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diameter at the lowest part. When the chimney is put together,
the upper end of the bottom piece is inserted about an inch
into the cone of the next piece above, and fixed there by three
ties or pins, so that the two pieces are firmly held together ; but
there is still plenty of air- way, from the surrounding atmosphere
into the chimney between them. The same arrangement holds
good with each succeeding piece. When the ventilating chimney
is fixed in its place, it is adjusted, so that the lamp-chimney
enters about \ an inch into the lower cone, and the top of the
ventilating chimney enters into the cowl or head of the lantern.

With this arrangement, it is found that the action of the
ventilating flue is to carry up every portion of the products of
combustion into the cowl ; none passes out of the flue into the
air of the lantern by the cone apertures, but a portion of the
air passes from the lantern by these into the flue, and so the
lantern itself is in some degree ventilated.

The important use of these cone apertures is, that when a
sudden gust, or eddy of wind, strikes into the cowl of the lantern,
it does not have any effect in disturbing or altering the flame.
It is found that the wind may blow suddenly in at the cowl, yet
the effect never reach the lamp. The upper, or the second,
or the third, or even the fourth portion of the ventilating flue
might be entirely closed, yet without altering the flame. The
cone junctions in no way interfere with the tube in carrying up
all the products of combustion; but if any downward current
occurs, they dispose of the whole of it into the room, without
ever affecting the flame. The ventilating flue is, in fact, a tube
which, as regards the lamp, can carry everything up, but
conveys nothing down.

In lighthouses with many separate lamps and reflectors, the
case is more difficult and the arrangement more complicated,
yet the conditions before referred to are more imperatively
called for, because any departure from them was found to have
greater influence in producing harm. The object has been
attained thus: A system of gathering pipes has been applied
to the lamps which may be considered as having the different

1843.] On the Ventilation of Lighthouse Lamps. 365

beginnings at each lamp, and being fixed to the frame which
supports the lamps, is made to converge together and to the
axis of the frame by curved lines. The object is to bring the
tubes together behind the reflectors, as soon as convenient,
joining two or more into one, like a system of veins, so that one
ventilating flue may at last carry off the whole of the lamp pro-
ducts. It is found that a pipe |ths of an inch in diameter is
large enough for one lamp; and where, by junction, two or
more pipes have become one, if the one pipe has a sectional
area, proportionate to the number of lamps which it governs,
the desired effect is obtained.

Each of the pipes, Jths of an inch in diameter, passes down-
wards through the aperture in the reflector over the lamp, and
dips an inch into the lamp-glasses ; it is able
to gather and carry off all the products of
combustion, though, perhaps, still 2 inches
from the top of the flame, and therefore not
interfering in any respect with it, nor coming
as a shade between it and any part of the
reflector : the flame and reflector are as free
in their relation to each other as they were
before. Neither does this tube hide from
the observer or mariner, a part of the re-
flector larger than about 1^ square inch of
surface, and it allows of a compensation to
two or three times the amount ; for, when
in its place, all the rest of the aperture over the lamp which is
left open and inefficient in the ordinary service, may be made
effectual reflecting surface, simply by filling it up with a loose,
fitly formed, reflecting plate.

At this termination of the ventilating flue an important ad-
justment is effected. If the tube dip about an inch into the
lamp-glass, the draught up it is such that not only do all the
products of combustion enter the tube, but air passes down
between the top edge of the lamp-glass and the tube, going,
finally, up the latter with the smoke. In this case, however,
an evil is produced, for the wick is charred too rapidly ; but if
the ventilating flue descends until only level with the top of
the lamp-glass, the whole of the burnt air does not usually go
up it, but some passes out into the chamber, and at such times

366 Thoughts on Ray-vibrations. [1846.

the charring of the wick is not hastened. Here, therefore,
there is an adjusting power, and it was found by the trials
made, that when the tube dipped about J an inch into the lamp-
glass, it left the burning of the lamp unaltered, and yet carried
off all the products of combustion.

