O I L. 
fea, immediately renders it fmooth, fo as to permit the 
light to pafs through the water, undifturbed by various 
and irregular refraftions. The Bermudians, it is faid, 
are enabled to fee and ftrike filh, which would be con¬ 
cealed from their view through the roughnefs of the fea, 
by pouring a little oil upon it. And the Lifbon filher- 
men effeft a fafe paffage over the bar of the Tagus, by 
emptying a bottle or two of oil into the fea, when the 
furf is fo great as to endanger its filling their boats. Our 
failors have alfo obferved, that the water is always much 
fmoother in the wake of a (hip that has been newly tal¬ 
lowed than it is in one that is foul. 
Dr. Franklin was led, by an accidental obfervation 
made at fea in 1757, to attend particularly to Pliny’s ac¬ 
count; and the various information which he afterwards 
received relating to it, induced him to try fome experi¬ 
ments on the fubjeft. Standing on the windward fide of 
a large pond, the furface of which w r as rendered very 
rough with the wind, he poured a tea-fpoonful of oil on 
the water. This fmall quantity produced an inftant calm 
over a fpace of feveral yards fquare, which fpread ama¬ 
zingly, and extended itfelf gradually, till it reached the 
lee-fide, making all that quarter of the pond, perhaps 
half an acre, as fmooth as a looking-glafs. On repeating 
this experiment, which conftantly fucceeded, one cir- 
cumftance (truck him with particular furprife ; this was 
the fudden wide and forcible fpreading of a drop of oil 
on the face of the water, which, he adds, “ I do not 
know that any body has coniidered.” When a drop of oil 
is put on a looking-glafs, or poliflied marble, it fpreads 
very little ; but on water it inftantly expands into a cir¬ 
cle extending feveral feet in diameter, becoming fo thin 
as to produce the prifmatic colours for a confiderable 
fpace, and beyond them fo much thinner as to be invifi- 
ble, except in its eft'efts of fmoothing the waves at a much 
greater diftance. It feems, fays Dr. Franklin, as if a mu¬ 
tual repulfion between its particles took place as foon as 
it touched the water; and a repulfion fo ftrong as to aft 
on otherbodies fwimmingon the furface, as ftraw's, leaves, 
&c. forcing them to recede every way from the drop, as 
from a centre, leaving a large clear fpace. The quantity 
of this force, and the diftance to which it will operate, 
the author fays, he has not yet afcertained ; but he thinks it 
a curious enquiry, and willies to underftand whence it 
arifes. In endeavouring to account for (he lingular ef¬ 
fects of oil, Dr. Franklin obferves, that there feems to 
be no natural repulfion between water and air, fo as to 
keep them from coming into contaft with each other. 
Therefore air, in motion, which is wind, in palling over 
the fmooth furface of water, may rub, as it were, on that 
furface, and raife it into wrinkles, which, if the wind 
continues, are the elements of future waves. The finall- 
eft wave does not immediately fublide; but, in fubfiding, 
raifes nearly as much of the water next to it. A fmall 
power, continually operating, will produce a great aftion : 
fo that the firft-railed waves, being continually afted 
upon by the wind, are, though the wind does not in- 
creafe in ftrength, continually increafed in magnitude, 
riling higher, and extending their bafes, fo as to include a 
vaftmafs of water in each wave, which, in its motion, 
afts with great violence. But, if there be a mutual repul¬ 
fion between the particles of oil, and no attraction be¬ 
tween oil and water, oil dropped on water will not be held 
together by adhefion to the fpot on which it falls ; it will 
not be imbibed by the water; but be at liberty to expand 
itfelf, and fpread on a furface, that prevents, perhaps by 
repelling the oil, all immediate contaft; the expanfion 
will continue till the mutual repulfion between the par¬ 
ticles of oil is weakened, and reduced to nothing by 
their diftance. Dr. Franklin imagines, that the wind 
blowing over water, thus covered with a film of oil, can¬ 
not eafily catch upon it, fo as to raife the firft wrinkles, 
but Hides over it, and leaves it as fmooth as it finds it. 
