circumstance of the atmosphere being magnified, prevent the
beneficial results that were to be expected from telescopes of
extraordinary size and power. In many parts of knowledge, man has
been almost constantly making some progress; in other parts, his
efforts have been invariably baffled. The savage would not
probably be able to guess at the causes of this mighty
difference. Our further experience has given us some little
insight into these causes, and has therefore enabled us better to
judge, if not of what we are to expect in future, at least of
what we are not to expect, which, though negative, is a very
useful piece of information.

As the necessity of sleep seems rather to depend upon the
body than the mind, it does not appear how the improvement of the
mind can tend very greatly to supersede this 'conspicuous
infirmity'.30 A man who by great excitements on his mind is able
to pass two or three nights without sleep, proportionably
exhausts the vigour of his body, and this diminution of health
and strength will soon disturb the operations of his
understanding, so that by these great efforts he appears to have
made no real progress whatever in superseding the necessity of
this species of rest.

There is certainly a sufficiently marked difference in the
various characters of which we have some knowledge, relative to
the energies of their minds, their benevolent pursuits, etc., to
enable us to judge whether the operations of intellect have any
decided effect in prolonging the duration of human life. It is
certain that no decided effect of this kind has yet been
observed. Though no attention of any kind has ever produced such