Keeping these points in mind, it is very remarkable that when Graham Bell, fourteen years later, followed Reis “into the field of telephonic research,” he selected the very same method of expressing the relations between sounds and the undulations which corresponded with them. To show how remarkably in agreement the views of Reis and Bell are upon this question of representing by a curve the undulations which correspond to the voice, we select the following paragraphs and place them in parallel columns. _Reis._ That which is perceived by the auditory nerve ... may be =represented graphically=, according to its duration and magnitude by a =curve=.--(Memoir ‘On Telephony’ in the Jahresbericht of the Physical Society of Frankfurt-a.-M. 1860-61, p. 59.) [p. 53.] =The height or depth of the sound produced= ... depends upon =the number of vibrations made in a given time=.--(_Ib._ p. 63.) [p. 59.] _Bell._ Electrical undulations, induced by a body capable of inductive action, can be =represented graphically=, without error by the same sinusoidal =curve= which expresses the vibration of the inducing body itself, and the effect of its vibration upon the air; for, as stated above, the rate of oscillation in the electrical current corresponds to the =rate of vibration= of the inducing body--that is, to =the pitch of the sound produced=.--(Specification of U. S. Patent No. 174,465, dated March 7, 1876.) _Reis._ The greater the condensation of the sound-conducting medium at any given moment, the greater will be the =amplitude= of vibration of the membrane.--(_Ib._ p. 58.) [p. 52.] _Bell._ The intensity of the current varies with the =amplitude= of the vibration--that is, with the loudness of the sound;--(_Ib._) _Reis._ ... each tone is dependent not only on the number of vibrations of the medium, but also on the =condensation or rarefaction= of the same.--(Legat’s Report, Zeitschrift des D.-Oesterr. Telegr. Vereins, 1863, p. 125.) [p. 77.] _Bell._ and the polarity of the current corresponds to the direction of the vibrating body,--that is, to the =condensations and rarefactions= of air produced by the vibration.--(_Ib._) _Reis._ Let us exhibit the condensation curves for three tones--each singly (Plate I): then, by adding together the ordinates corresponding to equal abscissæ, we can determine new ordinates and develop a new curve which we may call the =combination-curve=. Now this gives us just exactly what our ear perceives from the =three simultaneous tones=.--(Memoir ‘On Telephony,’ p. 59.) [p. 54.] _Bell._