fluidity depends, according to the most
general opinion, on the roundness, smoothness, and weak cohesion of the
component parts of any body, and as water acts merely as a simple fluid,
it follows that the cause of its fluidity is likewise the cause of its
relaxing quality, namely, the smoothness and slippery texture of its
parts. The other fluid vehicle of tastes is _oil_. This too, when
simple, is insipid, inodorous, colorless, and smooth to the touch and
taste. It is smoother than water, and in many cases yet more relaxing.
Oil is in some degree pleasant to the eye, the touch, and the taste,
insipid as it is. Water is not so grateful; which I do not know on what
principle to account for, other than that water is not so soft and
smooth. Suppose that to this oil or water were added a certain quantity
of a specific salt, which had a power of putting the nervous papillae of
the tongue into a gentle vibratory motion; as suppose sugar dissolved in
it. The smoothness of the oil and the vibratory power of the salt cause
the sense we call sweetness. In all sweet bodies, sugar, or a substance
very little different from sugar, is constantly found. Every species of
salt, examined by the microscope, has its own distinct, regular,
invariable form. That of nitre is a pointed oblong; that of sea-salt an
exact cube; that of sugar a perfect globe. If you have tried how smooth
globular bodies, as the marbles with which boys amuse themselves, have
affected the touch when they are rolled backward and forward and over
one another, you will easily conceive how sweetness, which consists in a
salt of such nature, affects the taste; for a single globe (though
somewhat pleasant to the feeling), yet by the regularity of its form,
and the somewhat too sudden deviation of its parts from a right line, is
nothing near so pleasant to the touch as several globes, where the hand
gently rises to one and falls to another; and this pleasure is greatly
increased if the globes are in motion, and sliding over one another; for
this soft variety prevents that weariness, which the uniform disposition
of the several globes would otherwise produce. Thus in sweet liquors,
the parts of the fluid vehicle, though most probably round, are yet so
minute, as to conceal the figure of their component parts from the
nicest inquisition of the microscope; and consequently, being so
excessively minute, they have a sort of flat simplicity to the taste,
resembling the effects of