GEOLOGICAL WORK IN NORTH AMERICA.
This is a summary of their doings on the opposite side of the Atlantic
in Lyell's own words: "In all, we were absent about thirteen months,
less than one of them being spent on the ocean, nearly ten in active
geological field work, and a little more than two in cities, during
which I gave by invitation some geological lectures to large and most
patient audiences."
To this may be added "three dozen boxes of specimens," and a mass of
notes on the raised beaches of the Canadian lakes, the glacial drift,
the falls of Niagara, and other questions of post-tertiary geology, as
well as on the tertiary, cretaceous, coal, and older rocks. These
afterwards produced a crop of about twenty papers, which appeared in
various scientific periodicals. The principal results and the general
impressions of the journey were worked up into a book entitled "Travels
in North America," which was published in 1845.
A geologist who has been trained among the scenery of Britain finds his
first view of the Alps to be the beginning of a new chapter in the Book
of Nature, but a visit to America more like the beginning of a new
volume. There almost everything is on a colossal scale--rivers, lakes,
forests, prairies, distances, such as cannot be matched, at any rate in
the more accessible parts of Europe. One may read of plains where the
sun rises and sets as from a sea; of lakes, like Superior, as big as
Ireland; of falls, like Niagara, where the neighbouring ground never
ceases to quiver with the thud of the precipitated water; of rivers well
nigh half a league wide while their waters still are far from the sea.
But such things must be seen to be realised. In our own island Nature
seems to be working at the present time on a scale comparatively puny;
she must be watched as she puts forth her full strength before the
adequacy of modern causes can be duly appreciated, and the history of
the past can be understood by comparing it with that of the present.
The invitation to cross the Atlantic hardly could have reached Lyell at
a more opportune epoch of his life. In his forty-fourth year, he was in
full vigour both of mind and of body. A long course of study and of
travel in Europe had trained him to be a keen observer, had enabled him
to appreciate the significance of phenomena, and had supplied him with
stores of knowledge on which he could draw for the interpretation of
difficulties. America also offered a splendid field for work. Much of
the country had been settled and brought under cultivation at no distant
date; new tracts were being made accessible almost daily. Geologists of
mark were few and far between, so that large areas awaited exploration,
and in many places the traveller found a virgin field. The Geological
Survey of Canada was just then being organised, the labours of the
National Survey in the United States had not yet begun, though State
surveys were at work, and had already borne good fruit. Indeed, while
Lyell was in the country, the third meeting of the Association of
American Geologists was held at Boston, and among those present were
several men whose names will always occupy an honoured place in the
history of the science. Still, at almost every step the observer might
be rewarded by some discovery or by some fascinating problem which would
give a direction to his future work.
The Lyells left Liverpool on July 20th, 1841, and reached Halifax on the
31st of the month, whence they went on to Boston, arriving there on
August 2nd. The close resemblance of the shells scattered on the shore
at the latter place to those in a similar situation in Britain was one
of the first things which Lyell noted; for he found that about one-third
were actually identical, a large number of the remainder being
geographical representatives, and only a few affording characteristic or
peculiar forms. For this correspondence, which, as he writes, had a
geological significance, he was not prepared. The drifts around Boston,
good sections of which had been exposed in making cuttings for railways,
resembled very closely the deposits which he had seen in Scandinavia.
Were it not, he says, for the distinctness of the plants and of the
birds, he could have believed himself in Scotland, or in some part of
Northern Europe. These masses of sand and pebbles, derived generally
from the more immediate neighbourhood, though containing sometimes huge
blocks which had travelled from great distances, occasionally exceeded
200 feet in depth. Commonly, however, they were only of a moderate
thickness, and were found to rest upon polished and striated surfaces of
granite, gneiss, and mica-schist. The latter effects, at any rate, would
now be generally attributed to the action of land ice, but Lyell thought
that the great extent of low country, remote from any high mountains,
made this agent practically impossible, and supposed that the work both
of transport and of attrition had been done during a period of
submergence by floating ice and grounding bergs.
After a few days' halt at Boston, they moved on to Newhaven, where
Professor Silliman showed him dykes and intrusive sheets of columnar
greenstone altering red sandstone, their general appearance and
association recalling Salisbury Crags and other familiar sections near
Edinburgh. In this district Lyell found the grasshoppers as numerous and
as noisy as in Italy, watched the fireflies sparkling in the darkness,
and had his first sight of a humming-bird, and of a wildflower hardly
less gorgeous, the scarlet lobelia.
