difficult one for the chemist to deal with—he must necessarily say
much upon it, and is equally obliged to omit abstract details which
are often necessary to its explanation, and yet too prolix and bulky
for an elementary chemical work. So that it requires considerable
acquaintance with the subject to give a perspicuous and yet concise
abstract, [p063] such as may be useful to the student. Dr. Turner
has not been very successful in effecting this _desideratum_, and
has unnecessarily introduced two sections, the one on electricity,
the other on galvanism. He also talks of the “science of galvanism,”
which is in bad taste, and erroneously asserts that the energy of the
pile is proportional to the degree of chemical action which takes
place; a statement by no means correct, inasmuch as the energy of De
Luc’s column is directly proportional to the number of alternations,
and appears entirely independent of chemical action; and again, a
series of 2000 plates, arranged in the usual Voltaic apparatus, when
perfectly bright and clean, and the cells filled with distilled water
only, give a much more powerful shock, and cause a greater divergence
of the leaves of the electrometer than when the apparatus is charged
with diluted acids. Here, those very singular phenomena, which
electricians distinguish by the terms _quantity_ and _intensity_,
appear perfectly distinct; and between these our author does not
sufficiently discriminate, but jumbles the whole under the term
_activity_. In describing the chemical energies, too, of the pile, or
its decomposing powers, the Doctor entirely overlooks the important
and curious influence of water. He says that acids and salts are all
decomposed, without exception, one of their elements appearing at one
side of the battery, and the other at its opposite extremity; (_i.
e._ we presume, at its positive and negative poles.) But the fact is,
that, excepting where it merely acts as a source of heat, nothing
is decomposable by electricity without the intervention of water;
the hydrogen and oxygen of which respectively accompany the elements
of the other compounds. Not an atom of potassium can be obtained
unless the potassa be moistened; nor can any salt be decomposed
except water be present. Sir Humphry says, it is required, to render
the substance a conductor; but its operation is more recondite, and
there is something mysterious and still unexplained in the uniform
appearance of hydrogen and oxygen at the opposite poles, when far
apart in water, and in all other cases of true polar electro-chemical
decomposition. At page 86, the unfortunate protectors of ships’
bottoms are introduced—a subject about which the less is said the
better;—and, as to electro-magnetism, it is merely mentioned as to
its leading phenomena, in the space of three or four pages; nor
is anything new suggested upon the “Theory of the Pile,” as it is
called, which concludes the subject, and which is dismissed in the
brief limit of a page and a half. [p064]
The second part of Dr. Turner’s work is said to comprise “Inorganic
Chemistry,” and therefore embraces a very extensive field of inquiry.
To the _arrangement_ we have already objected; and many of the
typographical and verbal errors that occur, have been noticed in a
contemporary Journal, so that we shall chiefly attend to the details
of the sections.
Under the head, “Affinity,” some of the leading facts and doctrines
of chemical attraction are perspicuously set forth; but we could have
wished that a variety of exploded opinions and erroneous notions had
been altogether passed over, as they occupy space which might have
been better employed, and can never prove of any other use to the
student than to show him the errors and fallacies to which acute
philosophers are sometimes liable. Of this kind, especially, are
Berthollet’s notions upon the subject of affinity. The doctrine of
definite proportion is, on the whole, well and clearly explained; but
it would have been much better and clearer, had Dr. Turner confined
himself to facts, and meddled less with opinions concerning their
cause; he is moreover, in many respects, historically inaccurate. He
ascribes much to Dalton that honestly belongs to Higgins;—is much
too merciful to Berzelius and his CANONS; and lenient beyond all
endurance to the plagiarisms of “Dr. Thomson’s admirable Treatise on
the first Principles of Chemistry.”
