long thought the plough might be used in levelling roads and
clearing the foundations for fortifications. In 1824 he had an
opportunity of applying it in the construction of a canal required
to furnish a motive force for the service of the rock-salt works of
Friedrichshall. The bed was to have a section of 700 square feet, and
it had been calculated that the excavations would require 200 men for
two years, whereas the king of Wurtemburg wished it to be done in one
year from the spring of 1824.
Three ploughs were employed; the first had two handles, a coulter,
and a share, the latter being in the form of a wedge. This plough
was preferred in the beds and gravelly grounds; and it was found
advantageous to give it an oscillatory movement by the handles during
its progress. Drawn by eight horses, it could turn up 25,000 cubic
feet of an argillaceous soil, in three hours; with ten horses it
turned up 19,800 cubic feet of a gravelly soil, in the same time.
This plough was tried in 1815, against fifteen others of the ordinary
kind, in the construction of a watercourse for a mill; all the
fifteen were quickly broken by the work.
The second plough had two handles and a coulter, but the share had
only one cutting edge, which was rounded and with an ear. It was
made five times as strong as an ordinary plough, and succeeded well
in compact and argillaceous soils, where, with eight horses and four
men, it moved 48,000 cubic feet of earth in three hours. In case of
fracture ten minutes sufficed to change the coulter and share, and,
during the work, 2,300,000 cubic feet of earth were loosened by it.
The third plough was smaller and lighter, it had two handles, a
coulter, an ear, and a share, the latter lance-shaped. It was used
for excavating the sides of the canal, on which the horses attached
to the first plough found it difficult to walk because of the
inclination. It was worked by ten or twelve men.
To establish an accurate comparison between the work of these ploughs
and that done by the pickaxe and spade, a piece of ground was wrought
solely in the latter manner by six strong working men. The result of
a long trial was the breaking of 150 cubic feet of ground by each man
in nine hours. Comparing this result with the work of the ploughs,
the following are the results:—The first plough did the work of 477
men, the second of 960 men, and the third that of 50 or 60 men. The
canal was finished on April 30th, 1825, the ploughs having saved
32,000 days, according to the work-day of a labourer.—_Bull. Univ._
D. vii. 343. [p198]
4. _Discovery of Rocks under the Surface of the Sea_.—The fishers
of the Mediterranean use an apparatus for the discovery of rocks
beneath the surface in those places where they wish to cast their
nets, which supplies, in a great measure, the insufficiencies of the
ordinary means of taking soundings. The method consists in carrying
a long and thin cord over the bottom to be examined, and which, when
it meets with an obstacle, is stopped by it and becomes folded in
the place where it occurs. It will easily be understood, that when a
cord has been carried over a certain space without meeting with any
resistance, that proof is obtained of the non-existence of rocks or
other obstacles, at a depth less than that to which the cord has been
sunk; and as the examination can easily be carried on to 100 feet
below the surface, it may be said that, wherever such an apparatus
has passed unimpeded, the navigation is free. If, on the contrary,
some isolated rocks are found during the examination, the place where
the cord becomes doubled points out the locality, which may then
be determined more accurately by other trials, and the summit and
neighbourhood of the submersed rocks be accurately examined by means
of soundings.—_Annales Marit._; _Bull. Univ._ F. viii. 44.
5. _Paper to resist Humidity_.—This process, which is due to M.
Engle, consists in plunging unsized paper once or twice into
clear solution of mastic in oil of turpentine, and drying it by a
gentle heat. The paper, without becoming transparent, has all the
properties of writing-paper, and may be used for the same purposes.
It is especially recommended for passports, workmen’s books, legal
papers, &c. When preserved for years it is free from injury, either
by humidity, mice, or insects. It is further added, that a solution
of caoutchouc will produce even a still better effect.—_Kunst und
Gewerbe-blatte_.
