Scientific American Supplement, No. 392, July 7, 1883 by Various
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Various >> Scientific American Supplement, No. 392, July 7, 1883
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10 Produced by Olaf Voss, Don Kretz, Juliet Sutherland,
Charles Franks and the DP Team
[Illustration]
SCIENTIFIC AMERICAN SUPPLEMENT NO. 392
NEW YORK, JULY 7, 1883
Scientific American Supplement. Vol. XVI, No. 392.
Scientific American established 1845
Scientific American Supplement, $5 a year.
Scientific American and Supplement, $7 a year.
* * * * *
TABLE OF CONTENTS.
I. ELECTRICITY AND MAGNETISM.--Improved Dynamo Machine.
Eight figures.
An Improved Manganese Battery.--By GEO. LEUCHS.
The Cause of Evident Magnetism in Iron, Steel, and other Magnetic
Metals.--By Prof. D. E. HUGHES. Neutrality.--Superposed
Magnetism.--Elastic Nature of the Ether Surrounding the Magnetic
Molecules. 3 figures.
II. ENGINEERING.--The Westinghouse Brake. 2 figures.
Hydraulic Elevators and Motors.--By B. F. JONES.--Bearing
upon the Water Supply of Cities.--Cost of Water used.--Objectionable
effects on Water Works.--Best method of arranging water
supply.--Cause of Accidents.--Advantages of Water Motors over
Steam Engines.--Rates for Water Motors.
Water Supply of Small Towns.--Process of Softening Hard
Water. Six figures.
Improved Water Meter. Several figures.
III. TECHNOLOGY.--Washing Machine for Wool. 1 figure.
Increasing the Illuminating Power of Gases, etc.--By V. POPP.--
3 figures.
Preventing Iron from Rusting.
An Elastic Mass for Confectioners' Use.
Caoutchouc.
Photographic Action Studied Spectroscopically.
Salt and Lime.
Renewing Paint without Burning.
A Green or Golden Color for all Kinds of Brass.--By E. PULCHER.
Vinegar.
The Preservation of Meat by Carbonic Acid.
On the Adulteration of Soap.--By Dr. H. BRACKEBUSCH.
IV. CHEMISTRY.--Testing Olive Oil.--By Dr. O. BACH.
On the Theory of the Formation of Compound Ethers.
The Alizarine Industry.
Reduction of Oxidized Iron by Carbonic Oxide.
V. MEDICINE AND HYGIENE.--Bovine and Human Milk; the Difference
in its Action and Composition.--By C. HUSSON.
Cereal Foods in their Relation to Health and Disease.--By F. R.
CAMPBELL.
Moist Air in Living Rooms.
The Developmental Significance of the Human Physiognomy.--
By E. D. COPE.--Numerous illustrations.
VI. NATURAL HISTORY.--The Diamond Fields of South Africa.
Sponges at the Bahamas.
Testing Fish Ova for Impregnation.
VII. MISCELLANEOUS.--The Production of Fire. 4 figures.
St. Blaise.--The winner of the Derby. 1 illustration.
* * * * *
IMPROVED DYNAMO MACHINE.
The continuous current and the alternating current generators invented
by Dr. J. Hopkinson and Dr. Alexander Muirhead are peculiarly
interesting as being probably the first in which the bobbins of the
armature were wound with copper ribbon and arranged on a disk armature
much in the same way as was afterward done by Sir William Thomson and by
Mr. Ferranti. In the Muirhead-Hopkinson machine the armature coils are
attached to a soft iron ring, whereas in the Ferranti the iron core is
dispensed with, and a gain of lightness in the armature or rotating part
effected; this advantage is of considerable importance, though Messrs.
Hopkinson and Muirhead can of course reduce the weight of this iron core
to insignificant proportions.
[Illustration: HOPKINSON & MUIRHEAD'S DYNAMO-ELECTRIC GENERATOR.]
The general form of this generator is clearly shown by the side and end
elevation.
The armature is made by taking a pulley and encircling it with a rim of
sheet-iron bands, each insulated from the other by asbestos paper. On
one or both sides of the rim thus formed, radial slots are cut to admit
radial coils of insulated copper wire or ribbon, so that they lie in
planes parallel to the plane of the pulley. In the continuous current
machine coils are placed on both sides of the iron rim and arranged
alternately, that on the one side always covering the gap between two on
the other side. In this way, when a coil on one side of the rim is at
its "dead point" and yields its minimum of current, the corresponding
coil on the other side is giving out its maximum.
