Copyright
D. S. (David Samuel) Margoliouth.

The Popular science monthly (Volume 19) online

. (page 8 of 110)
Online LibraryD. S. (David Samuel) MargoliouthThe Popular science monthly (Volume 19) → online text (page 8 of 110)
Font size
QR-code for this ebook


tion of the effects of the enormous pressure which is acting under the
deep waters. The Americans have introduced the method of using
fine twine and a heavy weight, both of which may be sacrificed at
every sounding, to obviate the inconveniences arising from overweight
of rope. The practice of observing the rate at which successive equal
lengths of line pass out has been found useful in cases where ordinary
observation or feeling does not suffice to indicate when the shot has
reached the bottom. Iron wire was first used instead of twine about
1850, by Lieutenant Walsh, of the United States schooner Taney.

When the surveys for telegraphic cables were begun, it became
important to ascertain the nature of the ground at the bottom. The
apparatus invented by Midshipman Burke, of the United States Navy,
in 1854, answered this purpose. It consisted of a cannon-ball with a
hole drilled through it. Through this hole passed a straight rod,



DEEP-SEA INVESTIGATION. 6i

lit ted at its upper end with peculiar disengaging hooks. The weight
was slung to these hooks by means of a wire which passed from a ring
slipped over the rod under the weight, up on each side of the cannon-
hall to the hooks. The sounding-line was attached to eyes in these
hooks, and, as long as the lower end of the rod was not resting on
anything, the weight was kept securely in its place, and was available
for taking out the sounding-line. As soon, however, as bottom was
reached, and the rod came to be supported on its lower end, the hooks
at the upper end fell forward, and allowed the wire to disengage itself.
The weight was thus released, and, on the line being pulled up, the
rod came away through the perforation of the shot, and brought with
it specimens of the mud in small quill tubes fitted in a recess in the
lower end of the rod. This apparatus has been improved by substi-
tuting a tube for the rod, and so arranging the attachment of the
weight that it shall continue till the hauling in is begun, whereby its
mass and momentum are available for forcing the tube as deep into
the ground as possible. Captain Shortland devised another modifica-
tion of the apparatus in 1868, for the soundings between Bombay and
Aden. The essential part was the insertion of two butterfly valves
in the lower end, and two conical valves opening upward in the middle
of the tube, between which a sample of the bottom water is secured,
while a specimen of the mud is brought up in the lower segment of
the tube. It was used with general satisfaction during the fii'st year
of the cruise of the Challenger. The chief objection to it was founded
on the smallness of the samples of bottom which it brought up. This
machine, the " Hydra," was replaced after the first year by the " Bai-
ley," an apparatus having a larger tube fitted to bring up more consid-
trable samples of mud.

An apparatus which the author has devised for sounding the Scot-
tish lakes, and found to act well, consists of a straight brass tube an
inch in diameter, carrying a shoulder about one foot from the lower
end. A cylindrical leaden sinker of suitable weight is slipped over
the upper end, and rests on the shoulder. The line is made fast to
;in eye at the top of the tube, and the part of the tube below the
.shoulder can be unscrewed, and the mud which it has brought up
squeezed out. The tubes bury themselves readily in soft mud and
clay, and bring up considerable samples.

It is necessary, in making a sounding in deep water, to load the
end of the line with such a weight that in the deepest water that may
be reasonably expected the velocity of descent shall not be dimin-
ished to an excessive extent by the friction of the increasing length
of line in passing through the water. Wire has been largely employed
for the line, and has great advantages in this respect over hemp. For
example, in water of fifteen hundred fathoms a sinker weighing three
hundred-weight is twenty minutes in reaching the bottom, with the
1)est hempen sounding-line ; while with wire and a sinker of thirty



62



THE POPULAR SCIENCE MONTHLY.



pounds the sounding may be completed in from twenty-five to thirty
minutes. Wire, however, is less flexible than hemp, and breaks under
the influence of kinks and twists, which do not affect the strength of
hemp in any degree. The balance of advantages is in favor of wire,
but it is well to have ropes of both kinds.

The anchor used by the author for holding his vessel in place, dur-
ing his explorations on the west coast of Scotland during the summer
of lS78, brought up so many fine specimens from the mud in which it





1



sank before taking hold on the bottom, that he determined to provide
himself with one which should retain the mud. For this purpose he
bad an anchor made with an open frame, instead of a solid bar con-
necting the two palms, to which was laced a stout canvas bag, into
which any mud sticking to the palm at the moment of its breaking
out of the ground would fall (Fig. 1). The instrument proved a use-
ful one for exploring the bottom, particularly when the object was
to collect the mud itself rather than the things living on its surface,
and was, moreover, eflicient as an ordinary kedge-anchor.

