CHAPTER IV.

Terrestrial phenomena--Footmarks on rocks--The Logan
stone--Sounds in stones--The cave of St. Paul--Atmospherical
phenomena--Intermitting springs--Waters of magical power.


In proceeding to illustrate the operation of natural laws, we may look
now at some of the phenomena connected with the globe we inhabit, of
which, where little knowledge is possessed, erroneous and frequently
superstitious opinions are still entertained.

Marvellous tales are often told of rocks. There is, for example, a
tradition of a nobleman being engaged in the chase, or pursued by his
enemies, without being hurt; whose horse left the prints of his feet
on a mass of stone, over which he passed. But, unhappily for the tale,
other impressions have been observed besides those of the horse’s feet;
and it is affirmed by various naturalists, deserving of credit, that
they must have been made by very different animals, at a remote period,
before the stone had completely hardened. Other instances of the same
kind might easily be given. In the British Museum, there is a slab
having similar impressions, obviously produced by the same means. It
was dug from a great depth; a mass of stone, many feet in thickness,
having been formed above the layer which received, in a soft state, the
impression from the feet of several animals.

Other impressions, of which we read or hear, are nothing more than
tricks of art. Such, most probably, is the impression of the foot
of Budda upon the Peak of Adam, at Ceylon; the print of the foot of
the idol Gaudama, in the Burmese empire, which has been three times
reproduced; and most certainly this is the case with the so-called
impressions of the feet of our blessed Lord and Saviour, shown to the
present day, on Mount Olivet.

The cave of St. Paul, at Civita Vecchia, the former capital of the
island of Malta, is an excavation, about nineteen feet in height, and
fifty in circumference; in a soft, white, limestone rock, more friable
than chalk. A belief that the stone was endowed with miraculous medical
virtues, led people to carry away large quantities of it during the
sway of the knights. In 1770, when visited by Brydone, the cave was
in the highest celebrity; not only every house in the island had a
medical chest of it, but large quantities were sent to different
countries in Europe, and even to the East Indies. It was supposed to
have a miraculous power which preserved it from diminution; which may
be accounted for by a natural law--the calcareous process of formation
still going on--while its healing power is to be attributed to its
having some of the properties of magnesia; which leads, according
to Dr. Walsh, to its still being given as a purgative-sudorific in
eruptive or fever complaints.

One instance of gross superstition, as connected with rocks, is too
important to be omitted. The trial by ordeal appears to have been very
early practised among the Celtic tribes of Europe, who were always
under the influence of an artful and domineering priesthood. Thus, it
is said that in cases of doubtful accusation the Druids made use of the
rocking-stones which were common in Britain, and that the culprit was
acquitted or condemned according as he succeeded or failed in shaking
them. Mason alludes to this trial in the following lines:--

“Behold yon huge
And unknown sphere of living adamant,
Which, poised by magic, rests its central weight
On yonder pointed rock; firm as it seems,
Such is its strange and virtuous property,
It moves obsequious to the gentlest touch
Of him whose heart is pure; but to a traitor,
Though e’en a giant’s prowess nerved his arm,
It stands as fixed as Snowdon.”

A little knowledge would have disabused the mind of this delusion. The
celebrated Logan or Logging-stone, near the Land’s End in Cornwall, is
an immense block, weighing about sixty tons. The surface in contact
with the under rock is, however, of very small extent; and the whole
mass is so nicely balanced, that, notwithstanding its magnitude, the
strength of a single man is sufficient to make it oscillate, when
applied to the under edge. It is the nature of granite to disintegrate
or decompose by the action of the air and moisture; a huge mass is thus
split into several blocks, and at length, by the continued operation of
the elements, one is suspended on the rest.

