Fig. 7 shows a combination in which the styles _a_, _a′_, of two sending instruments cause the interruption of the current from the same battery B, so that the given vibrations should be between them in the relation of a tierce major, that is in the relation of four to five. Under such conditions, the currents are intermittent, and four contacts of _a_ are produced in the same space of time as the five contacts of _a′_, and the corresponding electric intensities will be represented by the indentations we see in A^2 and in B^2: the combination of these intensities A^2 + B^2 will produce the indentations at unequal intervals which may be observed on the third line. It is evident that although the current maintains a uniform intensity, there is less time for the breaks when the interrupting styles act together than when they act separately, so that when there are a number of contacts effected simultaneously by styles working at different degrees of velocity, the effects produced will have the effect of a continuous current. The maximum number of distinct effects which can be produced in this way will, however, greatly depend on the relation which exists between the durations of the make and break of the current. The shorter the contacts are, and the longer the breaks, the more numerous will be the effects transmitted without confusion, and _vice versâ_. By the aid of pulsatory currents the transmission of musical sounds is effected in the way indicated in fig. 8, and it is seen that when they are produced simultaneously, the result A^2 + B^2 is analogous to that which would be produced by a continuous current of minimum intensity. In the case of undulatory currents the result is different, but in order to produce them it is necessary to have recourse to inductive effects, and fig. 9 indicates the manner in which the experiment should be made. In this case, ‘the current from the battery B is thrown into waves by the inductive action of iron or steel reeds M, M, vibrated in front of electro-magnets _e_, _e_, placed in circuit with the battery: A^2 and B^2 represent the undulations caused in the current by the vibration of the magnetised bodies, and it will be seen that there are four undulations of B^2 in the same time as five undulations of A^2. The resultant effect upon the main line is expressed by the curve A^2 + B^2, which is the algebraical sum of the sinusoidal curves A^2 and B^2. A similar effect is produced when reversed undulatory currents are employed, as in fig. 10, where the current is produced by the vibration of permanent magnets united upon a circuit, without a voltaic battery.