Scientific American Supplement, No. 492, June 6, 1885 by Various

V >> Various >> Scientific American Supplement, No. 492, June 6, 1885

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The sensitiveness to change of battery power is also independent of the
sensitiveness to reversal of direction of the current. Among the best "L
B cells," some are "anode cells" and others are "cathode cells," while
still others are absolutely insensitive to reversal of current or to the
action of light.

_Constancy of the resistance_.--A noticeable point in my cells is the
remarkable constancy of the resistance in sunlight. Allowing for
differences in the temperature, the currents, and the light, at different
times, the resistance of a cell in sunlight will remain practically
constant during months of use and experiments, although during that time
the treatments received may have varied the resistance in dark hundreds
of thousands of ohms--sometimes carrying it up, and at others carrying it
down again, perhaps scores of times, until it is "matured," or reaches
the condition in which its resistance becomes constant.

As has already been stated, the sensitiveness of a cell to light is
increased by proper usage. This increased sensitiveness is shown, not by
a lowered resistance in light, but by an increased resistance in dark.
This change in the cells goes on, more or less rapidly, according as it
is retarded or favored by the treatment it receives, until a maximum is
reached, after which the resistance remains practically constant in both
light and dark, and the cell is then "matured," or finished. The
resistance in dark may now be 50 or even 100 times as high as when the
cell was first made, yet, whenever exposed to sunlight it promptly shows
the same resistance that it did in the beginning. The various treatments,
and even accidents, through which it has passed in the mean time, seem
not to have stirred its molecular arrangement under the action of light,
but to have expended their forces in modifying the positions which the
molecules must normally assume in darkness.

_Practical applications_.--There are many peculiarities of action
occasionally found, and the causes of such actions are not always
discernible. In practice, I have been accustomed to find the
peculiarities and weaknesses of each cell by trial, developing its
strongest properties and avoiding its weaknesses, until, when the cell is
finished, it has a definite and known character, and is fitted for
certain uses and a certain line of treatment, which should not be
departed from, as it will be at the risk of temporarily disabling it. In
consequence of the time and labor expended in making cells, in the small
way, testing, repairing damages done during experiments, etc., the cost
of the cells now is unavoidably rather high. But if made in a commercial
way, all this would be reduced to a system, and the cost would be small.
I may say here that I do not make cells for sale.

The applications or uses for these cells are almost innumerable,
embracing every branch of electrical science, especially telegraphy,
telephony, and electric lighting, but I refrain from naming them. I may
be permitted, however, to lay before you two applications, because they
are of such general scientific interest. The first is my

_Photometer_.--The light to be measured is caused to shine upon a
photo-electric current-generating cell, and the current thus produced
flows through a galvano-metric coil in circuit, whose index indicates
upon its scale the intensity of the light. The scale may be calibrated by
means of standard candles, and the deflections of the index will then
give absolute readings showing the candle power of the light being
tested. Or, the current produced by that light and that produced by the
standard candle may be compared, according to any of the known ways of
arranging and comparing different lights--the cell being lastly exposed
alternately to the two lights, to see if the index gives exactly the same
deflection with each light.

This arrangement leaves untouched the old difficulty in photometry, that
arising from the different _colors_ of different lights. I propose to
obviate that difficulty in the following manner. As is well known, gold
transmits the green rays, silver the blue rays, and so on; therefore, a
cell faced with gold will be acted upon by the green rays, one faced with
silver by the blue rays, etc. Now, if we construct three cells (or any
other number), so faced that the three, collectively, will be acted upon
by all the colors, and arrange them around the light to be tested, at
equal distances therefrom, each cell will produce a current corresponding
to the colored rays suited to it, and all together will produce a current
corresponding to all the rays emitted by the light, no matter what the
proportions of the different colors may be. The three currents may act
upon the same index, but each should have its own coil, not only for the
sake of being able to join or to isolate their influences upon the index,
but also to avoid the resistances of the other cells. If a solid
transparent conductor of electricity could be found which could be thick
enough for practical use and yet would transmit all the rays perfectly,
i.e., transmit white light unchanged, that would be still better. I have
not yet found a satisfactory conductor of that kind, but I think the plan
stated will answer the same purpose. This portion of my system I have not
practically tested, but it appears to me to give good promise of removing
the color stumbling-block, which has so long defied all efforts to remove
it, and I therefore offer it for your consideration.