From Newhaven they went to New York, and up the Hudson River in one of
the great steamers, past the noble colonnade of basalt called the
Palisades, and along the winding channel through the gneissic hills to
Albany. Here a geological survey had been established by the State, and
its members had already done good work, which, however, was not
altogether welcome to its employers, for they had dispelled all hopes of
finding coal within the limits of the State. This, as Lyell says, was a
great disappointment to many; but it did good in checking the rashness
of private speculation, and in preventing the waste of the large sums of
money which had been annually squandered in trials to find coal in
strata which really lay below the Carboniferous system. The advantage to
the revenues of the state by the stoppage of this outlay and the more
profitable direction given to private enterprise were sufficient, Lyell
remarks, "to indemnify the country, on mere utilitarian grounds, for
the sum of more than two hundred thousand dollars so munificently
expended on geological investigation."
From Albany Lyell travelled to Niagara. The journey was planned in order
to give him an opportunity of examining a connected series of formations
from the base of the Palaeozoic, where it rested on the ancient gneiss,
to the coalfield of Pennsylvania; and he had the great advantage of
being accompanied by one of the most eminent of American geologists, Mr.
James Hall.
"In the course of this third tour," Lyell writes,[95] "I
became convinced that we must turn to the New World if we
want to see in perfection the oldest monuments of the
earth's history, so far as relates to its earliest
inhabitants. Certainly in no other country are these ancient
strata developed on a grander scale, or more plentifully
charged with fossils; and as they are nearly horizontal, the
order of their relative position is always clear and
unequivocal. They exhibit, moreover, in their range from the
Hudson River to the Niagara some fine examples of the
gradual manner in which certain sets of strata thin out when
followed for hundreds of miles; while others, previously
wanting, become intercalated in the series."
He observed, also, that while some species of the fossils contained in
these rocks were common to both sides of the Atlantic, the majority were
different; thus disproving the statement which at that time was often
made--namely, that in the rocks older than the Carboniferous system the
fossil fauna in different parts of the globe was almost everywhere the
same, and showing that, "however close the present analogy of forms may
be, there is evidence of the same law of variation in space as now
prevails in the living creation."
Lyell made a thorough study of the Falls of Niagara, to which he paid a
second visit before his return to England. The first view of these
Falls, like the first sight of a great snow-clad peak, is one of those
epochs of life of which the memory can never fade. It stirred Lyell to
an unwonted enthusiasm. At the first view, from a distance of about
three miles, with not a house in sight--it would be impossible, we
think, to find such a spot now; "nothing but the greenwood, the falling
water, and the white foam"--he thought the falls "more beautiful but
less grand" than he had expected; but, after spending some days in the
neighbourhood, now watching the river sweeping onwards to its final
plunge, here in the turmoil of the rapids, there in its gliding, so
smooth but so irresistible; now gazing at that mighty wall of 'shattered
chrysoprase' and rainbow-tinted spray, which floats up like the steam of
Etna; now looking down from the brink of the crags below the fall upon
those rapids, where the billows of green water roll and plunge like the
waves of the ocean, he "at last learned by degrees to comprehend the
wonders of the scene, and to feel its full magnificence."
