so, and could see, as before, the green gleam of the mighty curve
sweeping over the uipper ledge, and the fitful plunge of the water, as
the spray between us and it alternately gathered and disappeared. An
eminent friend of mine often speaks of the mistake of those physicians
who regard man's ailments as purely chemical, to be met by chemical
remedies only. He contends for the psychological element of cure. By
agreeable emotions, he says, nervous currents are liberated which
stimulate blood, brain, and viscera. The influence rained from
ladies' eyes enables my friend to thrive on dishes which would kill
him if eaten alone. A sanative effect of the same order I experienced
amid the spray and thunder of Niagara. Quickened by the emotions
there aroused, the blood sped exultingly through the arteries,
abolishing introspection, clearing the heart of all bitterness, and
enabling one to think with tolerance, if not with tenderness, on the
most relentless and unreasonable foe. Apart from its scientific
value, and purely as a moral agent, the play was worth the candle. My
companion knew no more of me than that I enjoyed the wildness of the
scene; but as I bent in the shelter of his large frame he said, 'I
should like to see you attempting to describe all this.' He rightly
thought it indescribable. The name of this gallant fellow was Thomas
Conroy.
We returned, clambering at intervals up and down, so as to catch
glimpses of the most impressive portions of the cataract. We passed
under ledges formed by tabular masses of limestone, and through some
curious openings formed by the falling together of the summits of the
rocks. At length we found ourselves beside our enemy of the morning.
Conroy halted for a minute or two, scanning the torrent thoughtfully.
I said that, as a guide, he ought to have a rope in such a place; but
he retorted that, as no traveller had ever thought of coming there, he
did not see the necessity of keeping a rope. He waded in. The
struggle to keep himself erect was evident enough; he swayed, but
recovered himself again and again. At length he slipped, gave way,
did as I had done, threw himself towards the bank, and was swept into
the shallows. Standing in the stream near its edge, he stretched his
arm towards me. I retained the pitchfork handle, for it had been
useful among the boulders. By wading some way in, the staff could be
made to reach him, and I proposed his seizing it. 'If you are sure,'
he replied, 'that, in case of giving way, you can maintain your grasp,
then I will certainly hold you.' Remarking that he might count on
this, I waded in, and stretched the staff to my companion. It was
firmly grasped by both of us. Thus helped, though its onset was
strong, I moved safely across the torrent. All danger ended here. We
afterwards roamed sociably among the torrents and boulders below the
Cave of the Winds. The rocks were covered with organic slime, which
could not have been walked over with bare feet, but the felt shoes
effectually prevented slipping. We reached the cave and entered it,
first by a wooden way carried over the boulders, and then along a
narrow ledge, to the point eaten deepest into the shale. When the
wind is from the south, the falling water, I am told, can be seen
tranquilly from this spot; but when we were there, a blinding
hurricane of spray was whirled against us. On the evening of the same
day, I went behind the water on the Canada side, which, after the
experiences of the morning, struck me as an imposture.
Still even this latter is exciting to some nerves. Its effect upon
himself is thus vividly described by Bakewell, jun: 'On turning a
sharp angle of the rock, a sudden gust of wind met us, coming from
the hollow between the fall and the rock, which drove the spray
directly in our faces, with such force that in an instant we were wet
through. When in the midst of this shower-bath the shock took away my
breath: I turned back and scrambled over the loose stones to escape
the conflict. The guide soon followed, and told me that I had passed
the worst part. With that assurance I made a second attempt; but so
wild and disordered was my imagination that when I had reached half
way I could bear it no longer.' [Footnote: 'Mag. of Nat. Hist,' 1830,
pp. 121, 122.]
To complete my knowledge I desired to see the fall from the river
below it, and long negotiations were necessary to secure the means of
doing so. The only boat fit for the undertaking had been laid up for
the winter; but this difficulty, through the kind intervention of Mr.
Townsend, was overcome. The main one was to secure oarsmen
sufficiently strong and skilful to urge the boat where I wished it to
be taken. The son of the owner of the boat, a finely-built young
fellow, but only twenty, and therefore not sufficiently hardened, was
willing to go; and up the river, it was stated, there lived another
man who could do anything with the boat which strength and daring
could accomplish. He came. His figure and expression of face
certainly indicated extraordinary firmness and power. On Tuesday,
November 5, we started, each of us being clad in oilcloth. The elder
oarsman at once assumed a tone of authority over his companion, and
struck immediately in amid the breakers below the American Fall. He
hugged the cross freshets instead of striking out into the smoother
water. I asked him why he did so, and he replied that they were
directed outwards, not downwards. The struggle, however, to prevent
the bow of the boat from being turned by them, was often very severe.