[Illustration]

Sounds emitted from rocks have often been regarded as portentous. Mr.
G. Bennett, when at Macao, had his attention directed to a mass of
granite rocks, appearing as if separated by some convulsion of nature,
many of which were found, when trodden on, to be movable. The first,
and by far the most sonorous, was partially excavated underneath;
and, by striking it upon the upper part, a deep sound, “like that of
a church bell,” was produced. “The battered appearance of the stone
above,” it is said, “bore several proofs of how many visitors had made
this lion roar.” Many of the other rocks were also sonorous, but not so
loud as the first, and, from their situations, “they were movable when
trodden on; but it could not be seen, whether, like the preceding, they
were excavated, and, in consequence of being so, sonorous.”

In the chain of El-Heman, and not far from the Red Sea, is the Jebal
Narkous, or “Mountain of the Bell.” It forms one of a ridge of low
calcareous hills, which are connected by a sandy plain, extending,
with a gentle rise, to their base. It is composed of a light-coloured
friable sandstone, about the same as the rest of the chain; but an
inclined plane of almost impalpable sand rises at an angle of about
forty degrees with the horizon, and is bounded by a semi-circle of
rocks, presenting broken, abrupt, and pinnacled forms, and extending to
the base of this remarkable hill. Its height is about four hundred feet.

Lieutenant Wellsted observed, that the shape and arrangement of the
rocks resembled, in some respects, a whispering-gallery; but he
ascertained, by experiment, that their irregular surface rendered
them but ill-adapted for the production of an echo. Seated on a rock
at the base of the sloping eminence, he directed a Bedouin to ascend;
and it was not till he had reached some distance that the lieutenant
perceived the sand in motion, rolling down the hill to the depth of a
foot. It did not, however, descend in one continued stream, but, as
the Arab scrambled upwards, it spread out laterally and above, until a
considerable portion of the surface was in motion. As the sand began
to fall, the sounds produced might be compared to the faint strains
of an Eolian harp when its strings first catch the breeze. When the
sounds became more violently agitated by the increased velocity
of the descent, the noise more nearly resembled that produced by
drawing the moistened fingers over glass. As it reached the base,
the reverberations attained the loudness of distant thunder, causing
the rock on which lieutenant Wellsted was seated to vibrate; and the
camels, animals not easily frightened, became so alarmed, that their
drivers could only retain them with difficulty. The noise, it was
remarked, did not issue from every part of the hill alike, the loudest
being produced by disturbing the sand on the northern side, about
twenty feet from the base, and about ten from the rocks that bound it
in that direction. The tradition is, that the bells of a convent were
buried here; the Bedouins trace the sounds to several wild and fanciful
causes; but, in the experiment now described, it was evident that the
sounds sometimes fell quicker on the ear, and at other times were more
prolonged, according to the Arab’s increasing or retarding the velocity
of his descent.

Dr. Chladni made many curious experiments on the figures assumed by
sand and similar substances, when strewed over vibrating sonorous
bodies. The reader may easily try an experiment of this kind. Let a
square piece of glass be taken, such as that used for windows, not less
than four or five inches over, the edges of which are to be smoothed
by grinding. Spread over the plate, as evenly as possible, a little
sand, and, holding it between the thumb and fore-finger, in the middle,
pass the bow of a violin against one of its edges, drawing it either
upwards or downwards, in a direction perpendicular to its surface. A
tremulous motion will be immediately observed, and the sand will assume
some particular and fixed figure. If the bow be passed over the middle
of one of the sides, the sand will arrange itself in the direction of
the two diagonals, dividing the square into four isosceles triangles.
If the bow be applied at any point which is one-fourth the length of
the square from any angle, the arrangement of the sand will represent
the two diameters of the square, dividing it into four equal figures
of the same form. If the square be held at the two extremities of
either diameter, and the bow be applied to the extremities of the other
diameter, the sand will take the figure of an oval, having its major
axis in the same direction as one of the diameters.