But, keenly as he might be impressed with the poetic grandeur of the
falls, he could not forget the scientific questions which were ever
present to his mind. The gorge of Niagara offered a problem for solution
which had for him a special fascination. Not only did it illustrate on a
grand scale the potencies of water in rapid motion, but also it
furnished data for estimating the period during which this agent had
been at work. The gorge has been carved in a plateau of Silurian rock,
which terminates, seven miles below the falls, in a precipitous
escarpment overhanging Queenstown. There was a time when that gorge did
not exist, when the river first took its course along the plateau on its
way from Lake Erie, and plunged over the brink of the escarpment. The
valley at first was nothing more than a shallow trench excavated in the
drift which covers the surface of the country--such an one as may still
be seen between Lake Erie and the falls--but the river, slowly and
steadily, has cut its way back through the rocky plateau from the first
site of the falls near Queenstown to their present position. The upper
part of this plateau consists of a thick bed of hard limestone, but
beneath this the deposits become softer; and the lowest bed is the most
perishable. The water, as it plunges down, undermines the overlying
rock. The gorge began at once to be developed, and it has ever since
continued to retreat towards Lake Erie. Every year makes some slight
change. This becomes more marked when old histories are consulted and
old drawings compared with the present aspect of the scene. Father
Hennepin's sketch, of which Lyell gives a copy,[96] rude and incorrect
as it is, proves beyond all question that the changes in the
neighbourhood of Table Rock have been very considerable, for it shows
that on this side a third and much narrower cascade fell athwart the
general course of the main mass of water. This cascade, by the time of
Kalm's[97] visit in 1751, had ceased to be conspicuous, and had quite
disappeared before the date of Lyell's visit. The Horseshoe Fall also at
the present time is less worthy of the name than it was at that date,
for its symmetry has been seriously marred by a deep notch which the
northern stream has cut in the more central part of the curve.[98]
Careful inquiry convinced Lyell that the slow recession of the falls was
an indubitable fact, and that its rate, on an average, was about a foot
a year. As the gorge is about seven miles long, this would fix its
beginning about 35,000 years ago.[99]
From Niagara Falls they travelled, still in Mr. Hall's company, by
Buffalo to Geneva, examining on the way some red, green, and bluish-grey
marls, with beds of gypsum and occasional salt springs, which, though
older than the coal measures of England, closely resembled in appearance
the upper part of the New Red Sandstone of Britain. Finally, after
crossing the outcrops of the Devonian system, they reached Pennsylvania,
where Lyell obtained his first view of the coal measures of North
America, and was no less interested than surprised to find how closely
the whole series corresponded with that of Britain. He saw sandstones
"such as are used for building in Newcastle or Edinburgh, dark shales
often full of ferns 'spread out as in a herbarium,' beds and nodules of
clay-ironstone, seams of bituminous coal, varying in thickness from a
few inches to some yards, and, beside these, an underlying coarse grit,
passing down into a conglomerate, which was very like the millstone grit
of England. The underclays beneath the seam of coal were full of stems
and rootlets of Stigmaria, and the sight of these confirmed him in the
opinion that the coal was formed of the remains of plants which had
grown upon the spot."[100] After examining the district, they returned
to Albany, and went thence to New York and Philadelphia, picking up on
the way as much geological information as was possible.
New Jersey afforded some highly interesting sections of rocks belonging
to the Cretaceous system, for these, though in mineral character
resembling the greensands on the eastern side of the Atlantic, contained
fossils which corresponded more closely with those of the white chalk,
some species being actually identical. This fact was another proof that,
though there had been in past ages a general similarity in the fauna of
any period, geographical provinces had existed no less than they do at
the present time.
Lyell had examined, as mentioned above, the bituminous coals in the
undisturbed region of Pennsylvania, the next step was to study the beds
of anthracite, with the associated strata, in the folded and broken
ridges of the Alleghany Mountains. In this part of his work he had the
inestimable advantage of being guided by Professor H. O. Rogers, whose
name is inseparably connected with the geology of that classic region.
The Alleghanies or Appalachians consist of a series of Silurian,
Devonian, and Carboniferous strata in orderly sequence, "folded" (to use
Lyell's words) "as if they had been subjected to a great lateral
pressure when in a soft and yielding state, large portions having
afterwards been removed by denudation. The long uniform, parallel
ridges, with intervening valleys like so many gigantic wrinkles and
furrows, are in close connection with the geological structure," and the
rocks are most disturbed on the south-eastern flank of the chain, where
the folds sometimes bend over to the west; in other words, the greatest
disturbances are on the side nearest to the fundamental gneiss and the
basin of the Atlantic--facts which probably stand in the relation of
effect and cause.
It was a surprise to Lyell, on reaching the anthracite district around
Pottsville on the Schuylkill, to see "a flourishing manufacturing town
with the tall chimneys of a hundred furnaces, burning night and day, yet
quite free from smoke." Special contrivances, of course, are requisite
to secure the combustion of anthracite, especially in household
fireplaces, but he had no hesitation in declaring that he preferred the
use of it, notwithstanding the stove-like heat produced, to that of the
bituminous coal consumed in London, with the penalty of living in an
atmosphere dark with smoke and foul with smuts.
The seams of anthracite in this district are sometimes worked in
open-air excavations, but as the strata have been bent into a vertical
position the beds above and below, when the anthracite has been quarried
out, are left like the walls of a fissure, and thus can be examined
with the greatest ease.