_Photo-electric regulator_.--My regulator consists of a
current-generating cell arranged in front of a light, say an electric
lamp, whose light represents the varying strength of the current which
supports it. The current produced in the cell by this light flows through
an electro-magnetic apparatus by means of which mechanical movement is
produced, and this motion is utilized for changing resistances, actuating
a valve, rotating brushes, moving switches, levers, or other devices.
This has been constructed on a small scale, and operates well, and I
think it is destined to be largely used, as a most sensitive, simple, and
perfect regulator for currents, lights, dynamos, motors, etc., etc.,
whether large or small.

In conclusion, I would say that the investigation of the physical
properties of selenium still offers a rare opportunity for making very
important discoveries. But candor compels me to add that whoever
undertakes the work will find it neither an easy nor a short one. My own
experience would enable me to describe to you scores of curious
experiments and still more curious and suggestive results, but lack of
time prevents my giving more than this very incomplete outline of my
discoveries.

* * * * *

ELECTRICITY APPLIED TO THE MANUFACTURE OF VARNISH.

Messrs. Muethel & Luetche, of Berlin, recommend the following process for
the manufacture of varnish: The oils are treated by gases or gaseous
mixtures that have previously been submitted to the action of electric
discharges. The strongly oxidized oxygenated compounds that are formed
under such circumstances give rise, at a proper elevation of temperature,
to compounds less rich in oxygen, and the oxygen that is set free acts
upon the fatty acid that it is proposed to treat. A mixture of equal
parts of chlorine and steam may be very advantageously employed, as well
as anhydrous sulphuric acid and water, or oxygen, anhydrous sulphuric
acid and protoxide of nitrogen, nitrogen, oxygen, and hydrogen, protoxide
of nitrogen and air, or oxygen, and so on.

The apparatus is shown in section in the accompanying engraving; a is a
steam-pipe running from the boiler to the motor. From this pipe branch
conduits, b, that enter the vessels, B, in which the treatment is
effected, and that run spirally through the oil. At the lower part of the
vessel, B, there is tube wound into a flat spiral, and containing a large
number of exceedingly small apertures.

The oxidizing apparatus is shown at p. The gaseous mixture enters through
the tube, n, traverses the apparatus, p, and enters the vessel, B,
through the tubes, g and D. Fig. 2 gives the details of the oxidizing
apparatus, which consists of two concentric glass tubes, A and F,
soldered at x. A is closed beneath and held in a cylinder, C; F contains
a small aperture through which passes a tube, E. The gaseous mixture
enters through the latter, traverses the annular space between the tubes,
A and F, and then makes its exit through H, whence it goes to a similar
apparatus placed alongside of the other. The shaded parts of the
engraving represent bodies that are good conductors of electricity and
that communicate with the two poles of any electrice source whatever.

[Illustration: FIGS. 1 AND 2.]

The operation is as follows: After opening the tube, e, linseed oil is
introduced into the vessel, B, until the latter is half full, and, after
this, e is closed and the worm, S, is allowed to raise the temperature to
between 60 deg. and 80 deg.. Then the cock of the tube, d, which communicates
with an air pump, is opened, and the pressure is diminished to about 730
mm. of mercury. At this moment the oxidizing apparatus are put in
communication with an induction bobbin that is interposed in the circuit
of a dynamo, while through the tube, n, there is made to enter a mixture
of equal parts (in volume) of sulphurous acid, oxygen, and air. At the
same time, the cock of the tube, g, is opened, while the stirrer, T, is
set in motion. In this way we obtain, in a much shorter time than by
ordinary processes, a very liquid, transparent varnish, which, when
exposed to the air, quickly hardens. It is possible, with the same
process, to employ a mixture (in volumes) of two parts of protoxide of
nitrogen with one and a half parts of atmospheric air, or even protoxide
of nitrogen alone.

