days, and I feel ill, or rather I feel low-spirited.

Whence come those mysterious influences which change our
happiness into discouragement, and our self-confidence into
diffidence? One might almost say that the air, the invisible air,
is full of unknowable Forces, whose mysterious presence we have
to endure. I wake up in the best of spirits, with an inclination
to sing in my heart. Why? I go down by the side of the water, and
suddenly, after walking a short distance, I return home wretched,
as if some misfortune were awaiting me there. Why? Is it a cold
shiver which, passing over my skin, has upset my nerves and given
me a fit of low spirits? Is it the form of the clouds, or the
tints of the sky, or the colors of the surrounding objects which
are so change-able, which have troubled my thoughts as they
passed before my eyes? Who can tell? Everything that surrounds
us, everything that we see without looking at it, everything that
we touch without knowing it, everything that we handle without
feeling it, everything that we meet without clearly
distinguishing it, has a rapid, surprising, and inexplicable
effect upon us and upon our organs, and through them on our ideas
and on our being itself.

How profound that mystery of the Invisible is! We cannot fathom
it with our miserable senses: our eyes are unable to perceive
what is either too small or too great, too near to or too far
from us; we can see neither the inhabitants of a star nor of a
drop of water; our ears deceive us, for they transmit to us the
vibrations of the air in sonorous notes. Our senses are fairies
who work the miracle of changing that movement into noise, and by
that metamorphosis give birth to music, which makes the mute