The field magnets are made in a similar manner to the armature and run
in circles parallel to the rim of the latter. The cores may be built up
of wrought iron as the rim of the armature is; but it is found cheaper
to make them of solid wrought or cast iron. To stop the local induced
currents in the core, however, Messrs. Muirhead and Hopkinson cut
grooves in the faces of the iron cores, and fill them up with sheet-iron
strips insulated from each other, similar to the sheet-iron rim of the
armature.
The coils, both in the armature and electro-magnets, are packed as
closely as they may to each other, and have thus a compressed or
quadrilateral shape. The arrangement is shown in Figs. 1 and 2, which
represent, in side view and plan, the armature pulley with the soft iron
rim and coils attached. There a is the pulley which is keyed to the
shaft of the machine, and is encircled with bands of sheet iron, b,
insulated from each other by ribbons of asbestos paper laid between
every two bands. When the rim has been built up in this way, radial
holes are drilled through it from the outer edge inward, and the whole
rim is bound together by bolts, d, inserted in the holes and secured by
cottars, e. Radial slots are then cut on each side of the rim all round,
and the coils of wire mounted on them.
Figs. 3 and 4 show the armature of the continuous current dynamo, with
the coils on one side of the rim, half way between the coils on the
other side, so as to give a more continuous current. In the alternating
current machine the slots on the opposite faces are face to face.
Figs. 5 and 9 illustrate the complete continuous current machine, Fig.
9 showing the internal arrangement of the field magnets, and Fig. 5 the
external frame of cast iron supporting them. In these figures a is the
armature already described, b b are the cores of the electro-magnets
with a strong cast iron backing, c c; d d are the exciting coils or
field magnets, so connected that the poles presented to the armature are
alternately north and south, thus bringing a south pole on one side of
the armature opposite a north pole on the other side.
The commutator, e, is arranged to prevent sparking when the brushes
leave a contact piece. This is done by splitting up the brushes into
several parts and inserting resistances between the part which leaves
the contact piece last and the rest of the circuit. This resistance
checks the current ere the final rupture of contact takes place.
Figs. 6 and 7 will explain the structure of the commutator. Here a a a
are the segments or contact pieces insulated from each other, and b' b
b are the collecting brushes carried on a spindle, c c'. One of these
brushes, b', is connected to the spindle, c, through an electrical
resistance of plumbago, arranged as shown in Fig. 7, where d e are metal
cylinders, d being in contact with the brush, b', while e is in contact
with the spindle, c. The space, f, between these two cylinders, d e, is
filled with a mixture of plumbago and lampblack of suitable resistance,
confined at the ends by ivory disks. The brush, b', is adjusted by
bending till it remains in contact with any segment of the commutator
for a short time after the other brushes have left contact with that
segment, and thus instead of sudden break of circuit and consequent
sparking, a resistance is introduced, and contact is not broken until
the current has been considerably reduced.
The contact segments are supported at both ends by solid insulating
disks; but they are insulated from each other by the air spaces between
them, where the brushes rub upon them.
The alternating current dynamo of Drs. Hopkinson and Muirhead differs
little in general construction from that we have described; except that
the commutator is very much simplified, and the armature bobbins are
placed opposite each other on both sides of the rim. Instead of forming
the coils into complete bobbins, Dr. Muirhead prefers to wind them in a
zigzag form round the grooved iron rim after the manner shown in Fig. 8,
which represents a plan and section of the alternating current armature.
This arrangement is simpler in construction than the bobbin winding, and
is less liable to generate self-induction current in the armature. Sir
William Thomson has adopted a similar plan in one of his dynamos. In
Fig. 8, a is the pulley fixed to the spindle of the machine, b b is
the iron rim, and c c are the zigzag coils of copper ribbon. The field
magnets are also wound in a similar manner.
It will be seen from our description that Drs. Hopkinson and Muirhead
have scarcely had sufficient credit given them for this interesting
machine, which so closely approximates to the Ferranti. One of their
alternating dynamos has been built, and was shown at the Aquarium
Exhibition. It works well, and is capable of supporting 300 Swan lights,
while in size and appearance it resembles the Ferranti machine in a
very striking manner. Drs. Muirhead and Hopkinson have also designed
a magneto-electric alternating current machine; but as it closely
resembles the machines described, with the exception that permanent
magnets are employed as field magnets, we need not dwell upon it
further.--_Engineering_.
