-------
34. RIESS’S EXPERIMENT. ELECTRIC IMAGES. _Riess’s Reibungs._ vol. 2, §
739.—He laid a coin upon a plate of glass and charged the same
electrically about one-half of an hour or more. Upon removing the coin
and sprinkling the plate with dust, an engraving of the coin was visible
upon the glass. § 13. A suitable dust is licopodium powder.
35. SANFORD AND MCKAY’S EXPERIMENT. ELECTROGRAPHS. ORIGINAL CONTRIBUTION
BY PROF. MCKAY OF PACKER INST., Brooklyn, May, ’96.—The picture of the
coins in Fig. IX, was produced by the apparatus shown in Fig. VIII, _t_,
_t_, tinfoil, _p_, photographic plate with coins on sensitive side, all
wrapped in black paper. Fig. VIII represents the general arrangement for
taking electrographs. This particular one was made by removing the upper
tinfoil and touching each coin successively with wire from one of the
poles, while the other wire was connected with tinfoil on the opposite
side. The condenser thus formed is charged and discharged many times by
a Holtz machine or induction coil. This is not a new discovery, it was
first described by Prof. Sanford, I think, of Leland Stanford
University, two or three years ago. Other claimants of earlier date
probably exist.
36. LICHTENBERG’S EXPERIMENT. DUST FIGURES. PICTURES DRAWN WITH ANODE
AND CATHODE. _Göttingen_, 1778-79. MOTUM FLUIDI ELECTRICITI.—He drew two
independent superposed pictures upon a flat surface of an insulating
material, for example, rosin. One picture was drawn with one terminal of
a charged Leyden jar. Another picture was drawn with the other terminal
of a charged Leyden jar. He sprinkled upon the surface over the two
pictures, a dust made of a mixture of red lead and sulphur powder. The
former became attracted to the picture drawn with the cathode, and the
latter to that made with the anode, so that the two figures were clearly
visible. Before sprinkling the powders upon the surface it is necessary
to stir them together whereby they become oppositely electrified.
[Illustration:
VIII
ARRANGEMENTS FOR TAKING ELECTROGRAPHS. § 35, p. 19.
]
[Illustration:
FROM ELECTROGRAPHS OF COINS. § 35, p. 19.
Taken by Prof. McKay.
]
[Illustration:
X
]
The sulphur arranges itself in tufts with diverging branches and the red
lead in small circular patches. The particular materials, namely, the
sulphur and red lead were first used by Villarsy. In case only one
powder is employed, for example, licopodium, it adheres to both the
positively and negatively electrified portion of the insulating plate,
but in larger quantities upon the latter portions. Fig. X, shows rosin
disc covered with licopodium powder after touching the disc with the
knob of a Leyden jar.
36_a_. HAMMER’S PHOTO-ELECTRIC DUST FIGURES. _From personal
interview._—According to experiments of Elster and Geitel, hereinafter
noted, § 98, Hammer’s dust figures shown in the accompanying half-tone
cut may possibly be accounted for on the principle of the discharge of
negatively electrified bodies by light. Mr. William J. Hammer, _Mem.
Amer. Inst. Elect. Eng._, has a historical collection of incandescent
lamps (_Elect. Eng._, N.Y., April 29, ’96, p. 446.) which were arranged
on shelves in a glass case standing obliquely in the sunlight about an
hour a day. After the lapse of many months, the very fine dust within
the case lodged upon the inner surface of the glass in such a manner as
to produce oval dust figures corresponding somewhat to the shapes of the
lamps and some of them, appear after reproduction by the half-tone
process in the accompanying cut. When the figures are inspected closely
and the circumstances are known, no one can doubt that the sun and lamps
acted as agents in their formation. As to the correct explanation, the
matter has not been sufficiently discussed by scientists (presented here
for the first time) to enable the author to render the opinions of
others, but it is of interest in connection with Roentgen rays and the
discharge of electrified bodies by light. As a matter of course, the
surfaces of the lamps would reflect the light in such a way as to make
bright spots (movable, however, with the sun) upon the glass of the
containing case, and if the latter were in any sense charged by negative
atmospheric electricity, this light would cause a variable amount of
dust to be attracted according to the intensity of the rays striking the
glass. These remarks are in the nature merely of a suggestion of a
hypothesis. The heavy curved black line in the cut is a part of the
frame of the glass case. The incandescent lamps do not show, simply
because the case was empty when the photograph was taken. That the
figures were not due to chemical action was shown by rubbing off some of
the dust with the fingers. Finger marks were pictured on the figures.