The power already referred to, of dividing a chimney into
separate and independent parts, and yet enabling it to act
perfectly as a whole, as shown in the single central chimney,
was easily applicable in the case of several lamps, and gave a
double advantage ; for it not only protected the lamps from any
influence of down draught, but it easily admitted of the rotation
of the system of gathering flues, fixed to the frame sustaining
the lamps and reflectors in a revolving lighthouse, and of the
delivery of the burnt air, &c., from its upper extremity into
the upper immoveable portion of the flue. This capability in
a revolving light is essential, for in all, the support of the frame-
work is of such a nature, as to require that the upper part of
the flue should be a fixture.

The author explains, that it is as an officer of the Trinity
House, and under its instructions, that he entered into the
consideration of this subject ; that, as to the central chimney,
its action has been both proved and approved, and that all the
central lights are ordered to be furnished with them ; that as
respects the application to separate and revolving lamps, the
experiment has been made under the direction of the Trinity
House on a face of six lamps, being a full-sized copy of the
Tynemouth revolving light, and, so far to the satisfaction of the
Deputy Master and Brethren, that the plan is to be applied
immediately to two lighthouses which suffer most from conden-
sation on the glass : he believes it will be with full success.

Thoughts on Ray -vibrations*.

To Richard Phillips, Esq.

DEAR SIR, At your request I will endeavour to convey to you
a notion of that which I ventured to say at the close of the last
Friday-evening Meeting, incidental to the account I gave of
VVheatstone's electro-magnetic chronoscope ; but from first to

* Philosophical Magazine, 1846, vol. xxviii. p. 345.

1846.] Thoughts on Ray -vibrations. 367

last understand that I merely threw out as matter for specula-
tion, the vague impressions of my mind, for 1 gave nothing as
the result of sufficient consideration, or as the settled conviction,
or even probable conclusion at which I had arrived.

The point intended to be set forth for the consideration of
the hearers was, whether it was not possible that the vibrations
which in a certain theory are assumed to account for radiation
and radiant phenomena may not occur in the lines of force
which connect particles and consequently masses of matter
together ; a notion which, as far as it is admitted, will dispense
with the ether which, in another view, is supposed to be the
medium in which these vibrations take place.

You are aware of the speculation* which I some time since
uttered respecting that view of the nature of matter which
considers its ultimate atoms as centres of force, and not as so
many little bodies surrounded by forces, the bodies being-
considered in the abstract as independent of the forces and ca-
pable of existing without them. In the latter view, these little
particles have a definite form and a certain limited size ; in the
former view such is not the case, for that which represents size
may be considered as extending to any distance to which the
lines of force of the particle extend : the particle indeed is sup-
posed to exist only by these forces, and where they are it is.
The consideration of matter under this view gradually led me
to look at the lines of force as being perhaps the seat of the
vibrations of radiant phenomena.

Another consideration bearing conjointly on the hypothetical
view both of matter and radiation, arises from the comparison
of the velocities with which the radiant action and certain powers
of matter are transmitted. The velocity of light through space
is about 190,000 miles in a second; the velocity of electricity
is, by the experiments of Wheatstone, shown to be as great as
this, if not greater : the light is supposed to be transmitted by
vibrations through an ether which is, so to speak, destitute of
gravitation, but infinite in elasticity ; the electricity is transmitted
through a small metallic wire, and is often viewed as transmitted
by vibrations also. That the electric transference depends on
the forces or powers of the matter of the wire can hardly be
doubted, when we consider the different conductibility of the

* Philosophical Magazine, 1844, vol. xxiv. p. 136 or Experimental Re-
searches in Electricity, vol. ii. p. 284.

368 Thoughts on Ray-vibrations. [1846.

various metallic and other bodies ; the means of affecting it by
heat or cold ; the way in which conducting bodies by combina-
tion enter into the constitution of non-conducting substances,
and the contrary ; and the actual existence of one elementary
body, carbon, both in the conducting and non-conducting state.
The power of electric conduction (being a transmission of force
equal in velocity to that of light) appears to be tied up in and
dependent upon the properties of the matter, and is, as it were,
existent in them.

