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2 Magazine of Literature, Science, and Art.
VOL. V.-MAY, 1855.-N0. XXIX.
THE LAST WORD OF GEOLOGY.
- in a brief article in this Magazine, to coal. To these succeed the yet later glance at the general principles on series of strata which geologists havo which modern Geology is founded, and conventionally divided into the Permito notice very cursorily the important an, Triassic, Jurassic, Cretaceous, and work of Professor Hall, yet in progress Tertiary systems, each, wherever found, under the patronage of the State of lying above its predecessors, and the New York. The appearance of the contained fossils of each later formation two other standard books cited belowshowing an advance more and more toone containing the most thorough ex- wards that condition of things which, in amination of a particular group of fossil the upper and newer Tertiary, merges relics ever made within a limited dis- into the historical period of Man, and trict, the other a general survey and connects itself with the present. resumé of the facts collected by geolo- Left, as we are, without trustworthy gists working in the older rocks over data by which to estimate, even approxithe whole hitherto explored area of our matively, the duration of the periods globe, forms a fair occasion for a second during which these great piles of matter, paper on a subject in which an intelli- with their organic contents, were formgent interest is more widely felt every ed in the old ocean beds, our geological year.
chronology is but a rude one; and its The Silurian system is now under- periods, like the dynasties of old Egypt, stood to embrace all the strata contain- may be imagined indefinitely longer or ing relics of organic life, from the first shorter; though there is no doubt of traces of animated existences on our their real existence, and any reasonable planet up to a certain, or rather an un- restriction of their limits must leave certain limit, defined most distinctly as on the mind the vague impression of that at which the remains of fishes be- enormous cycles. We can only speak gin to occur in considerable abundance. of them indefinitely, as in human history At this point it merges into and is cov- we allude to the dark ages, to the period ered by the strata of the second great of Roman empire, the epoch of early period, during which fishes abounded, Egyptian civilization, the centuries of land plants became common, and rep- Celtic or Pictish barbarism. The antitiles made their appearance. This quary can refer the relics which he - Devonian system” (embracing within finds, generally to some such period, it the old red sandstone) is covered and yet he often knows not, within many succeeded by the carboniferous system, centuries, the lapse of time since their
Système Silurien de Boheme. Par J. BARRANDE. Vol. I. Trilobites. Prague, 1853.--Siluria. The History of the oldest known Rocks containing Organic Remains. By Sir RODERICK IMPEY MORCHISON. London, 1854.-- Palaontology of New York. By JAMES HALL. Tois I. and II. Albany, 1847, 1852.
fabrication. The dates of some his- is thus written on the successive layers torical events seem to oscillate for a of a series of slate, sandstone, shale
, thousand or two thousand years, now and limestone strata, piled to the thickappearing quite within the light of ness of from four thousand to twenty thirty centuries, now sinking back in- thousand feet, and its characters are the to the dim and indefinite shadows fragments of the living forms of its of the dawn of history, which prevent parent sea. even a random estimate of the distance Since its formation, it has been in from which their ghostly outlines loom many places covered by newer deposits and flicker on our vision. Thus it is so as to be buried far below our reach with geological periods. No one In many places the ocean still rests upon say whether the epoch of the coal for- it. In many places where it has been mation dates back one million of our raised above water and bared of more moyears, or seven, or seventy millions. dern masses, it has been so baked and These epochs are like the distances of changed by the earth's internal heat, the stars, and all we know is that some so doubled up and distorted by the are far more distant than others, and crumpling of our globe's crust, or so that the nearer, though infinitely remote, worn away by the action of the eleseem close at hand compared with ments, and swept seaward to form newthose which lie on the limits of our per- er systems of strata, that it is only here ception.*
and there that we find portions of it The reader may therefore assume well preserved for our examination. In any lapse of time which pleases him, England and Wales it is sadly distorted since the old Silurian strata were laid and broken up, though distinctly tracedown, particle by particle, by the pri- able both in its stratification and its fosmal ocean. We have only to say that sils ; it is well seen in Scandinavia ; there appears to be a bottom to the and extensively developed in North Great Cemetery, a geological ne plus Russia, though concealed by wide ultra, below which no relics of organic plains of alluvial earth ; in France, life are found, at which the geologic Spain, and on the Rhine, it has been record begins. The previous leaves of successfully traced and studied. Hither" the stone book" are blank, and these to, however, its best exposures are in first decipherable inscriptions commence the northern United States, and in Bothe chapter of the Silurian system. It hemia.t
Efforts have been made to obtain some idea of the actual amount of time elapsed during the geological history, One means of calculation has been drawn from the belief that the plants of the coal formation must have required a temperature of 22° Reaumur. The mean temperature of the coal districts being now only go Reaumur, it is considered that the earth has lost 140 of heat by cooling since the carboniferous epoch. By such experiments as have been made in regard to the cooling of rock, and the radiation of heat, M. Unger has calculated that for the earth to lose 14° of Reaumar would require nine millions of years. M. Hibert reduces this to five millions.