Off hand, Mr. Hammer and Prof. Anthony intimate air convection by
differentiation of temperature, as a possible cause.
[Illustration:
FIG. 1.—HAMMER’S DUST-FIGURE ON GLASS. § 36., p. 21.
]
[Illustration:
FIG. 2.—HAMMER’S HISTORICAL COLLECTION OF INCANDESCENT LAMPS,
CONTAINED IN CASE HAVING THE DUST FIGURES. § 36, p. 21.
]
36_b_. Independently of the above peculiar phenomenon, Mr. Hammer
recently had on exhibition at the Electrical Exposition of the National
Electric Light Association in New York, 1896, a portrait formed of fine
dust upon a pane of glass. The circumstances were as follows, as
remembered by the author. Mr. Hammer happened to be in some place where
an artisan was removing a photograph from an old frame. The glass which
protected the portrait exhibited a fac-simile in dust on the inner
surface. The glass had not been in contact with the photograph, because
of a thick passe-partout surrounding the picture. Neither was the glass
an old negative photographic plate. Further test and inspection tended
to prove that the dust picture was executed by some action of the heat
or light of the sun. Prof. Benjamin F. Thomas, of the University of the
State of Ohio, in an interview, scarcely thought that the result was due
to convection, because the dust print was so sharply defined. The
principle of the discharge of bodies by light may be applicable perhaps,
but further experiment would be necessary as a more secure foundation.
It is common to find the print of a picture in a book upon the opposite
page, being due merely to the pressure of the inked surface, as in the
art of printing. This explanation cannot be applied to the dust
portrait, because there was no contact between the photograph and the
glass.
37. KARSTEN’S EXPERIMENT. ELECTRICAL IMAGES DEVELOPED BY CONDENSED
MOISTURE. _Riess’s Reibungselect._, vol. II., § 739.—He arranged the
following articles in the following order: First, a metal plate suitably
insulated; secondly, a piece of a glass plate on top of the metal plate,
and, thirdly, a coin or small metal object on top of the glass. Sparks
were then allowed to pass for several minutes from a Holtz or similar
machine to the coin. The image of the latter appeared by removing the
glass plate and breathing upon it. The bas-relief of the image on the
coin also was visible in all its details, appearing as in Sanford’s
Electrograph, § 35. Theoretical considerations led others to believe
that the figures of Riess and Karsten are due to a different cause from
that involved in the figures of Lichtenberg, for the former are thought
to be due to a molecular action of a permanent nature upon an insulating
material. A slight change in the color often occurs, thereby outlining
the object.
[Illustration:
DUST-PORTRAIT ON GLASS, § 36., p. 23, DISCOVERED BY WILLIAM J. HAMMER.
Lighter portions, dust; darker portions, due to less or no dust.
Finger-marks across the shoulder and at right. Exposure 8 years.
Portrait as sharp and clear as a daguerreotype. During exposure in
frame, distance of glass from photograph, 1/16 inch. Above half tone
was made _from a photograph of the dust-portrait_ only after several
unsuccessful attempts by different photographers. The original
dust-portrait is scarcely visible. Let every one examine closely
glass plates when taken from old frames.