In the third and following sections, the simple non-metallic
substances are described in an order of arrangement which must be
very perplexing to the student; otherwise the details are well
given, except that here and there the line between theory and fact
is not sufficiently marked. Thus we are told that “hydrogen is
exactly 16 times lighter than oxygen, and _therefore_ that 100 cubic
inches _must_ weigh 33.888/16, or 2.118. Its specific gravity is
consequently 0.0694, as stated some years ago by Dr. Prout.” Now this
is a theoretical deduction, founded upon the specific gravity and
constitution of ammonia, (and not upon the composition of water,) and
probably correct as applied to _pure_ hydrogen;—but if we weigh the
gas, as usually obtained, even with the utmost caution, and of the
utmost purity, we shall never procure it so light as here stated,
notwithstanding all the learning and argument that our worthy friend,
Dr. Thomas Thomson, has issued upon the subject in his various
essays in the Annals, and in his _magnum opus_. We also object to
the stress which is often laid upon the whims of individuals, and
upon [p065] exploded opinions; instances of which will occur to the
reader under the subject of the composition of nitrogen, and the
constitution of the atmosphere. We further caution our author against
admitting hints, allusions, and inuendos as to the possibility of
future inventions and discoveries, as claims upon the merits of such
discoveries, when they are actually made. Berzelius has talked a vast
deal of nonsense about the composition of nitrogen; and should that
discovery ever be made, he will doubtlessly assume the credit of
having suggested the steps which led to it. Some foolish persons are
apt to think that the Marquis of Worcester was the inventor of Watt’s
steam-engine, because he said he had means of raising water by steam,
in his _Century of Inventions_; and we have heard that an eminent
chemist of the present day considers himself entitled to all the
merit that may belong to Mr. Brunel’s carbonic acid engine, because
he had previously stated the possibility of such an application of
Mr. Faraday’s important discoveries. The fact is, that these are
woeful days for science; all the good feeling and free communication
that used to exist among its active cultivators in this country, has
given way to petty jealousies and quibbling scandal; one person is
exalted for the purpose of depreciating another; and those causes of
disgust, which some years ago induced one of our most amiable and
able men of science to quit the field, and even leave the country,
are becoming daily more prevalent. Were it not an invidious task, we
could easily explain and unfold the sources of all this mischief, and
shall indeed feel it our duty so to do, should not matters in due
time take a more favourable turn; but the task is at once serious
and disagreeable, and we therefore postpone it, in the hope of more
favourable events. We really believe that, had it not been for the
scientific conversationes held during the last season at the houses
of a few private gentlemen connected with the learned societies,
and more especially the weekly meetings at the Royal Institution,
which kept up a friendly intercourse among those who were willing
to profit by it, that the whole scientific world would have been at
loggerheads, and in that state of anarchy of which the evils may be
learned by a short residence at a “northern seat of learning.”
The main object of this digression is to deprecate _party_ in
science; and we were led to it by observing, or thinking that we
observe, something of such a tendency in the writer whose book is
before us—we hope we are mistaken.
The next section comprises “the compounds of the simple [p066]
non-metallic acidifiable combustibles with each other.” It includes
the important subject of ammonia, of the varieties of carburetted
hydrogen, sulphuretted and phosphuretted hydrogen, and cyanogen
and its compounds. The metals are then treated of, and to these
succeed their salts; and though the execution of this part of the
work betrays some haste, it shows also considerable reading, and
some originality: the general views are well and clearly sketched,
but there are many points upon which we are entirely at variance
with our author; and we more especially object to his account of the
action of chlorides upon water, and to his notions concerning the
“muriates of oxides,” a class of compounds of which, with one or two
exceptions, we are disinclined to admit the existence. If common
salt be a _chloride_ of _sodium_, and experiment obliges us so to
regard it, what is there in its aqueous solution that should lead us
to consider it as containing a _muriate_ of _soda_; what evidence of
any new arrangement of elements? Dr. T. is certainly in mistake, when
he says, “for all practical purposes, therefore, the solution of a
metallic chloride in water may be viewed as the muriate of an oxide,
and on this account I shall always regard it as such in the present
treatise.” This inconsiderate dogma taints much of the reasoning
upon the chlorides, &c., and is manifestly culled in the Thomsonian
school, though we have indeed heard that a Professor at Edinburgh
thus addresses his pupils upon the above subject: “The elaborate
researches of the illustrious Davy have taught us that common salt
is a binary compound of chlorine and sodium, a chloride, therefore,
or a chloruret of sodium. But it is only chloride of sodium whilst
quiescent in the salt-cellar; for no sooner does it come into
contact with the salivary humidity of the fauces, than, by the play
of affinities, which I have elsewhere explained, the sodium becomes
soda, and the chlorine generates muriatic acid;—that, therefore,
which upon the table is chloride of sodium, is muriate of soda in
the mouth; and this again, when desiccated or deprived of humidity,
retrogrades into its former state.”