But supposing the whole earth once to have been in a melted state, the time which must have elapsed, in its cooling to its present condition, is fixed at the liberal allowance of three hundred and fifty millions of years.
Anoiher form of calculation occurs to us. Wherever strata are formed, it must be from the waste of existing land. Consequently, an average deposit of one foot of rock (supposing the sea and land to be equal in area) implies an average reduction in the hight of the continents of an equal amount. Thus if we know how fast the continents have been worn down, we can tell approximately how fast the sea has filled up. Now the Mississippi is estimated by Mr. Lyell to discharge annually 3700 millions of cubic feet of earthy matter, which is an average waste from its basin of about one million square miles. A little calculation shows that this amount of waste implies an annual reduction of the surface of this basin to the amount of about 1-7.534 of a foot, or one foot in about 7.500 years. At this rate, to form an average deposit of ten thousand feet of fossiliferous strata over the globe (which is, perhaps a fair random estimate of its real thickness), would have required
seventy-five millions of years, which would thus be the age of the lower Silurian strata. Other estimates of the discharge of solid matter by the Mississippi vary from that we have quoted. Some are one third less, which would give a slower rate of wear to the continent, and increase our seventy-five millions to one hundred. The highest estimate makes the sediment of the river seven times greater than that adopted above, and would reduce our seventy-five millions to only ten. On the other hand, the sediment of the river is only ball the weight and solidity of ordinary rock, and it would require two cubic feet of it, when condensed, to form one of such as the old strata. Moreover, if the proportion of land to sea be estimated as it now is, only one to three, this supposition would require three feet of waste from the land to fill the sea one foot, and thus would extend
our estimate of time threefold. Our figures therefore stand at 10, 20, 60, 75, or 100 millions of years for the age of the oldest trilobites and fossil shells; and if this calculation proves nothing else, it shows the vagueness of all attempts to reduce to our measures of time the vast but indefinite periods of geology.
| The appreciation which is now bestowed on our remarkable development of the older rocks, and the labors among them of American geologists, is fairly stat d in an article on Sir R. Murchison's book in the London Quarterly Review for October last. It is understood to be from the pen of one of the first authorities, Prof. Edward Forbes,
whose untimely death bas lately disappointed so many hoper, and oalled forth so many tributes of regret in Europe and America. We extract a few sentences :**North America might almost be said to be the head quarters of Silurianism. A glance at the excellent map appended to Sir Charles Lyell's travels will show how vast are the regions there occupied, even superficially, by Silurian deposits. Exceedingly prolific in organic remains and varied in mineral character, these beds have furnished the subjects of some of the most excellent geological treatises that have appeared during the last ten years. They are too numerous to be cited. It certainly is one of the most striking features of the science of the United States, that geology has taken root there deeply, and has Sourished, perhaps, beyond any of the sister sciences. The American geologists have gained a worldvide fame, and deservedly. Their works are text-books in Europe, and standard members of our scientific libraries. A considerable number of these excellent monographs have been published at the cost of different States of the Union, whose local governments have thus shown an advanced and enlightened artrit, and a just appreciation of the advantages that must accrue to their citizens through the timely development of the resources of the land. We have much yet to hope from the onward-striding pace of American geology."