]
37_a_. MCKAY’S EXPERIMENT. MAGNETOGRAPHS. FROM PERSONAL NOTES BY
REQUEST. April, 1896.—Although this experiment does not belong to that
class connected with discharge tubes, yet the phenomenon has a
theoretical interest in connection with X-rays. He obtained a photograph
of different objects in the dark by means of radiations from the poles
of an electro-magnet after two hours’ exposure, but it need not have
been so long, as he obtained clear images in five minutes in one
experiment with frequent variations of current by means of a rheostat,
and by approach and recession of the armature. The elements involved in
the experiment were arranged in the following order: First, a large
inverted magnet for supporting 100 lbs., the poles hanging downward.
Next in order was a wooden board pressing flatwise against the ends of
the poles of the magnet. Next, the objects and the sensitive plates
backed thereby and all enclosed in a completely opaque wrapping
extending over the sides, face, back, etc., of these two elements. Next
in order was an armature about as heavy as the magnet would support. The
cut herein represents the photograph that was produced of the different
objects named. By reading Prof. McKay’s very detailed description in the
_Scientific American_, April 18, 1896, p. 249, the reader may feel
certain that the photograph was not due to light for he tried the
experiments in different ways and with various precautions. In a course
of experiments carried on by student Austin, about Feb. 15, ’96, in the
Dartmouth laboratory, a sciagraph of what appeared to be the lines of
force was obtained by means of X-rays, but upon repeating the experiment
the result was negative. See _Elect. Engineer_, Mar. 11, ’96, p. 257.
Article by E. B. Frost.
[Illustration:
XI
]
38. PILTCHIKOFF’S EXPERIMENT. LIQUID BAS-RELIEF FACSIMILES BY ELECTRIC
DISCHARGE. _Pro. Acad. Sci._, Paris, March, ’94. _The Electr._, Lon.,
April 13, ’94, p. 656.—These shadow pictures were obtainable either with
the anode or cathode, the particular machine employed being a large
Voss. To either pole was electrically connected a pointed wire which was
held just above the surface of castor oil, in a copper pan. A remarkable
effect was obtained of the shadow of a piece of mica, Fig. XI, of
whatever shape, located between the point and the surface. § 24. Let it
be observed that this shadow was not one in the sense of light and
darkness but it consisted of a plateau within a depression, the former
being of the same shape as though it were a shadow of the mica triangle.
To illustrate the experiment better, let the mica be supposed to be
removed, then will there be a depression formed in the oil upon bringing
the metallic point near to the surface. Now insert the insulating sheet
between the point and the surface, then will there be an elevation
within the depression of the same shape that the shadow would be.
39. GERNEZ’S EXPERIMENT. DISTILLATION OF LIQUIDS BY DISCHARGE. _Phys.
So._, Paris, 1879. _Nature_, Nov. 20, 1879, p. 72.—In order that the
apparatus with which he experimented may be understood, imagine a tube
standing vertically in another tube. The two concentric tubes
communicate with each other at the top only. The Holtz machine is the
generator. The liquids in the two tubes at the beginning stand at the
same level. Sparks are passed through the adjacent air, which is in
contact with both liquids. The liquid at the cathode rises and at the
anode falls. § 38. Such was the experiment performed by Gernez. He was
inclined to conclude that the effect was due to “An electrical transport
of liquids along the moistened surfaces of the tubes.” When the liquid
was alcohol, it actually went over as by distillation, three times as
fast as water. A soluble salt in water increased the rate of
distillation; and so also did the addition of a small quantity of
sulphuric acid or ammonia. No distillation of bi-sulphide of carbon,
tetra chloride of carbon, nor turpentine occurred. Query: Can alcohol be
concentrated or practically distilled upon this principle?
40. DE LA RUE AND MÜLLER’S EXPERIMENT. STRIAE. BLACK PRINTS ON WALLS OF
TUBE. _Phil. Trans._, 59, ’78.—Particles of the metal of the electrodes
were deposited upon the inside of the glass forming permanent black
striae or bands § 44, at points corresponding to the spaces between the
luminous striae. § 6. near the end.
------------------------------------------------------------------------