I suppose we may compare together the matter of the ether
and ordinary matter (as, for instance, the copper of the wire
through which the electricity is conducted), and consider them
as alike in their essential constitution ; i. e. either as both
composed of little nuclei, considered in the abstract as matter,
and of force or power associated with these nuclei, or else both
consisting of mere centres of force, according to Boscovich's
theory and the view put forth in my speculation ; for there is
no reason to assume that the nuclei are more requisite in the
one case than in the other. It is true that the copper gravitates
and the ether does not, and that therefore the copper is
ponderable and the ether is not ; but that cannot indicate the
presence of nuclei in the copper more than in the ether, for of
all the powers of matter gravitation is the one in which the
force extends to the greatest possible distance from the supposed
nucleus, being infinite in relation to the size of the latter, and
reducing that nucleus to a mere centre of force. The smallest
atom of matter on the earth acts directly on the smallest atom
of matter in the sun, though they are 95,000,000 of miles apart ;
further, atoms, which, to our knowledge, are at least nineteen
times that distance, and indeed, in cometary masses, far more,
are in a similar way tied together by the lines of force extending
from and belonging to each. What is there in the condition
of the particles of the supposed ether, if there be even only one
such particle between us and the sun, that can in subtilty and
extent compare to this ?

Let us not be confused by the ponderability and gravitation
of heavy matter, as if they proved the presence of the abstract
nuclei ; these are due not to the nuclei, if they exist at all,
but to the force superadded to them ; and, if the ether par-
ticles be without this force, which according to the assump-
tion is the case, then they are more material, in the abstract

184-6.] Thoughts on Ray-vibrations. 3G9

sense, than the matter of this our globe; for matter, according
to the assumption, being made up of nuclei and force, the ether
particles have in this respect proportionately more of the nucleus
and less of the force.

On the other hand, the infinite elasticity assumed as be-
longing to the particles of the ether, is as striking and positive
a force of it as gravity is of ponderable particles, and produces
in its way effects as great ; in witness whereof we have all the
varieties of radiant agency as exhibited in luminous, calorific,
and actinic phenomena.

Perhaps I am in error in thinking the idea generally formed
of the ether is that its nuclei are almost infinitely small, and
that such force as it has, namely its elasticity, is almost infinitely
intense. But if such be the received notion, what then is left
in the ether but force or centres of force ? As gravitation and
solidity do not belong to it, perhaps many may admit this con-
clusion ; but what is gravitation and solidity ? certainly not the
weight and contact of the abstract nuclei. The one is the con-
sequence of an attractive force, which can act at distances as
great as the mind of man can estimate or conceive ; and the
other is the consequence of a repulsive force, which forbids
for ever the contact or touch of any two nuclei ; so that these
powers or properties should not in any degree lead those
persons who conceive of the ether as a tiling consisting offeree
only, to think any otherways of ponderable matter, except
that it has more, and other, forces associated with it than the
ether has.

In experimental philosophy, we can, by the phenomena pre-
sented, recognize various kinds of lines of force ; thus there are
the lines of gravitating force, those of electro-static induction,
those of magnetic action, and others partaking of a dynamic
character might be perhaps included. The lines of electric
and magnetic action are by many considered as exerted through
space like the lines of gravitating force. For my own part, I
incline to believe that when there are intervening particles of
matter (being themselves only centres of force), they take part
in carrying on the force through the line, but that when there
are none, the line proceeds through space*. Whatever the

* Experimental Researches in Electricity, pars. 1161, 1613, 1663, 1710,
1729, 1735, 2443.

370 Thoughts on Ray-vibrations. [1846.

view adopted respecting them may be, we can, at all events,
affect these lines of force in a manner which may be conceived
as partaking of the nature of a shake or lateral vibration. For
suppose two bodies, A B, distant from each other and under
mutual action, and therefore connected by lines of force, and
let us fix our attention upon one resultant of force having an
invariable direction as regards space ; if one of the bodies move
in the least degree right or left, or if its power be shifted for a
moment within the mass (neither of these cases being difficult
to realize if A and B be either electric or magnetic bodies),
then an effect equivalent to a lateral disturbance will take place
in the resultant upon which we are fixing our attention ; for,
either it will increase in force whilst the neighbouring resultants
are diminishing, or it will fall in force as they are increasing.

