study of the aurora borealis, so frequent in his country, was attached
to the polar expedition made in 1868 by Nordenskjold. He was led to
begin a series of important observations. In 1871 he visited Finnish
Lapland, and, after a series of ingenious researches, constructed an
apparatus that permitted him to artificially reproduce the light of the
aurora, and to present science with a summary of new and incontestable
facts.
Mr. Lemstrom has observed a large number of auroræ, and before touching
upon theoretic questions, we shall give his description of one of
the phenomena that seems to him to be the completest. On the 18th of
October, 1868, the steamer Sophia was nearing the coast of Norway,
after battling with a furious sea for three days in succession.
"To the west of the horizon we remarked two strata of clouds that were
clearly separated by a blue band of the heavens, crossed by a band
striated with a pale yellow. It was the feeble beginning of an aurora,
whose splendor was soon to surpass all the phenomena of the same kind
that we had up till then observed. The edges of the upper stratum of
clouds gradually lighted up, and we soon saw isolated flames issuing
from them that sometimes rose to the zenith. Suddenly, the phenomenon
embraced the entire horizon. Everywhere were flames, everywhere were
jets of brilliant light, yellow below, green in the center, and reddish
violet above. In an instant, all the rays united in a regular and
dazzling crown, situated in the heavens to the south of the zenith.
When the phenomenon reached the maximum of its intensity, it reminded
us of the immense vault of a temple, with a brilliant chandelier in the
center. The apparition lasted but a few minutes, but, on vanishing,
left behind it a luminous zone between the banks of clouds. From the
upper bank there continued to emanate, at short intervals, isolated
rays that rose to the zenith, and there formed the fragments of a
crown. The edges of the banks of clouds remained luminous, although the
rays had disappeared."
[Illustration: Fig. 4.--AURORAL LIGHT AROUND THE SUMMIT OF A MOUNTAIN.]
[Illustration: Fig. 2.--AURORA BOREALIS OBSERVED IN LAPLAND. ]
[Illustration: Fig. 3.--AURORA BOREALIS OBSERVED AT THE PRESBYTERY OF
ENARE. ]
[Illustration: Fig. 1.--AURORA BOREALIS OBSERVED NEAR THE COAST OF
NORWAY.]
According to Mr. Lemstrom, Fig. 1 gives an idea, although a feeble
one, of the phenomenon at its height. It reproduces only half of the
horizon, and the reader may supply the missing portion of this grand
spectacle in imagination. The streams of light verging toward a common
center were alternately rose colored and pale yellow, and overlooked an
immense violet zone. The rosette in the center was of a beautiful red,
and stood out upon a greenish blue circle.
Fig. 2 represents an aurora that was observed on the 19th of November,
1871, in Finnish Lapland. At the beginning, and at 30° above the
horizon, it formed an arch from whence rose waves of light, and which
gradually ascended. The figure shows it when it had reached about 60°
above the horizon. The base of the aurora was yellow, and the oblique
and very brilliant rays were, slightly higher up, rosy, violet, and
blue. The colors of the polar light are usually clear and bright, but
never did they exhibit greater luster than on this occasion.
Fig. 3 gives an idea of the variety of forms that the phenomenon may
affect. It represents an aurora that was observed at the presbytery
of Enare on the 16th of November, 1871. The aurora this time took on
the form of a glowing red band, curved as shown in the figure. The two
extremities bordered on yellow and green.
There is another form of aurora frequently observed in northern
countries, and that is the one that is seen to occur above clouds, and
that has the appearance of a wide piece of drapery with undulating
folds. As it is the form most usually represented, we shall not dwell
upon it. On the contrary, we shall speak of other phenomena of the same
origin, and much less known, that Mr. Lemstrom describes. It concerns
those auroral lights that shine at the edges of clouds, or that form
around the tops of the mountains in Spitzbergen or in the Alpine
districts of Lapland. According to the Finnish observer, it would be
impossible to tell by the naked eye whence this light comes, but, by
means of a spectroscope, we find that it is of the same nature as the
aurora. Sometimes, these strange lights take on the form of flames of
but little brightness, which, at short intervals, rise from the crest
of the mountain and suddenly vanish (Fig. 4).