Doubts have sometimes been thrown on the trustworthiness of
deep soundings with the line and heavy sinker. First, it was asserted
that under some great pressure the density of water would become



DEEP-SEA IXVESTIGATIOy. 63

equal to that of lead, and the sinkers would float instead of sinking.
This might be the case were water as compressible as air, and if the
lead could escape compression ; but the amount of pressure that will
double the density of air will increase that of water by only one-
twenty-thousandth part, and it would require the pressure of more
than two hundred thousand atmospheres to squeeze water to the den-
sity of lead. The deepest water, live thousand fathoms, is not subject
to a pressure that can raise its density as much as one-twentieth part.
Moreover, the weight of lead is increased by pressure much faster
than that of water, so that, however dense the water may be, it would
have to encounter a still denser lead. This objection, however, falla-
cious as it has been shown to be, has been admitted by persons of high
authority, of course without sufficient thought.

A more real but exaggerated objection to the trustworthiness of
deep soundings is founded on the existence of currents likely to cause
deviations in the direction of the line, and to change the position of
the ship. There is no doubt concerning surface-currents ; they are
observed and measured every day, and form an important factor in
the navigator's daily reckoning. It has been inferred that they may
be complemented by return under-currents which will be harder to
deal with because they can not be so easily detected and measured.
Soundings taken in the presence of such currents are, it must be ad-
mitted, less to be relied upon than those taken in manifestly quiet
waters ; but the extent of under-currents has been very much exag-
gerated. By far the greater part of the ocean is, for sounding pur-
poses, practically still water. The surface-currents of any importance
are easily recognized, and so also are the under-currents. Just as a
physician can, by bringing his experience to bear on the sounds trans-
mitted to hira by the stethoscope, divine what is taking place inside
the body of his patient, so the experienced seaman can, by observing
the behavior of his sounding-line, form a fair diagnosis of what is
taking place in the depths of the sea. When the sinker passes into a
belt of under-current, the fact is very soon apparent ; but, even with
the greatest care, soundings taken under such circumstances are of
doubtful value, unless bottom is brought up. In the latter case, we
know the depth is not greater than the length of line used, and a cor-
rection, suggested by observation and experience, may be applied,
which will bring our estimate of the depth very near the truth. It is
evident that this can not be satisfactorily done by the sounding-line
alone, and it early occurred to those who thought on the subject that
the method which promised most success was that which should give
the depth in terms of the height of the column of water ; in other
words, the barometrical measurement of altitudes was extended from
tlie land to the sea. The instruments which have been suggested for
this purpose are constructed with a view to record the amount of
I impression produced on a given mass of a certain elastic substance.



64



THE POPULAR SCIEXCE MONTHLY.



From the known law regulating the variation in volume of the sub-
stance with variation in the pressure, the maximum pressure to whicli
the instrument has been exposed can be deduced, and from the known
density of the water the height of the column of it which would pro-
duce that amount of pressure can be calculated ; this height represent>
the depth to which the instrument has been sunk. Perkins, about
1812, constructed a piezometer, or instrument for measuring pressure,
consisting of a glass tube sealed at one end, filled with water, and in-
verted in a cup of mercury. A steel index placed within the tube
rose with the mercury, and was retained by a spring at the highest
point reached. Instruments made on this principle were used by him,
by Aime in the Mediterranean, in 1848, and by the United States
Coast Survey a few years later. Essentially the same instrument,
with certain convenient practical modifications, was used by the author
in the Challenger Expedition.

pjg 2. Another method of measuring the pressure, and through

it the depth, of the sea, is by means of an instrument (Fig. 2)
much resembling in principle the aneroid barometer. Its
simplest form is that usually given to a mercurial thermo-
meter. When the pressure on the outside of the instrument
is increased, the bulb tends to collapse, and, flattening, to
force the mercury into the stem. The amount of com-
pression may be shown as before by an index on the col-
umn of mercury. The use of mercury in this instrument
is, however, unsatisfactory, because its contraction under
the diminished temperature of the lower depths tends to
counteract the effect of pressure in pushing it forward. It
is, nevertheless, adapted to waters of a uniform tempera-
ture, as in the polar regions.