6. _Professor Amici’s Microscopes_.—This distinguished personage has
lately exhibited to the _savans_ of this country two microscopes of
his own workmanship,—an achromatic refractor, and a reflector of his
own particular invention. The object-glass of his refractor is of a
very complicated construction, and is composed of three double-object
glasses combined together in the space of about an inch. The
flint-glass from which his concaves are formed is of the manufacture
of Frauenhofer; his convexes are of Dutch plate, crown-glass, and
French plate, separately. Each object-glass detached has but a small
aperture, and is of long focus; but when the three are combined
together, the angle of aperture is very considerable, and the focus
short. By this ingenious arrangement the trouble and difficulty
of manipulating deep single-object-glasses of large aperture is
avoided; but advantages gained one way, in practical optics, are
generally lost in another, and the twelve surfaces of the objective
produce a kind of softness and muddiness in [p199] the image strongly
contrasted by the effect of a good single triple-glass of equivalent
power. When, however, only two of the object-glasses are combined,
the effect is very fine. Between the object-glass and eye-glasses is
placed one of those prisms originally invented by Sir I. Newton to
act as an eye-piece of his telescope, and of which a description may
be seen in his correspondence at the end of Dr. Gregory’s Optics. The
utility of the introduction of this device appears very questionable
in an instrument already so complicated. The diversion of the rays
into a course at a right angle to their original progress (merely to
give an horizontal instead of a vertical position to the body) is
surely no warrant for the employment of two extra refracting surfaces
and one reflexion, which cannot fail to have a pernicious influence
on the formation of the image. An horizontal position of the body
is attained with the utmost facility by a proper construction of
the mounting, &c. Setting aside the dulness of the image produced
by the numerous refractions, the performance of the instrument on
test-objects was highly respectable and satisfactory.
The reflector is a modification of the original construction
recommended by the Professor, who seems to have profited by the
schooling he received from Dr. Goring, and now sails much closer
to the wind than he did. His objective metal is now two inches
focus, with an aperture of 1-1/2 inch; but half an inch is cut
off for the purpose of preventing the bad effect of the marginal
rays, so that only 1 inch of the central portion of the metal is
employed;—the diameter of the diagonal mirror is also reduced to its
proper standard, by which means the blot in the centre of the visual
pencil is rendered as small as possible. It may be asserted of this
instrument, that it does as much as can possibly be expected from an
objective part of 2 inches focus, showing many test-objects faintly,
and with much effort; but it is totally unable to compete with deeper
ones equally perfect and of the same angular opening. The Professor
has, in some of his instruments, reduced the focus of the elliptic
metal to 1-1/2 inch, and will, no doubt, gradually slide into the
adoption of that radical reform in his instrument, so happily carried
into effect in this country by Dr. Goring, in conjunction with Mr.
Cuthbert,—at least if the figuration of elliptic metals of 3/10
inch focus with 2/10 inch of aperture shall not surpass his powers
of execution. During the Professor’s stay in this country there
was a grand field-day at his hotel, at which _both his microscopes
were tried against the Goringian modification of the reflector, the
superior weight of metal of which completely beat every thing opposed
to it_. For the honour of the Professor it must be stated, that he
admitted this defeat with great candour and good sense, and even had
some difficulty in believing in the identity of some of the objects
used, so differently was the ordinary apparent structure developed
by the English improvements on his instrument. It may with safety
be averred that no refractor, at least, will ever be [p200] made
to surpass _Dr. Goring’s improved Amician Engiscope_; and it seems
equally certain that no other reflector will ever be invented capable
of the same facilities of application to the examination of both
opaque and transparent objects. If Professor Amici has been beaten,
it has been done with his own weapons,—the copy has surpassed the
original,—the child, by virtue of foreign nursing and tuition, has
exceeded the stature and strength of the father.
II. CHEMICAL SCIENCE.
1. _On the Specific Heat of Gases, by_ MM. de la Rive _and_
Marcet.—The principle on which these philosophers proceeded in
their researches, was, to expose equal volumes of different gases
to an equal source of heat during equal times, and to judge, by the
augmentation of elastic force in each gas, the temperature which it
had acquired. The apparatus was a kind of manometer, and consisted
of a glass balloon to retain the gas, and a bent tube attached to
it, which, descending into a vessel of mercury, served to show, by
the column of metal within it, what was the elasticity of the gas.
