Having made these prefatory observations, which to many present may have appeared too obvious and familiar for mention, but which I have introduced on the presumption that some of my younger hearers may not have had it in their power to pay attention even to these bare rudiments of mental philosophy, I proceed to consider what there is in common between the processes of thought in sleep, and those in our waking hours.

A very considerable majority of revived impressions consist of objects of sight, so that some have even asserted that we never dream of anything else. But this is obviously a great misapprehension; for, independently of the fact that the persons whose forms appear to the dreamer fire-quently seem to converse with him, it might be proved from the ideas and feelings associated with the visual reproduction that something more than the impression of sight recurs to the mind. When the friend of by-gone times revisits us in sleep, we do not recognize his form merely as one that had been seen before; but with its presence return some at least of the occurrences in his life, the points in his character, his sentiments, and his familiar talk. So far is it from being true, that visual images only are produced in dreams, that it often happens that the remains of several sensations are simultaneously renewed. While our eyes seem to be feasting on the most glorious scenery of mountains, forests, rivers and ocean, we may at the same time hear the roar of thunder, the songs of birds, the rushing of torrents, or the deep boom of the tide on the shore; we may inhale the fragrance of flowers, feel the soft breath of the sea-breeze, and hear the voice of the companion who sympathizes in our pleasure.

Still, it must be allowed that as the perceptions of the organ of sight are the most frequent and vivid of our waking sensations, so they abound most in our dreams. There is great variety in the mode of their reproduction. They may arise as mere copies of former visions; or, to speak more correctly, the individual conceptions may appear in the same groups as when they were first presented to us; or they may be assembled so differently, as to produce the effect of entire novelty. In the first instance, the dreamer may renew his youth, - breathing once more the air of his birth-place, and once more immersed in the joys or transient sorrows of those early days ; or he may re-enact the toils of his manhood; and all the stirring energies, or the weariness and solicitude of his daily avocations may recur in dreams, so that the days are again lived over in the nights. In the other instance, the mind may be recreated by visions of fairy scenes and unearthly forms, such as his waking eye never beheld; or it may be haunted by combinations of forms more . hideous than were ever conceived even by an artist of the hag-ridden middle ages. These new assemblages of former impressions would exemplify the process of thought which we call imagination in our waking hours, only that the mind is quite passive. It does not actively and artificially work up the old materials into new forms, under the command of the will or desire, but the forms are forced upon it whether wished for or not. Many minds would be quite unable, however much they might try, to call up before their mental eyes such scenes and forms as appeared to them in sleep. But the man of genius is distinguished by his capability of effecting such combinations for a particular purpose. It is true that they are often produced in such minds with so little effort, as to arise by a sort of inspiration, or as in dreams; but they differ still from the latter, in being entirely subservient to the designs of such creative power. It is an interesting fact, that the highest feats of the intellect, or, in other words, the most excellent combinations of ideas, have been such as have occurred without effort. The ingenious man, or the man of quick fancy, may put thoughts and things together, so as to produce most striking and agreeable effects; but we see that they are put together by a voluntary or even laborious effort, one the reverse of what ever occurs in dreaming. But in the works of genius, we perceive no such marks of elaboration, unless in the finishing-off. There are no lines of junction or dove-tailing. The paradise of Milton is not such as we could conceive by assembling the different elements of all the fine landscapes and gardens which we may have surveyed ; but it gives us the idea of its having been seen at once by the poet's eye just as it is described, or as our own nightly visions appear to us. The imagination of the genius, and that of the dreamer, are thus closely allied in so far as they work by an " art unteachable, untaught; " but they differ widely in being attended and guided in the one case by the operations of the judgment, and in the other as being independent of such sway or assistance.

The remembrances which occur in dreams are often of a most interesting character, and not such as might have been expected. They bring back people of whom we have not thought for many years, - whom we have seen perhaps but once, and in the most incidental manner; and not only persons, but also places and things, and even transient thoughts; and, what is still more curious, the subjects of former dreams. I do not now dwell on these facts, because I shall have to recur to them bye and bye. I may only suggest, that it is a fearful liability of our nature to have the past summoned before us, when we may have fondly hoped that it was hid for ever in deepest night, - to anticipate what is to occur hereafter: -

"Each faintest trace that memory holds So darkly of departed years, In one broad glance the soul beholds, And all that was at once appears."

This tendency is strongly manifested in dreams. Dreams which in the morning we may fail with all our endeavours to recall, will recur many days afterwards, when their proper associations have chanced to arise; and, on the other hand, events which we had entirely forgotten, may be re-enacted in sleep with all the semblance of novelty; and their source will not be recognised after awaking, till other associations and remembrances have arisen. This fact will be important to remember, when we have to consider the apparent fulfilment of dreams.