Dr. Turner again falls into error, as we humbly conceive, in calling
certain salts, such, for instance, as those of the peroxide of iron,
_sesquisalts_, a term properly applied in those cases only where one
proportional of a protoxide unites with one and a half of an acid,
such for instance as the _sesquicarbonate of soda_, &c., but in the
sesquisulphate of iron, one proportional of the peroxide contains
1.5 of oxygen, and [p067] necessarily, therefore, (according to
Berzelius’ canon, if the Doctor pleases,) requires 1.5 of acid to
convert it into a salt; just as the commonly constituted peroxides
(containing two proportionals of oxygen) require two of acid. Dr.
Thomson, with all his nomenclatural pretensions, has fallen into the
same error.
The part of our author’s work which treats of the chemistry of
organic bodies is, upon the whole, an unexceptionable and accurate
epitome of that complicated branch of the science. It has its
inaccuracies, but they apparently arise out of the difficulty of
condensing into the space of a few pages, matter which, as we have
elsewhere remarked, would require an ample volume for its extended
and perspicuous details.
In our hasty account of this work, we have rather dwelt upon its
defects than its merits, in the hope of seeing another and more
extended edition, free from what we consider as serious obstacles
to the success and usefulness of the present production. We hope
that Dr. Turner will not feel offended at the freedom with which
our remarks are offered. We are anxious that a writer of such good
information should be induced to think for himself; at least, that
he should accurately weigh the pretensions, and inquire into the
originality of those views and researches upon which he bestows such
unqualified and, in our opinion, undeserved praise, and to which he
assents with a facility unbecoming one who evidently possesses the
means of testing their merits.
_Experiments on Audition_.
[Communicated by Mr. C. Wheatstone.]
The recent valuable experiments of Savart[23] and of Dr. Wollaston
have added to our stock of information several important and
hitherto unnoticed phenomena relating audition; but, notwithstanding
the investigations of these distinguished experimentalists, and
though the physiology of the ear has been an object of unceasing
attention for many centuries, yet we are far from possessing a
perfect knowledge of the functions of the various parts of this
organ. The description of new facts illustrative of this subject
cannot, therefore, be devoid of interest; [p068] and though I do not
anticipate that the observations contained in this communication will
lead to any important results, their novelty may claim for them some
attention from the readers of your Journal.
§ 1.
If the hand be placed so as to cover the ear, or if the entrance
of the meatus auditorius be closed by the finger without pressure,
the perception of external sounds will be considerably diminished,
but the sounds of the voice produced internally will be greatly
augmented: the pronunciation of those vowels in which the cavity of
the mouth is the most closed, as _e_ _ou_, &c., produce the strongest
effect; on articulating smartly the syllables _te_ and _kew_, the
sound will be painfully loud.
Placing the conducting stem of a sounding tuning-fork[24] on any part
of the head, when the ears are closed as above described, a similar
augmentation of sound will be observed. When one ear remains open,
the sound will always be referred to the closed ear, but when both
ears are closed, the sound will appear louder in that ear the nearer
to which it is produced. If, therefore, the tuning-fork be applied
above the temporal bone near either ear, it will be apparently heard
by that ear to which it is adjacent; but on removing the hand from
this ear (although the fork remains in the same situation) the sound
will appear to be referred immediately to the opposite ear.
In the case of the vocal articulations, the augmentation is
accompanied by a reedy sound, occasioned by the strong agitations
of the tympanum. When the air in the meatus is compressed against
this membrane by pressing the hand _close_ to the ear, or when
the eustachian tube is exhausted by the means indicated by Dr.
