riol; after BRUCE'S MINES, another locality, add Copper glance, Erubescite add PRINCE'S LOCATION, on Lake Huron (see above, SILVER GLANCE). The author is indebted for the list of Canada localities to Logan's Rep. Geol. Canada, and to Mr. T. S. Hunt.

P. 498.-On the Geological Ages of the Crystalline Limestones; (Communicated). --The crystalline limestones of northern New York, and those of the whole of the north side of the St. Lawrence Valley are by Mr. T. S. Hunt referred to the Laurentian [Azoic] System of rocks, which underlies the New York system, while the marbles of western Vermont, of Berkshire Co., Mass., of northwestern and southwestern Connecticut, and of southern New York, N. Jersey and Pennsylvania belong to the Trenton group of Lower Silurian rocks. The serpentines and dolomites which are found all along the eastern line of these limestones from Lower Canada through Vermont and Massachusetts, to Winchester and Litchfield, Conn., and which are again seen at New Haven, Milford and Hoboken, appear to belong to the upper part of the Hudson River group; while the limestones extending from Lake Memphremagog, down the Connecticut River Valley, to Halifax, Vt., and thence through Coleraine, Ashfield, Deerfield, Whately and Bernardstown in Mass., are Upper Silurian; to which also belong the calcareo-micaceous rocks of western Connecticut, and probably those of Bolton farther east in the same State. The limestones of eastern Massachusetts, as in Chelmsford, Bolton and Boxborough, and those of Walpole and Attleborough, he supposes to be of Devonian and Carboniferous age. The same crystalline minerals occur alike in the highly altered rocks of the Laurentian, Lower Silurian and Devonian systems. See Mr. Hunt's paper in the Am. Jour. Sci., [2], xviii, 193.

ART. XXXVII.-Review of Murchison's Siluria.*

THE geologist whose field of observation has been within the limits of the United States where the formations are spread out on so grand a scale and where there are such immense gaps in the series, can hardly look at the geological map of England without wondering at the perfection of the sequence in that country and the smallness of the space into which so great a variety of formations have been crowded. Hardly a link in the chain, as recognised by European geologists, can be said to be wanting: of the 28 étages, or groups, into which all the fossiliferous rocks have been divided by d'Orbigny, only two have not been recognised in England, and of these, one, the ètage Danien, is only a few yards in thickness. And how much of the ardor and success with which geology has been cultivated in England is due to the multiplicity and variety of the facts forcing themselves, as it were, into the notice of every one who ever cast a glance at the rocks beneath his feet. The facilities which that country affords for obtaining a clear insight into the structure of the earth gives to the English geologist, in some important respects, very great advantages over his co-laborers in the same science in this country. Not to speak of the physical suffering which must be gone through in exploring the remote portions of our territory, how

*SILURIA: The History of the Oldest known Rocks containing Organic Remains, with a brief sketch of the Distribution of Gold over the earth; by Sir RODERICK IMPEY MURCHISON, &c. &c. London, 1854.

much we lose in the rapidity and accuracy of our observations for want of good geographical maps. European geologists have as a basis for their operations almost an exact miniature copy of the surface, on which every elevation, every undulation of the ground, every land-mark, every stream and almost every house is laid down. With such maps he is not obliged to be his own surveyor, topographer and draughtsman, and he is never at a loss to know where he is in the world. Another great advantage which an old and thickly inhabited country possesses over a new one, is the aid afforded by artificial sections of the rocks, such as are furnished by canal and railway cuttings, deep wells, mines or quarries. When the structure of a country is complicated, such helps become of the greatest importance, and the geologist who is deprived of their aid is often obliged to leave the most interesting problems unsolved. Great Britain, small as is the space she occupies on the map of the world, is the first of nations in mineral and metallic wealth, and depends more exclusively for her national prosperity on that branch of her industry with which geology is most intimately connected, than any other country. Thus it is that this science has at all times been a favorite there, and its cultivators have been numerous, devoted and highly successful.

