in this manner is about one two-millionth of a second. This is the
time of propagation of a magnetic wave over four hundred feet long.
The waves used in wireless telegraphy are not more than four feet in
length--about one hundredth the length of those we can photograph.
The photographic method thus reveals a mechanism of the spark which
is entirely hidden from the eye and will always be concealed from
human sight. It reveals, however, a greater mystery which it seems
incompetent to solve--the mystery of what is called the pilot spark,
the first discharge which we see on our photograph (Fig. 9) stretching
intact from terminal to terminal, having the prodigious velocity of one
hundred and eighty thousand miles a second. None of our experimental
devices suffice to penetrate the mystery of this discharge. It is this
pilot spark which is chiefly instrumental in sending out the magnetic
pulses or waves which are powerful enough to reach forty or fifty
miles. The preponderating influence of this pilot spark--so called
since it finds a way for the subsequent surgings or oscillations--is
a bar to the efforts to make wireless telegraphy secret. We can see
from the photograph how much greater its strength is than that of the
subsequent discharges shown by the mere brightening of the terminals.
A delicate coherer will immediately respond to the influence of this
pilot spark, and the subsequent oscillations of this discharge will
have little effect. How, then, can we effectively time a receiving
circuit so that it will respond to only one sending station? We can not
depend upon the oscillatory nature of the spark, or adopt, in other
words, its rate of vibration and form a coherer with the same rate.
It seems as if it would be necessary to invent some method of sending
pilot sparks at a high and definite rate of vibration, and of employing
coherers which will only respond to definite powerful rates of magnetic
pulsation. Various attempts have been made to produce by mechanical
means powerful electric surgings, but they have been unsuccessful. Both
high electro-motive force and strength of current are needed. These can
be obtained by the employment of a great number of storage cells. The
discharge from a large number of these cells, however, is not suitable
for the purpose of wireless telegraphy, although it may possess the
qualifications of both high electrical pressure and strength of current.
The only apparatus we have at command to produce quick blows on the
ether is the Ruhmkorf coil. This coil, I have said, has been in all our
physical cabinets for fifty years. It contained within itself the germ
of the telephone transmitter and the method of wireless telegraphy,
unrecognized until the present. In its elements it consists, as we have
seen, of two electrical circuits, placed near each other, entirely
unconnected. A battery is connected with one of these circuits, and
any change in the strength of the electrical current gives a blow to
the ether or medium between the two circuits. A quick stopping of the
electrical current gives the strongest impulse to the ether, which
is taken up by the neighboring circuit. For the past fifty years
very little advance has been made in the method of giving strong
electrical impulses to the medium of space. It is accomplished simply
by a mechanical breaking of the connection to the battery, either by
a revolving wheel with suitable projections, or by a vibrating point.
All the various forms of mechanical breaks are inefficient. They do not
give quick and uniform breaks. Latterly, hopes have been excited by the
discovery of a chemical break, called the Weynelt interrupter, shown in
Fig. 1. The electrical current in passing through a vessel of diluted
sulphuric acid from a point of platinum to a disk of lead causes
bubbles of gas which form a barrier to its passage which is suddenly
broken down, and this action goes on at a high rate of speed, causing
a torrent of sparks in the neighboring circuit. The medium between
the two circuits is thereby submitted to rapid and comparatively
powerful impulses. The discovery of this and similar chemical or
molecular interruptions marks an era in the history of the electrical
transformer, and the hopes of further progress by means of them is far
greater than in the direction of mechanical interruptions.
We are still, however, unable to generate sufficiently powerful and
sufficiently well-timed electrical impulses to make wireless telegraphy
of great and extended use. Can we not hope to strengthen the present
feeble impulses in wireless telegraphy by some method of relaying or
repeating? In the analogous subject of telephony many efforts have
also been made to render the service secret, and to extend it to great
distances by means of relays. These efforts have not been successful up
to the present. We still have our neighbors' call bells, and we could
listen to their messages if we were gossips. The telephone service
has been extended to great distances--for instance, from Boston to
Omaha--not by relays, but by strengthening the blows upon the medium
between the transmitting circuit and the receiving one, just as we
desire to do in what is called wireless telegraphy, the apparatus of
which is almost identical in principle to that employed in telephony.
