no man has yet
sufficiently considered how far it may influence the operations of the
genius, though every day affords instances of local understanding, of
wits and reasoners, whose faculties are adapted to some single spot, and
who, when they are removed to any other place, sink at once into silence
and stupidity. I have discovered, by a long series of observations, that
invention and elocution suffer great impediments from dense and impure
vapours, and that the tenuity of a defecated air at a proper distance
from the surface of the earth, accelerates the fancy, and sets at
liberty those intellectual powers which were before shackled by too
strong attraction, and unable to expand themselves under the pressure of
a gross atmosphere. I have found dulness to quicken into sentiment in a
thin ether, as water, though not very hot, boils in a receiver partly
exhausted; and heads, in appearance empty, have teemed with notions upon
rising ground, as the flaccid sides of a football would have swelled out
into stiffness and extension.

For this reason I never think myself qualified to judge decisively of
any man's faculties, whom I have only known in one degree of elevation;
but take some opportunity of attending him from the cellar to the
garret, and try upon him all the various degrees of rarefaction and
condensation, tension and laxity. If he is neither vivacious aloft, nor
serious below, I then consider him as hopeless; but as it seldom
happens, that I do not find the temper to which the texture of his brain
is fitted, I accommodate him in time with a tube of mercury, first
marking the points most favourable to his intellects, according to rules
which I have long studied, and which I may, perhaps, reveal to mankind
in a complete treatise of barometrical pneumatology.

Another cause of the gaiety and sprightliness of the dwellers in garrets
is probably the increase of that vertiginous motion, with which we are
carried round by the diurnal revolution of the earth. The power of
agitation upon the spirits is well known; every man has felt his heart
lightened in a rapid vehicle, or on a galloping horse; and nothing is
plainer, than that he who towers to the fifth story, is whirled through
more space by every circumrotation, than another that grovels upon the
ground-floor. The nations between the topicks are known to be fiery,
inconstant, inventive, and fanciful; because, living at the utmost
length of the earth's diameter, they