The spray was in general blinding, but at times it disappeared and
yielded noble views of the fall. The edge of the cataract is crimped
by indentations which exalt its beauty. Here and there, a little
below the highest ledge, a secondary one juts out; the water strikes
it and bursts from it in huge protuberant masses of foam and spray. We
passed Goat Island, came to the Horseshoe, and worked for a time along
its base, the boulders over which Conroy and myself had scrambled a
few days previously lying between us and the cataract. A rock was
before us, concealed and revealed at intervals, as the waves passed
over it. Our leader tried to get above this rock, first on the
outside of it. The water, however, was here in violent motion. The
men struggled fiercely, the older one ringing out an incessant peal of
command and exhortation to the younger. As we were just clearing the
rock, the bow came obliquely to the surge; the boat was turned
suddenly round and shot with astonishing rapidity down the river. The
men returned to the charge, now trying to get up between the
half-concealed rock and the boulders to the left. But the torrent set
in strongly through this channel. The tugging was quick and violent,
but we made little way. At length, seizing a rope, the principal
oarsman made a desperate attempt to get upon one of the boulders,
hoping to be able to drag the boat through the channel; but it bumped
so violently against the rock, that the man flung himself back and
relinquished the attempt.
We returned along the base of the American Fall, running in and out
among the currents which rushed, from it laterally into the river.
Seen from below the American Fall is certainly exquisitely beautiful,
but it is a mere frill of adornment to its nobler neighbour the
Horseshoe. At times we took to the river, from the centre of which
the Horseshoe Fall appeared especially magnificent. A streak of cloud
across the neck of Mont Blanc can double its apparent height, so here
the green summit of the cataract shining above the smoke of spray
appeared lifted to an extraordinary elevation. Had Hennepin and La
Hontan seen the fall from this position, their estimates of the height
would have been perfectly excusable.
*****
From a point a little way below the American Fall, a ferry crosses
the river, in summer, to the Canadian side. Below the ferry is a
suspension bridge for carriages and foot-passengers, and a mile or two
lower down is the railway suspension bridge. Between ferry and bridge
the river Niagara flows unruffled; but at the suspension bridge the
bed steepens and the river quickens its motion. Lower down the gorge
narrows, and the rapidity and turbulence increase. At the place
called the 'Whirlpool Rapids' I estimated the width of the river at
300 feet, an estimate confirmed by the dwellers on the spot. When it
is remembered that the drainage of nearly half a continent is
compressed into this space, the impetuosity of the river's rush may be
imagined. Had it not been for Mr. Bierstädt, the distinguished
photographer of Niagara, I should have quitted the place without
seeing these rapids; for this, and for his agreeable company to the
spot, I have to thank him. From the edge of the cliff above the
rapids, we descended, a little, I confess, to a climber's disgust, in
an 'elevator,' because the effects are best seen from the water level.
Two kinds of motion are here obviously active, a motion of translation
and a motion of undulation--the race of the river through its gorge,
and the great waves generated by its collision with, and rebound from,
the obstacles in its way. In the middle of the river the rush and
tossing are most violent; at all events, the impetuous force of the
individual waves is here most strikingly displayed. Vast pyramidal
heaps leap incessantly from the river, some of them with such energy
as to jerk their summits into the air, where they hang momentarily
suspended in crowds of liquid spherules. The sun shone for a few
minutes. At times the wind, coming up the river, searched and sifted
the spray, carrying away the lighter drops, and leaving the heavier
ones behind. Wafted in the proper direction, rainbows appeared and
disappeared fitfully in the lighter mist. In other directions the
common gleam of the sunshine from the waves and their shattered crests
was exquisitely beautiful. The complexity of the action was still
further illustrated by the fact, that in some cases, as if by the
exercise of a local explosive force, the drops were shot radially from
a particular centre, forming around it a kind of halo.
The first impression, and, indeed, the current explanation of these
rapids is, that the central bed of the river is cumbered with large
boulders, and that the jostling, tossing, and wild leaping of the
water there, are due to its impact against these obstacles. I doubt
this explanation. At all events, there is another sufficient reason
to be taken into account. Boulders derived from the adjacent cliffs
visibly cumber the sides of the river. Against these the water rises
and sinks rhythmically but violently, large waves being thus produced.
On the generation of each wave, there is an immediate compounding of
the wave-motion with he river-motion. The ridges, which in still
water would proceed in circular curves round the centre of
disturbance, cross the river obliquely, and the result is that at the
centre waves commingle, which have really been generated at the sides.
In the first instance, we had a composition of wave-motion with
river-motion; here we have the coalescence of waves with waves. Where
crest and furrow cross each other, the motion is annulled; where
furrow and furrow cross, the river is ploughed to a greater depth; and
where crest and crest aid each other, we have that astonishing leap of
the water which breaks the cohesion of the crests, and tosses them
shattered into the air. From the water level the cause of the action
is not so easily seen; but from the summit of the cliff the lateral
generation of the waves, and their propagation to the perfectly
obvious. If this explanation be correct, the phenomena observed at
the Whirlpool Rapids form one of the grandest illustrations of the
principle of _interference_. The Nile 'cataract,' Mr. Huxley informs
me, offers more moderate examples of the same action.