Here also the "roof" of the seam proved to be a dark shale full of the
usual plant-remains, among which were some British species of ferns, and
the "floor" was an "underclay" containing the stems and rootlets of
Stigmaria. Lyell also observed that the beds of detrital
materials--sandstones, shales, etc.--were less persistent than those of
coal, and that the way in which the former became thicker towards the
south-east indicated that this was the direction of the ancient land
region from which they had been derived. The result of his examination
satisfied him that the anthracite of the Appalachians was identical in
age, generally speaking, with the bituminous coal which he had
previously examined, and was merely a fragment of the great continuous
coalfield of Pennsylvania, Virginia, and Ohio, which lies about forty
miles away to the westward.
After returning to Philadelphia Mr. and Mrs. Lyell went, _via_ New York,
to Boston, where he had been engaged to deliver a course of twelve
lectures on geology at the Lowell Institute. To the courses here
admission was free, but the tickets were given under certain
restrictions. For Lyell's lectures about 4,500 were issued, and the
class, he states, usually consisted of more than 3,000 persons. It had
therefore to be sub-divided and each lecture to be repeated. The
audience was composed "of persons of both sexes, of every station in
society, from the most affluent and eminent in the various learned
professions to the humblest mechanics, all well-dressed, and observing
the utmost decorum."
At the conclusion of the lectures the Lyells travelled southwards, so
that he might take advantage of the more genial climate and continue his
geological work in the open air. He first halted at Richmond in
Virginia, and from that place visited the Tertiary deposits in the
vicinity of the James River. The more interesting of these are of
Miocene age, and he observed that the fossils of Maryland and Virginia
resembled those of Touraine and the neighbourhood of Bordeaux more
closely than those from the coralline Crag of Suffolk, especially in the
presence of genera indicative of a warm climate.
From this place they travelled across the "pine barrens"--where their
train was stopped for the night by the slippery condition of the
rails--to Weldon in North Carolina. Here Lyell saw the Great Dismal
Swamp, a morass which extends for about forty miles from the
neighbourhood of this town to Norfolk in Virginia. Like the bogs of
Ireland, this marshy plain, some five-and-twenty miles across, is rather
higher at the middle than at the edges. Its surface "is carpeted with
mosses, and densely covered with ferns and reeds, above which many
evergreen shrubs and trees flourish, especially the white cedar
(_Cupressus thyoides_), which stands firmly supported by its long
tap-roots in the softest parts of the quagmire. Over the whole, the
deciduous cypress (_Taxodium distichum_) is seen to tower with its
spreading top, in full leaf, in the season when the sun's rays are
hottest, and when, if not interrupted by a screen of foliage, they might
soon cause the fallen leaves and dead plants of the preceding autumn to
decompose, instead of adding their contributions to the peaty mass. On
the surface of the whole morass lie innumerable trunks of large and
tall trees, blown down by the winds, while thousands of others are
buried at various depths in the black mire below. They remind the
geologist of the prostrate position of large stems of Sigillaria and
Lepidodendron, converted into coal in ancient Carboniferous rocks."[101]
At Charleston they had practically passed beyond the southern limit of
the winter snowfall, the greatest enemy of the field-geologist, and
could carry on work without fear of interruption. Here they found
flowers "at the end of December still lingering in the gardens," and
were in the region of the palmetto palm. Few things during this rather
lengthy journey impressed Lyell more than the facility of locomotion in
a district which, comparatively speaking, was a new settlement, and was
still in places thinly peopled, together with the general good quality
of the accommodation for travellers. In this respect they had fared much
worse during the previous year, when they were travelling through some
of the more populous parts of France, such as Touraine and Brittany.
After a journey through the pinewoods, they reached Augusta in Georgia,
where another group of Tertiary deposits invited a halt. Those belonging
to the Eocene period lie further down the Savannah River, so that a
journey was made for the purpose of examining them, in the course of
which, near the town of the same name as the river, Lyell also saw the
clay in which remains of the mastodon and of other extinct mammals had
been found. The muddy beach, with the tracks of racoons and opossums,
gave him some hints as to the history of fossil footprints, so that on
the whole very much interesting geology was the reward of a three weeks'
stay in South Carolina. Then they once more turned their faces
northward, and made their way, working at geology as they went, to
Philadelphia, where they found themselves again in the region of colder
winters at the present, and of erratic boulders as memorials of the
past.
Six weeks were spent in Philadelphia, but Lyell's time was largely taken
up by the delivery of a short course of lectures on geology.