In the course of the development of English geology those rocks naturally got the first attention which were most accessible, most thickly filled with organic remains, and most simple in their stratigraphical position. The remoter districts of Wales and the north of England were comparatively neglected, under the idea that the rocks of those regions were too scantily supplied with fossils and too much metamorphosed ever to be reduced to a system of consecutive groups. The same was the case on the continent. The German geologists had contented themselves with calling all the rocks below the Old Red Sandstone primary and transition; but the line of division between them was rarely attempted to be drawn. Grauwacke was one of those indefinite names under which were ranged a great variety of rocks of different ages. Some attempts were made, it is true, to separate the transition rocks in Germany into groups; but as these classifications were based on mineralogical and not on palæontological grounds, they were of no value in any general application; they implied no real progress in the task of unravelling the order of succession of the older rocks. The first step in the right direction seems to have been taken by Hisinger, who showed, in 1826, that the older fossiliferous rocks of Sweden might be separated into two groups, according to the nature of their fossil contents. In this country we were quite as completely in the dark on the subject of our older geological formations as they were in Europe in regard to their own. In the words of Murchi

son, "Before the labors which terminated in the publication of the 'Silurian System,' no one had unravelled the detailed sequence and characteristic fossils of any strata of a higher antiquity than the Old Red Sandstone; and even that formation was only known to be the natural base of the carboniferous or mountain limestone, and to contain a few undescribed fossil fishes. Not only were the relations and contents of the inferior strata undefined, but even many rocks which are now known to be younger than the Silurian, were then considered to be of much more remote antiquity. No one had then surmised that the great series of hard slates with limestones and fossils, which have been termed Devonian, is an equivalent of the Old Red Sandstone, and younger than, as well as distinct from, the deposits of the still older Silurian era. On the contrary, British authorities believed (and I was myself so taught) that the schistose and subcrystalline rocks of Devonshire and Cornwall were about the most ancient of the vast undigested heaps of grey wacke. In short, the best geologists of my early days were accustomed to leave off with such rocks, as constituting obscure heaps of sediment, in and below which no succession of strata as identified by their fossils' could be detected.'"

It was in 1831 that Murchison, desirous of throwing some light on this dark subject, under the advice of Dr. Buckland, began his explorations along the borders of England and Wales, where the older rocks are well developed. At the same time Prof. Sedgwick, with similar intentions, selected North Wales as the field of his labors, and for many years both these gentlemen labored indefatigably to elucidate the order of succession of the palæozoic strata. In 1833 and 1834, Murchison presented various papers containing the results of his observations to the Geological Society of London, and in the last named year prepared a classification of these ancient strata, which is essentially the same as the one now sustained by him, the rocks below the Old Red being grouped into four formations (Ludlow rocks, Wenlock and Dudley rocks, Horderly and May Hill rocks, afterwards named Caradoc, and Builth and Llandeilo flags) the whole underlaid by the unfossiliferous greywacke of the Longmynd. In 1835 the name Silurian was given to these four groups, and the distinction between upper and lower Silurian was established. Eight years of persevering labor were at length worthily crowned by the appearance of the magnificently illustrated quarto, entitled, "The Silurian System," which appeared in 1838. In this work, so well known to every geologist, the fossils which up to that time have been discovered in the Silurian groups were described and figured by the most eminent English palæontologists, and thus the means were placed in the hands of geologists throughout the world of studying their older formations and comparing them

with those of England. Nothing could have been more opportune for American geologists than the promulgation of the Silurian System. The study of our fossiliferous rocks had just been seriously commenced in this country by the organization of the geological surveys of the great states of New York and Pennsylvania, which are chiefly occupied by the strata of the same age as those studied by Murchison, but developed on a vastly greater scale and in a much completer sequence. At this time the greatest confusion prevailed in regard to the position, age and nomenclature of our palæozoic strata. The Silurian and Devonian rocks of Pennsylvania were simply designated as "secondary" by the State Geologist in his first report (1836). In the same year Mr. Featherstonhaugh described all the rocks of the Northwest, including the whole series from Lower Silurian up to the coal, as being of carboniferous age, and in his report for the previous year he had made still greater confusion in attempting to classify the rocks of the Atlantic States. Troost had also considered the Silurian of Tennessee as carboniferous, and Eaton had identified rocks of the same age in New York as of the age of the New Red Sandstone.

