Next as to the sense of Hearing. Peculiar difficulties attend the explanation of this sense. There is only one main line of access to the inner ear, where the nerves are distributed, namely, the solid chain of bones of the middle ear; and that line can hardly be supposed capable of conveying at the same instant a plurality of different series of vibrations. Yet we fancy that we hear a concurring plurality of sounds. Of what avail would be a band of a hundred performers if there were no power of taking in simultaneous pulses of sound? There is, however, an absence of accurate investigation of this point; no one has endeavoured to ascertain how much of the complex effect is due to the rapid transitions of the ear from one sound to another, how much to the concurrence of several series of pulses in one augmented series, and how much to the composition of successive effects in the ear into a synchronous whole in the emotional wave, or general excitement of the brain. It will be found, by any careful observer, that in listening to a band, we are really occupied with very few of the sounds at the same instant of time; we perform a number of rapid movements of the attention from one to another; while, at each moment, we are under an influence remaining from the recently occurring beats, to which we are not now giving our full attention. Touch is exactly parallel to Sight, and need not be dwelt upon. In Smell, and in Taste, we may have a plurality of distinguishable effects at one moment: we often experience complex odours and tastes. The above remarks will apply to these. The undoubted tendency of the mind is to single out, for attention, the separate constituents by turns, and to pass with rapidity from one to another; while it is also true that the individual effects that are for the moment seemingly neglected, still exercise an influence on the consciousness; which would be decisively shown (as in the case of sight) on any occasion of their suddenly increasing in force, or suddenly vanishing. Also, in their state of having fallen out of attention, they still leave an influence to modify the present sensation, the effect of their being attended to in the previous instant. Until we can measure the rapidity of those transitions of the attention, we are not in a position to affirm absolutely the power of double, triple, or multiple attention, although to all practical intents such a power is possessed.