Other experiments of the same kind have since been made by M. Voigt,
and also by the celebrated Oersted. The latter covered a plate of
metal or glass with the lycopodium seed, or the seed of the club-moss,
instead of sand; he then tried to produce a sound in the manner of
Chladni, and instantly he saw the dust distribute itself into a number
of little regular tumuli, which put themselves in motion at their
extremities, or formed the figures discovered by this naturalist. They
always ranged themselves in the form of a curve, the convexity of which
was in proportion to the point touched by the violin bow, or towards
the point which has an analogous situation; the nearer that each of
these little heaps was to these points, the greater was its height,
a circumstance which gave remarkable regularity to the figure. The
interior of the small elevations thus obtained, were in constant motion
during the continuance of the sound, and the duration of the vibrations
might be observed on a plate from four to six inches in diameter. At
one moment the height increased, at another it diminished, and the dust
had the appearance of arranging itself in small globules, which rolled
one above another.

We may now return from these very interesting facts, to others on a
far larger scale. Near the Kom-el-Hett’an, or the mound of sandstone,
which makes the site of one of the palaces and temples of Amunoph III.,
are two sitting colossi, which seem to assert the grandeur of ancient
Thebes. The easternmost of the two is doubtless the statue reported
by ancient authors to utter a sound at the rising of the sun. It was
said to resemble the breaking of a metallic ring, or harp-string. The
superstition of its Roman visitors ascribed the colossus to Memnon, and
a multitude of inscriptions attributed to him miraculous powers. The
memory of its daily performance is still retained in the traditional
appellation of Salamat, “salutations,” by the modern inhabitants
of Thebes. It is said to have “saluted” the emperor Adrian and his
queen Sabina twice; but some persons, of course of humble rank, were
disappointed on their first visit, and obliged to return another
morning to satisfy their curiosity.

And yet there is ample reason to believe that the whole was an artifice
of the priests. In the lap of the statue is a stone; and as sir
Gardiner Wilkinson discovered, on examining the inscriptions, that
one Ballilla had compared the sound the stone emitted, when struck,
to the striking of brass, he determined to put the matter to the
test. Accordingly, posting some peasants below, and ascending to the
lap of the statue, he struck the sonorous block with a small hammer,
and inquiring what was heard by the peasants, they answered, “You
are striking brass.” “This,” says sir Gardiner, “convinced me that
the sound was the sound that deceived the Romans, and led Strabo to
observe that it appeared to him as the effect of a slight blow.” “The
Theban priests,” he adds, “must have been considerable gainers by the
credulity of those who visited their _lion_.”

The reader who may have taken the delightful walk from Tunbridge Wells
to the High Rocks, and examined particularly those huge masses, will
not fail to remember the one called “the Bell Rock.” On entering the
space between this one and the next, it may be struck with a stick,
when a sound will be heard like that produced, on a large metallic body
being smitten.

In the road cut by Napoleon between Savoy and France, and about two
miles from Les Echelles, there is a gallery twenty-seven feet high and
broad, and nine hundred and sixty feet in length, formed in the solid
rock. When this road was nearly complete, and the excavations commenced
at each end almost met, the partition was broken through by a pick-axe,
and a loud and deep sound was heard. We are indebted to Mr. Bakewell
for the following solution of this phenomenon. The mountain rises full
one thousand feet above the passage, and fifteen hundred above the
valley. The air, on the eastern side of the mountain, is sheltered both
on the south and west from the sun’s rays; and consequently must be
much colder than on the western side. The mountain, therefore, formed
a partition between the hot air of the valley, and the cold air of the
ravines on the eastern side. When the opening was made, the cold, and
therefore denser air, rushed into that rarefied by heat, and a loud
report was produced, in the same manner as when a bladder, placed over
an exhausted air-pump receiver, is burst.

Baron Humboldt informs us, on credible authority, that subterranean
sounds, resembling the tones of an organ, are heard on the banks of the
Oroonoko. He supposes that they arise from a difference of temperature
between the external atmosphere and the air confined in the crevices
of the adjacent granitic rocks. He concludes that, as the temperature
of the confined air is greatly increased during the day from the
conduction of heat by the rocks; and as the difference of temperature
between it and the atmosphere will reach its maximum about sunrise, the
sounds are produced by the escaping current.