The traveler who turns aside from days will be disappointed. Here the his forty-mile-an-hour race through shells and corals lie, not as on the coast New York, at Utica, to spend an after- of Cuba, where in half a day we may noon at Trenton Falls, visits a spot examine miles of beach, where at a where some of the most interesting glance the eye can sweep over many layers of this old deposit are laid open yards, and where the soft sand permits to our view. The West Canada Creek us to pick from it with the fingers has not only removed the beds of gravel whatever object may attract our attenand clay which usually conceal the tion. No. These relics are not so rocks, but has worn a deep and pre- easy of collection. Those which, like cipitous chasm through the hard strata, the trilobites, were composed of many exposing their edges in all to the depth pieces, nine times out of ten before of two or three hundred feet. Some they were buried, decayed and fell into seventy or eighty feet of this thickness fragments. The shells and corals also lie between the head of the staircase suffered more or less from decomposiand the black, foam-streaked pool below, tion, some of the larger shells Being every successive layer older than that almost unknown in an entire state. above it, and each one formed by the And then with what an iron gripe does gradual accumulation of many years, the rock hold them-penetrating every Past the fern-draped and moss-covered pore and cavity, adhering to every edges of these layers the visitor de- roughness of the surface, enveloping scends, step by step, lower and lower closely every spine or projection. The into the records of the past, until, reach- collector is tantalized by the sight of so ing the broad, level platforms of rock many a fossil which is beyond his hope, which extend along the brink of the projecting from some obstinate pile of swift amber current, he can sit down, layers, of many ruined by the wear of and, closely examining the water-worn the elements, and of those which he black limestone, see in it the dead and attempts to secure he sees the greater petrified shells and corals and trilobites portion fall into fragments under his which lived in the old Silurian days. hammer. A day of hard labor enables No pleasanter hours are within our re- him to break up only a few cubic feet membrance than those spent on these of rock, and but a small proportion of rocky ledges, where the mind alternates its contents will be secured in any from the mystical interest of the past tolerable condition. to the fresh beauty of the present; When in addition to this difficulty in where the monotonous roar of the collecting, we remember that it is only torrent mingles with your reverie until in limited localities, quarries, cliffs, or it seems the murmur of the old Silurian ravines, miles asunder, that these old ocean itself; until, raising your eyes, deposits are accessible to us; that probsuddenly appear the gray precipice, the ably not one square yard of an hunsolemn hemlocks, and the white sheet dred thousand can be seen at all, we of the cascade, and you are recalled to may wonder that so much has been acthe living charms of a spot which is left complished in their examination, and with most regret after the longest fa- that Mr. Hall has been able to recogmiliarity.
nize and describe three hundred differThis is one locality of the Silurian ent species of fossils from the lowest strata, one point where the oldest tombs one-third of our Silurian strata. It is of the Great Cemetery lie open, and only by years of constant devotion to where its remains are abundant. Yet the pursuit, that so great a portion the visitor who expects to gather a large of these old-world relics have been collection of fossils in a few hours or recovered, and so much learned of
their nature and relationship to living formations, wherever portions of them forms.
remain accessible to our scrutiny. The results of such labors in remote Thus it is, that, in North and South portions of the globe are now being America, Europe, Asia, Australia and connected into one great system. The Africa, the stony records of the first work of Sir R. Murchison gives a coup period of organic life on our planet have d'ail of the present state of knowledge been found, and, to a considerable deof the Silurian rocks throughout the gree, connected and identified with each world, traced out and identified as they other. have been by the peculiar character of We know, by such investigations, their fossil remains. The same families the comparative ages of continents. of shells, corals, crustaceans, and encri- The Alps and Himalayas being made nites characterize them in all regions up of rocks not older than the Jurassic yet explored, and more especially do period, while Northern New York apthe trilobites mark and define these
pears never to have been covered with strata. It is true that these fossils vary newer deposits than the Silurian ; we considerably in remote districts, yet may know that the former have been their general correspondence is well raised during comparatively modern marked. As we find at the present day, times, being geological parvenues, while that in comparing the living shells of our Adirondacks are of the very first the British and American coasts of the families of mountains, a relic of the earAtlantic, about one-third are identical liest dry land of the older world. Their on both shores, while of the remainder heads have been kept above water from a large proportion are of analagous or the most ancient period; the trilobites corresponding forms, and but few are crawled round their subaqueous slopes, widely different; so among the fossils while the Trenton limestone was beginleft by an earlier ocean in remote dis- ning to settle from the sea; and since then, tricts, we find some identical through- they have seen the whole series formed, out, being species which lived in all carboniferous, secondary, tertiary and parts of the ancient sea; many others all. No wonder that they are deeply more restricted in their extension, but furrowed and worn. Thousands of feet represented beyond their own limits by of their hard granite have been washed very similar or related forms; others
away by rain and storm, and Mount stili, very peculiar and confined to nar- Tahawus is now but the mere stump, row localities. Thus, when we find a the remaining core or nucleus of the large proportion of the fossils of one pile which once stood there, overlookrock in America identical, or closely ing the primal ocean. similar to those of another in England - Tennyson, in finally disposing of especially if a similar correspondence his sleeping beauty and her prince, reis traceable between the succeeding or cognizes the superior antiquity of this preceding also—we are warranted in
part of our planet : concluding that these rocks are nearly cotemporary in date. Such a corres
"And on her lover's arm she leant,
As round her waist she felt it fold, pondence is evident between our Niaga- And far across the hills they went ra limestone and shale and the Wenlock
In that New World which is the Old." limestone and shale of England. The identity of many of their fossils proves
This poetical use of a geological fact that when these masses were forming
comes appropriately from an author, at the ocean bottom, three thousand
who, in his Princess, tells us of his miles asunder, the same billows rolled
heroine, how she one day and the same living forms inhabited them in the remote regions where are
The dip of certain strata to the North," now the fertile plains of western New York and the green hills of Shrop
and saw, projecting from the sheer 'edge shire.