When it is judged that the operation is finished, the tube, g, is opened,
the stirrer is stopped, and the tube, c, is opened after d has been
closed. The steam then forces the varnish to pass through the tube, f,
and traverse the washing apparatus, which is filled half full of water,
that is slightly ammoniacal, and is heated by a circulation of steam, S.
Finally, the product, washed and free from every trace of acid is
collected upon making its exit from the tube, h.--_La Lumiere
Electrique._

* * * * *

NAGLO BROTHERS' TELEPHONE SYSTEM.

We borrow from the _Elektrotechnische Zeitung_ the following details in
regard to the telephonic installations made by the Brothers Naglo at
Berlin. Fig. 1 gives the general arrangement of a station, where J is an
inductor set in motion through a winch, K, and a pair of friction
rollers; W, a polarized call; U, an ordinary two-direction commutator; B,
a lightning protector; and L and T, the two terminals of the apparatus,
one of them connecting with the line and the other with the earth. The
interesting point of this system is the automatic communication which
occurs when the inductor, J, is moved. At the same moment that the winch,
K, is being moved, the disk, P, is carried from right to left and brought
into contact with the spring, f_{2}. As soon as the winch is left to
itself a counter-spring forces the disk, P, to return to a contact with
the spring, f_{1}. Figs. 2 and 3 show the details of such communication.
The winch, K, is keyed to one of the extremities of a sleeve that carries
the disk, P, at its other extremity. This sleeve is fixed upon the axle
of the first friction roller, that is to say, upon the axle that controls
the motion of the inductor, and is provided at the center with two
helicoidal grooves, e, at right angles with one another. In these grooves
slides a tappet, n, connected with the axle.

[Illustration: FIG. 1.]

Under the influence of the counter-spring at the left of the disk, P, the
latter constantly tends to occupy the position shown in Fig. 2, which is
that of rest. As soon as the winch, K, is revolved, whatever be the
direction of the motion, the axle can only be carried along when the
tappet, n, has come to occupy the position shown in Fig. 3, that is to
say, when the disk has moved from right to left a distance corresponding
to the fraction of the helix formed in the sleeve.

This stated, it is easy to understand the travel of the currents. Fig. 1
shows the station at rest. The current that arrives through L passes
through the lightning protector, the body of the commutator, U, the
terminal, v, and the call, W, bifurcates at P, and is closed by the
earth. The inductor is in circuit, but, as it is in derivation, upon a
very feeble resistance, v, nearly the whole of the current passes through
the latter. When it is the station that is calling, the call, W, is put
in derivation upon the circuit, f_{2} p, h, so that the portion of the
circuit that passes through q W v is exceedingly feeble, and incapable of
operating the bell of the post that is calling.

[Illustration: FIGS. 2 AND 3.]

Finally, when the telephone is unhooked, the inductor, J, and the bell,
W, are thrown out of circuit, and the telephone is interposed between d
and i, that is, between L and T.--_La Lumiere Electrique_.

* * * * *

THE GERARD ELECTRIC LAMP.

In the Gerard incandescent lamp the carbons have the form of a V. They
are obtained by agglomerating very finely powdered carbon, and passing it
through a draw plate. At their extremity they are cemented together with
a small quantity of carbon paste, and their connection with the platinum
conducting wires is effected by means of a cylinder of the same paste
surmounted by a cone. These couplings secure a good contact, and, by
their dimensions, prevent the attachments from becoming hot and
consequently injuring the carbon at this point. The cone forms a
connection of decreasing section, and prevents the carbon from getting
broken during carriage.

This process of manufacture permits of obtaining lamps of all
intensities, from 3 candles up. The following, according to Mr. Gerard,
are the consumptions of energy in each size of lamp:

Candles. Volts. Amperes.
No. 0. 10 16 1.5
" 1. 25 25 2
" 2. 50 30 2.5

[Illustration: GERARD'S INCANDESCENT LAMP.]

It will be seen that these lamps require a relatively intense current
with much less fall of potential than the Swan, for example--this being
due to the diameter of the filament. But, what is an inconvenience as
regards mounting, if we wish to supply them by ordinary machines (for
they must be mounted in series of 3 on each derived circuit if the
machine gives, as most frequently the case, 100 volts), is an advantage
as regards the quality and steadiness of the light and the duration of
the lamps.