This method was adopted, because, i. The gas was not altered in
volume by the change of temperature, its elasticity only changing:
ii. The temperature was indicated by the gas itself, and not by a
thermometer: iii. Water was easily separated previously from the
gases, and excluded from the apparatus: iv. All the gases were placed
in exactly the same circumstances, so as to render it unnecessary to
refer to any calculation for the purpose of comparison.
Two methods of applying heat were resorted to: in one the balloon,
containing the gas at a certain temperature, was placed in water at
a higher but constant degree, for a certain time (generally 4′),
and the elevation of temperature noticed: in the other, the balloon
with the gas was inclosed in a larger copper balloon, blackened
inside, and the space between the two exhausted as much as possible
of air; the apparatus being then immersed in warm water, the heat
gained access slowly to the gas, and the time of each experiment
was increased, at the same time that certain sources of error were
avoided.
The gases experimented with were, atmospheric air, oxygen, azote,
hydrogen, carbonic acid, olefiant gas, oxide of carbon, nitrous
oxide, nitrous gas, sulphuretted hydrogen, ammonia, sulphurous
acid, muriatic acid, and cyanogen. Great care was taken in their
preparation. The result of the experiment was very unexpected; for,
during the five minutes allotted for each, all had acquired the same
temperature,—a circumstance which proves that they all have the
_same specific heat_. The equal volumes of gas at the pressure of
65 centimeters (15.59 inches) and the temperature of 20°C., being
exposed to a source of heat at 30° C., acquired a mean temperature
of 6.32 degrees in five minutes, the extreme difference, in any of
the experiments, not being more than 0.04 of a [p201] degree. One gas
only forms an exception to the above statement, namely, hydrogen,
which was always heated more than the others, namely, to 6.6 degrees
in the five minutes. This effect is considered as due not to any
difference in specific heat, but to a difference in conducting power.
Experiments were then made with dilated gases, to ascertain whether
dilatation caused any change in capacity, and it was found to
diminish slowly but regularly with the diminution of pressure. These
results, with a third which is also interesting, have been thus
generally expressed by the authors at the end of their memoir.
i. All gases in equal volumes, and at the same pressure, have the
same specific heat.
ii. Other circumstances being the same, the specific heat of gases
diminishes with diminution of pressure, and equally for all the
gases: the progression converges slightly and in a ratio much less
than that of the pressures.
iii. Each gas has a different conducting power, _i.e._, all the gases
have not the some power of communicating or receiving heat.—_Ann. de
Chimie_, xxxv. 5.
2. _On the Incandescence and Light of Lime_.—The experiments made
by Lieutenant Drummond upon the light of lime and other earths when
highly ignited, with the highly interesting application which he has
made of that emitted from lime, to the purpose of geodesical surveys,
has induced M. Pleischel to repeat and vary the results. He states
that the utmost light is given by lime; the earth being pulverised
and exposed on burning charcoal to the heat excited by a jet of
oxygen falling upon it. He endeavours to account for the effect, by
supposing a kind of pulverulent atmosphere disengaged from the lime
at the high temperature used, and considers that the substances which
are competent to emit molecules only in the gaseous state, cannot
produce this intense light.—_Zeitschrift für Physik_, &c.
3. _Evolution of Heat during the Compression of Water_. May 14,
1827.—M. Arago announced to the Academy of Sciences, that M. Despretz
had ascertained experimentally, that the compression of water by
a force equal to 20 atmospheres, caused the disengagement of one
sixty-sixth part of a degree of heat.
4. _On Electrical Excitation_.—M. Walcker affirms positively from
experiments made with great care, that three bodies of different
exciting power are necessary, in every case of excitation of
electricity by contact, and that all the phenomena of this kind are
subject to this condition. If, for instance, two portions of the same
metal being put in contact, electricity is produced, it is because
there are three different states of temperature brought into play,
one being the result of the other two, and a mean between them. One
fact which more than any other sanctioned this idea, was, that the
electric [p202] currents were the more apparent as this third state
of temperature was made more sensible.—_Bull. Univ._, A. vii. 374.
