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in the inside may be a thawing process on the outside. Mr.
Faraday then referred to Mr. Thomson's memoirs on the effect
of pressure on the freezing-point. Mr. Thomson has shown
that immense pressure will prevent water from freezing at 32
ice naturally occupies a greater volume than that of the water
which forms it ; and we may conceive that when ice is pressed
the tendency is to give it both the water bulk and state.

In conclusion, Mr. Faraday noticed briefly, and chiefly by
way of suggestion, the molecular condition of ice as presenting
many curious results, and called attention to the strangeness of
striae being found in a body of such uniform composition as
pure water frozen into ice.

On Ice of Irregular Fusibility**

HAVE the following remarks, made in reference to the
irregular fusibility of ice, to which you drew my attention,

any interest to you, or by an occasional 32

bearing on such cases, any value in 33

themselves? Deal with them as you 34

like. 35

Imagine a portion of the water of a 3G

lake about to freeze, the surface S being 37

in contact with an atmosphere con- 38

siderably below 32, the previous action 39

of which has been to lower the tempe- 40

rature of the whole mass of water, so 40

that the portion below the line M is at 40

* From Tyndall's paper " On some Physical Properties of Ice," Phil. Trans.
1858, p. 228.


1858.] On Ice of Irregular Fusibility. o75

40, or the maximum density, and the part above at progressive
temperatures from 40 upwards to 32 ; each stratum keeping
its place by its relative specific gravity to the rest, and having
therefore, in that respect, no tendency to form currents either
upwards or downwards. Now generally, if the surface became
ice, the water below would go on freezing by the cold con-
ducted downwards through the ice ; but the successive series
of temperatures from 32 to 40 would always exist in a layer
of water contained between the ice and the dense water at 40
below M. If the water were pure, no action of the cold would
tend to change the places of the particles of the water or cause
currents ; because the lower the cold descended, the more
firmly would any given particle tend to retain its place above
those beneath it : a particle at e, for instance, at 36 Fahr.,
would, when the cold had frozen what was above it, be cooled
sooner and more than any of the particles beneath, and so
always retain its upper place as respects them.

But now, suppose the water to contain a trace of saline
matter in solution. As the water at 32 froze, either at the
surface or against the bottom of the previously-formed ice,
these salts would be expelled ; for the ice first formed (and
that always formed, if the proper care be taken to displace
the excluded salts) is perfectly free from them, and PURE.
The salts so excluded would pass into the layer of water
beneath, and there produce two effects : they would make
that layer of greater specific gravity than before, and so give
it a tendency to sink into the warmer under layer ; but they
would also make it require a lower temperature than 32 for
congelation ; this it would acquire from the cold ice above,
and by that it would become lighter and float, tending to
remain uppermost; for it has already been shown that the
diminution of temperature below 32 in sea water and solution
of salts, is accompanied by the same enlargement of bulk as
between 32 and 40 with pure water. The stratum of water,
therefore, below the ice, would not of necessity sink because
it contained a little more salt than the stratum immediately
below it ; and certainly would not if the increase of gravity
conferred by the salts was less than the decrease by lowering
of temperature. An approximation of the strata between
the freezing place and the layer at 40 would occur, i. e. the

376 On Ice of Irregular Fusibility. [ 1 858.

distance between these temperatures would be less, but the
water particles would keep their respective places.

When water freezes, it does not appear that this process is
continuous, for many of the characters of the ice seem to show
that it is intermittent; i. e. either a film of ice is formed, and
then the process stops until the heat evolved by solidification
has been conducted away upwards, and the next stratum of
water has been sufficiently cooled to freeze in turn; or else the
freezing being, so to speak, continuous, still is not continued
at the same constant rate, but, as it were, by intermittent
pulsations. Now it may well be, when a layer next the pre-
viously-formed ice, and containing an undue proportion of salts,
has been cooled down to its required temperature for freezing
(which would be below 32) , that on freezing, the congelation
will pervade at once a certain thickness of the water, excluding
the salts from the larger portion of ice formed, but including
them as a weak solution within its interstices. The next in-
crement of cold conducted from the ice above would freeze up
these salts in the ice containing them, at the same time that a
layer of pure ice was formed beneath it. Thus a layer of ice
fusible at a lower temperature than the ice either above or
below it might be produced ; and by a repetition of the process
many such layers might be formed.

