cause.

People of genius have, very frequently, impaired their
constitutions by study, or careless inattention to their health,
and the violence of their passions bearing a proportion to the
vigour of their intellects, the sword's destroying the scabbard has
become almost proverbial, and superficial observers have inferred
from thence, that men of genius have commonly weak, or to use a
more fashionable phrase, delicate constitutions. Yet the contrary,
I believe, will appear to be the fact; for, on diligent inquiry, I
find that strength of mind has, in most cases, been accompanied by
superior strength of body, natural soundness of constitution, not
that robust tone of nerves and vigour of muscles, which arise from
bodily labour, when the mind is quiescent, or only directs the
hands.

Dr. Priestley has remarked, in the preface to his biographical
chart, that the majority of great men have lived beyond forty-five.
And, considering the thoughtless manner in which they lavished
their strength, when investigating a favourite science, they have
wasted the lamp of life, forgetful of the midnight hour; or, when,
lost in poetic dreams, fancy has peopled the scene, and the soul
has been disturbed, till it shook the constitution, by the passions
that meditation had raised; whose objects, the baseless fabric of a
vision, faded before the exhausted eye, they must have had iron
frames. Shakespeare never grasped the airy dagger with a nerveless
hand, nor did Milton tremble when he led Satan far from the
confines of his dreary prison. These were not the ravings of
imbecility, the sickly effusions of distempered brains; but the
exuberance of fancy, that "in a fine phrenzy" wandering, was not