5. _Magnetic Repulsion_.—A very remarkable result has been obtained
by M. Becquerel, from the use of an extremely delicate magnetic
arrangement, which he has for the present called a _sideroscope_. Its
use is exactly the same in principle as that of the magnetic needle,
indicating iron, for instance, by the attraction manifested; but
it is so delicate that it will show it in the most minute quantity
possible, as, for instance, in gold, silver, or copper money,
innumerable minerals, &c. This instrument shows no magnetic power or
attraction in gold, silver, copper, palladium, tin, lead, zinc, or
brass, when chemically pure, and a great many vegetable and mineral
substances have no action on it: but the most curious result is, that
very pure bismuth and even that of commerce has a _repulsive_ power,
which, if it be found ultimately to be independent of any magnetic
_polarity_, is the first fact of the kind that has been made known.
Antimony also presents the same phenomenon.
6. _Diminished Solubility of Substances by Heat_.—Mr. Graham
has added one to the few facts of this kind with which we were
acquainted, and has accompanied its description with some very
interesting considerations, which may be found at length in the
Philosophical Magazine, N. S., ii. 20. The salt experimented with by
Mr. Graham is the phosphate of magnesia; which may be prepared by
mixing a solution of 21 parts of phosphate of soda with one of 15.375
parts of sulphate of magnesia: within 24 hours the phosphate of
magnesia precipitates in acicular crystals; they should be agitated
with repeated portions of water, then thrown upon a filter with more
water, and left to dry.
Solutions were obtained by occasionally agitating this salt with
water in the proportion of 2 ounces to a pint of the fluid, for
four days; being then decanted and filtered, they had a sweetish
taste. A quantity of this fluid being heated in a water-bath, became
turbid before the temperature had attained 120° F.; at 212° a cloudy
precipitate slowly subsided, and the supernatant fluid became nearly
transparent. The precipitate was found to be anhydrous phosphate of
magnesia; and, by further experiment, the difference in solubility
was found to be such, that water at 45°, dissolving 1/744th part its
weight of the anhydrous salt, water at 212° only dissolved 1/1151th
part. When in the state of crystals, or as hydrate, the proportions
of salt were 1/322 and 1/498 to 1 of water.
Mere continuance of the heat had no effect in increasing the
precipitate either of this salt, or from aqueous solution of lime,
provided no part of the solution was at any time converted into
vapour; but if the solution only occupied a small part of the vessel,
and ebullition came on, then, although all the water might be
returned to the solution, yet the precipitation went on, and might
be [p203] increased _ad libitum_, particularly in the case of lime
water. The cause of the precipitate appears to be the same in all
these cases. The moment a drop of the solution is converted into
vapour, it deposits the quantity of lime or salt which it held in
solution; and in the case of bodies which dissolve so sparingly and
with so much difficulty, although the water be returned again to the
solution, it is incapable of re-dissolving what it has deposited. We
know that it would be a hopeless task to form a saturated solution of
lime by agitating with the water no more than the few grains which
it is capable of dissolving; and in the case of ebullition, when the
lime is once deposited, there should be the same difficulty in taking
it up.
Mr. Graham states that he has observed this effect not only in
lime-water and in solution of phosphate of magnesia, but to a certain
extent in all bodies of difficult solubility, in the sulphate of
lime, for instance, even when greatly diluted; and he believes that
the deposite from slight boiling observed in many mineral waters,
and generally attributed to the dissipation of carbonic acid gas,
depends, in some instances, upon this cause. However weak the
solution may be, it is evident that a portion of the salt may be
deposited in this way.
7. _On the Composition of Cyanic Acid_.—M. Wohler some time since
announced the production of cyanic acid, and cyanates, corresponding
in composition to the substance presumed to exist in the fulminating
compounds of silver, mercury, &c., the nature of which was made out
by MM. Liebig and Gay Lussac. M. Liebig, upon repeating M. Wohler’s
experiments upon his cyanate of silver, obtained only 71.012 per
cent. of oxide of silver, instead of 77.23, which was the quantity
present according to M. Wohler’s analysis, and concluded that the
acid was the cyanous, and not the cyanic. The latter philosopher was
consequently induced to repeat his experiments: one of his methods
of decomposing the cyanate of silver was by muriatic acid gas: at
first liquid cyanic acid forms, which is very soon transformed into
a white crystalline mass; but, on continuing the operation, and
applying a higher heat, a large quantity of muriate of ammonia and
cyanic acid is evolved. This process indicated 77.5 per cent. of
oxide of silver in the salt. Another process consisted in dissolving
the cyanate in nitric acid, and precipitating the silver by muriatic
acid, the result was 77.05 of oxide per cent. A third analysis, made
by reducing the silver of the salt, gave a result of 77.35 per cent.