These phenomena sometimes exhibit themselves at the level of the
earth's surface, or upon the roofs of houses.
Finally, Mr. Lemstrom describes the diffuse light which sometimes fills
the atmosphere of the polar regions, thus proving that the phenomenon
shows itself from time to time in the vicinity of the earth itself.
Meteors of the same nature as the light of the auroræ boreales do not
occur solely in the polar regions, and the author demonstrates, not
without attaching much importance to it from the standpoint of the
theories to which he has been led, that they are observed in other
countries of the earth. In Peru, Bolivia, and Chili the summits of the
mountains are often seen illuminated by a brilliant light. This light,
which occurs especially in summer, has been compared to heat lightning
by scientists.
Similar observations have been made in the Swiss Alps. Dr. De Saussure
has seen electricity escape through all the projecting parts of
objects, and the same phenomena have been observed upon the high
plateaus of Mexico. Again, we may cite the fact that Brewster observed
a light upon a church tower during an aurora borealis. In every country
phenomena similar to polarized light may occur.--_La Nature_.
* * * * *
IN 1886, 17 Gloucester fishing vessels were lost, worth
$115,800, and 115 fishermen never came home. The year was remarkable
for the small inshore catch, almost all the fishing being done on the
high seas.
The Latest Yankee Craze.
At the forthcoming American Exhibition in London, we are promised,
among other novelties, a house of straw, which is now being made
in Philadelphia. This house is to represent an American suburban
villa, announced to be "handsome and artistic in design," two and a
half stories high, and covering a space of 42 feet by 50 feet. It is
constructed entirely of materials manufactured from straw--foundations,
timbers, flooring, sheathing, roofing, everything in fact, including
the chimneys--the material being fire proof as well as water proof. The
inside finish is to be in imitation rosewood, mahogany, walnut, maple,
ash, ebony, and other fine woods, the straw lumber taking perfectly
the surface and color of any desired wood. This straw house is, in
the first place, to illustrate Philadelphia's commercial, financial,
and industrial interests by means of large photographs of the leading
buildings; but it will also demonstrate how far the inventive Yankee
has succeeded, not in showing us how to make bricks without straw, but
how to produce timber from straw. If, after this brilliant exhibition
of inventive genius, we do not bow down and worship him as the "licker"
of creation, we may consider ourselves lost to all sense of what is
proper under the circumstances.--_Iron._
EFFECT OF A TORPEDO ON AN IRONCLAD.
The British government lately strengthened up the bottom of the old
ironclad Resistance, and tried the effect of firing off a 90 lb.
guncotton torpedo against the vessel. To the surprise of every one,
the ship was not seriously damaged. The _Engineer_ comments upon the
experiment as follows:
The Resistance experiments so far tend to demonstrate that the total
disablement or destruction of a modern ironclad is not so easy as
many people imagined. It was too hastily assumed that the explosion
of a charge of 90 lb. of guncotton in contact with any portion of the
hull under water would have such destructive effect as to overcome
the protection afforded by a thick lining of coal and the cellular
system of construction now always adopted in vessels of war. There
are, however, certain considerations attached to this experiment
which, if duly weighed, should reassure the advocates of the torpedo,
and restrain the exultation of naval architects within reasonable
bounds. We shall endeavor to place these before our readers briefly
and impartially, reserving a fuller summing-up until the remaining
experiments are concluded, as they are of greater importance than any
of those preceding. It is the more essential to do this because the
_Times_, in a leading article of November 3, leads us to believe that
as this attack failed, in the broad sense of the word, similar attempts
under different conditions would have a like result: and that although
serious damage would be caused, the ship would remain "floating and
seaworthy, with her offensive powers not materially impaired." We are
not prepared to accept this conclusion, for the following reasons:
First, let us consider the general effect of a submarine explosion. It
closely resembles the action of gunpowder when ignited in a gun. We
know that in the latter case a quantity of heated gas is formed, which
in its power of expansion exerts force in all directions. Prevented
from expanding by its rigid confinement, except in the direction
of the bore, the gas attains its object by the displacement of the
projectile. This is, in fact, the line of least resistance. When the
same explosive is ignited under water, the heated gas presses outward
in all directions, forcing the surrounding molecules of water against
their neighbors, which are, in turn, propelled forward with great
violence. This effect continues until the back pressure of the liquid
medium equals the now reduced pressure of the gas due to its expansion
in the space vacated by the displaced water, which is likewise to some
extent compressed by the action of the gas. Though brought actually
to a state of rest, the surrounding water is under the influence of
great pressure, which by the law of fluids is transmitted equally in
all directions. When a vessel is sufficiently near the explosion to be
struck by the water which has been so violently disturbed, it will act
upon her like a huge projectile, and it is obvious this range will be
in proportion to the amount of explosive employed. This, combined with
the resistance her hull offers, will also determine the effect produced.
