little." Franklin at first thought that this
must be a mystification—a tale for the
marines; but, recollecting Pliny's statement,
he resolved, if an opportunity should offer, to
try the experiment for himself in ever so small
a way. Some years afterwards, being at Clapham,
he determined to make an oleaginous
experiment upon a large pond. On a
windy day, when the surface of the pond
was rough, he brought a cruet of oil, and
poured a little into the pond; his first
experiment was not very successful, for he
stood on the leeward side of the pond, and
the wind blew the oil back again upon the
shore; but, upon going to the windward side,
he found that even a single tea-spoonful of oil
produced an instant calm over a space several
yards square, and that, spreading and spreading
by degrees, it reached the leeward side,
covering, probably, half an acre with a film
of oil of exquisite tenuity. Franklin bore
the character of a truthful man; and when
he describes this experiment with unmistakeable
clearness in the Philosophical Transactions,
we must not reject it merely because it
is marvellous. He declares that this spoonful
of oil made half an acre of water "as smooth
as a looking-glass." Ponds are not yet
banished from England, nor oil, nor cruets,
nor tea-spoons; and it would not be a
very difficult matter for a curiously-disposed
person to imitate this experiment for
himself.

Franklin repeated the experiment soon
after at Ormathwaite, near Leeds, in the
presence of Smeaton and Jessop, the
celebrated engineers; and, on another occasion
he determined to try, somewhere near Portsmouth,
whether he could lessen the surf on a
lee shore, by means of oil. He selected a
windy day, which gave the character of a
lee-shore to the spot between Haslar Hospital
and Gillkicker point. A long boat was
anchored about a quarter of a mile from the
shore. A barge plied to windward of the
long boat, as far from her as she was from
the shore, making trips of about half a mile
each; oil being continually poured from her,
out of a large stone bottle, through a hole
in the cork about as large as a goose-quill. A
party of observers placed themselves on the
shore, in a position to note if any change
were produced in the surf by the action of
the oil. Franklin did not find the effect
upon the surf to be so great as he expected;
but the persons in the long-boat could
observe a tract of smooth water the whole length
of the distance on which the oil was poured,
gradually spreading in breadth towards the
long-boat. This water was smooth, but not
actually level. The swell continued; but the
surface was not ruffled by wrinkles or
smaller waves; and there were none of the
waves called by sailors "white caps" (waves
whose tops turn over in foam), although
there was abundance of this kind of wave
both to windward and leeward of the oily
space. A wherry, that came round the
point under sail, in her way to Portsmouth,
seemed to turn into that oily track by choice,
and to use it from end to end as a piece of
turnpike road.

It was not likely that a man such as
Franklin would abstain from speculating on
the cause of such curious results. There are
two inquiries involved—Why does oil spread
on water? and why, when so spread, does it
still the wavy surface? If a drop of oil be put
upon a polished marble table, or on a looking-
glass placed horizontally, it remains in its
place, spreading very little; but when put on
water, it spreads instantly all round, becoming
so thin as to produce the prismatic colours
for a considerable space; and, beyond the
region ot these colours, to present that peculiar
blackness which optical philosophers know to
be attributable to a film whose thickness is
to be estimated by millionths rather than by
thousandths of an inch. It would appear as
if a mutual repulsion took place between the
particles of oil as soon as it touches water: a
repulsion so strong as to act on other bodies
swimming on the surface, as straws, leaves,
chips, &c., forcing them to recede every way
from the drop as from a centre, leaving a
large clear space.

But then, even if we can explain all this
by means of repulsion, how happens it that
so thin a film of oil can still the waves?
When air is in motion over water, with any
of the degrees of velocity between a gentle
breeze and a perfect hurricane, the air
encounters a sort of friction in passing over the
surface of the water, and it rubs up the water
into wrinkles; these wrinkles grow and grow
and grow, until they become big waves. Now
Franklin supposed that, when a film of oil
is on the surface of water, the air has nothing
to catch hold of; it slips over the oil, as a
greasy pig's tail would slip out of the hands
of Hodge at a fair: it cannot wrinkle the
oil, and it cannot wrinkle the water beneath
the oil. True, there are slower and larger
heavings, especially in deep water; but there
are not the little crumplings and ripplings
which surface of water usually exhibits. There
are two phases or stages in this process. If oil
be poured upon water already in a state of wavy
undulation, it will not stop the deep, full wave:
it will only kill the little undulations with
which these greater waves are embroidered.
If the oil be poured upon the weather-side
of water only just beginning to be affected
by wind, it may, says Franklin, stifle the
waves at their birth: by preventing them
from being even little, it may effectually
prevent them from ever being large. Whether this
theory be true or not, it is clear and intelligible,
and deserves attention. In the Great Pacific
of Clapham Common, when Franklin poured
the oil near the lee-side of the pond, he failed
to obtain a mastery over the waves; but when
he operated on the weather-side (the side
whence the wind blows), he nipped them in