It may be asked, what lines of force are there in nature,
which are fitted to convey such an action, and supply for the
vibrating theory the place of the ether ? I do not pretend to
answer this question with any confidence ; all I can say is, that
I do not perceive in any part of space, whether (to use the
common phrase) vacant or filled with matter, anything but forces
and the lines in which they are exerted. The lines of weight
or gravitating force are, certainly, extensive enough to answer in
this respect any demand made upon them by radiant phenomena;
and so, probably, are the lines of magnetic force : and then, who
can forget that Mossotti has shown that gravitation, aggregation,
electric force, and electro-chemical action may all have one
common connexion or origin; and so, in their actions at a
distance, may have in common that infinite scope which some
of these actions are known to possess ?

The view which I am so bold as to put forth considers,
therefore, radiation as a high species of vibration in the lines
of force which are known to connect particles and also masses
of matter together. It endeavours to dismiss the ether, but
not the vibrations. The kind of vibration which, I believe, can
alone account for the wonderful, varied, and beautiful phe-
nomena of polarization, is not the same as that which occurs
on the surface of disturbed water, or the waves of sound in
gases or liquids, for the vibrations in these cases are direct, or
to and from the centre of action, whereas the former are lateral.
It seems to me, that the resultant of two or more lines of force

1846.] Thoughts on Hay-vibrations. 371

is in an apt condition for that action which may be considered as
equivalent to a lateral vibration ; whereas a uniform medium,
like the ether, does not appear apt, or more apt than air or water.
The occurrence of a change at one end of a line of force easily
suggests a consequent change at the other. The propagation
of light, and therefore probably of all radiant action, occupies
time ; and, that a vibration of the line of force should account
for the phenomena of radiation, it is necessary that such vibra-
tion should occupy time also. I am not aware whether there
are any data by which it has been, or could be ascertained,
whether such a power as gravitation acts without occupying
time, or whether lines offeree being already in existence, such
a lateral disturbance of them at one end as I have suggested
above, would require time, or must of necessity be felt instantly
at the other end.

As to that condition of the lines of force which represents
the assumed high elasticity of the ether, it cannot in this respect
be deficient : the question here seems rather to be, whether
the lines are sluggish enough in their action to render them
equivalent to the ether in respect of the time known experi-
mentally to be occupied in the transmission of radiant force.

The ether is assumed as pervading all bodies as well as space:
in the view now set forth, it is the forces of the atomic centres
which pervade (and make) all bodies, and also penetrate all
space. As regards space, the difference is, that the ether
presents successive parts or centres of action, and the present
supposition only lines of action ; as regards matter, the difference
is, that the ether lies between the particles, and so carries on
the vibrations ; whilst as respects the supposition, it is by the
lines of force between the centres of the particles that the
vibration is continued. As to the difference in intensity of
action within matter under the two views, I suppose it will be
very difficult to draw any conclusion ; for when we take the
simplest state of common matter and that which most nearly
causes it to approximate to the condition of the ether, namely
the state of rare gas, how soon do we find in its elasticity and
the mutual repulsion of its particles, a departure from the law,
that the action is inversely as the square of the distance !

And now, my dear Phillips, I must conclude. I do not think
I should have allowed these notions to have escaped from me,