At some distance below the Whirlpool Rapids we have the celebrated
whirlpool itself. Here the river makes a sudden bend to the
north-east, forming nearly a right angle with its previous direction.
The water strikes the concave bank with great force, and scoops it
incessantly away. A vast basin has been thus formed, in which the
sweep of the river prolongs itself in gyratory currents. Bodies and
trees which have come over the falls, are stated to circulate here for
days without finding the outlet. From various points of the cliffs
above, this is curiously hidden. The rush of the river into the
whirlpool is obvious enough; and though you imagine the outlet must be
visible, if one existed, you cannot find it. Turning, however, round
the bend of the precipice to the north-east, the outlet comes into
view.
The Niagara season was over; the chatter of sightseers had ceased, and
the scene presented itself as one of holy seclusion and beauty. I
went down to the river's edge, where the weird loneliness seemed to
increase. The basin is enclosed by high and almost precipitous
banks--covered, at the time, with russet woods. A kind of mystery
attaches itself to gyrating water, due perhaps to the fact that we are
to some extent ignorant of the direction of its force. It is said
that at certain points of the whirlpool, pine-trees are sucked down,
to be ejected mysteriously elsewhere. The 'water is of the brightest
emerald-green. The gorge through which it escapes is narrow, and the
motion of the river swift though silent. The surface is steeply
inclined, but it is perfectly unbroken. There are no lateral waves,
no ripples with their breaking bubbles to raise a murmur; while the
depth is here too great to allow the inequality of the bed to ruffle
the surface. Nothing can be more beautiful than this sloping liquid
mirror formed by the Niagara, in sliding from the whirlpool.
The green colour is, I think, correctly accounted for in the last
Fragment. While crossing the Atlantic in 1872-73 I had frequent
opportunities of testing the explanation there given. Looked properly
down upon, there are portions of the ocean to which we should hardly
ascribe a trace of blue; at the most, a mere hint of indigo reaches
the eye. The water, indeed, is practically black, and this is an
indication both of its depth and of its freedom from mechanically
suspended matter. In small thicknesses water is sensibly transparent
to all kinds of light; but, as the thickness increases, the rays of
low refrangibility are first absorbed, and after them the other rays.
Where, therefore, the water is very deep and very pure, all the
colours are absorbed, and such water ought to appear black, as no
light is sent from its interior to the eye. The approximation of the
Atlantic Ocean to this condition is an indication of its extreme
purity.
Throw a white pebble into such water; as it sinks it becomes greener
and greener, and, before it disappears, it reaches a vivid blue-green.
Break such a pebble into fragments, each of these will behave like the
unbroken mass; grind the pebble to powder, every particle will yield
its modicum of green; and if the particles be so fine as to remain
suspended in the water, the scattered light will be a uniform green.
Hence the greenness of shoal water. You go to bed with the black
Atlantic around you. You rise in the morning, find it a vivid green,
and correctly infer that you are crossing the bank of Newfoundland.
Such water is found charged with fine matter in a state of mechanical
suspension. The light from the bottom may sometimes come into play,
but it is not necessary. A storm can render the water muddy, by
rendering the particles too numerous and gross. Such a case occurred
towards the close of my visit to Niagara. There had been rain and
storm in the upper lake-regions, and the quantity of suspended matter
brought down quite extinguished the fascinating green of the
Horseshoe.
Nothing can be more superb than the green of the Atlantic waves, when
the circumstances are favourable to the exhibition of the colour. As
long as a wave remains unbroken no colour appears; but when the foam
just doubles over the crest, like an Alpine snow-cornice, under the
cornice we often see a display of the most exquisite green. It is
metallic in its brilliancy. But the foam is necessary to its
production. The foam is first illuminated, and it scatters the light
in all directions; the light which passes through the higher portion
of the wave alone reaches the eye, and gives to that portion its
matchless colour. The folding of the wave, producing as it does, a
series of longitudinal protuberances and furrows which act like
cylindrical lenses, introduces variations in the intensity of the
light, and materially enhances its beauty.
*****
We have now to consider the genesis and proximate destiny of the Falls
of Niagara. We may open our way to this subject by a few preliminary
remarks upon erosion. Time and intensity are the main factors of
geologic change, and they are in a certain sense convertible. A
feeble force acting through long periods, and an intense force acting
through short ones, may produce approximately the same results. To
Dr. Hooker I have been indebted for some specimens of stones, the
first examples of which were picked up by Mr. Hackworth on the shores
of Lyell's Bay, near Wellington, in New Zealand. They were described
by Mr. Travers in the 'Transactions of the New Zealand Institute.'