The following illustrative experiment is not a little curious:--If a
tube formed of some elastic and sonorous substance be taken, and a jet
of inflamed hydrogen be introduced, a musical sound will be heard. This
will take place in a tube closed at one end, if it be large enough
to admit a sufficient quantity of atmospheric air to support the
combustion of the gas; but if the tube be open at both extremities,
the musical sound will be clear and full. Various conclusions have
been arrived at in reference to this phenomenon; but they have been
set aside by the experiments of Mr. Faraday, who attributes the sounds
produced by flames in tubes to a continual series of detonations or
explosions.

The first philosopher who exhibited the longitudinal vibration of
solids was Dr. Chladni. According to him, the best method of producing
these vibrations in rods, is by rubbing them, in the direction of their
length, with some soft substance, covered with powdered resin, or by
the finger. When glass tubes are employed, they should be rubbed with a
piece of rag spread over with fine sand, the tube being held by one of
the ends.

“In all longitudinal vibrations,” says the same writer, “the tones
depend merely on the length of the sonorous body, and on the quality
of the substance, the thickness and form being of no consideration;
yet the tones are not varied by the specific gravity of the vibrating
substance; for fir-wood, glass, and iron, give almost the same tone
as brass, oak, and the shanks of tobacco-pipes.” He also mentions
several kinds of longitudinal vibration; in one, to use his own words,
“there is a certain point in the middle at which the vibration of
each half-stops; in the next there are two, each at the distance of a
fourth part from the end; and, in the following, there are three, or
more. The tones correspond with the natural series of the numbers 1,
2, 3, 4, etc. If a rod be fastened at one end, during the first kind
of longitudinal vibration, the alternate expansion and contraction of
the whole rod will take place in such a manner, that they stop at the
fixed end; in the next tone there is a resting-point at the distance of
one-third from the free end; and in the following there are two. The
tones correspond with the numbers 1, 3, 5, 7, and the first of these
tones is an octave lower than the first tone of the same rod when
perfectly free.”

When examining the nature of sonorous bodies, Dr. Chladni imagined
the possibility of producing musical sounds by rubbing glass tubes
longitudinally. It, however, became a difficult question to determine
in what way an instrument of this kind should be constructed. After
much and long-continued unsuccessful thought, he returned home one
evening exhausted with walking, and he had scarcely closed his eyes
to fall asleep in his chair, when the arrangement he had so long been
seeking, occurred to his mind. He soon after completed an instrument,
which in every respect answered his expectations.

The euphone, signifying an instrument having a pleasant sound,
consists of forty-one fixed and parallel cylinders of glass, equal in
length and thickness. In its external appearance it resembles a small
writing-desk, which, when opened, presents a series of glass tubes
about sixteen inches long, and the thickness of a quill. They are fixed
in a perpendicular sounding-board, at the back of the instrument. When
used, the tubes are wetted with a sponge, and stroked in the direction
of their length with wet fingers; the intensity of the tone being
varied by greater or less pressure.

The singular phenomenon of sound occasioned by the vibration of soft
iron, produced by a galvanic current, was recently discovered by Mr.
Sage, and has been since verified by the observations of a French
philosopher, M. Marian. The experiments were made on a bar of iron,
which was fixed at the middle, in a horizontal position, each half
being inclosed in a large glass tube. By appropriate arrangements,
the galvanic circle was completed; and the longitudinal sound could
be distinguished, although it was feeble. The origin of the sound has
therefore been ascribed to a vibration in the interior of the iron bar;
and to the same cause are probably attributable many phenomena.