oxide. The mean of these is 77.3, and the theoretical number obtained
by calculation is 77.23, so that the acid appears to be truly the
cyanic; and the curious fact of its being the same in composition
with that in the fulminating compounds of silver and mercury, but
very unlike in properties, still remains undisturbed.—_Bull. Univ._,
A. viii. 53.
8. _Iodous Acid_.—According to M. Wohler, the iodous acid of [p204]
M. Sementini[35] is nothing more than a mixture of chloride of iodine
and iodine. When saturated with carbonate of soda, the iodine in
solution is precipitated, and on evaporating the solution to dryness,
and heating it strongly, the residue fuses, and by proper tests is
found to be a mixture of chloride and iodide of sodium.
These statements apply only to the iodous acid: as to the oxide of
iodine, no source of chlorine exists in the process last described by
M. Sementini.
FOOTNOTE:
[35] See the last volume of this Journal, p. 477.
9. _On Manganesic Acid, by_ M. Unverdorben.—When manganesate
of potash is distilled with a little anhydrous sulphuric acid,
manganesic acid is evolved in the form of a red transparent gas,
which dissolves in water, forming a red solution. The gas frequently
decomposes spontaneously in the retort, with explosion, producing
oxide of manganese and oxygen.
Manganesate of potash was analysed by distilling it with excess of
sulphuric acid, collecting the oxygen disengaged, and estimating the
proportion of protoxide of manganese and salts of potash remaining in
the retort. According to these experiments the acid consists of
Manganese 58.74
Oxygen 41.26
------
100.00
And the manganesate of potash of Or being calcined
Potash 25.63 32.75
Manganese acid 52.44 67.25
Water 21.93 ------
------ 100.00
100.00
_Ann. des Mines_, 1827, p. 145.
10. _Heavy Muriatic Ether, and Hydrocarburet of Chlorine or Chloric
Ether_.—Some comparative experiments have been made on these two
substances by M. Vogel. He prepared the former of them by passing
chlorine gas into alcohol. The muriatic acid was then separated by
distilling the fluid from off chalk, in which operation the muriatic
ether and alcohol passed over together, and these were divided by the
addition of water, which dissolved the latter, and left the former.
The chloric ether was made as usual from chlorine and olefiant
gases. The results that were obtained by acting on these substances
by a high temperature, potash, phosphorus, &c., induced M. Vogel
to consider them as identical in composition, notwithstanding some
differences in their physical properties; the specific gravity of the
muriatic ether was 1.134, that of the chloric ether 1.214, and the
odour of the latter is more aromatic, and the taste more sweet than
of the former.
Whilst passing the chlorine into the alcohol, M. Vogel observed
[p205] that if the sun shone upon the substances when the action was
nearly complete, each bubble of chlorine as it entered the alcohol
produced a bright purple flame, a dense white vapour, and caused
violent concussions in the liquid; another curious instance, in
addition to the many that are known, of the power of solar light over
chemical action.—_Journ. de Pharm._ 1826, p. 627.
11. _Test for the Presence of Nitric Acid_.—The following method is
one devised by Dr. Liebig, for the detection of this substance, which
it will effect, he says, when there is not more than a four-hundredth
part of the acid present. The liquid to be examined must be mixed
with sufficient sulphuric solution of indigo to acquire a distinct
blue colour, a few drops of sulphuric acid added, and the whole
boiled. If the liquid contains a nitrate, it will be bleached, or,
if the quantity is very small, rendered yellow. By adding a little
muriate of soda to the liquid before applying heat, a five-hundredth
of nitric acid may easily be discovered.—_Ann. de Chimie_, xxxv. 80.