Wollaston, the reedy sound is no longer heard, and the augmentation
is considerably diminished. The ringing [p069] noise which
simultaneously accompanies a very intense sound, proceeds from the
same cause, and may be prevented by the same means. This ringing may
be produced by applying the stem of a sounding tuning-fork to the
hand when covering the ear, or by whistling when a hearing trumpet
is placed to the ear. As a proof that the resulting augmentation,
which, when great, excites the vibrations of the tympanum, is owing
to the reciprocation of the vibrations by the air contained within
the closed cavity, it may be mentioned, that when the entrance of the
meatus is closed by a fibrous substance, as wool, &c., no increase is
obtained.
If the meatus and the concha of one ear be filled with water, the
sounds above-mentioned will be referred to the cavity containing the
water in the same way as when it contained air, and was closed by
the hand; it will be indifferent whether any partition be interposed
between the cavity and the external air; as the water is equally well
insulated by a surface of air as by a solid body.
§ 2.
The preceding experiments have shown, that sounds immediately
communicated to the closed meatus externus are very greatly
augmented; and it is an obvious inference, that if _external_ sounds
can be communicated, so as to act on the cavity in a similar manner,
they must receive a corresponding augmentation. The great intensity
with which sound is transmitted by solid rods, at the same time that
its diffusion is prevented, affords a ready means of effecting this
purpose, and of constructing an instrument, which, from its rendering
audible the weakest sounds, may with propriety be named a Microphone.
Procure two flat pieces of plated metal, each sufficiently large
to cover the external ear, to the form also of which they may be
adapted; on the outside of each plate directly opposite the meatus,
rivet a rod of iron or brass wire about 16 inches in length, and
one-eighth of an inch in diameter, and fasten the two rods together
at their unfixed extremities, so as to meet in a single point. The
rods must be so curved, that when the plates are applied to the
ears, each rod may at one end be perpendicularly inserted into its
corresponding plate, and at the other end may meet before the head in
the plane of the mesial [p070] line. The spring of the rods will be
sufficient to fix the plates to the ears, but for greater security
ribands may be attached to each rod near its insertion in the plate,
and be tied behind the head.
[Illustration: untitled, Microphone]
A more simple instrument may be constructed to be applied to one ear
only, by inserting a straight rod perpendicularly into a similar
plate to those described above.
The Microphone is calculated only for hearing sounds when it is in
immediate contact with sonorous bodies; when they are diffused by
their transmission through the air, this instrument will not afford
the slightest assistance.
It is not my intention in this place to detail all the various
experiments which may be made with this instrument, a few will
suffice to enable the experimenter to vary them at his pleasure.
1. If a bell be rung in a vessel of water, and the point of the
microphone be placed in the water at different distances from the
bell, the differences of intensity will be very sensible. 2. If
the point of the microphone be applied to the sides of a vessel
containing a boiling liquid, or if it be placed in the liquid itself,
the various sounds which are rendered may be heard very distinctly.
3. The instrument affords a means of ascertaining, with considerable
accuracy, the points of a sonorous body at which the intensity of
vibration is the greatest or least; thus, placing its point on
different parts of the sounding board of a violin or guitar, whilst
one of its strings is in vibration, the points of greatest and least
vibration are easily distinguished. 4. If the stem of a sounding
tuning-fork be brought in contact with any part of the microphone,
and at the same time a musical sound be produced by the voice, the
most uninitiated ear [p071] will be able to perceive the consonance
or dissonance of the two sounds; the roughness of discords, and the
beatings of imperfect consonances, are thereby rendered so extremely
disagreeable, and form so evident a contrast to the agreeable
harmony and smoothness of two perfectly consonant sounds, that it is
impossible that they can be confounded.
§ 3.
Apply the broad sides of two sounding tuning-forks, both being
unisons, to the same ear; on removing one fork to the opposite ear,
allowing the other to remain, the sensation will be considerably
augmented.
It is well known, that when two consonant sounds are heard together,
a third sound results from the coincidences of their vibrations;
and that this third sound, which is called the grave harmonic, is
always equal to unity, when the two primitive sounds are represented
by the lowest integral numbers. This being premised, select two
tuning-forks, the sounds of which differ by any consonant interval
excepting the octave; place the broad sides of their branches, while
in vibration, close to one ear, in such a manner that they shall
nearly touch at the acoustic axis, the resulting grave harmonic will
then be strongly audible, combined with the two other sounds; place
afterwards one fork to each ear, and the consonance will be heard
much richer in volume, but no audible indications whatever of the
third sound will be perceived.