If the charge is too near the surface of the water, the liquid layer
above it will not restrain the liberated gas sufficiently to allow of
its full power being exerted in other directions, and hence permits
its escape into the atmosphere, throwing up the water in its way to a
greater or less height, according to the thickness of the layer. The
spectacular effect, therefore, afforded by the upheaval of a large and
lofty column of water is no criterion of the efficiency of a submarine
explosion, but, on the contrary, shows that much of its energy has
been expended in the wrong direction. The amount of submersion to give
the greatest lateral effect to different charges of explosive has been
ascertained by practical experiments. For 100 lb. of gunpowder, it
is stated to be 10 ft., while for the same quantity of guncotton it
should be 15 ft. As the charge employed against the Resistance was 90
lb. of guncotton placed 10 ft. below the surface, it is probable that
some loss of power was sustained in the manner we have indicated. At a
greater depth also the charge would have been to some extent under the
vessel, where its explosive effect would have been more severe, and
where the construction of the hull cannot be as strongly fortified with
coal as was the case in the Resistance. We are unable to state why a
depth of 10 ft. was selected on this occasion; but it may be due to the
fact that up to a late date most of our locomotive torpedoes have not
carried a larger charge than 40 lb. of guncotton, and are usually run
at 10 ft. below the surface.
Considerable stress has been laid on the fact that in this experiment
the charge was in actual contact, and yet did not effect complete
penetration. It is even gravely asserted that an actual torpedo would
have rebounded a certain distance before explosion took place, and
this would diminish its effect. In the first place, the detonation of
guncotton is practically instantaneous, so that impact and explosion
would be simultaneous. We are hardly prepared to allow an inch rebound,
but will concede that until actual proof convicts us of error. In
the second place, it is possible that a distance of three or four
feet between charge and ship would rather augment than diminish the
effect produced in the case of such an explosive as guncotton when
sufficiently immersed. It is possible the intervening water thrown
against the side of the ship would do more damage than the gas
liberated in actual contact. At any rate, experiments some years ago
with smaller quantities of both dynamite and guncotton showed that when
exploded 4 ft. from the bottom of a ship, enormous damage was inflicted
on her.
Although it is generally estimated that guncotton is about four times
more powerful than gunpowder, this does not appear to hold good under
all conditions; while, on the other hand, for certain purposes, ten
times the amount of gunpowder would not produce the same result. This
is proved by the ease with which the strongest chain cable and wire
rope can be ruptured by a small charge of guncotton, which even more
than ten times the amount of gunpowder could not accomplish. This is
due to the peculiar shattering action of detonated guncotton, which the
slower burning substances does not possess, its characteristic being
more of the nature of a push than a blow. Taking into consideration the
method in which the hull of the Resistance had been strengthened for
this experiment, and the exact locality chosen for the explosion, it is
probable that less than twice the amount of gunpowder would have caused
a more complete breach through the coal protection. The torpedo is
stated to have had everything in its favor; whereas, in our opinion,
all the advantages were on the side of the ship. The attack was made
at her strongest point, where the coal was specially disposed, and her
shape under water lent no assistance to the explosive. To assume from
this that if a similar torpedo struck lower down, or further aft, or
against the propeller, the ship would still have "her offensive powers
not materially impaired," is to express an opinion with which few will
be found to concur.