It does not follow necessarily that the layers would be per-
fectly exact in their disposition. Very slight circumstances
tending to disturb the regularity of the water-molecules would
be sufficient, probably, to disturb the layers more or less. Ice
contains no air, and the exclusion of a minute bubble of air
from the water in the act of freezing might disturb the direction
and progress of the congelation, and cause accumulation of the
extra saline liquid in one spot rather than another. So might
the tendency to the formation of little currents, either arising
from the separation of the saline water from the forming ice, or
from the elevation of temperature in different degrees at those
places where the congelation was going on at different rates.

The effect would not depend upon the quantity of salts con-
tained in the freezing water, though its degree would. The
proportion of salts necessary to be added to pure water to lower
its freezing-point 1 Fahr. may be very sensible to chemical
tests, but the proportion required to make the difference T J^th

1858.] On Regelation. 377

or T^oflth of a degree would be far less : and if we suppose that
only g^th of a piece of ice is brought into the condition of melt-
ing before the rest of the mass, and that the salts in that pro-
portion were originally in the whole of the water, then its quan-
tity there may be so small as to escape detection except by very
careful analysis. However, it would be desirable to examine
the water chemically which is produced by ice distinguished
by having in its interior much, that liquefies before the rest.

It is easy to make ice perfectly free from air, and, as I believe,
from salts, by a process I formerly described*. It would be
interesting to see if such ice had within it portions melting at a
lower temperature than the general mass. I think it ought not.

Ever truly yours,

Royal Institution, Dec. 9, 1857. M. FARADAY.

On Regelation.

THE subject of regelation has of late years acquired very great
interest through the experimental investigations of Tyndall,
J. Thomson, Forbes and others, and in its present state will
perhaps justify a few additional remarks on my part as to the
cause. On the first observation of the effect eight years ago,
I attributed it 10 the greater tendency which a particle of fluid
water had to assume the solid state, when in contact with ice
on two or more sides, above that it had when in contact on one
side only f. Since then Mr. Thomson has shown that pressure
lowers the freezing-point of water J, and has pointed out how
such an effect occurring at the places where two masses of ice
press against each other, may lead first to fusion and then
union of the ice at those places ; and so he explains the fact of
regelation. Prof. J. D. Forbes does not think that pressure
causes regelation in this manner, though it favours it by moulding
the touching surfaces to each other. He admits Person's view
of the gradual liquefaction of ice||, and assumes that ice must
be essentially colder than ice-cold water, i. e. the water in con-
tact with it.

* P. 373. t Pp. 373, 374.

Belfast Society Proceedings, December 2, 1857.

Royal Society Edinburgh Proceedings, April 19, 1858.

|| Comptes Renclus, 1850, xxx. 526.

378 On Regelation. [1858.

I find no difficulty in thinking it would be easy to arrange
a mixture of water arid snow in such a manner that it might
be kept for hours and days without any transition of heat either
to or from it ; but I find great difficulty in thinking that the par-
ticles of snow, small as they may be made, would remain for the
whole of the time at a lower temperature by 0*3 F. than the
particles of water intermingled with them : still admitting for
the present the possibility that Prof. Forbes's view may be cor-
rect, and also the truthfulness of Mr. Thomson's principle, and
its possible action in regelation, I wish to say a few words on
the other principle already referred to, which was originally
assumed by myself, which in relation with the mechanical
theory of heat, has been adopted by Dr. Tyndall, and which,
after all, may be the sole cause of the effect.

