after being taken from the quarry. Blocks have been quar ried weighing two hundred and forty tons. From certain peculiarities in the appearance of the stratification, Mr. Latrobe is induced to believe, that the wind has been the agent in accumulating the sand, which, becoming indurated, forms the stone here described. PHILADELPHIA TRANSACTIONS. No. L. Observations to serve for the Mineralogical Map of the State of Maryland. By S. Godon. THE observations contained in this paper relate to that portion of the state of Maryland, situated between Baltimore and the city of Washington. This tract is remarkably barren in vegetable productions, and uninteresting to the mineralogist, except as forming a part of that vast alluvial deposit, extending on the sea coast from Long Island to the Mississippi. The only mineral here found, is a ferruginous sandstone, forming a stratum from six lines to a foot or more in thick ness. "Washington city is built on the alluvial land; but Rock Creek, which separates this capital from Georgetown, appears to present the boundary line between the primitive and alluvial soil.” Above Rock Creek, on the eastern bank of the Potomac, the primitive soil appears in gneiss and greenstone. In the bed of the Potomac are found fragments of a very singular mineral, brought down by the waters. M. Godon describes it as " an amygdaloid of a dark color, including globules of a substance sometimes white, sometimes of a fine rose-color. In the centre of these globules, another substance, of a fibrous texture, and of a fine green color, often occurs. This substance seems to be epidote. These several substances are disposed in the rock in a very elegant manner." PHILADELPHIA TRANSACTIONS. No. LXII. Observations on the Geology of the United States, &c. By W. Maclure. DISTINCTIVE lines between geology and mineralogy, as different branches, have become perfectly well defined. Although a successful pursuit of geological inquiries necessarily presupposes an acquaintance with mineralogy, yet the posses. sion of a very considerable share of mineralogical knowledge may be obtained without any attention to geology. We here employ the term geology in its modern signification. Its researches are confined to the earthy crust, which envelopes our globe. It observes the various aggregate minerals, which go to compose this crust, their extent, position, direction, stratification, relative situation, and relative heights or supraposition. It regards classes or formations of rocks of the same sort, without descending to notice, except for some occasional purpose, the various minerals, which may be disseminated in them. It is but a short time since the just and universally received rules of philosophy have been applied in exploring the mineral kingdom. No one seems to have thought of establishing a system by induction from observation. Theories either preceded observation, or the theorist remained satisfied with the labors of the closet, and the sportiveness of his own imagination. But within a few years the attention of philosophers has been devoted to the observation and accumulation of geological facts. In this, as it has been in other branches of science, theories will be offered the public before a sufficient number of facts have been collected. But it is perhaps true, that systems, if only partially correct, are on the whole not without their advantages in the infancy of any science. They stimulate to inquiry, whether with design to support or oppose, The only evil to be apprehended from premature systems arises from the undue bias, which they may produce on the mind, while observing facts. Mr. Maclure, the author of this paper, is one of the most indefatigable geologists of the present day; and we hope this is but the first fruits of his geological inquiries. Mr. Maclure has repeatedly examined the soil of the United States in nearly its whole extent. He has also inspected many of the more interesting mineral districts in Europe, where he is now employed in completing his observations. Our attention will be devoted chiefly to the author's mode of observing, and an abstract of the present state of our knowledge of the geology of the United States. To complete our intended view of Mr. Maclure's geological researches in the United States we shall be under the necessity of making some use of another paper, published by the same author, and relative to the same subject.* Mr. Maclure has adoped the nomenclature of Werner, for which he assigns two reasons. "1st, Because it is the most perfect and extensive in its general outlines. 