* * * * *
AN IMPROVED MANGANESE BATTERY.
By GEORGE LEUCHS.
The Leclanche battery is distinguished for its simplicity, its small
internal resistance (0.7 to 1.0 Siemens unit), and that all chemical
action ceases when the current is broken, that it is not sensitive to
external influence, and by the self-renewal of the negative electrodes.
But on the opposite side the action is not very great (= 1.20 or 1.48
D.), and the zinc as well as the sal ammoniac are converted into
products that cannot be utilized.
I replace the solution of sal ammoniac by one of caustic potash or
soda (12 to 15 per cent.), and the thin zinc rods by zincs with larger
surfaces. In this manner, I obtain a powerful and odorless battery,
having all the valuable qualities of the Leclanche, and one that
permits of a renewal of the potash solution as well as of the negative
electrode.
The electromotive power of this element may be as high as 1.8 D. The
same pyrolusite (binoxide of manganese) cylinder used with the same thin
rod of zinc will precipitate 75 per cent. more copper from solution in
an hour when caustic potash is used than when sal ammoniac is employed.
But by replacing the thin zinc rod by a zinc cylinder of large surface,
2½ times as much copper is precipitated in the same time.
The more powerful action of such a pair is explained by the stronger
excitation and more rapid regeneration that the negative electrodes
undergo from the oxidizing action of the air in the potash solution, as
well as by the fact that this solution is a better conductor than the
sal ammoniac solution. The potash solution does not crystallize easily,
hence the negative electrode remains free from crystals and does not
require filling up with water. Zinc dissolves only while in contact
with negative bodies, hence there is no unnecessary consumption of zinc
either in the open or closed circuit.
When the potash lye has become useless, I regenerate it by removing the
zinc in the following manner: I pour the solution from the cells, put
it in a suitable vessel, where I add water to replace that already
evaporated, and then shake it up well at the ordinary temperature with
hydrated oxide of zinc (zincic hydrate). Under this treatment the
greater portion of the zinc that had been chemically dissolved by the
potash is precipitated in the form of zinc hydrate, along with
some carbonate. The liquid is now allowed to settle, and the clear
supernatant solution is poured back again into the battery cells. The
battery has rather greater electromotive force when this regenerated lye
is used, because certain foreign matters from the carbon, like sulphur,
chlorine, sulphuric acid, etc., are removed by this treatment.
The regeneration of the (brown coal) carbon goes on of itself, beneath
the lye, through the oxidizing action of the atmospheric air; it is
advantageous to have a part of the carbon sticking out of the liquid. Of
course the regeneration takes place much more quickly if the electrodes
are taken out and exposed to the air. In this case the carbon electrode
need not be very thick, and can be flat or of tubular form. In the
former case it must have a large volume, and the massive cylindrical
form is recommended. The zinc electrode must be kept covered deeply with
potash. The cells must have free access of air, and the potash must be
replaced as soon as it is exhausted.--_Chem. Zeit_.
* * * * *
[Concluded from SUPPLEMENT No. 390, page 6217.]
THE CAUSE OF EVIDENT MAGNETISM IN IRON, STEEL, AND OTHER MAGNETIC
METALS.
[Footnote: Paper lately read before the Society of Telegraph Engineers
and Electricians.]
By Professor D. E. HUGHES, F.R.S., Vice-President.
NEUTRALITY.
The apparatus needed for researches upon evident external polarity
requires no very great skill or thought, but simply an apparatus to
measure correctly the force of the evident repulsion or attraction; in
the case of neutrality, however, the external polarity disappears, and
we consequently require special apparatus, together with the utmost care
and reflection in its use.
From numerous researches previously made by means of the induction
balance, the results of which I have already published, I felt convinced
that in investigating the cause of magnetism and neutrality I should
have in it the aid of the most powerful instrument of research ever
brought to bear upon the molecular construction of iron, as indeed of
all metals. It neglects all forces which do not produce a change in the
molecular structure, and enables us to penetrate at once to the interior
of a magnet or piece of iron, observing only its peculiar structure
and the change which takes place during magnetization or apparent
neutrality.
The induction balance is affected by three distinct arrangements of
molecular structure in iron and steel, by means of which we have
apparent external neutrality.