Pennsylvania, however, added to his experiences in another way, for the
state had passed through a commercial crisis, and was unable to pay the
interest on its funded debt. The soreness produced by this repudiation
will not be readily forgotten, for nearly two-thirds of the stock--the
whole amount of which was eight millions sterling--was held by British
owners, so that the loss was felt heavily on this side of the Atlantic.
In his "Travels" Lyell gives a brief history of this transaction, and
discusses the political causes of a crisis which had been hardly less
disastrous in America than in England.
They reached New York in the month of March, and spent several weeks
there, for in that neighbourhood both the ancient crystalline rocks and
the modern drift, with its erratics, afforded Lyell ample materials for
study, each of these being then reckoned (and they have not ceased to be
so counted) among the most difficult questions of geology. Towards the
middle of April he proceeded northward, in order to examine the
perplexing schists and less altered sedimentary deposits of the Taconic
range, rocks which from that time to this have given ample employment to
geologists. After this he found an opportunity of making use of the
lessons learnt on the flats by the James River, for he went to
Springfield and examined the famous footprints in the sandstone of
Connecticut. As the deposit was referred to the Trias, and the
footprints to birds, they were supposed to indicate the existence of
this class of the animal kingdom at the beginning of the Secondary era.
They have, however, now lost their special interest, since they are
generally assigned to reptiles. After the middle of April was past, the
travellers again reached Boston, from which city an excursion was made
in order to study the Tertiary deposits of the island called Martha's
Vineyard, off the coast of Massachusetts.
Returning to Philadelphia early in May, they went by Baltimore westward
to the valley of the Ohio, in order to examine the undisturbed country
beyond the folded district of the Alleghany Mountains. By this journey
another section was, in fact, run across the great coalfield of the
Eastern States, but considerably to the south of that which had been
examined in the autumn of the preceding year. This proved no less
interesting than the former one. At Brownsville, to take one instance
only, a seam of bituminous coal, ten feet in thickness, was seen
cropping out in the river cliff by the side of a large tributary of the
Ohio, where it was worked by horizontal galleries. Pittsburg and other
interesting localities in the neighbourhood were also visited, and then
the Lyells descended the Ohio River to Cincinnati. He had thus traversed
in descending order the succession of strata from the Carboniferous to
the Lower Silurian or Ordovician system, which is exposed in the
neighbourhood of that town. This, however, was not the only attraction
offered by Cincinnati. Some two-and-twenty miles distant is the famous
Big Bone Lick in Kentucky. Here some saline springs break out on a
nearly level and boggy river plain, which are still attractive to wild
animals, and often in past time lured them to their death in the
adjacent quagmires. Here the bones of the mastodon and the elephant, of
the megalonyx, stag, horse, and bison, have all been found, some in
great numbers; and the last-named animals had frequented the springs
within the memory of persons who were living at the time of Lyell's
visit. These bones are generally embedded in a black mud, at a depth of
about a dozen feet below the surface of the creek. Lyell suggests that
very probably the heavy mastodons and elephants were lost by shoving one
another off the tracks and into the more marshy ground as they struggled
to satisfy themselves at the springs; just as horses, cattle, and deer
get pushed into the stream in thronging to the rivers on the pampas of
South America.
From Cincinnati the travellers struck northward to Cleveland on Lake
Erie, going across a region which at that time was still being cleared
and settled, and getting an experience of that American form of
travellers' torture called a corduroy road. The lake-ridges--curious
mounds or terraces of water-worn materials--in the neighbourhood of
Cleveland afforded a new subject for an investigation which was
continued in the vicinity of Ontario. But before reaching this lake
Lyell spent a week at the Falls of Niagara, revising and enlarging the
work already done. During the time he investigated the buried channel
which appears to lead from the whirlpool to St. Davids, a league or so
to the west of Queenstown. This was supposed by Lyell and many
subsequent geologists to indicate part of an old course of the St.