The individual call in telephony is not a success for nearly the same
reasons that exist in the case of wireless telegraphy. Perfectly
definite and powerful rates of vibration can not be sent from point to
point over wires to which only certain definite apparatus will respond.
There are so many ways in which the energy of the electric current can
be dissipated in passing over wires and through calling bells that the
form of the waves and their strength becomes attenuated. The form of
the electrical waves is better preserved in free space, where there
are no wires or where there is no magnetic matter. The difficulty
in obtaining individual calls in wireless telegraphy resides in the
present impossibility of obtaining sufficiently rapid and powerful
electrical impulses, and a receiver which will properly respond to a
definite number of such impulses.
The question of a relay seems as impossible of solution as it does in
telephony. The character of speech depends upon numberless delicate
inflections and harmonies. The form, for instance, of the wave
transmitting the vowel _a_ must be preserved in order that the sound
may be recognized. A relay in telephony acts very much like one's
neighbor in the game called gossip, in which a sentence repeated more
or less indistinctly, after passing from one person to another, becomes
distorted and meaningless. No telephone relay has been invented which
preserves the form of the first utterance, the vowel _a_ loses its
delicate characteristics, and becomes simply a meaningless noise. It is
maintained by some authorities that such a relay can not be invented,
that it is impossible to preserve the delicate inflections of the
human voice in passing from one circuit to another, even through an
infinitesimal air gap or ether space. It is well, however, to reflect
upon Hosea Bigelow's sapient advice "not to prophesy unless you know."
It was maintained in the early days of the telephone that speech would
lose so many characteristics in the process of transmission over wires
and through magnetic apparatus that it would not be intelligible.
It is certain that at present long-distance transmission of speech
can only be accomplished by using more powerful transmitters, and by
making the line of copper better fitted for the transmission--just as
quick transportation from place to place has not been accomplished by
quitting the earth and by flying through space, but by obtaining more
powerful engines and by improving the roadbeds.
The hopes of obtaining a relay for wireless telegraphy seem as small
as they do in telephony. The present method is practically limited to
distances of fifty or sixty miles--distances not much exceeding those
which can be reached by a search-light in fair weather. Indeed, there
is a close parallelism between the search-light and the spark used in
Marconi's experiments: both send out waves which differ only in length.
The waves of the search-light are about one forty-thousandth of an
inch long, while the magnetic waves of the spark, invisible to the
eye, are three to four feet--more than a million times longer than the
light waves. These very long waves have this advantage over the short
light waves: they are able to penetrate fog, and even sand hills and
masonry. One can send messages into a building from a point outside. A
prisoner could communicate with the outer world, a beleaguered garrison
could send for help, a disabled light-ship could summon assistance, and
possibly one steamer could inform another in a fog of its course.
Wireless telegraphy is the nearest approach to telepathy that has
been vouchsafed to our intelligence, and it serves to stimulate our
imagination and to make us think that things greatly hoped for can be
always reached, although not exactly in the way expected. The nerves
of the whole world are, so to speak, being bound together, so that a
touch in one country is transmitted instantly to a far-distant one. Why
should we not in time speak through the earth to the antipodes? If the
magnetic waves can pass through brick and stone walls and sand hills,
why should we not direct, so to speak, our trumpet to the earth,
instead of letting its utterances skim over the horizon? In regard
to this suggestion, we know certainly one fact from our laboratory
experiences: that these magnetic waves, meeting layers of electrically
conducting matter, like layers of iron ore, would be reflected back,
and would not penetrate. Thus a means may be discovered through the
instrumentality of such waves of exploring the mysteries of the earth
before success is attained in completely penetrating its mass.