372 On Ice and Freezing Water. [1850.

had I not been led unawares, and without previous consideration,
by the circumstances of the evening on which I had to appear
suddenly and occupy the place of another. Now that I have
put them on paper, I feel that I ought to have kept them much
longer for study, consideration, and, perhaps, final rejection ;
and it is only because they are sure to go abroad in one way or
another, in consequence of their utterance on that evening,
that I give them a shape, if shape it may be called, in this reply
to your inquiry. One thing is certain, that any hypothetical
view of radiation which is likely to be received or retained as
satisfactory, must not much longer comprehend alone certain
phenomena of light, but must include those of heat and of
actinic influence also, and even the conjoined phenomena of
sensible heat and chemical power produced by them. In this
respect, a view, which is in some degree founded upon the
ordinary forces of matter, may perhaps find a little consideration
amongst the other views that will probably arise. I think it
likely that I have made many mistakes in the preceding pages,
for even to myself, my ideas on this point appear only as the
shadow of a speculation, or as one of those impressions on the
mind which are allowable for a time as guides to thought and
research. He who labours in experimental inquiries knows
how numerous these are, and how often their apparent fitness
and beauty vanish before the progress and development of real
natural truth.

I am, my dear Phillips, ever truly yours,
Royal Institution, April 15, 1846. M. FARADAY.

On Certain conditions of Freezing Water. A Discourse, $c. *

[Royal Institution, Friday Evening, June 7, 1850.]

THE chief object of the discourse was the great, various, and
extraordinary forms of affinity which exist between the particles
of water. Having experimentally illustrated the combining
power of water, and shown how this attraction passes from a
physical to a chemical force, Mr. Faraday confined the rest of
his discourse to ice, as being that condition of water in which
its particles are allowed to associate with each other without
the intervention of foreign matter. Such ice as is now imported
* Athenaeum, 1850, p. 640. The report is by the author.

1850.] On Ice and Freezing Water. 373

into this country under the name of the Wenham Lake ice
(though it is chiefly supplied from Norway) may be regarded
as one of the purest natural substances. Mr. Faraday first
showed how entirely colouring matter, salts and alkalies are
expelled in freezing*. A solution of sulphate of indigo, diluted
sulphuric acid, and diluted ammonia were partially frozen in
glass test-tubes : as soon as the operation had been carried on
long enough to produce an icy lining of each tube, the unfrozen
liquid was poured out and the ice dislodged. This ice was
found in every instance perfectly colourless, and, when dissolved,
perfectly free from acid or alkali, although the unfrozen liquid
exhibited in the first experiment a more intense blue colour, in
the second a stronger acid, and in the third a more powerful
alkaline reaction than the liquor which was put into the freezing
mixture. Mr. Faraday also devised a method for making this
ice perfectly clear and transparent as well as colourless. By
continually stirring the liquid, while freezing, with a feather, he
brushed away globules of air as fast as they were dislodged
from the freezing fluid, and thus prevented their becoming
imbedded in the ice. Having noticed the rapidity with which
water absorbs air as soon as it is thawed, Mr. Faraday called
attention to the importance of this natural arrangement to
aquatic plants and animals, to whose life air is as indispensable
as to those which live on land. Mr. Faraday then referred to
Mr. Donny's discovery, that water, when deprived of air, does
not boil till it reaches the temperature of 270, and that at that
degree of heat it explodes. He mentioned that he suggested
to Mr. Donny that ice when placed in oil (so as to prevent its
receiving any air from the atmosphere on thawing) would pro-
bably explode on reaching a sufficient temperature. This
experiment had been successfully tried by Mr. Donny, and was
as successfully repeated on this occasion. Mr. Faraday then
invited attention to the extraordinary property of ice in solidi-
fying water which is in contact with it. Two pieces of moist
ice will consolidate into one. Hence the property of damp
snow to become compacted into a snowball an effect which
cannot be produced on dry, hard-frozen snow. Mr. Faraday
suggested, and illustrated by a diagram, that a film of water
must possess the property of freezing when placed between two
* See ice from solution of chlorine, p. 82.

374 On Ice of Irregular Fusibility. [1858.

sets of icy particles, though it will not be affected by a single
set of particles. Certain solid substances, as flannel, will also
freeze to an icy surface, though other substances, as gold-leaf,
cannot be made to do so. In this freezing action latent heat
becomes sensible heat ; the contiguous particles must therefore
be raised in temperature while the freezing water is between
them. It follows from hence, that, by virtue of the solidifying
power at points of contact, the same mass may be freezing and
thawing at the same moment, and even that the freezing process

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