Soundings from vessels in motion may be taken with
Massey's machine, in which the friction of the passing wa-
ter as it sinks causes a screw-fan to make rotations which
are registered by an index. Sir William Thomson has pro-
posed the use of a glass tube, sealed at one end, and coated
internally with a chemical preparation, the color of which is changed
by the action of sea-water. The sea-water forces itself in as the tube
sinks, changing the color of the coating to an extent from Avhich the
depth may be calculated. Each of these instruments is good for only
one sounding.

The author has patented a device by which the depth of com-
pression to which an inclosed mass of air has been subjected is mea-
sured by the water which has gained admittance to the instrument.
It is represented in Fig. 3. It consists of a glass tube open at both
ends, but capable of being closed by a stopper or other means. At
some part of the tube a spout is introduced, and the tube is bent
over through two right angles immediately above it. When the



DEEP-SEA IXVESTIGATIOX.



65



Fio. 4.



instrument is to be used, the end is closed, and the line let go ;
when bottom has been reached it is brought up again, and "we find
that a certain amount of water has lodged in the
lower part of the tube. It is evident that, as the
instrument descends and the air in it is compressed,
the water forces its way in through an orifice, and
past the spout. This spout is so formed that it de-
livers the water against the walls of the tube, down
Avhich it runs, and collects at the bottom. When
the motion of ascent begins, the air, by its elastici-
ty, tends to recover its original volume, and ex-
pands in the direction of greatest freedom. Now,
all the water Avhich has entered has collected below
the spout ; consequently, in reexpanding, this water
will be left undisturbed.

Assuming that the volume of the mass of air in
the instrument varies inversely with the pressure
to which it is subjected, we require, in order to be
able to construct a scale for our instrument, and so
to inteqjret its results, to know the total volume of
the tube, the volume of the part which I call the
vestibule, the dimensions and volume of the narrow
tube, and of the wide one.

Fig. 4 represents an instrument modified so that
it can be used either for great or small depths, ac-
cording as either end is closed. Mr. Hunt, of the /
United States Coast Survey, has invented an ap-
paratus consisting of an air-tight bag, made of
flexible material, with a long, flexible tube attached
to it. The bag, being filled with air, is sunk to the
bottom (in a moderate depth of water), while the
other end of the flexible tube is connected with a
Bourdon's pressure-gauge in the ship or boat, the
observation of which gives an exact profile of the
bottom as the bag is towed over it.

Bottom temperatures may be measured by com-
mon thei-mometers protected so as to be uninflu-
enced in coming up through the warmer upper
strata of water, by bringing the water to the sur-
face and taking its temperature, or by self -register-
ing thermometers, such as Cavendish's and Six's.
A great amount of ingenuity has been displayed in
the invention of machines for registering the ac-
tual temperature of the water at any given depth, independently of
that of the water above it, all of which require some assistance from
VOL. XIX.— 5



66 THE POPULAR SCIEXCE MONTHLY.

the observer in bringing about a catastrophe which shall leave its
mark on the condition of the instrument.

All the self-registering thermometers are liable to error from the
effects of pressure, which may amount to five or six hundred atmos-
pheres on the outside of tlie instrument, while inside it is never
greater than was that of the atmosphere when the tube was sealed up.
Attempts to obviate them have been made by placing the thermome-
ters or their bulbs in protecting inclosures, and by the device of leav-
ing the instrument open at one end. This was adopted by Aime in
some of his experiments, when the effect of pressure on the apparent
volume of the liquid was determined independently, and a correction
Fig. 5. applied accordingly. The author has devised and construct-
I j_u I ed a mercurial thermometer, or piezometer (Fig. 5) on the
j ~ same principle, but his object in admitting the water-press-

ure to the inside of the instrument was to utilize it in shift-
ing the scale of the thermometer as the depths changed.
The thing registered in such instruments is always the ap-
parent volume of the liquid, and this varies with the tem-
perature and the pressure. Hence the indications will rep-
y V i i resent the sum of the effects of the change of temperature
Y — x\ I , ^^^ of pressure. If from any independent source we know
cither of these, we can determine the other. In a sea of
uniform temperature throughout its depth, the apparent
volume of the liquid would diminish as the pressure in-
creased, and, if the temperature increased with the depth,
the apparent volume of the liquid would diminish at a slower
rate ; but it would be always possible to determine the true
temperature as long as it did not increase at so great a rate
as to dilate the liquid more than it was compressed by the increasing
pressure. For the investigation of seas such as the Mediterranean,
this form of instrument is most valuable. No one instrument, how-
ever, fulfills all the conditions requii-ed of a perfect deep-sea ther-
mometer, and the investigator must use his judgment in selecting the
one or more best suited to his particular purpose.