EMIGRANT DIAMONDS IN AMERICA.
BY PROF. WILLIAM HERBERT HOBBS.
To discover the origin of the diamond in Nature we must seek it in
its ancestral home, where the rocky matrix gave it birth in the form
characteristic of its species. In prosecuting our search we should very
soon discover that, in common with other gem minerals, the diamond has
been a great wanderer, for it is usually found far from its original
home. The disintegrating forces of the atmosphere, by acting upon the
rocky material in which the stones were imbedded, have loosed them from
their natural setting, to be caught up by the streams, sorted from
their disintegrated matrix, and transported far from the parent rock,
to be at last set down upon some gravelly bed over which the force of
the current is weakened. The mines of Brazil and the Urals, of India,
Borneo, and the "river diggings" of South Africa either have been or
are now in deposits of this character.
The "dry diggings" of the Kimberley district, in South Africa, afford
the unique locality in which the diamond has thus far been found in
its original home, and all our knowledge of the genesis of the mineral
has been derived from study of this locality. The mines are located
in "pans," in which is found the "blue ground" now recognized as the
disintegrated matrix of the diamond. These "pans" are known to be the
"pipes," or "necks," of former volcanoes, now deeply dissected by the
forces of the atmosphere--in fact, worn down if not to their roots, at
least to their stumps. These remnants of the "pipes," through which
the lava reached the surface, are surrounded in part by a black shale
containing a large percentage of carbon, and this is believed to be the
material out of which the diamonds have been formed. What appear to
be modified fragments of the black shale inclosed within the "pipes"
afford evidence that portions of the shale have been broken from the
parent beds by the force of the ascending current of lava--a common
enough accompaniment to volcanic action--and have been profoundly
altered by the high temperature and the extreme hydrostatic pressure
under which the mass must have been held. The most important feature
of this alteration has been the recrystallization of the carbon of the
shale into diamond.
[Illustration: GLACIAL MAP OF THE GREAT LAKES REGION
Driftless Areas. Older Drift. Newer Drift.
Moraines. Glacial Striae. Track of Diamonds.
Diamond Localities E. Eagle O. Oregon K. Kohlsville D. Dowagiac M.
Milford. P. Plum Crk. B. Burlington.
We are indebted to the University of Chicago Press for the above
illustration.]
[Illustration: Copyright, 1899, by George F. Kunz.
FIVE VIEWS OF THE EAGLE DIAMOND (sixteen carats); enlarged about three
diameters. (Owned by Tiffany and Company.)
We are indebted to the courtesy of Mr. G. F. Kunz, of Tiffany and
Company, for the illustrations of the Oregon and Eagle diamonds.]
This apparent explanation of the genesis of the diamond finds strong
support in the experiments of Moissan, who obtained artificial diamond
by dissolving carbon in molten iron and immersing the mass in cold
water until a firm surface crust had formed. The "chilled" mass was
then removed, to allow its still molten core to solidify slowly. This
it does with the development of enormous pressures, because the natural
expansion of the iron on passing into the solid condition is resisted
by the strong shell of "chilled" metal. The isolation of the diamond
was then accomplished by dissolving the iron in acid.
The prevailing form of the South African diamonds is that of a rounded
crystal, with eight large and a number of minute faces--a form called
by crystallographers a _modified octahedron_. Their shapes would be
roughly simulated by the Pyramids of Egypt if they could be seen,
combined with their reflected images, in a placid lake, or, better
to meet the conditions of the country, in a desert mirage. It is a
peculiar property of diamond crystals to have convexly rounded faces,
so that the edges which separate the faces are not straight, but gently
curving. Less frequently in the African mines, but commonly in some
other regions, diamonds are bounded by four, twelve, twenty-four, or
even forty-eight faces. These must not, of course, be confused with the
faces of cut stones, which are the product of the lapidary's art.