Under the alternative circumstances mentioned, half the amount of
explosive might practically disable the vessel, though her flotation
need not be overcome. Whitehead torpedoes need not necessarily be
limited to a depth of 10 ft., as by slightly strengthening their
construction they could be run 20 ft. below the surface. We presume
it will be allowed that this would increase their destructive power,
especially in the vicinity of engines and boilers, which now occupy so
much space. In a similar manner there is no difficulty in increasing
the charge of a locomotive torpedo to a point at which it becomes
irresistible, whatever system of internal protection may be devised.
This has, in fact, been going on for some time; more than one nation
possesses torpedoes armed with 100 lb. of guncotton, and if we do not,
it is simply because former experiments led us to believe sufficient
damage would be caused by a less quantity. We can only consider that
disproved on demonstration by further trials under conditions less
favorable to the ship, and we venture to predict some delusions will
then be dispelled which this particular experiment seems to have
occasioned.
[Illustration: TORPEDO EXPERIMENTS AT PORTSMOUTH--DAMAGE DONE TO THE
PORT SIDE OF H.M.S. RESISTANCE.]
Steel Wire Brush Patent.
Before Judges McKennan and Acheson of the United States Circuit Court
for the Western District of Pennsylvania, at Pittsburg, Pa., No. 16
of November term, 1886, a question arose as to whether a steel wire
brush for cleaning castings, and a steel wire brush for cleaning
boiler flues, was an infringement on what is generally known as the
Wright patent, No. 59,733, and the reissue, No. 2,598, owned by Joseph
McArthur, of New York city.
The Wright patent consists of a wooden block with a series of pairs of
holes. A bundle of wire splints is doubled and the ends inserted in
the holes, being held by the wooden bridge between the holes and by a
wooden back screwed to the block.
Joseph H. Davis, of Sewickley, Pa., the defendant, under his casting
brush patent, No. 232,600, the construction of which consists in the
doubling of the wire splints and inserting in one hole of a wooden
block, and fastening by means of weaving a wire through the loop,
the wire being held in place by a wooden back fastened on by driving
wrought iron nails through the block and back and clinching on the
back, thus making the block and back practically inseparable.
The Davis flue brush patent, No. 181,416, is made by sticking the wire
splints through holes in an iron cylinder, there being no wood about
its construction.
Several cases had been tried in other States involving the validity
of the Wright patent, which had resulted in Mr. McArthur's favor, but
after exhaustive argument in the case at Pittsburg, Pa., the court held
the Davis brush not to be an infringement on the Wright patent.
How Long Should a Nervous Patient be Treated?
The question of how long treatment should be continued in a neurotic
case when no evident benefit is produced has recently been raised
in a Hamburg law court. A medical man, says the _Lancet_, having as
a patient a merchant suffering from "nervousness," treated him by
galvanism. Altogether he galvanized him 445 times, but the nervousness
did not disappear. Then came the matter of fees. The sum claimed was
$556. The merchant disputed this on the ground that the treatment ought
not have been continued so long, as it was not producing any benefit.
The court referred the matter to the medical board, which gave as its
opinion that the doctor ought to have asked the patient, after some
fifty sittings, whether he would like to continue them, as it was
doubtful whether the treatment was doing any good. The court, however,
declined to accept this view, holding that it was for the patient to
say when he had tried the treatment as long as he was disposed to
pay for it, and so gave judgment for the full amount claimed. This
judgment seems to accord with the principle that applies to newspaper
subscriptions. A man must pay for his paper as long as he takes it from
the post office.
TORPEDO BOAT ARMED WITH PNEUMATIC DYNAMITE GUNS.
In former issues of the SCIENTIFIC AMERICAN we have given
illustrations and detailed descriptions of the pneumatic dynamite gun
invented by Lieutenant E. L. Zalinski, of the U. S. Artillery Corps.
This gun, it will be remembered, was designed to throw a projectile
loaded with dynamite or nitro-glycerine by means of compressed air;
and so successful were the experiments carried on with it at Fort
Lafayette, under the supervision of a board of naval experts, that
Congress eventually appropriated $350,000 for building a swift torpedo
boat, large enough to go to sea, and to be armed with three of these
guns. Contracts for this boat have been signed with the Cramps.
