Mississippi. Its interior boundary is marked by a line from near Amboy, passing by Trenton, Philadelphia, Baltimore, Washington, Fredricksburg, Richmond, Smithfield in North Carolina, Augusta on Savannah river, Fort Hawkins on Ockmulgee river, Hawkinstown on Flint river, and thence a little south of west across the Alibama and Tombigbee rivers to the Mississippi, a little below the Natehez. Concerning the rivers of the United States, which empty into the Atlantic Mr. Maclure remarks thus: "Tide water in all the rivers from the Mississippi to the Roanoke stops at a distance from thirty to one hundred and twenty miles short of the western limits of the alluvial; from the Appomattox to the Delaware, the tide penetrates through the alluvial, and is only stopped by the primitive ridge. The Hudson is the only river in the United States where the tide passes through the alluvial, primitive, transition, and into the secondary; in all the northern and eastern rivers, the tide runs a small distance only into the primitive formation."

The next formation, proceeding from the ocean toward the lakes, is the primitive. To the eastward of the Hudson the

soil is, with a few exceptions, entirely primitive, and on one side is washed by the sea. This formation diminishes in width, while passing through New Jersey, Pennsylvania, and Maryland; but in Virginia it very much enlarges its breadth. Westward of the Hudson, its visible boundary on the southeast is the aforementioned alluvial deposit; but it undoubtedly extends more or less under the alluvial. Its northwestern boundary is marked by a line, which commences* to the eastward of Lake Champlain, and about twenty five miles westward of Connecticut river; thence passes near Stockbridge; and a little to the eastward of Poughkeepsie; skirts the highology of Long Island; in which he assigns reasons for believing nearly the whole of Long Island to be alluvial. He thinks the only primitive strata are at Hurlgate, forming a mere margin of the shore for four or five miles.

*The northeastern extremity of the United States, including the greater part of the District of Maine, has not yet been examined.

lands; crosses the Hudson at Phillipsburg; passes near Sparta in New Jersey; a little to the eastward of Eastown on the Delaware, and of Reading on the Schuylkill; joins the Blue Ridge not far from Middleton on the Susquehannah, and continues with it to Magothy Gap; thence near Austinville, in a southwest direction, until it meets the alluvial near the Alibama river. The strata of this primitive range vary in direction from N. and S. to N. E. and S. W. and almost universally dip to the S. E. at an angle of more than 45o.

Northwest of the primitive lies the transition formation, extending from a little to the eastward of Lake Champlain, to near the Alibama river; and in general from twenty to forty miles in breadth. The direction of the strata is the same, as in the primitive; but it dips to the northwest: usually at an angle less than 45°. In addition to limestone, grau-wacke, &c. usually found in this formation, Mr. Maclure informs us, that it contains many rocks, not hitherto named or described.

Northwest of the transition lies the secondary formation, extending from the Hudson to the Mississippi, and from the transition formation just mentioned to the lakes. Mr. Maclure thinks there is good reason for believing that this formation extends westward of the Mississippi nearly to the foot of the Stony Mountains. If this be the case, we have here a secondary deposit, covering an extent of surface of about 1500 by 1200 miles; equal, if not superior in extent to any hitherto observed.

Such is a general view of the four grand formations of rocks, which form the surface of the United States. We have not room to notice a few exceptions, in which transition or secondary rocks are found within the limits given to the primitive formation; nor to describe the different kinds of rocks, which compose each of these extensive general formations.

We cannot forbear to notice the very careless punctuation and division of sentences, which appear in this paper. One would suppose it, in many places, a mere transcript of the author's travelling notes, rather than a memoir, prepared by their assistance.

MEMOIRS OF THE CONNECTICUT ACADEMY.

No. IV. Sketch of the Mineralogy of the town of New-Haven. By B. Silliman.

WHEN the attention of philosophers is indiscriminately directed to all the objects of general science, there is no reason to expect any very important results. To effect much, some particular department of knowledge must be selected; some definite object must confine the attention. But, when there is no decided preponderance in favor of any particular object of research, the mind will remain quietly glancing from one object to another, as casually presented to view, till some external motive excite to increased activity. It was therefore a very useful and expedient measure of the Connecticut Academy to stimulate and direct inquiry by proposing questions and defining objects of research. This paper is in answer to one of these questions.