Geological conditions remarkably like those observed at the Kimberley
mines have recently been discovered in Kentucky, with the difference
that here the shales contain a much smaller percentage of carbon, which
may be the reason that diamonds have not rewarded the diligent search
that has been made for them.
Though now found in the greatest abundance in South Africa and in
Brazil, diamonds were formerly obtained from India, Borneo, and from
the Ural Mountains of Russia. The great stones of history have, with
hardly an exception, come from India, though in recent years a number
of diamond monsters have been found in South Africa. One of these,
the "Excelsior," weighed nine hundred and seventy carats, which is in
excess even of the supposed weight of the "Great Mogul."
[Illustration: Copyright, 1899, by George F. Kunz.
FOUR VIEWS OF THE OREGON DIAMOND; enlarged about three diameters.
(Owned by Tiffany and Company.)]
Occasionally diamonds have come to light in other regions than those
specified. The Piedmont plateau, at the southeastern base of the
Appalachians, has produced, in the region between southern Virginia and
Georgia, some ten or twelve diamonds, which have varied in weight from
those of two or three carats to the "Dewey" diamond, which when found
weighed over twenty-three carats.
It is, however, in the territory about the Great Lakes that the
greatest interest now centers, for in this region a very interesting
problem of origin is being worked out. No less than seven diamonds,
ranging in size from less than four to more than twenty-one carats, not
to mention a number of smaller stones, have been recently found in the
clays and gravels of this region, where their distribution was such
as to indicate with a degree of approximation the location of their
distant ancestral home.
In order clearly to set forth the nature of this problem and the method
of its solution it will be necessary, first, to plot upon a map of the
lake region the locality at which each of the stones has been found,
and, further, to enter upon the same map the data which geologists
have gleaned regarding the work of the great ice cap of the Glacial
period. During this period, not remote as geological time is reckoned,
an ice mantle covered the entire northeastern portion of our continent,
and on more than one occasion it invaded for considerable distances
the territory of the United States. Such a map as has been described
discloses an important fact which holds the clew for the detection of
the ancestral home of these diamonds. Each year is bringing with it new
evidence, and we may look forward hopefully to a full solution of the
problem.
In 1883 the "Eagle Stone" was brought to Milwaukee and sold for
the nominal sum of one dollar. When it was submitted to competent
examination the public learned that it was a diamond of sixteen carats'
weight, and that it had been discovered seven years earlier in earth
removed from a well-opening. Two events which were calculated to arouse
local interest followed directly upon the discovery of the real nature
of this gem, after which it passed out of the public notice. The woman
who had parted with the gem for so inadequate a compensation brought
suit against the jeweler to whom she had sold it, in order to recover
its value. This curious litigation, which naturally aroused a great
deal of interest, was finally carried to the Supreme Court of the State
of Wisconsin, from which a decision was handed down in favor of the
defendant, on the ground that he, no less than the plaintiff, had been
ignorant of the value of the gem at the time of purchasing it. The
other event was the "boom" of the town of Eagle as a diamond center,
which, after the finding of two other diamonds with unmistakable marks
of African origin upon them, ended as suddenly as it had begun, with
the effect of temporarily discrediting, in the minds of geologists, the
genuineness of the original "find."
Ten years later a white diamond of a little less than four carats'
weight came to light in a collection of pebbles found in Oregon,
Wisconsin, and brought to the writer for examination. The stones had
been found by a farmer's lad while playing in a clay bank near his
home. The investigation of the subject which was thereupon made brought
out the fact that a third diamond, and this the larges of all, had
been discovered at Kohlsville, in the same State, in 1883, and was
still in the possession of the family on whose property it had been
found.