The upper view in the accompanying engraving is a longitudinal vertical
section, the lower one being a plan view. The following details
regarding the boat we take from the _Sun_. The boat will be 250 ft.
long, 26 ft. beam, and will draw 8 ft. of water. Her displacement will
be about 800 tons. The engines will be of the triple expansion type, of
the best known design, and the guaranteed power will be 3,200. She will
be propelled by twin screws, and it is expected that the guaranteed
speed of 20 knots an hour will be exceeded.
The three dynamite guns are to be placed side by side, at the elevation
indicated in the upper view. They are to be fired in their places, but
their range can be varied by increasing or diminishing the charge of
air let in behind the projectile. An extreme range of one mile is put
down in the contract, and the weight of gelatine to be thrown is 200
pounds; but the guns, as now building, will throw 400 pounds instead of
200 pounds, and the effective range will probably be about two miles.
Air chambers and compressors of sufficient size and power are provided
to enable fifteen shots to be fired to the distance of one mile without
stopping; but if the boat were heading for the enemy at full speed,
thirty shells could be thrown before the air would be exhausted and the
cruiser obliged to turn tail. Thirty shells would mean the explosion of
12,000 pounds of nitro-glycerine about the enemy.
In fixing the gun permanently in its place, the designer has followed
out the old idea of making the ship simply a floating gun carriage. The
new British cruiser Polyphemus is built on the same idea, and there are
other floating gun carriages. In this cruiser the firing is entirely
under the control of the officer in the pilot house. He has simply to
head his boat for the enemy, dash ahead at full speed, and blaze away.
The trained pilot, even in the excitement of battle, would steer his
ship instinctively, so there would be little trouble with the aim,
except, perhaps, in getting the range.
Each gun can be fired once in two minutes, or the three successively in
two minutes.
The new cruiser has a freeboard of about four feet above water. This
is quite enough to enable her to travel anywhere along the coast. She
carries enough coal to travel 5,000 miles at 12 knots an hour. This
would take her about 700 miles at full speed. She could probably turn
a complete circle of a radius of twice her length in between two and
three minutes. She can carry 100 or even a much greater number of
torpedoes with her when going on a cruise. To show how she compares
with the best of the latest English built torpedo boats, it may be said
that the Destructor, built for the Spanish Government, carries but ten
torpedoes, although she has five tubes to fire them from, and this
is the usual number carried. The range of the best of these foreign
torpedoes is 600 yards, under the most favorable circumstances, and in
a seaway not more than 100 or 200 yards. The exploding charge is 75
pounds of gun-cotton, an explosive that is exceedingly inefficient when
compared with nitro-glycerine.
The new boat will also be armed with the usual rapid-firing guns which
are placed on foreign torpedo boats. These are to be used in battle
with craft like herself and small boats. It is expected that she will
be finished in six months.
[Illustration: TORPEDO BOAT ARMED WITH PNEUMATIC DYNAMITE GUNS.]
The Strength of Snails.
Perceiving a common snail, _Helix aspersa_, crawling up the window
blind one evening, it occurred to me to try what it could draw up
perpendicularly. Accordingly, I attached to its shell four reels of
cotton, fastening one after the other until I ascertained that a
greater load would exceed the limit of its strength. I then weighed
the entire load, and found that it weighed 2¼ ounces, while the snail
weighed only ¼ ounce. Thus it was able to lift perpendicularly nine
times its weight. I then made an experiment with a larger snail,
weighing one-third ounce, the load being composed chiefly of the same
material as the last, but so placed as to be drawn in a horizontal
position on the table. Reels of cotton to the number of twelve were
fastened to it, with a pair of scissors, a screw driver, a key, and a
knife, weighing altogether seventeen ounces, or fifty times the weight
of the snail. The same snail when placed on the ceiling was able to
travel with a weight of four ounces suspended from its shell. I next
tried it on a piece of common thread, suspended and hanging loose with
another snail of its own weight, which it carried up the thread with
apparent ease. After this I tried it on a single horsehair strained in
a horizontal position, but it had then enough to do to crawl over this
narrow bridge without a load.--_E. Sandford, in Zoologist_.
CHEVREUL'S BLACK.
T. O'CONOR SLOANE, PH.D.