Fig 1 shows several polar directions of the molecules as indicated
by the arrows. Poisson assumed as a necessity of his theory, that
a molecule is spherical; but Dr. Joule's experimental proof of the
elongation of iron by one seven-hundred and-twenty-thousandth of its
length when magnetized, proves at least that its form is not spherical;
and, as I am unable at present to demonstrate my own views as to its
exact form, I have simply indicated its polar direction by arrows--the
dotted oval lines merely indicating its limits of free elastic rotation.
In Fig. 1, at A, we have neutrality by the mutual attraction of each
pair of molecules, being the shortest path in which they could satisfy
their mutual attractions. At B we have the case of superposed magnetism
of equal external value, rendering the wire or rod apparently neutral,
although a lower series of molecules are rotated in the opposite
direction to the upper series, giving to the rod opposite and equal
polarities. At C we have the molecules arranged in a circular chain
around the axis of a wire or rod through which an electric current
has passed. At D we have the evident polarity induced by the earth's
directive influence when a soft iron rod is held in the magnetic
meridian. At E we have a longitudinal neutrality produced in the same
rod when placed magnetic west, the polarity in the latter case being
transversal.
In all these cases we have a perfectly symmetrical arrangement, and I
have not yet found a single case in well-annealed soft iron in which I
could detect a heterogeneous arrangement, as supposed by Ampere, De la
Rive, Weber, Wiedermann, and Maxwell.
We can only study neutrality with perfectly soft Swedish iron. Hard
iron and steel retain previous magnetizations, and an apparent external
neutrality would in most cases be the superposition of one magnetism
upon another of equal external force in the opposite direction, as shown
at B, Fig. 1. Perfectly soft iron we can easily free, by vibrations,
from the slightest trace of previous magnetism, and study the neutrality
produced under varying conditions.
[Illustration: FIG. 1.]
If we take a flat bar of soft iron, of 30 or more centimeters in
length, and hold it vertically (giving while thus held a few torsions,
vibrations, or, better still, a few slight blows with a wooden mallet,
in order to allow its molecules to rotate with perfect freedom), we find
its lower end to be of strong north polarity, and its upper end south.
On reversing the rod and repeating the vibrations, we find that its
lower end has precisely a similar north polarity. Thus the iron is
homogeneous, and its polarity symmetrical. If we now magnetize this rod
to produce a strong south pole at its lower portion, we can gradually
reverse this polarity, by the influence of earth's magnetism, by
slightly tapping the upper extremity with a small wooden mallet. If
we observe this rod by means of a direction needle at all parts, and
successively during its gradual passage from one polarity to the other,
there will be no sudden break into a haphazard arrangement, but a
gradual and perfectly symmetrical rotation from one direction to that of
the opposite polarity.
If this rod is placed east and west, having first, say, a north polarity
to the right, we can gradually discharge or rotate the molecules to
zero, and as gradually reverse the polarity by simply inclining the rod
so as to be slightly influenced by earth's magnetism; and at no portion
of this passage from one polarity to neutrality, and to that of the
opposite name, will there be found a break of continuity of rotation or
haphazard arrangement. If we rotate this rod slowly, horizontally or
vertically, taking observations at each few degrees of rotation of an
entire revolution, we find still the same gradual symmetrical change
of polarity, and that its symmetry is as complete at neutrality as in
evident polarity.
In all these cases there is no complete neutrality, the longitudinal
polarity simply becoming transversal when the rod is east and west.
F, G, H, I, J, Fig. 1, show this gradual change, H being neutral
longitudinally, but polarized transversely. If, in place of the rod,
we take a small square soft iron plate and allow its molecules freedom
under the sole influence of the earth's magnetism, then we invariably
find the polarity in the direction of the magnetic dip, no matter in
what position it be held, and a sphere of soft iron could only be
polarized in a similar direction Thus we can never obtain complete
external neutrality while the molecules have freedom and do not form an
internal closed circle of mutual attractions; and whatever theory we may
adopt as to the cause of polarity in the molecule, such as Coulomb's,
Poisson's, Ampere's, or Weber's, there can exist no haphazard
arrangement in perfectly soft iron, as long as it is free from all
external causes except the influence of the earth; consequently these
theories are wrong in one of their most essential parts.
We can, however, produce a closed circle of mutual attraction in iron
and steel, producing complete neutrality as long as the structure is not
destroyed by some stronger external directing influence.