As these stones were found in the deposits of "drift" which were left
by the ice of the Glacial period, it was clear that they had been
brought to their resting places by the ice itself. The map reveals
the additional fact, and one of the greatest significance, that all
these diamonds were found in the so-called "kettle moraine." This
moraine or ridge was the dumping ground of the ice for its burden of
bowlders, gravel, and clay at the time of its later invasion, and hence
indicates the boundaries of the territory over which the ice mass was
then extended. In view of the fact that two of the three stones found
had remained in the hands of the farming population, without coming
to the knowledge of the world, for periods of eleven and seven years
respectively, it seems most probable that others have been found,
though not identified as diamonds, and for this reason are doubtless
still to be found in many cases in association with other local
"curios" on the clock shelves of country farmhouses in the vicinity
of the "kettle moraine." The writer felt warranted in predicting, in
1894, that other diamonds would occasionally be brought to light in the
"kettle moraine," though the great extent of this moraine left little
room for hope that more than one or two would be found at any one point
of it.
[Illustration: THREE VIEWS OF THE SAUKVILLE DIAMOND (six carats);
enlarged about three diameters. (Owned by Bunde and Upmeyer, Milwaukee.)
We are indebted to the courtesy of Bunde and Upmeyer, of Milwaukee, for
the illustrations showing the Burlington and Saukville diamonds.]
In the time that has since elapsed diamonds have been found at the rate
of about one a year, though not, so far as I am aware, in any case
as the result of search. In Wisconsin have been found the Saukville
diamond, a beautiful white stone of six carats' weight, and also the
Burlington stone, having a weight of a little over two carats. The
former had been for more than sixteen years in the possession of the
finder before he learned of its value. In Michigan has been found the
Dowagiac stone, of about eleven carats' weight, and only very recently
a diamond weighing six carats and of exceptionally fine "water" has
come to light at Milford, near Cincinnati. This augmentation of the
number of localities, and the nearness of all to the "kettle moraines,"
leaves little room for doubt that the diamonds were conveyed by the ice
at the time of its later invasion of the country.
Having, then, arrived at a satisfactory conclusion regarding not only
the agent which conveyed the stones, but also respecting the period
during which they were transported, it is pertinent to inquire by what
paths they were brought to their adopted homes, and whether, if these
may be definitely charted, it may not be possible to follow them in a
direction the reverse of that taken by the diamonds themselves until we
arrive at the point from which each diamond started upon its journey.
If we succeed in this we shall learn whether they have a common home,
or whether they were formed in regions more or less widely separated.
From the great rarity of diamonds in Nature it would seem that the
hypothesis of a common home is the more probable, and this view finds
confirmation in the fact that certain marks of "consanguinity" have
been observed upon the stones already found.
[Illustration: FOUR VIEWS OF THE BURLINGTON DIAMOND (a little over two
carats); enlarged about three diameters. (Owned by Bunde and Upmeyer,
Milwaukee.)]
Not only did the ice mantle register its advance in the great ridge
of morainic material which we know as the "kettle moraine," but it
has engraved upon the ledges of rock over which it has ridden, in a
simple language of lines and grooves, the direction of its movement,
after first having planed away the disintegrated portions of the rock
to secure a smooth and lasting surface. As the same ledges have been
overridden more than once, and at intervals widely separated, they
are often found, palimpsestlike, with recent characters superimposed
upon earlier, partly effaced, and nearly illegible ones. Many of
the scattered leaves of this record have, however, been copied by
geologists, and the autobiography of the ice is now read from maps
which give the direction of its flow, and allow the motion of the ice
as a whole, as well as that of each of its parts, to be satisfactorily
studied. Recent studies by Canadian geologists have shown that one of
the highest summits of the ice cap must have been located some distance
west of Hudson Bay, and that another, the one which glaciated the lake
region, was in Labrador, to the east of the same body of water. From
these points the ice moved in spreading fans both northward toward the
Arctic Ocean and southward toward the States, and always approached the
margins at the moraines in a direction at right angles to their extent.
Thus the rock material transported by the ice was spread out in a great
fan, which constantly extended its boundaries as it advanced.