the distal telephone.