Oersted discovered that an external magnetic needle places itself
perpendicular to an electric current; and we should expect that, if the
molecules of an iron wire possessed inherent polarity and could rotate,
a similar effect would take place in the interior of the wire to that
observed by Oersted. Wiedermann first remarked this effect, and it has
been known as circular magnetism. This circle, however, consists really
in each molecule having placed itself perpendicular to the current,
simply obeying Oersted's law, and thus forming a complete circle in
which the mutual attractions of the molecules forming that circle are
satisfied, as shown as C, Fig. 1. This wire becomes completely neutral,
any previous symmetrical arrangement of polarity rotating to form its
complete circle of attractions; and we can thus form in hard iron and
steel a neutrality extremely difficult to break up or destroy. We have
evident proof that this neutrality consists of a closed chain, or
circle, as by torsion we can partially deflect them on either side; thus
from a perfect externally neutral wire, producing either polarity, by
simple mechanical angular displacement of the molecules, as by right or
left handed torsion.
If we magnetize a wire placed east and west, it will retain this
polarity until freed by vibrations, as already remarked. If we pass an
electric current through this magnetized wire, we can notice the gradual
rotation of the molecules, and the formation of the circular neutrality.
If we commence with a weak current, gradually increasing its strength,
we can rotate them as slowly as may be desired. There is no sudden break
or haphazard moment of neutrality: the movements to perfect zero are
accomplished with perfect symmetry throughout.
We can produce a more perfect and shorter circle of attractions by the
superposition of magnetism, as at B, Fig. 1. If we magnetize a piece
of steel or iron in a given direction with a strong magnetic directing
power, the magnetism penetrates to a certain depth. If we slightly
diminish the magnetizing power, and magnetize the rod in a contrary
direction, we may reduce it to zero, by the superposition of an exterior
magnetism upon one of a contrary name existing at a greater depth; and
if we continue this operation, gradually diminishing the force at each
reversal, we can easily superpose ten or more distinct symmetrical
arrangements, and, as their mutual attractions are satisfied in a
shorter circle than in that produced by electricity, it is extremely
difficult to destroy this formation when once produced.
The induction balance affords also some reasons for believing that the
molecules not only form a closed circle of attractions, as at B, but
that they can mutually react upon each other, so as to close a circle
of attractions as a double molecule, as shown at A. The experimental
evidence, however, is not sufficient to dwell on this point, as the
neutrality obtained by superposition is somewhat similar in its external
effects.
We can produce a perfectly symmetrical closed circle of attractions of
the nature of the neutrality of C, Fig. 3, by forming a steel wire into
a closed circle, 10 centimeters in diameter, if this wire is well joined
at its extremities by twisting and soldering. We can then magnetize this
ring by slowly revolving it at the extremity of one pole of a strong
permanent magnet; and, to avoid consequent poles at the part last
touching the magnet, we should have a graduating wedge of wood, so that
while revolving it may be gradually removed to greater distance. This
wire will then contain no consequent points or external magnetism: it
will be found perfectly neutral in all parts of its closed circle. Its
neutrality is similar to C, Fig. 3; for if we cut this wire at any point
we find extremely strong magnetic polarity, being magnetized by this
method to saturation, and having retained (which it will indefinitely)
its circle of attractions complete.
I have already shown that soft iron, when its molecules are allowed
perfect freedom by vibration, invariably takes the polarity of the
external directing influence, such as that of the earth, and it does so
even with greater freedom under the influence of heat. Manufacturers of
electro-magnets for telegraphic instruments are very careful to choose
the softest iron and thoroughly anneal it; but very few recognize the
importance as regards the position of the iron while annealing it under
the earth's directing influence. The fact, however, has long since been
observed.
Dr. Hooke, 1684, remarked that steel or iron was magnetized when heated
to redness and placed in the magnetic meridian. I have slightly varied
this experiment by heating to redness three similar steel bars, two
of which had been previously magnetized to saturation, and placed
separately with contrary polarity as regards each other, the third being
neutral. Upon cooling, these three bars were found to have identical and
similar polarity. Thus the molecules of this most rigid material, cast
steel, had become free at red heat, and rotated under the earth's
magnetic influence, giving exactly the same force on each; consequently
the previous magnetization of two of these bars had neither augmented
nor weakened the inherent polarity of their molecules. Soft iron gave
under these conditions by far the greatest force, its inherent polarity
being greater than that of steel.
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