While communicating the valuable observations, contained in this paper, we must avail ourselves of additional informa tion, relative to the same minerals, contained in a second paper, recently read before the Connecticut Academy by Professor Silliman, and published in the third number of Dr. Bruce's Mineralogical Journal.

The city of New-Haven is situated on the southern side of a plain, whose mean diameter is about 2 or 3 miles. This plain is entirely alluvial; and has, within the memory of gentlemen now living, encroached on the waters of the harbor. It is composed of siliceous sand and gravel in strata nearly parallel. This sand, which varies in size from a pebble of an inch or two in diameter to that of a grain, has arisen from the disintegration of the surrounding high land, and been conveyed by the waters to its present deposit, Flint, jasper, agate, sappare (cyanite), &c. are occasionally found in it. The only rock formation, which exists in this plain, is a friable sandstone, composed of the same materials, as the loose sand.

This plain is surrounded on all sides, excepting the S. and

S. W. where it meets the water, by a circular range of hills, rising in two instances to a very considerable altitude. This range of hills is composed principally of secondary greenstone, reposing on red sandstone, which is very coarse, approaching in some instances to a conglomerate or pudding stone. Το this greenstone Professor Silliman applies the names of basalt, or whin, in the paper under review; but in the other paper, above referred to, correctly denominates it secondary greenstone. Northeast and northwest from the city of New-Haven two perpendicular precipices exhibit the naked rock. These have received the names of east and west rock, of which the former is about four hundred and fifty feet high. The front of these precipices exhibits an assemblage of columns, generally assuming a prismatic form, variable however in the number of sides. The columns are usually perpendicular; but in some instances are very much inclined; "a remarkable instance of which occurs at the junction of the Hartford and Cheshire turnpike roads, where the columns do not form an angle of more than 8° or 10° with the horizon, and rest upon a stratum of sandstone, having the same inclination in degree and direction." Horizontal seams intersect these colums; whence result the columnar fragments, into which this rock either spontaneously falls, or may be broken. At the foot of the precipices lie masses of broken columns, precipitated by the freezing of water; which had penetrated their numerous seams and rents.

Professor Silliman speaks of a compact whin or greenstone lying southeast of the east rock. We are not certain, whether by the epithet compact he intends to distinguish this from columnar greenstone. We however take the liberty of referring him to a passage in "Williams' Natural History of the Mineral Kingdom," with regard to basalt or whin; as it may be useful to observe, whether the same remark will apply to the greenstone of New Haven.

"The basaltine rock," says Mr. Williams, "is to be judged of and denominated from its quality, and color, and component parts, and not only from the figure, it sometimes assumes, which is merely accidental, arising from situation,

more than from the quality of the stone. It is frequently found formed into globous, spherical, and other figures, as well as the columnar; but always, where it now is, and we have good reason to suppose, that it always was exposed to the external air. Wherever we trace a stratum of basaltes under the cover of other incumbent rocks, it is not then formed into any regular figure. Wherever we cut through it in sinking coal-pits, we do not find it regularly formed. Wherever the face of a regularly formed basaltine rock is quarried away, until it goes under other incumbent rocks, we soon lose the angular figures, and an uniform face of a rock comes in without the least appearance of a prismatical, globous, or any other regular figure." We do not know, that any of the greenstone in the vicinity of New-Haven is covered by other rocks; but it may be the case in some parts of this secondary formation.

The exterior surface of this greenstone is reddish brown, arising from the oxidation of the iron it contains. This stone is fusible into a blackish glass; and is exceedingly useful as a building stone, from its regularity of form. It contains several simple minerals; among these are the sulphurets of iron and copper, prehnite, and zeolite.

The hills of New-Haven Professor Silliman considers the commencement of several ranges of greenstone, which extend into the interior of New-England, showing themselves in precipices at Mount Tom, and Mount Holyoke, near Northampton, Mass. He also notices the remarkable resemblance of the greenstone around New-Haven to the rock of Salisbury Craig, Scotland. The latter also rests on red sandstone.

name.

Leaving the west-rock, and proceeding through West-Haven near to the Derby turnpike, a new rock presents itself, to which the Professor finds it difficult to apply a suitable He thus describes it: "Its color is bluish, inclining to white, its fracture hackly, its hardness is such, that it may be scratched even by the nail. Its structure is schistose, the laminæ are often variously contorted, and frequently striated with laminæ of quartz, and sometimes of mica, so that in many places it may be called micacious schistus, and from its soapy