The part in which the energy is expended is homogeneous, as might be
supposed from the mode of manufacture, and as may be ascertained from a
microscopical examination, and it is exempt from those variations in
composition that are found in carbons of a vegetable nature, like the
Edison. Besides, being of relatively large diameter, the lamp is capable
of supporting a very great increase of temperature.

The process employed for fixing the lamps is as simple as can be. Each
platinum wire is soldered to a piece of copper that surrounds the base of
the lamp and that is fixed to the glass with a special cement. These two
armatures intertwine, but at a sufficient distance apart to prevent
contact. They carry a longitudinal projection and an inflation that fit
by hard friction into two copper springs connected electrically with the
circuit. It is only necessary to lift the lamp in order to remove it from
the support; and the contrary operation is just as easy.--_Le Genie
Civil_.

* * * * *

A NEW REFLECTING GALVANOMETER.

Fig. 1 shows an elevation of the instrument and a horizontal section of
the bobbins. Two pairs of bobbins, cc, cc, are so arranged that the axes
of each pair are parallel and in the same vertical plane. Each pair is
supported by a vertical brass plate, and the two plates make an angle of
about 106 deg. with each other, so that the planes containing the axes of the
bobbins make an angle of about 74 deg.. Two horseshoe magnets, m m, made of
1/25 inch steel wire, are connected by a very light piece of aluminum and
placed at such a distance from each other that, on being suspended, the
two branches of each of the magnets shall freely enter the respective
bores of the two bobbins fixed upon the same plate, and, when the whole
system is in equilibrium and the bobbins free from current, the two
branches of each of the magnets shall nearly coincide with the axes of
such bores. The magnets are not plane, but are curved so as to form
portions of a vertical cylinder whose axis coincides with the direction
of the suspension wire, and to which the axes of the bobbins are tangent
at their center, approximately to the points where the poles of the
magnets are situated.

[Illustration: FIG. 1. GRAY'S GALVANOMETER.]

The needles have been given this form so that their extremities shall not
touch the sides of the bore during considerable deflections.

In the instrument which the inventors, Messrs. T. & A. Gray, used in
their experiments upon the resistance of glass, the needles were arranged
so that their poles of contrary name were opposite.

[Illustration: FIG. 2.]

The system of needles is suspended from the extremity of a screw, p,
which passes into a nut, n, movable between two stationary pieces. On
revolving the nut, we cause the screw to rise or lower, along with the
entire suspended part, without twisting the thread.

The four bobbins are grouped for tension, and have a total resistance of
30,220 ohms. They contain 16,000 feet of No. 50 copper wire, forming
62,939 revolutions, nearly equally divided between the four bobbins. When
a current is passing through the bobbins, the poles of one of the
horseshoe magnets are attracted toward the interior of the corresponding
bobbins, while those of the other are repelled toward the exterior by the
two other bobbins. We thus have a couple which tends to cause the system
to revolve around the suspension axis. A mirror, which is fixed upon a
vertical piece of aluminum, a, gives, in the usual manner, a reflected
image upon a scale, thus allowing the deflections to be read. A
compensating magnet, M, is supported by a vertical column fixed to the
case, above the needles. This magnet may be placed in the different
azimuths by means of a tangential screw, t. The extremities of the bobbin
wires are connected with three terminals, T, T', T squared, and the
instrument may, by a proper arrangement, became differential. These
terminals, as well as the communicating wires, are insulated with
ebonite.

Thus arranged, the instrument is capable of making a deflection of one
division of 1/50 inch upon a scale placed at a distance of a little more
than a yard, with the current produced by one daniell of 10 ohms. This is
a degree of sensitiveness that cannot be obtained with any of the astatic
instruments known up to the present. By regulating the needles properly,
a greater degree of sensitiveness may be attained, but then the duration
of the needles' oscillation becomes too great. The sensitiveness of the
instrument is sufficiently great to allow it to be used in many cases,
even with a moderate duration of oscillation.

In their experiments upon the resistance of glass, the inventors employed
an instrument that was not arranged for giving great sensitiveness, and
one with which resistances of from 10^{4} to 10^{5} megohms could be
measured by the use of a pile of 120 daniells.