2dly, The nature and relative situation of the minerals in the United States, which are certainly the most extensive of any field yet examined, may perhaps be found to be the most correct elucidation of the general exactitude of that theory, as respects the relative position of the different series of rocks." Mr. Maclure does by no means appear attached to any favorite system, nor to possess a servile regard for any master. He thus writes. "In adopting the nomenclature of Werner I do not mean to enter into the origin or first creation of the different substances, or into the nature or properties of the agents, which may have subsequently modified or changed the appearance and form of those substances; I am equally ignorant of the relative periods of time, in which those modifications or changes may have taken place. All that I mean by a formation is a mass of substances, whether adhesive, as rocks; or separate, as sand and gravel; uniform and similar in their structure and relative position, occupying extensive ranges, with few or no interpolations of the rocks, belonging to another series, class, or formation." In his geological inquiries Mr. Maclure has not proceeded, Suite des observations sur la Géologie des Etats-Unis servant a l'explication de la Carte ci-jointe-published in the Journal de Physique. as is usual in other branches of science, from the observation, collection, and arrangement of particulars to the formation of general maxims or laws. He has not selected a limited portion of the earth's surface, minutely examined the various rocks, which there present themselves, the arrangement of their component parts, their various accidental changes, &c. and then, by combining many of these limited portions, endeavoured to deduce general facts and constant laws. On the other hand, he has first attempted to delineate the outlines, to trace the limits, which separate the principal classes of rocks, and to mark their situation and relative extent. In doing this however, the determination of the different sorts of rocks, embraced in each formation, has been subjected to general principles, previously established and admitted. To adopt this inverted mode he was induced by the following reasons. First, in proceeding from the minute examination of particulars to general facts, the immense variety of rocks, and the imper ceptible gradation, by which they pass into each other, necessarily produce minute and tedious description. Volumes would be necessary to describe the different rocks found within a small extent of some primitive formations, and to detail the changes, which the same rocks present, while passing a little to the right or left. But to trace the exterior limits only of different formations or classes of rocks, a few pages are sufficient, and enable the reader fully to understand their relative situations. Secondly, when small portions of the earth's surface are thus minutely examined, the observer can hardly avoid framing a system, which, though perfectly well adapted to the territory under examination, is totally inapplicable to other districts. This difficulty arises entirely from a want of general views. We confess we were at first somewhat alarmed at the consequences, which might result from this unphilosophical mode of proceeding. And we are still of opinion, that it must be admitted under certain limitations. If it be employed merely for the purpose of obtaining general views, preparatory to a more minute investigation, we think it decidedly advantageous. When different and extensive strata intersect each other, when the stratification is broken and discontinued; when certain portions of a formation are inaccessible; when superincumbent strata have become disintegrated by the gradual action of air and moisture, or removed by the force of torrents or rivers, thereby producing confusion of strata in consequence of presenting an artificial arrangement, we think a general view, previously acquired, will save much vexation and fruitless labor. In this way also anomalies either in composition or arrangement will be more easily determined. But in the hands of a geologist less persevering, and less ardent, than Mr. Maclure, we should apprehend that the liberty of dealing in general views would terminate in a series of superficial observations, and a careless theory. After some general remarks on the structure, Mr. Maclure describes the boundaries, extent, and relative situation of the four grand formations of rocks, as found in the United States; the alluvial, primitive, transition, and secondary for. mations. The reader is much assisted in the description by the geological chart, annexed to this paper; in which the four abovementioned formations are delineated in different colors. The mineral masses of the United States are character. ized by the great extent, uniformity of structure and regularity of stratification of individual formations. Thus magnetic iron ore, which we find in Franconia, New Hampshire, occasionally makes its appearance, as in the vicinity of Phillipstown, on the Hudson, and at Ringwood, New Jersey, with the same direction of stratification, till it disappears near Blackwater; a range of nearly three hundred miles. A formation of red sandstone extends, with but few intervals, from the Connecticut to the Rappahannoc. Several other similar instances might be cited. No volcanic productions have been found east of the Mississippi. The great alluvial formation commences with Long Isl and,* and on the southeast is bounded by the ocean to the * Mr. Maclure has delineated the northern half of Long Island as primitive, and the southern half alluvial. Dr. Mitchell of New York has a paper in the third number of Bruce's Mineralogical Journal, on the ge |