§ 4.
Very acute sounds, such as the chirping of the gryllus campestris,
&c., are rendered inaudible by exhausting the air from the Eustachian
tube, and thereby producing a tension of the membrane of the
tympanum; the different thicknesses or tensions of this membrane
may therefore occasion that diversity of the limits of audibility,
with regard to the acute sounds which Dr. Wollaston has pointed out
as existing in different individuals; if so, it would be desirable
to ascertain this limit in individuals in whom the tympanum is
perforated, or destroyed.
§ 5.
When the auricula is brought forward, all _acute_ sounds are rendered
much more intense, but no sensible difference is [p072] perceived
with regard to the grave sounds. The _higher_ tones of glass
staccados, or of an octave flute, the ticking of a watch, all kinds
of sibilant sounds, &c. are thus greatly augmented: the experiment
is easily tried, by whistling very shrill notes. A still greater
augmentation of the acute sounds is obtained, by placing the hands
formed into a concave behind the ears, and by bending downwards the
upper part of the auricula, so as to obtain a more complete cavity.
§ 6.
I will conclude with the following observation: I had, in consequence
of a cold, a very slight pain in my left ear; on sounding the regular
notes of the piano-forte, C^3 and C^4 were much louder than the
others, and the loudness was much increased, by placing the hand
in the manner above described to the left ear. When it was pressed
close, or when the Eustachian tube was closed, the intensities of
all the notes were equalized. I attribute this affection to the
diminished tension of the membrana tympani, which was again increased
by the operation described.
FOOTNOTES:
[23] Recherches sur les usages de la membrane du tympan et de
l’oreille externe; par M. Felix Savart. _Annales de Chimie_, tom.
xxvi. p. 1.
[24] The tuning-fork consists of a four-sided metallic rod, bent so
as to form two equal and parallel branches, having a stem connected
with the lower curved part of the rod, and contained within the
plane of the two branches. The branches are caused to vibrate by
striking one end against a hard body, whilst the stem is held in the
hand. The sound produced by this instrument when insulated is very
weak, and can only be distinctly heard when its branches are brought
close to the ear; but instantly its stem is connected with any
surface capable of vibrating, a great augmentation of sound ensues
from the communicated vibrations. The facility of its insulation and
communication renders it a very convenient instrument for a variety
of acoustical experiments.
_On the Petromyzon Marinus_.
On entering the harbour of Dublin a few weeks ago, we were becalmed
off the Hill of Howth, and to pass the tedious time until a breeze
sprung up, we found some lines on board, and began to fish from the
quarter-deck. We caught a number of grey gurnet; but our attention
was particularly attracted by a pull of uncommon force on one of
the lines. Having rendered assistance to the person who held it, we
were all astonished to see rise out of the water a large fish, with
apparently a double body, which, after floundering on the surface
of the water, we pulled on deck. On examining this phenomenon for
a short time, we were again surprized to see it separate into two
parts; and then found that there were _two_ large fish taken up on
the same hook, the head of one having been buried under the throat
of the other, to which it had firmly attached itself. When separated
by force, it wiggled about on the deck with extraordinary strength
and agility, and again darted on its prey, to which [p073] it adhered
so firmly, that it required very considerable exertion to detach
it; for it suffered itself to be raised up by the tail, and shaken,
still holding the other fish suspended from its jaws. When finally
separated, it showed great ferocity, darting at every thing near it,
and at last seizing the deck, which it held very fast, writhing with
its tail and body as if in the act of tearing it to pieces. When
detached, its teeth left a deep circular impression on the wood, the
fibres of which were drawn into the cavity of its jaws, so as to be
raised up in the form of a cone. I now directed, that it should be
put into a bucket of sea water, in the hope of preserving it alive
until we arrived in Dublin, but it died in a shorter time than could
be expected, from the energy and activity it had displayed, long
after the other fish was dead. We had handled it very roughly, and so
perhaps had mortally hurt an animal otherwise very tenacious of life.
[Illustration: untitled, Fish]