to its operations; we can place no limit to them.  We sometimes, in sleep, lose the beginning and end of a dream, and recollect the middle of it, and one dream has no connection with another; and yet we are conscious of an infinite variety of dreams, and there is a strong analogy for believing in an infinity of past existences, which must have had connection; and human life may be regarded as a type of infinite and immortal life, and its succession of sleep and dreams as a type of the changes of death and birth to which from its nature it is liable.  That the ideas belonging to the mind were originally gained from those classes of sensations called organs it is impossible to deny, as it is impossible to deny that mathematical truths depend upon the signs which express them; but these signs are not themselves the truths, nor are the organs the mind.  The whole history of intellect is a history of change according to a certain law; and we retain the memory only of those changes which may be useful to us—­the child forgets what happened to it in the womb; the recollections of the infant likewise before two years are soon lost, yet many of the habits acquired in that age are retained through life.  The sentient principle gains thoughts by material instruments, and its sensations change as those instruments change; and, in old age, the mind, as it were, falls asleep to awake to a new existence.  With its present organisation, the intellect of man is naturally limited and imperfect, but this depends upon its material machinery; and in a higher organised form, it may be imagined to possess infinitely higher powers.  Were man to be immortal with his present corporeal frame, this immortality would only belong to the machinery; and with respect to acquisitions of mind, he would virtually die every two or three hundred years—­that is to say, a certain quantity of ideas only could be remembered, and the supposed immortal being would be, with respect to what had happened a thousand years ago, as the adult now is with respect to what happened in the first year of his life.  To attempt to reason upon the manner in which the organs are connected with sensation would be useless; the nerves and brain have some immediate relation to these vital functions, but how they act it is impossible to say.  From the rapidity and infinite variety of the phenomena of perception, it seems extremely probable that there must be in the brain and nerves matter of a nature far more subtle and refined than anything discovered in them by observation and experiment, and that the immediate connection between the sentient principle and the body may be established by kinds of ethereal matter, which can never be evident to the senses, and which may bear the same relations to heat, light, and electricity that these refined forms or modes of existence of matter bear to the gases.  Motion is most easily produced by the lighter species of matter; and yet imponderable agents, such as electricity, possess force sufficient