We now pass on to the violent agitation of the air, which is often
productive of surprising results. A quantity of feathers, for example,
was scattered one day over the market-place of Yarmouth, to the great
astonishment of a large number of persons assembled there. But what
was the cause? The timid considered that the phenomenon predicted some
great calamity; the inquisitive indulged in a thousand conjectures;
and the curious in natural history sagely accounted for it by a gale
of wind in the north, blowing wild-fowl feathers from the island of
St. Paul’s! Yet, not one of them was right. No guess would explain the
cause, and yet it arose from the prank of a frolicsome boy. Astley,
afterwards well known as sir Astley Cooper, had taken two of his
mother’s pillows to the top of the church, and when he had climbed as
far as he could up the steeple, he ripped them open, and scattered
their contents to the wind.

The _Philosophical Magazine_ contains an account of a singular snow
phenomenon that occurred in Orkney. The paper was contributed by Mr.
Clouston, of Stromness. “One night a heavy fall of snow took place,
which covered the plain to a depth of several inches. ‘Upon this pure
carpet,’ says the writer, ‘there rested next morning thousands of large
masses of snow, which contrasted strangely with its smooth surface.’
These occurred generally in patches, from one acre to a hundred in
extent, while clusters were often half-a-mile asunder. The fields so
covered looked as if they had been scattered over with cart-loads of
manure, and the latter covered with snow; but, on examination, the
masses were all found to be cylindrical, like hollow fluted rollers, or
ladies’ swan-down muffs, bearing a strong resemblance to the latter.
The largest measured 3½ feet long, and 7 feet in circumference. The
centres were nearly but not quite hollow; and by placing the head
within when the sun was bright, the concentric structure of the
cylinder was apparent. They did not occur in any of the adjoining
parishes, and were limited to a space of about five miles. The first
idea, as to the origin of these bodies, was, that they had fallen from
the clouds, and portended some direful calamity. But, had they fallen
from the atmosphere, their symmetry and loose texture must have been
destroyed. The writer having examined them, was soon convinced that
they had been formed by the wind rolling up the snow as boys form
snow-balls. Their round form, concentric structure, fluted surface, and
position with respect to the weather side of eminences, proved this;
and it was also evident, from the fact of their lying lengthways, with
their sides to the wind; and sometimes their tracks were visible in the
snow for twenty or thirty yards in the windward direction, whence they
had evidently gathered up their concentric layers.”

A correspondent of the _Athenæum_, in a letter, dated Naples,
January 3rd, 1847, mentions another very striking phenomenon. He was
standing on a cliff overlooking the Mediterranean, accompanied by an
Italian friend. The air was perfectly tranquil, and yet in a moment
he felt himself grasped and encircled, as it were, by an unseen and
irresistible power, and, in spite of his struggles, he felt himself
sailing through the air at a balloon speed. After a few moments of
his aërial travelling, he was pitched halfway down the cliff into the
centre of an empty lime-kiln, not far from the sea. Nor was he alone;
there was another heavy fall; for his friend stood opposite him.
As they were encircled by a force, equal at all points, though the
shock was violent, they fell on their feet, but sank directly to the
ground, and there sat gazing at one another, unable either to move or
speak. Happily, no bones were broken; but so severe were the internal
injuries experienced, as to confine them to their beds for some time,
and they expect the internal effects of their involuntary and dangerous
voyage to remain for a considerable time.

As the population of the coasts of the Mediterranean are exceedingly
ignorant and superstitious, it is not surprising that the people in
the neighbourhood said that the Shal’ombre, the evil spirits, in the
lime-kiln, must have drawn the travellers in; and attributed their
deliverance to the intercession of the souls in purgatory for the acts
of charity they had performed!

To avoid any calamities, which the mariners of Naples generally
attribute to demoniacal influence, they resort to the practice of
witchcraft. Few are the barks that venture to the coral fishery, or the
coasting-trade, without having a magician on board. Persons of this
class, however, who practise the art supposed to be required at sea,
or who even reveal it to others, cannot receive absolution from an
ordinary confessor. It is comprehended under the head of “malaficia,”
one of the reserved sins to be found in the printed list of directions
appended to every confessional in Italy.