The water from the bottom is usually collected in the so-called
" slip " water-bottle. Water from intermediate depths is obtained
in an instrument represented in section in Fig. 6. It consists of a
cylinder, A, terminated at both ends by similar stopcocks, B, B, which
are connected by the rod C. This rod carries, near its upper extrem-
ity, a piece of stout sheet-brass, D, ten centimetres long by fifteen broad,
soldered to the casting E, which is movable about the axis e.

When intermediate water is to be obtained, the water-bottle is
firmly attached to the sounding-line, which carries at its end usually
a fifty-six pound or one hundred-weight lead ; the stopcocks are then
opened, giving them, with the rod C, the position represented in
the figure. During the passage of the bottle downward, the water






THE WILL-O'-THE-WISP AXD ITS FOLK-LORE. 67




courses freely through it, being considerably assisted by the conical
end-pieces K K. "When the requisite depth is reached, the line is
checked and is finally hauled in. Under the pressure p,g g

of the hauling, the flap D falls down into an horizontal
position, when it is caught by the movable piece of
brass F, which moves round an axis, /, and is sup-
ported on the side opposite to E by the rod G, which
rests on the spiral spring H. The water rushing past
D, when thus in an horizontal position, exercises a sufti-
cient pressure upon the rod to close the stopcocks B, B.
When the speed with which the bottle is hauled through
the water is increased, the pressure on D becomes so
great that it overcomes the tension of the spring H,
and E passes the catch F, when the rest of the journey
upward is performed with the flap D hanging down,
and therefore offering the least possible resistance to
the water. When the water-bottle has been brought
up, it is only necessary to substitute for the lower funnel
a small nozzle, by which the water may be drawn off,
and the instrument be made ready for immediate use
without having to detach it. It has been ascertained
by experiment that the water obtained by this instru-
ment is an average of the last two fathoms through
which it has passed.




THE AVILL-O'-TIIE-WISP AXD ITS FOLK-LOEE.



By T. F. TIIISELTON DYER.

AMOXG the many sources of superstition in this and other coun-
tries, the phenomenon well known as the Will-o'-the-Wisp has
from time immemorial held a prominent place. Indeed, it would be
no easy task to enumerate the various shapes in which the imagination
has pictured this mysterious appearance, not to mention the manifold
legends that have clustered round it. In days gone by, when our
credulous forefathers believed in the intervention of fairies in human
affairs, the Will-o'the-Wisp entered largely into their notions respect-
ing the agency of these little beings in their dealings Avith mankind ;
and, as will be seen in the course of the present paper, numerous
stories were often related in which some fairy disguised as Will-o'-
the-Wisp was the chief character. It is worthy, too, of note that,
although in these enlightened days every relic of primitive culture is
gradually fading from our gaze, the old superstitious fancies associated
with this nocturnal visitor still survive with more or less vigor, retain-
ing that hold on the vulgar mind which they formerly possessed.



68 THE POPULAR SCIEXCE MOXTHLY.

Thus, in remote Aullages and secluded country nooks the peasant,
while not forgetting the traditions handed down to him, continues to
believe with implicit faith in those quaint and weird fancies which
have invested the "\Vill-o'-the-Wisp with such a peculiar dread. This
terror, as we shall point out, in a great measure originated in the many-
tales and legends that were in past centuries framed to explain and
account for this deceptive phenomenon.

Referring, then, in the first place, to the various names assigned to
it — many of these are extremely curious, differing according to the
country and locality. Its most popular appellation, Will-o'-the-Wisp,
was probably derived from its customary appearance ; this wandering
meteor having been personified because it looked to the spectators like
a person carrying a lighted straw torch in his hand. Hence it has
been termed Jack, Gill, Joan, AVill, or Robin, indifferently, in accord-
ance with the fancy of the rustic mind ; the supposed spirit of the
lamp being thought to resemble either a male or female apparition.
Hentzner, for instance, in his " Travels in England " (1598), relates how,
returning from Canterbury to Dover, " there were a great many Jack-
a-lanthorns, so that we were quite seized with horror and amazement."