of the cliff, We have not room to follow out this subject, but we have said enough to in
“ The bones of some huge balk that lived ani dicate the manner in which the cotemporary age of strata is traced in different countries and continents, and to He, too, not only ornaments the walls show how we recognize the old Silurian of his ideal hall with the customary ar
"rode to take
roared Before Man was
mor and antlers, but spreads round its and in some instances standing on edge, pavement, among the
In these features of small extent, iso"Carved stones of the Abbey ruin in the park, lated position, and steep inclination of Huge ammonites, and the first bones of Time."
the strata, the Bohemian Siluria con
trasts strongly with ours. In New We subterranean philosophers owe a York, the rocks of equivalent age lie special debt of gratitude to Tennyson, nearly horizontal, as when first depowho has introduced us to the best sited, and spread away in vast unbroken literary society, so that the hammer
sheets, hundreds of miles within the and basket may be borne even on the limits of this State, and many hundreds slopes of Parnassus.
beyond, through Ohio, Kentucky, TenBut we have not yet spoken of M. nessee, Canada, traceable to the MisBarrande's book, which lies before us
sissippi on one side, and to the lonely in its full bulk of nearly one thousand island of Anticosti on the other. The quarto pages, accompanied by fifty same fossils may be found in them plates; all admirably printed and en- through all this extent, and the strata graved at the ancient city of Prague. cover each other in unmistakable sucWe have shown that it is only by the cession, undisturbed by faults or upmost energetic and persevering, re- lifts. These features give the greatest search that the relics of Siluria have value and trustworthiness to observabeen collected and illustrated. Mr.
tions here made, rendering them free Hall's book is an instance of this, being from the errors into which the student the fruit of fifteen or twenty years' is often led in disturbed regions. study under the patronage of an en- The Silurian basin of Bohemia has lightened State. This book of M. Bar
not these advantages, but they are comrande's is another, the result of twenty pensated by the abundance of its fossils, years' exploration in Bohemia, under especially its trilobites, which render the patronage of an enlightened prince, it, in the words of M. Barrande, “a the Comte de Chambord, formerly M. Silurian California.” Its limited extent Barrande's pupil. Private purses are has enabled him to explore it most rarely deep enough to enable their
thoroughly. We quote his own account owners to go far with such enterprises, of the manner in which he has reaped and it is equally honorable to the patron his harvest. and the explorer, when the union of “We have devoted many years to the means to scientific zeal and ability is exploration of the surface of this field, in thus made to subserve the noble object order to establish the extent of its fosof the acquisition of knowledge, and its siliferous portion. During this time, we diffusion among men.
have collected and noted everywhereM. Barrande's book is devoted en- in quarries, in ravines, in all localities tirely to the trilobites of Bohemia, where the rocks are laid bare-all traces other fossils being postponed to future of organic remains which came under volumes, and it certainly seems to be our observation. Having thus formed an exhaustion of the subject. The Si- an opinion as to which strata and localilurian rocks of Bohemia (considering ties promised us a harvest of fossils, only the fossiliferous strata apart from we organized, since 1840, a systematic the lower masses which are barren of exploration to make up for the insufficiorganic remains) extend nearly N.E. ency of our own arm and hammer. In and S.W., with a length of about fifty different districts we successively estabmiles and a width of fifteen, the capital lished workmen, either singly or associty of Prague lying within their north- ciated together, according to the difeastern limit. The strata are, in the ficulty of the task, to excavate the rocks lower part, slates and sandstones; in and to open and explore quarries. These the upper portion, limestone prevails ex- workmen, supplied with all necessary tensively.* Volcanic agencies have min- implements, and practically instructed gled among the layers large masses of by working for some time in our own trap rock, and the strata are so tilted up company, soon acquired the skill necesfrom their originally level position as to sary to distinguish, at first sight, any form a sort of basin, the strata dipping trace of the organic remains which were towards the centre, at an angle of from the object of our studies. We have 30° to 45°, sometimes as steep as 70°, often had occasion to admire the intel