Great was the impetus given to palæozoic geology by the establishment of the Silurian System, and geologists everywhere began to search among their transition and grey wacke rocks for the equivalents of the group, established by Murchison. No one however was more active in extending his system to foreign countries than our author himself, and with the especial object of finding fresh confirmation of the truth of the British palæozoic classification he visited Russia, and with the aid of de Verneuil and under the especial patronage of the Emperor, carried out, in the years 1840 and 1841, an extensive survey of Russia in Europe and the Ural mountains. In 1842, '3 and '4, farther investigations were made by Count von Keyserling in Russia and by Murchison himself in England, Germany and Scandinavia, and in 1845 the results of these laborious and costly researches appeared in the form of two quarto volumes entitled "The Geology of Russia in Europe and the Ural Mountains," a work printed and illustrated in a style of truly imperial magnificence. Besides this work and the "Silurian System," numerous papers by Murchison, either alone or associated with Sedgwick or Verneuil, appeared in the transactions and proceedings of the Geological Society of London, in the preparation of which the aid of the most accomplished palæontologists of England was obtained in their various departments.

The results of all these researches are presented by the author in a condensed form in the work now before us, an octavo of 523 pages, evidently prepared with the object of posting up the geology of the paleozoic formations to the present time and pre

senting to the public a volume which should not be too strictly scientific to interest any but the professional geologist, and which, at the same time, might not, like the works previously mentioned, be inaccessible to many on account of its great cost. For this purpose, the original plates of fossils drawn by Mr. Sowerby and engraved for the "Silurian System" have been reproduced by transferring to stone, with the exception of the corals, which being originally lithographs could not be thus made use of again. These latter however have been, with additions and corrections, drawn upon wood, and numerous species are also figured in this way which have been found in Great Britain since the "Silurian System" was published, or of which better specimens have been obtained; these were drawn on wood by Mr. Salter. Thus the "Siluria" is declared by its author to be "a faithful outline of his previous labors and also of our present knowledge of the older palæozoic rocks as registered in the noble series of organic life collected in the Government Museum of Practical Geology."

Having thus noticed the successive publications of our author, it is proposed to glance at some of the principal results and opinions which are discussed in the Siluria, with especial reference to the light thrown on them by the researches of geologists in other countries, and particularly in the United States.

The author of the "Silurian System" has been very much troubled during the last ten years, by the pertinacity with which his old friend and fellow-laborer, Prof. Sedgwick, has insisted on robbing his favorite system of its lower half in order to make out a "Cambrian System." The controversy on this subject has been warmly carried on by both parties and their respective friends. Its history is briefly this: While Murchison was investigating the geology of the border counties of England and Wales, the typical "Siluria," Sedgwick was equally hard at work in North Wales; both of these distinguished geologists having the same object in view, namely, the unravelling the order of succession of the lower palæozoic strata. Apart from all considerations of personal qualifications for success, it is evident that the region selected by Murchison was better adapted for the purpose to be obtained. The rocks of North Wales are so much broken up and invaded by igneous masses, and hence so complicated in their stratigraphical relations, and moreover so poorly supplied with fossils, that it has required all the skill of the government corps of geologists, working out every thing in the most detailed manner, to determine the structure of the region. Hence, while Murchison had elaborated his views and divided the Silurian rocks into a number of groups, which have, in the main, been recognised by the Government Geological Survey, and, what is of still higher importance, had caused the typical organic forms of his system to be described and figured, thus enabling