998 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
[June 14, 1873. 
bled down the lower faces of the barriers. Almost every 
valley in Switzerland furnishes examples of this kind; 
the untenable hypothesis of earthquakes, once so readily 
resorted to in accounting for these gorges, being now for 
the most part abandoned. 
“ And now we come to Niagara. Soon after Europeans 
had taken possession of the country, the conviction appears 
to have arisen that the deep channel of the river Niagara 
below the falls had been excavated by the cataract. In 
Mr. Bakewell’s ‘ Introduction to Geology,’ the prevalence 
of this belief has been referred to : it is expressed thus by 
Professor Joseph Henry in the ‘Transactions of the Al¬ 
bany Institute ‘ In viewing the position of the falls, 
and the features of the country round, it is impossible not 
to be impressed with the idea that this great natural race¬ 
way has been formed by the continued action of the 
irresistible Niagara, and that the falls, beginning at 
Lewiston have, in the course of ages, worn back the rocky 
strata to their present site.’ 
“ A. connected image of the origin and progress of the 
cataract is easily obtained. Walking northward from the 
village of Niagara Falls by the side of the river, we have 
to our left the deep and comparatively narrow gorge 
through which the Niagara flows. The bounding cliffs 
of this gorge are from 300 to 350 feet high. We reach 
the whirlpool, trend to the north-east, and after a little 
time gradually resume our northward course. Finally, at 
about seven miles from the present falls, we come to the 
edge of a declivity which informs us that we have been 
hitherto walking on table land. At some hundreds of feet 
below us is a comparatively level plain, which stretches 
to Lake Ontario. The declivity marks the end of the 
precipitous gorge of the Niagara. Here the river escapes 
from its steep mural boundaries, and in a widened bed pur¬ 
sues its way to the lake which finally receives its waters. 
“ The fact that in historic times, even within the memory 
of man, the fall has sensibly receded, prompts the ques¬ 
tion, how far has this recession gone ? At what point did 
the ledge which thus continually creeps backwards begin 
its retrograde course ? To minds disciplined in such re¬ 
searches the answer has been and will be, at the precipi¬ 
tous declivity which crossed the Niagara from Lewiston 
on the .American to Queenston on the Canadian side. 
Over this transverse barrier the united affluents of all the 
upper lakes once poured their waters, and here the work 
of erosion began. The dam, moreover, was demonstrably 
of sufficient height to cause the river above it to submerge 
Goat Island; and this would perfectly account for the 
finding by Sir Charles Lyell, Mr. Hall, and others, in the 
sand and gravel of the island, the same fluviatile shells as 
are now found in the Niagara River higher up. It would 
also account for those deposits along the sides of the 
river, the discovery of which enabled Lyell, Hall, and 
Ramsay, to reduce to demonstration the popular belief 
that the Niagara once flowed through a shallow valley. 
“ The physics of the problem of excavation, which I made 
clear to my mind before quitting Niagara, are revealed by 
a close inspection of the present Horseshoe Fall. Here 
we see evidently that the greatest weight of water bends 
over the very apex of the Horseshoe. In a passage in his 
excellent chapter on Niagara Falls, Mr. Hall alludes to 
this fact. Here we have the most copious and the most 
violent whirling of the shattered liquid; here the most 
powerful eddies recoil against the shale. From this por¬ 
tion of the fall, indeed, the spray sometimes rises without 
solution of continuity to the region of clouds, becoming 
gradually more attenuated, and passing finally through - 
the condition of true cloud into invisible vapour, which is 
sometimes reprecipitated higher up. All the phenomena 
point distinctly to the centre of the river as the place of < 
greatest mechanical energy, and from the centre the i 
vigour of the fall gradually dies away towards the sides. ; 
The horseshoe form, with the concavity facing downwards, ' 
is . an obvious and necessary consequence of this action. ] 
Right along the middle of the river the apex of the curve s 
pushes its way backwards, cutting along the centre a deep 1 
r and comparatively narrow groove, and draining the sides 
; as it passes them. Hence the remarkable discrepancy 
r between the widths of the Niagara above and below the 
• Horseshoe. All along its course, from Lewiston Heights 
to its present position, the form of the fall was probably 
that of a horseshoe; for this is merely the expression of the 
greater depth, and consequently greater excavating power, 
of the centre of the river. The gorge, moreover, varies 
in width as the depth of the centre of the ancient river 
varied, being narrowest where that depth was greatest. 
“ The vast comparative erosive energy of the Horseshoe 
Fall comes strikingly into view when it and the American 
1 all are compared together. The American branch of 
the upper river is cut at a right angle by the gorge of the 
Niagara. Here the Horseshoe Fall was the real exca¬ 
vator. It cut the rock and formed the precipice over 
which the American Fall tumbles. But since its forma¬ 
tion, the erosive action of the American Fall has been 
almost nil, while the Horseshoe has cut its way for 500 
yards across the end of Goat Island, and is now doubling 
back to excavate its channel parallel to the length of the 
island. This point, I have just learned, has not escaped 
the acute observation of Professor Ramsay. The river 
bends ; the Horseshoe immediately accommodates itself 
to the bending, and will follow implicitly the direction of 
the deepest water in the upper stream. The flexibility of 
the gorge, if I may use the term, is determined by the 
flexibility of the river channel above it. Were the Niagara 
above the fall sinuous, the gorge would obediently follow 
its sinuosities. Once suggested, no doubt geographers 
will be able to point out many examples of this action. 
The. Zambesi is thought to present a great difficulty to the 
erosion theory, because of the * sinuosity of the chasm 
below the Victoria Falls. But, assuming the basalt to be 
of tolerably uniform texture, had the river been examined 
before the formation of this sinuous channel, the present 
zigzag course of the gorge below the fall could, I am per¬ 
suaded, have been predicted, while the sounding of the 
present river would enable us to predict the course to be 
pursued by the erosion in the future. 
“But not only has the Niagara River cut the gorge, it 
has carried away the chips of its own workshop. The 
shale being probably crumbled is easily carried aw r ay. 
But at the base of the fall we find the huge boulders 
already described, and by some means or other these are 
removed down the river. The ice which fills the gorge 
in winter, and which grapples with the boulders, has been 
regarded as the transporting agent. Probably it is so to 
some. extent. But erosion acts without ceasing on the 
abutting points of the boulders, thus withdrawing their 
support and urging them gradually down the river. Solu¬ 
tion also does its portion of the work. That solid matter 
is carried down is proved by the difference of depth 
between the Niagara River and Lake Ontario, where the 
river enters it. The depth falls from 72 feet to 20 feet, 
in consequence of the deposition of solid matter caused by 
the diminished motion of the river. 
“ In conclusion, we may say a word regarding the proxi¬ 
mate future of Niagara. At the rate of excavation 
assigned to it by Sir Charles Lyell, namely, a foot a year, 
five thousand years or so will carry the Horseshoe Fall 
far higher than Goat Island. As the gorge recedes it 
will drain, as it has hitherto done, the banks right and 
left of it, thus leaving a nearly level terrace between 
Goat Island and the end of the gorge. Higher up it will 
totally drain the American branch of the river, the channel 
of which in due time will become cultivable land. The 
American Fall will then be transformed into a dry preci¬ 
pice, forming a simple continuation of the cliffy boundary 
of. the Niagara. At the place occupied by the fall at 
this moment we shall have the gorge enclosing a right 
angle, a second whirlpool being the consequence of this, 
lo those who visit Niagara a few millenniums hence I 
leave the verification of this prediction. All that can be 
said is, that if the causes now in action continue to act, it 
will prove itself literally true.” 