The principle I have in view being more distinctly expressed
is this : In all uniform bodies possessing cohesion, i. e, being
in either the solid or the liquid state, particles which are sur-
rounded by other particles having the like state with themselves
tend to preserve that state, even though subject to variations
of temperature, either of elevation or depression, which, if the
particles were not so surrounded, would cause them instantly
to change their condition. As water is the substance in which
regelation occurs, I will illustrate the principle by the phe-
nomena which it presents. Water may be cooled many degrees
below 32 Fahr.* and yet retain its liquid state, for as far as
we know any length of time, without solidification ; yet, intro-
duce a piece of the same chemical substance, ice, at a higher
temperature, and the cold water freezes and becomes warm.
It is certainly not the change of temperature which causes the
freezing, for the ice introduced is warmer than the water. I
assume that it is the difference in the condition of cohesion
existing on the different sides of the changing particles which
sets them free and causes the change. The cold water par-
ticles would willingly, as to temperature, have solidified without
the ice, but were held fluid by the cohesion with them of other
like fluid particles on all sides.

* Water may be cooled to 22 F. It is probable that if it were perfectly
freed from air it would remain fluid at a much lower temperature, for the air
is excluded at the freezing-point, and the occurrence of this exclusion would
break cohesion.

1858.] On Regelation. ^ 379

In the other direction, Donny's experiments have taught us
that the cohesion amongst the particles of water is so great
that it will support a column of the fluid four or more feet
high when there is no other power to sustain it ; or will cause
it to resist conversion into the state of vapour at temperatures
so much higher than its ordinary boiling- or condensing-point,
that explosion will occur when the continuity, and therefore
the cohesion, is destroyed. The water may be exalted to the
temperature of 70 Fahr. at the ordinary pressure of the
atmosphere, and remain as water ; but the introduction of the
smallest particle of air or steam will cause it at once to burst
into vapour, and at the same time its temperature falls.

This ability which water has to retain by cohesion its liquid
state, refusing to solidify when below the freezing-point, or
to become vapour when above the boiling-point, it has in
common with many other substances. Acetic acid, sulphur,
phosphorus, many metals, many solutions, may be cooled
below the congealing temperature prior to the solidification of
the first portions ; many other substances, such as alcohol,
sulphuric acid, ether, camphine, &c., boil with bumping, or
boil with different degrees of facility in vessels of different
substances*. The conclusion, that these differences are due
to a certain range of cohesion in the case of each body, seems
tome both simple and natural ; this cohesion enabling the sub-
stances to withstand a change of temperature, which, without
the cohesion, ought to have caused a change of state. The
effect of extraneous matters as nuclei also appears to me to
be simple ; for though when introduced, as into cooled or heated
water, their particles may exert a cohesive force (so to say)
upon the particles of the fluid, the force so exerted in the first
instance is rarely equal to the force exerted between the water
particles themselves. Extraneous substances require prepa-
ration before their adhesion to fluid is at a maximum : glass
will permit water to boil in contact with it at 212, or by pre-
paration will remain in contact with it at 270 Fahr., as in
Donny's experiment. It will also remain in contact with water
at 22 Fahr. without causing its solidification, and yet an
ordinary piece of glass will set it off at once.

Enough has been said, I think, to show that water particles

* Marcet.

380 On Re gelation. [1858.

surrounded by water tend to retain their fluid state in both
directions at temperatures which are abundantly sufficient to
make it equally retain the solid or the vaporous state when either
of them is conferred upon it. There is nothing against the
assumption that ice has the like kind of power, i. e. the power
of retaining its solid state at temperatures higher than the
temperature of ice against water. Nevertheless, the fact is
more difficult to show ; still some experiments may be quoted
in favour of the view. If hydrated crystals of sulphate
of soda, carbonate of soda, phosphate of soda, &c.*, be care-
fully prepared in clean basins, by spontaneous evaporation
of the water they will retain their form unbroken, and their
hydrated state undisturbed, through the high temperatures of
a whole summer ; though if broken or scratched even in winter,
they will commence to effloresce at the place where the cohesion,
and with it the balance of force was disturbed, and will from
thence change progressively throughout the whole mass f.
As regelation concerns the condition of water, there is per-
haps no occasion to go further. Such facts as the following,
however, concern the extension of the principle and illustrate
the power of cohesion, especially in cases where it is coming
into activity. Camphor in bottles, or iodide of cyanogen in
proper glass vessels produce crystals sometimes an inch or
two in length, which grow by the deposition of solid matter
on them from an atmosphere unable to deposit like solid
matter upon the surrounding glass, except at a lower tempe-
rature. Crystals in solution grow by the deposition of solid
matter on them which does not deposit elsewhere in the solu-
tion : many such like cases may be produced.