Unacquainted with their origin, you would certainly ascribe their
forms to human workmanship. They resemble knives and spear-heads,
being apparently chiselled off into facets, with as much attention to
symmetry as if a tool, guided by human intelligence, had passed over
them. But no human instrument has been brought to bear upon these
stones. They have been wrought into their present shape by the
wind-blown sand of Lyell's Bay. Two winds are, dominant here, and
they in succession urged the sand against opposite sides of the stone;
every little particle of sand chipped away its infinitesimal bit of
stone, and in the end sculptured these singular forms. [Footnote:
'These stones, which have a strong resemblance to works of human art,
occur in great abundance, and of various sizes, from half-an-inch to
several inches in length. A large number were exhibited showing the
various forms, which are those of wedges, knives, arrow-heads, &c, and
all with sharp cutting edges.
'Mr. Travers explained that, notwithstanding their artificial
appearance, these stones were formed by the cutting action of the
wind-driven sand, as it passed to and fro over an exposed
boulder-bank. He gave a minute account of the manner in which the
varieties of form are produced, and referred to the effect which the
erosive action thus indicated would have on railway and other works
executed on sandy tracts.
'Dr. Hector stated that although, as a group, the specimens on the
table could not well be mistaken for artificial productions, still the
forms are so peculiar, and the edges, in a few of them, so perfect,
that if they were discovered associated with human works, there is no
doubt that they would have been referred to the so-called "stone
period."'--Extracted from the Minutes of the Wellington Philosophical
Society, February 9, 1869.]
The Sphynx of Egypt is nearly covered up by the sand of the desert.
The neck of the Sphynx is partly cut across, not, as I am assured by
Mr. Huxley, by ordinary weathering, but by the eroding action of the
fine sand blown against it. In these cases Nature furnishes us with
hints which may be taken advantage of in art; and this action of sand
has been recently turned to extraordinary account in the United
States. When in Boston, I was taken by my courteous and helpful
friend, Mr. Josiah Quincey, to see the action of the sand-blast. A
kind of hopper containing fine silicious sand was connected with a
reservoir of compressed air, the pressure being variable at pleasure.
The hopper ended in a long slit, from which the sand was blown. A
plate of glass was placed beneath this slit, and caused to pass slowly
under it; it came out perfectly depolished, with a bright opalescent
glimmer, such as could only be produced by the most careful grinding.
Every little particle of sand urged against the glass, having all its
energy concentrated on the point of impact, formed there a little pit,
the depolished surface consisting of innumerable hollows of this
description.
But this was not all. By protecting certain portions of the surface,
and exposing others, figures and tracery of any required form could be
etched upon the glass. The figures of open iron-work could be thus
copied; while wire-gauze placed over the glass produced a reticulated
pattern. But it required no such resisting substance as iron to
shelter the glass. The patterns of the finest lace could be thus
reproduced; the delicate filaments of the lace itself offering a
sufficient protection. All these effects have been obtained with a
simple model of the sand-blast devised by my assistant. A fraction of
a minute suffices to etch upon glass a rich and beautiful lace
pattern. Any yielding substance may be employed to protect the glass.
By diffusing the shock of the particle, such substances practically
destroy the local erosive power. The hand can bear, without
inconvenience, a sand-shower which would pulverise glass. Etchings
executed on glass with suitable kinds of ink are accurately worked out
by the sandblast. In fact, within certain limits, the harder the
surface, the greater is the concentration of the shock, and the more
effectual is the erosion. It is not necessary that the sand should be
the harder substance of the two; corundum, for example, is much harder
than quartz; still, quartz-sand can not only depolish, but actually
blow a hole through a plate of corundum. Nay, glass may be depolished
by the impact of fine shot; the grains in this case bruising the
glass, before they have time to flatten and turn their energy into
heat.
And here, in passing, we may tie together one or two apparently
unrelated facts. Supposing you turn on, at the lower part of a house,
a cock which is fed by a pipe from a cistern at the top of the house,
the column of water, from the cistern downwards, is set in motion. By
turning off the cock, this motion is stopped; and, when the turning
off is very sudden, the pipe, if not strong, may be burst by the
internal impact of the water. By distributing the turning of the cock
over half a second of time, the shock and danger of rupture may be
entirely avoided. We have here an example of the concentration of
energy in time. The sand-blast illustrates the concentration of
energy in space. The action of flint and steel is an illustration of
the same principle. The heat required to generate the spark is
intense; and the mechanical action, being moderate, must, to produce
fire, be in the highest degree concentrated. This concentration is
secured by the collision of hard substances. Calc-spar will not
supply the place of flint, nor lead the place of steel, in the
production of fire by collision. With the softer substances, the
total heat produced may be greater than with the hard ones, but, to
produce the spark, the heat must be intensely localised.