And yet, were witchcraft available in any case, it could not be in
connexion with the natural operation, which the mariners call “trombe
di mare.” The travellers suffered, in fact, from a strong wind,
connected with the phenomenon of a water spout, observed, for the most
part, at sea, but sometimes also on shore. Its usual appearance is
that of a dense cloud, like a conical pillar, which seems to consist
of condensed vapour, and is seen to descend with the apex downwards.
When over the sea, there are generally two cones, one projecting from
the cloud, the other from the water below it. They sometimes unite,
and then a flash of lightning is observed; on other occasions, they
disperse before any junction takes place. The effect appears to be,
at least partly, electrical; the cones being in opposite states, the
positive and negative attraction ensue; and, when union takes place,
which is indicated by the flash, the bodies are restored to their
equilibrium.

The magicians on the coast practise what they call the art of “cutting”
the “trombe.” As soon as it is seen approaching in the direction of a
boat, the wizard goes forward, sends all the crew aft, that they may
not be eye-witnesses of what he does; and using certain signs or words,
and making a movement with his arms as if in the act of cutting, the
enemy falls in two, and disappears.

We are reminded by these circumstances of “the news from the country,”
which the _Spectator_ describes as brought to him by sir Roger de
Coverley. One part of it was, that Moll White was dead, and that about
a month after one of the baronet’s barns fell down, which led to the
shrewd remark: “I do not think the old woman had anything to do with
it.” Nor do we think that the wizard of the Mediterranean has anything
to do with “cutting the wind.” The probability is, that he seizes on
the time for his movements, which, from experience, he knows to precede
the dispersion of the cloud, and thus acquires credit to which he has
not the slightest claim.

This chapter may appropriately be concluded by a reference to the
waters of the earth, which are often represented as endued with a
supernatural power. The Ilissus, rising on Mount Hymettus, to the east
of Athens, and overflowing its banks, furnishes a supply of excellent
water to the monastery of Sergiani. On one side, are three small
caverns in the rock, with double entrances; apparently the work of
nature, but probably aided by art. They are still supposed, as they
have been during past ages, to have a mystic virtue; and “no remedy,”
says Dodwell, is considered so efficacious for a sick child as “to drag
it two or three times from one cave to another; by which it is either
killed or cured. Several ancient wells are observed in the rock on each
side of the river. Near these, the foundation of a wall crosses the bed
of the Ilissus.”

Springs, in various parts of this and other countries, alternately
ebbing and flowing, have been, and are still, in some cases, supposed
to be under the ban of witchcraft. And yet the phenomena are easily
explained by natural laws. If the shorter end of a bent tube, A, whose
branches are of an unequal length, be placed in a basin of water, and
the air is drawn from it, we have a syphon, which will decant the
water into any vessel. Now such tubes as these are naturally formed
in the earth, and if the water be drained into a cavity, B, having a
syphon-like channel, C, it is evident that it will flow as long as the
syphon can act, and it will then cease.

[Illustration]

Seneca describes a spring near to Tempe, in Thessaly, the waters of
which are fatal to animals, and penetrate iron and copper. Yet, it is
probable, as Dr. Thomson states, that “this spring contained either
free sulphuric acid, or a highly acidulous salt of that acid. This
acid has been detected in a free state, as well as hydrochloric acid,
in the water of the Rio Vindagre, which descends from the volcano
of Paraiè, in Columbia, South America. Sulphuric acid is also found
in the waters of other volcanic regions. The sour springs of Byron,
in the Genessee country, about sixty miles south of the Erie canal,
contain sulphuric acid. Such waters would rapidly corrode both iron
and copper, converting the former into green, the latter into blue
vitriol--sulphates of both metals.”[E]

It would be easy to extend these instances, in connexion with
the phenomena of the globe, but the present will suffice to show
that a little knowledge of natural science is an antidote to many
superstitions. We proceed now to illustrations of agencies in active
operation of a different character.