Lawrence, which had afterwards been blocked up by glacial drifts. It is,
however, according to Professor J. W. Spencer, only a branch of a buried
valley, outside the Niagara canyon and much shallower than it, which has
been cut through by the present St. Lawrence, and has merely produced an
elongation of the chasm at the Whirlpool.[102] Another series of
lake-ridges was examined in the neighbourhood of Toronto. Here Lyell
traced them to a height of 680 feet above the level of Ontario, seeing
in all no less than eleven, some of them much reminding him of the oesar
which he had examined in Sweden. In regard to these lake-ridges he
writes thus:--
With the exception of the parallel roads or shelves of
Glenroy and some neighbouring glens of the Western Highlands
in Scotland, I never saw so remarkable an example of banks,
terraces, and accumulations of stratified sand and gravel,
maintaining, over wide areas, so perfect a horizontality, as
in the district north of Toronto.[103]
Leaving Toronto on June 18th, they descended the St. Lawrence to
Montreal and Quebec. The neighbourhood of either town afforded
opportunities for much interesting work, especially in the drift
deposits; the underlying ice-worn surfaces of crystalline or Palaeozoic
rock reminding Lyell of what he had seen in Scandinavia. At Montreal,
the great hill, which gives its name to the town built upon its lower
slopes, affords some highly interesting sections. It is composed of
Palaeozoic limestone, which has been pierced by more than one mass of
coarsely crystalline intrusive rock and cleft by many dykes of a more
compact character. Near the junction with the larger intrusive masses
the limestone becomes conspicuously crystalline, and the fossils
disappear, just as in the cases which Lyell had already seen about the
border of granite in Scandinavia. Some also of the igneous rocks now
possess a further interest, for they contain nepheline, a mineral not
very common. This, however, had not been recognised at the time of
Lyell's visit. The limestone in some of the quarries is wonderfully
ice-worn, and the overlying drifts are in many ways remarkable. Of these
drifts, Lyell examined various sections, at heights of from 60 to 200
feet above the St. Lawrence, finding plenty of sea-shells,[104] the
common mussel being in one place especially abundant. He also examined
some sections of stratified drifts between Montreal and Quebec, but
without obtaining any fossils, though they had been found by Captain
Bayford and others. The drifts, however, near the latter city were more
prolific. With their shells, indeed, he was already, to some extent,
familiar, for in the year 1835 he had received a collection from Captain
Bayford. This happened to reach London at a time when Dr. Beck of
Copenhagen was with him, and "great was our surprise," he writes, "on
opening the box to find that nearly all the shells agreed specifically
with fossils which, in the summer of the preceding year, I had obtained
at Uddevalla in Sweden." The most abundant species were still living in
northern seas, some in those of Greenland and other high latitudes;
while in Sweden they were found fossil between latitudes 58 deg. and 60
deg. N., and here in latitude 47 deg. These fossil shells occur at
Beaufort, about a league below Quebec, and about a quarter of a mile from
the river, in deposits which have filled an old ravine in the Palaeozoic
rock. A laminated clay forms the lowest bed, above which comes a stratified
sand, and this is followed by a clay containing boulders, each of these
deposits being about twenty-five feet thick. They are without fossils,
which begin with the next bed, a stratified mass of pebbly sand and
loam, and become more frequent, till at last this passes into a mass
nearly twelve feet thick, consisting almost wholly of the well-known
bivalve _Saxicava rugosa_. This deposit was about 150 feet above the
level of the sea. Afterwards, in travelling southwards from Montreal,
whither he returned from Quebec, Lyell found marine shells on the border
of Lake Champlain, about eighty miles from the former town. Here they
occurred in a loam, which was covered by a sand, and rested on a clay
about thirty feet thick, containing boulders, some of them nine feet in
diameter.
Lyell sums up the results of his investigations by stating that, in his
opinion, the shells certainly belong to the same geological period as do
the boulders, and occur both above and below beds containing erratics;
while the fundamental rocks below the drift are "smoothed and furrowed
on the surface by glacial action." This effect Lyell at that time
attributed to the friction of bergs grounding as they floated, but it is
now referred by the majority of geologists to the action of land ice. Be
this, however, as it may, the shell-bearing beds must have been
deposited in the sea; so that either the land must have sunk as the ice
retreated, or the latter at the time of its greatest extension must have
trespassed on the domain of the sea, as it still does around parts of
the Antarctic continent.