In Worcestershire, the phenomenon is termed by the several names
of "Hob-and-his-Lanthorn," "Hobany's Lanthorn," and "Iloberdy's
Lanthorn " — the word Hob in each case being the same name as occurs
in connection with the phrase hobgoblin. It appears that, in days
gone by, Hob was a frequent name among common people, and, curi-
ously enough, Coriolanus (Act ii, sc. 3) speaks of it as used by the
citizens of Rome :

" Why in tliis wolvish gown should I stand here,
To beg of Hob and Dick, that do appear
Their needless vouches? "

Subsequently, Hob seems to have been used as a substitute for Hob-
goblin, as in Beaumont and Fletcher's " Monsieur Thomas " (Act iv,

sc. 6) :

" From elves, hobs, and fairies,
From fire-drakes or fiends.
And such as the devil sends,
Defend us, good Heaven ! "

A Northamptonshire name is Jinny Buntail, which is evidently a
corruption of Jinn with the burnt tail, or " Jild burnt tail," an allusion
to which occurs in Gayton's "Xotes on Don Quixote" (1654, 97),
where we read of " Will with the Wispe, or Gyl burnt tayle," and,
again (268), of *' An ignis fatuus, or exhalation, and Gillon a burnt
tayle, or Will with the Wispe." The Somersetshire peasant talks of
«' Joan-in-the-Wad," and " Jack-a-Wad," Wad and Wisp being synony-
mous. In Suffolk it was known as " A Gylham lamp," in reference to
which we are told in Gough's " Camden " (ii, 90) how, " in the low



THE WILL-O'-THE-WISP AXD ITS FOLK-LORE. 69

grounds at Sylhara, just by AVingfiekl, are the ignesj-atui, commonly
called Sylham lamps,- the terror and destruction of travelers, and even
of the inhabitants, who are frequently misled by them."

Another of its popular nicknames in former years was " Kit of the
Canstick" — i. e., candlestick ; and, in "Poor Robin's Almanack" for
177T, it is styled " Peg-a-lantern " :

" I should indeed as soon expect
That Peg-a-lantern would direct
Me straightway home on misty night ;
As wand'ring stars, quite out of sight,
Pegg's dancing light does oft betray,
And lead her followers astray."

The expression igiiis fatuus, or foolish fire, originated in its leading
men astray, as in the "Tempest" (Act iv, sc. 1), where Stephanio
says, " Monster, your fairy, which you say is a harmless fairy, has
done little better than played the jack with us " — a passage which is
explained by Johnson thus : " He has played Jack-with-a-lantern ; he
has led us about like an ignis fatuus, by which travelers are decoyed
into the mire." Thus Gray describes it :

"How "Will-a'-Wisp misleads night-gazing clowns
O'er hills, and sinking bogs, and pathless downs."

In Scotland, one of the names for this appearance is " Dank Will,"
and in Ireland it is known as " Miseann Many," an allusion to which
occurs in Croker's " Fairy Legends of the South of Ireland " in the
story of the " Spirit Horse," where Morty Sullivan is so sadly deluded
by it.

Again, the term " Fire-drake," * which is jocularly used in " Henry
VIII " (Act V, sc. 4) for a man with a red face, was one of the popu-
lar names for the Will-o'-the-Wisp ; in allusion to which Burton, in
his "Anatomic of Melancholy," says, "Fiery spirits or devils are such
as commonly work by fire-drakes or ignes fatui, which lead men often
in flumina et prmcipitia.'''' It appears, also, that in Shakespeare's day
" a walking fire " was another common name for the "\Vill-o'-the-"Wisp,
to which he probably refers in " King Lear " (Act \y, sc. 3), where,
Gloster's torch being seen in the distance, the fool says, " Look, here
comes a walking fire " ; whereupon Edgar replies : " This is the foul
fiend riil)boi*tigibet ; he begins at Curfew and walks till the first
cock." Hence Mr. Hunter f considers that Flibbertigibet was a name
for the Will-o'-the-Wisp. That, however, this phenomenon was known

* A "Firc-drakc" appears to have been also an artificial firework, as in Middleton's
•■ Five Gallants " :

"... But, like firedrakes,
Slounted a little, gave a crack, and fell."



Online LibraryD. S. (David Samuel) MargoliouthThe Popular science monthly (Volume 19) → online text (page 8 of 110)