It moves a little the oil indeed, which, being between 
it and the water, ferves it to Hide with, and prevents fric¬ 
439 
tion: hence the oil dropped on the windward fide of the 
pond proceeds gradually to leeward, as may be feen by 
the fmoothnefs it carries with it quite to the oppofite fide : 
for the wind, being thus prevented from railing the firft 
wrinkles, which he calls the elements of waves, cannot 
produce waves, which are to be made by continually afting 
upon, and enlarging, thofe elements; and thus the whole 
pond is calmed. 
Upon the whole, there is great room to fuppofe (not- 
withftanding the partial failure of an experiment made at 
Portfmouth by Dr. Franklin and others), that feafaring 
people may derive advantages from ufing oil on particular 
occafions, in order to moderate the violence of the waves, 
or to leffen the furf, which fometimes renders the landing 
on a lee-lhore dangerous or imprafticable. To this pur-* 
pofe, we are informed that the captain of a Dutch Eaft In¬ 
dia fhip, beingovertaken by a ftorm, found himfelfobliged, 
for greater fafety in wearing the fhip, to pour oil into 
the fea, to prevent the waves breaking over her; which 
had an excellent effeft, and fucceeded in preferving her. 
Phil. Tranf. vol. lxiv. 
To OIL, v. a. To linear or lubricate with oil.—Amber 
will attraft ftraws thus oiled, it will convert the needles 
of dials, made either of brafs or iron, although they be 
much oiled; for in thofe needles, confiding free upon their 
centre, there can be no adhefion. Brown s Vulg. Err. 
OI'L-CAKE, f. The cake which remains after the oil 
has been expreffed from flax, rape, and fome other forts 
of feeds. See p. 436. Cakes of the firft fort are found to 
be extremely beneficial in the fattening of cattle, fheep, 
and other animals, in different diftrifts, where they are 
made ufe of upon an extenfive fcale. 
A recent writer has ftated, that the late advances in the 
price of this article have probably rendered it incapable 
of being made ufe of with much profit, except in parti¬ 
cular cafes, and where manure is a principal objeft : with 
this fort of food it is the common praftice to give fome 
other fort of meat, fuch as hay, cut chaff, and otherfub- 
ftances of the fame nature ; and fome begin by giving to a 
beaft of a hundred llone, two cakes per day of about fix 
pounds each, for fix or eight weeks, and then increafe 
them to three, till the animals become fat; at firft, how¬ 
ever, as the animals feldom like it, much lefs may be found 
fufficient. In addition to the cake, from half a ftone to 
a ftone of hay is given each day, the whole conlumption 
in cake being about 21 cwt. and in hay 26 cwt. which, at 
the prices previous to the advance on thefe articles, ren¬ 
dered the expenfe of winter-fattening an animal of the 
above fize fomething more than feven guineas: lean cattle 
of the fmaller kinds have been made perfeftly fat in the 
courfe of eight or ten weeks by this fubllance, in the trials 
of Mr. Moody. The cake, in this application, is broken 
down into fmall parts, and frequently blended with the 
chaff or other fubftances that are made ufe of with it. On 
the continent, Mr. Young fays, iinfeed-cake is fome¬ 
times exhibited in a liquid ftate, being diffufed in hot 
water, and drunk by the cattle, hay and other fubftances 
being given at the fame time. And in the Lincolnlhire 
Report, a method is fuggefted of giving cake to cattle 
while in the paftures in a fmall proportion, with great 
fuccefs, a praftice which may be applicable, where the 
cake-fed beafts are not fully fattened for fale in the early 
fpring-months. It is an advantage, in fattening with this 
and other fimilar fubftances, that the animals may be com¬ 
pleted with them at much more advanced ages than in 
other modes of fattening. 
Mr. Calvert, at Albury, when oil-cake was much 
cheaper than at prefent, found it the molt advantageous 
and profitable food that he could give his cows ; three 
cakes a-day, with eight or ten pounds of hay, or four 
cakes and good ftraw, were the ufual allowance; two were 
given to cows in calf, and growing heifers : he praftifed 
this till cake advanced beyond 9I. a-thoufand. How far it 
mayanfwer at much higher prices, careful experiments will 
alone afcertain, which he himfelf would have made; but 
Swedilh 