Returning to the particular case of regelation, it is seen that
water can remain fluid at temperatures below that at which ice
forms, by virtue of the cohesion of its particles, and in so far
the change is rendered independent of a given temperature.
Next, I rest on the fact that ice has the same property as
camphor, sulphur, phosphorus, metals, &c., which cause the

* Philosophical Transactions, 1834, p. 74 ; or Exp. Res. Electricity, vol. i.
p. 191, note.

t Such a case shows combined solid water at a temperature ready to separate
and change into vapour, yet not changing, because, as far as we can see, the
undisturbed cohesion holds all together.

1858.] On Regelation. 381

deposition of solid particles upon them from the surrounding
fluid, that would not have been so deposited without the
presence of the previous solid portions; a fact sufficiently
proved by the growth of fine crystals of ice in ice-cold water.
This effect was admirably shown in Mr. Harrison's freezing
apparatus, where beautiful thin crystals of ice, six, eight, and
ten inches long, would form in the surrounding fluid ; and
these crystals, which could not be colder than the surrounding
fluid, exhibited the phenomena of regelation when purposely
brought in contact with each other.

The next point may be considered as an assumption : it is
that many particles in a given state exert a greater sum of their
peculiar cohesive force upon a given particle of the like substance
in another state than few can do ; and that as a consequence
a water particle with ice on one side and water on the other,
is not so apt to become solid as with ice on both sides ; also
that a particle of ice at the surface of a mass in water is not
so apt to remain ice as when, being within the mass, there is
ice on all sides, temperature remaining the same. If that be
admitted, then regelation is sufficiently accounted for. Dif-
ference of temperature above or below that of the changing
points of water is not alone sufficient to cause change of state,
the change being independent of temperature throughout a large
range. At such times the particles appear to be governed by
cohesion. Cohesion resolves itself into the force exerted on
one particle by its neighbours, and this force seems to me to be
sufficient, under the circumstances, to account for regelation.

Supposing this to be the true view of the state of things,
then a particle of ice within ice can exist at a temperature
higher than a like particle of ice on its surface in contact with
water ; and though it does not appear at present how a higher
temperature could be communicated to the interior of a mass
of freezing ice than that existing over its surface, still there
may be principles of action in radiation, and even in conduction
and liquefaction, producing that effect. Assuming, however,
that a piece of freezing ice is in such a state, then, if it were
to be pulverized, it ought to produce a mixed mass of ice and
water colder than the ice was before. Such seems to be the
result in one of Prof. Forbes's experiments, in which ice rapidly
pounded showed a temperature of 0*3 Falir, below the tern-

382 On Table-turning. [1853.

perature of snow in a thawing state. The experiment, however,
would require much consideration in every point of view, and
much care before it could be considered as telling anything
beyond the temperature of ice-cold water.

On the other hand, if a spherical cup of ice could be pre-
pared containing water within, to which no heat could pass
except by conduction through the ice itself, that water ought
to be a little colder than the ice cup around it: also if a
mixture of snow and water were pressed together, the tempe-
rature should rise whenever regelation occurred, being an effect
in the contrary direction to that which Prof. J. Thomson con-
templates ; and such a mixture, as a whole, ought to be warmer
than the water in the ice sphere mentioned above. No doubt
nice experiment will hereafter enable us to criticise such results
as these, and separating the true from the untrue, will establish
the correct theory of regelation.

September, 1858.

On Table-turning*.
To the Editor of the Times.