From Montreal they went, by way of Lake Champlain and over the Green
Mountains, to Boston, where they arrived about the middle of July, and
proceeded by steamer to Halifax. Here began the last stage of Lyell's
journey, the examination of the Carboniferous system in Nova Scotia, to
which work a full month was devoted. After studying the gypsum, red
marl, and sandstone of the lower part of that system, which bears some
resemblance to the Upper Trias (Keuper) of Britain, he crossed the Bay
of Mines to Minudie, in the heart of the Nova Scotian coalfield. The
cliffs by the sea-shore exhibit a fine series of sections, from the
gypseous rocks up to the coal measures, uninterrupted by faults, the
beds dipping steadily at an angle of nearly 30 deg. Sandstones, shales,
and seams of coal could be seen alternating in the usual manner; and from
the last-named, stumps of trees, sometimes two or three yards high, were
seen in places, as at South Joggins, projecting at right angles to the
surface of the bed. Of such stems he observed at least seventeen at ten
different levels. The stumps never pierced a coal-seam, but always
terminated downwards either in it or in shale, and never in sandstone,
thus indicating that they were a part of the vegetation from which the
coal had been formed, and that it, like a peat-bog in England, required
a subsoil impervious to water. Lyell also mentions that Mr. (now Sir) J.
W. Dawson, who was his companion for part of the time, had found a bed
of calamites in a similar position of growth.
But, in addition to much interesting work in various parts of the Nova
Scotian coalfield, Lyell had the opportunity of witnessing the noted
tides of the Bay of Fundy, where the difference between high and low
water is as great as, if not greater than, anywhere else on the globe.
On the muddy flats thus left bare he had another opportunity of studying
the tracks left by various animals, marine and terrestrial; and in
watching how these were hardened by the action of the sun, if they had
been made near the high-water mark of spring-tides, he gained further
hints for interpreting the fossil footprints of Connecticut and other
countries.
On the 18th of August the Lyells left Halifax for England, thus bringing
to a close a year of assiduous field-work, long journeys, and varied
experiences. It was a period of the most continuous outdoor labour, and
thus the most fruitful in the acquisition of knowledge which he had
spent since his marriage and the publication of the "Principles of
Geology"--a period comparable only with his journey, between May, 1828,
and February, 1829, in France, Italy, and Sicily, though it was still
longer and more fruitful, were this possible, in varied geological
experiences. He had not, indeed, seen in this part of America any
volcanoes, active or extinct--of which, however, he had already examined
plenty; but he had studied good and characteristic sections of almost
every formation which occurred in the more eastern states of America,
from the most ancient crystalline masses, the foundation stones of the
continent, to the most recent fossiliferous drifts. He had travelled
from a region which resembled Scandinavia to one where the climate was
more like that of the north coast of Africa, and had enlarged his
conceptions of the scale on which Nature worked. But, in addition, he
had been afforded an opportunity of studying the social and political
condition of a young and vigorous nation as it was developing,
unfettered by antiquated laws and hereditary customs. To this aspect of
the tour a brief reference will be made in a later chapter; now it is
enough to say that the long journeying of the twelvemonth had been
happily ended, without illness, without the slightest accident, without
anything that could be called an adventure. This good fortune followed
them to the very end, for even the homeward passage is dismissed with
the brief remark that it took nine days and sixteen hours; so that it
may be supposed to have been prosperously uneventful. Then in eight
hours after leaving Liverpool the travellers were back once more in
London.
FOOTNOTES:
[95] "Travels in North America," chap. i.
[96] "Travels in North America," chap. ii.
[97] See the plate in the _Gentleman's Magazine_, 1751.
[98] See map in "Man and the Glacial Period," by Dr. G. F. Wright
(International Scientific Series), p. 338.
[99] The estimates made by geologists have varied from 55,000 years
(Ellicott, in 1790) to not more than 7,000 years (United States
Geological Survey, 1886). Professor J. W. Spencer, who has recently
investigated the question, has arrived, by a different method, at a date
practically identical with that assigned by Lyell (Proc. Roy. Soc., vol.
lvi. (1894), p. 145).
[100] This was still a moot point with geologists. Lyell refers to the
confirmatory evidence which W. Logan had recently obtained in the South
Wales coalfield of Britain.
[101] "Principles of Geology," chap. xliv.
[102] Proc. Roy. Soc. lvi. (1894), p. 146.
[103] The lake-ridges and raised beaches around the Great Lakes,
indicating margins of the water when it stood at a higher level than
now, have received much attention of late years from Canadian and
American geologists. They are found to vary somewhat in level, thus
indicating unequal movements of the earth's crust. References to
literature prior to 1890 will be found in a paper by Professor J. W.
Spencer, Quart. Jour. Geol. Soc., vol. xlvi. (1890), p. 523.
[104] See, for descriptions of these sections and lists of the fossils,
Sir W. Dawson's "The Ice Age in Canada," chaps. vi. and vii. They occur
up to 560 feet above the sea.