The instrument can be given another form. The four bobbins may be
arranged symmetrically in the same plane, and the two horseshoe magnets
be supported by an S-shaped aluminum bar. The latter traverses the plate
that supports the bobbins, in such a way that one of the magnets enters
one of the bobbins that correspond to it on one side of the plate, and
the other on the other side, as shown in Fig. 2. The bobbins are so
connected that, when they are traversed by a current, both magnets are at
the same time attracted toward the interior or repelled toward the
exterior of the bobbins. Such a form of the instrument has the advantage
of being more easily constructed, while the regulation of the magnets
with respect to the bore of the bobbins is easier.

The chief advantage of the instrument results from the fact that, owing
to the arrangement of the magnets and bobbins, a large portion of the
wires of the latter is situated very near the poles of the magnets, and
in a position very favorable for electro-magnetic action. The instrument
presents no difficulties as regards construction, and costs no more than
an ordinary one.

We might even arrange a single horseshoe magnet, or an S-shaped one,
horizontally, and employ but a single pair of bobbins, and thus have a
non-astatic apparatus based upon the same principle. But in astatic
instruments it is better to place the magnets in such a way that the two
branches shall be in the same vertical plane.

Were the line that joins the two poles vertical, the system would be
perfectly astatic in a uniform field, since each magnet in particular
would then be perfectly astatic. A pair of horseshoe magnets may thus be
regulated in such a way as to form a perfectly astatic system in a
uniform field and to preserve an almost invariable zero, this being
something that it is very difficult to obtain with the ordinary
arrangement of needles, especially when a compensating magnet is used;
for, in such a case, one of the needles becomes more or less magnetized,
while the other becomes demagnetized, according to the position of the
compensating magnet.--_La Lumiere Electrique_.

* * * * *

HISTOLOGICAL METHODS.

A cat, dog, rabbit, or Guinea pig will furnish parts from which sections
can be cut for the study of histology. Whichever animal is selected
should be young and well developed. Put it under influence of chloroform,
and open into the cavity of the chest; make an incision into the right
ventricle, and allow the animal to bleed to death; cut the trachea and
inject the lungs with a solution of one and a half drachms of chromic
acid in one quart of water, care being taken not to overdistend the lung.
Tie the severed end to prevent the escape of the fluid, and carefully
remove the lung. It is a difficult thing to do this without rupturing it,
but with care and patience it can be done. Place the lungs in a solution
of the same strength as used for injecting; after fifteen or twenty hours
change it to a fresh solution, and allow it to remain for about a month,
and then change it to rectified spirits, in which it may remain until
required.

Cut the tongue into several transverse and longitudinal pieces, also the
small intestines, and put them into a solution of fifteen and one-half
grains chromic acid, thirty grammes bichromate of potash, and three pints
of water; change the solution the next day, and let them remain two weeks
and then place in spirits. Cut longitudinal and transverse portions of
the stomach and large intestines, wash in a weak solution of salt and
water, and put them in the same solution as used for the lungs, and treat
similarly.

Cut the kidneys longitudinally and transversely, and put them in a
solution of six and one-half drachms bichromate of potash, two and
one-half drachms sodium sulphate, one quart of water; change the solution
the next day, and at the end of four weeks transfer to alcohol. Wash the
inner surface of the bladder with salt and water, and after cutting it
longitudinally and transversely, put the sections in a solution of three
drachms bichromate of potash in a quart of water. Cut the liver into
small parts, and place in the same solution as used for the kidneys;
change the solution after a day, and let them remain four or five weeks,
then change to spirits. The spleen and portions of the thin abdominal
muscles may be placed in a solution of three drachms chromic acid to one
quart of water, and transferred to alcohol after three or four weeks.
Carefully remove an eye and divide it behind the crystalline lens, put
the posterior portion in a solution made by dissolving fifteen grs.
chromic acid in five drachms water, and slowly adding five and one-half
ounces alcohol; change to spirits in two weeks. The lens should be put in
the same solution, but should remain a few days longer. Open the head,
remove the brain, and place transverse and longitudinal sections of it
in spirits for eighteen hours, then transfer to a solution of one drachm
chromic acid in a quart of water, and let it remain until hard enough to
cut. Place the uterus in a solution of one and one-half drachms chromic
acid in one quart of water, change to a new solution the next day, and at
the end of a month transfer to alcohol.

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