ust be, to begin with.

Every cloud that can be, is thus primarily definable: "Visible
vapor of water floating at a certain height in the air." The second
clause of this definition, you see, at once implies that there is
such a thing as visible vapor of water which does _not_ float at a
certain height in the air. You are all familiar with one extremely
cognizable variety of that sort of vapor--London Particular; but
that especial blessing of metropolitan society is only a
strongly-developed and highly-seasoned condition of a form of
watery vapor which exists just as generally and widely at the
bottom of the air, as the clouds do--on what, for convenience'
sake, we may call the top of it;--only as yet, thanks to the
sagacity of scientific men, we have got no general name for the
bottom cloud, though the whole question of cloud nature begins in
this broad fact, that you have one kind of vapor that lies to a
certain depth on the ground, and another that floats at a certain
height in the sky. Perfectly definite, in both cases, the surface
level of the earthly vapor, and the roof level of the heavenly
vapor, are each of them drawn within the depth of a fathom. Under
_their_ line, drawn for the day and for the hour, the clouds will
not stoop, and above _theirs,_ the mists will not rise. Each in
their own region, high or deep, may expatiate at their pleasure;
within that, they climb, or decline,--within that they congeal or
melt away; but below their assigned horizon the surges of the cloud
sea may not sink, and the floods of the mist lagoon may not be
swollen.

That is the first idea you have to get well into your minds
concerning the abodes of this visible vapor; next, you have to
consider the manner of its visibility. Is it, you have to ask, with
cloud vapor, as with most other things, that they are seen when
they are there, and not seen when they are not there? or has cloud
vapor so much of the ghost in it, that it can be visible or
invisible as it likes, and may perhaps be all unpleasantly and
malignantly there, just as much when we don't see it, as when we
do? To which I answer, comfortably and generally, that, on the
whole, a cloud is where you see it, and isn't where you don't;
that, when there's an evident and honest thundercloud in the
northeast, you needn't suppose there's a surreptitious and slinking
one in the northwest;--when there's a visible fog at Bermondsey, it
doesn't follow there's a spiritual one, more