SIR, I have recently been engaged in the investigation of table-
turning. I should be sorry that you should suppose I thought
this necessary on my own account, for my conclusion respecting
its nature was soon arrived at, and is not changed ; but I have
been so often misquoted, and applications to me for an opinion
are so numerous, that I hoped, if I enabled myself by experi-
ment to give a strong one, you would consent to convey it to all
persons interested in the matter. The effect produced by table-
turners has been referred to electricity, to magnetism, to
attraction, to some unknown or hitherto unrecognized physical
power able to affect inanimate bodies to the revolution of the
earth, and even to diabolical or supernatural agency. The
natural philosopher can investigate all these supposed causes
but the last ; that must, to him, be too much connected with
credulity or superstition to require any attention on his part.
The investigation would be too long in description to obtain a
place in your columns. I therefore purpose asking admission

* Times, June 30, 1853.

1853.] On Table-turning. 383

for that into the ' Athenaeum ' of next Saturday, and propose
here to give the general result. Believing that the first cause
assigned namely, a quasi involuntary muscular action (for
the effect is with many subject to the wish or will) was the
true cause ; the first point was to prevent the mind of the
turner having an undue influence over the effects produced
in relation to the nature of the substances employed. A
bundle of plates, consisting of sand-paper, millboard, glue,
glass, plastic clay, tinfoil, cardboard, gutta-percha, vulcanized
caoutchouc, wood, and resinous cement, was therefore made up
and tied together, and being placed on a table, under the hand
of a turner, did not prevent the transmission of the power ;
the table turned or moved exactly as if the bundle had been
away, to the full satisfaction of all present. The experiment
was repeated, with various substances and persons, and at
various times, with constant success ; and henceforth no objec-
tion could be taken to the use of these substances in the con-
struction of apparatus. The next point was to determine the
place and source of motion, i. e. whether the table moved the
hand, or the hand moved the table ; and for this purpose indi-
cators were constructed. One of these consisted of a light
lever, having its fulcrum on the table, its short arm attached to
a pin fixed on a cardboard, which could slip on the surface of
the table, and its long arm projecting as an index of motion.
It is evident that if the experimenter willed the table to move
towards the left, and it did so move before the hands, placed
at the time on the cardboard, then the index would move to
the left also, the fulcrum going with the table. If the hands
involuntarily moved towards the left without the table, the index
would go towards the right ; and, if neither table nor hands
moved, the index would itself remain immoveable. The result
was, that when the parties saw the index it remained very steady ;
when it was hidden from them, or they looked away from it, it
wavered about, though they believed that they always pressed
directly downwards ; and, when the table did not move, there
was still a resultant of hand force in the direction in which it
was wished the table should move, which, however, was exer-
cised quite unwittingly by the party operating. This resultant
it is which, in the course of the waiting time, while the fingers
and hands become stiff, numb, and insensible by continued

384 On Table-turning. [18513.

pressure, grows up to an amount sufficient to move the table
or the substances pressed upon. But the most valuable effect
of this test-apparatus (which was afterwards made more perfect
and independent of the table) is the corrective power it possesses
over the mind of the table-turner. As soon as the index is
placed before the most earnest, and they perceive as in my
presence they have always done that it tells truly whether
they are pressing downwards only or obliquely, then all effects
of table-turning cease, even though the parties persevere,
earnestly desiring motion, till they become weary and worn out.
No prompting or checking of the hands is needed the power
is gone ; and this only because the parties are made conscious
of what they are really doing mechanically, and so are unable
unwittingly to deceive themselves. I know that some may say
that it is the cardboard next the fingers which moves first, and
that it both drags the table, and also the table-turner with it.
All I have to reply is, that the cardboard may in practice be
reduced to a thin sheet of paper weighing only a few grains,
or to a piece of goldbeaters' skin, or even the end of the lever,
and (in principle) to the very cuticle of the finger itself. Then
the results that follow are too absurd to be admitted : the table
becomes an incumbrance, and a person holding out the fingers
in the air, either naked or tipped with goldbeaters' skin or
cardboard, ought to be drawn about the room, &c. ; but I refrain
from considering imaginary yet consequent results which have

Online LibraryMichael FaradayExperimental researches in chemistry and physics → online text (page 37 of 49)