what these animals have already done in the Parks, how much mischief they are capable of effecting. In the year 1780, an insect,* of the same natural family as the Hylesinus destructor, made its appearance in the pine forests of the Hartz, and was neglected. In the year 1783, whole forests had disappeared, and, for want of fuel, an end was nearly put to the mining operations of this extensive range of country. At the present moment, also, the French government is in alarm at the devastation committed in their arsenals, by an insect well known to naturalists, under the name of Lymexylon navale. About ten years ago, the principal naval engineer at Toulon, M. de Cerisier, who happened to be conversant with entomology, discovered this insect in the dock-yards, and recommended certain precautions to be taken for the preservation of the timber there lodged. The French Government objected to the expense requisite for obviating an evil, of which, as yet, they had no experience; and now, when perhaps it is too late, the minister of Marine has determined to follow M. de Cerisier's advice. It is from such instances that we perceive the truth of an observation made by a French academician, while alluding to the devastation which such insects may occasion: "L'histoire de ces animaux merite d'ètre connu, à raison de son extrême importance, de tous les grands proprietaires et surtout par les inspecteurs généraux de nos forêts; elles ont aussi leurs insectes destructeurs, et ils verroient combien de causes qui dans le principe ne fixent au moment l'attention peuvent par négligence devinir funestes à l'état."

April, 1824.

ART. XXIX.-Remarks on the Geology of Boston and its Vicinity. By J. W. WEBSTER, M. D. &c.

THE peninsula upon which the city of Boston is built has as yet afforded little to interest the geologist, and the sections of the strata composing it, which have been made, are as yet too inconsiderable to enable us to arrive at any very satisfactory conclusions as to its geological structure. Future and more extensive observations will, it is to be hoped, authorize a more minute description than can at present be given. The

* Bostrychus typographus, Fab.

notes of the borings for water and the sections made in constructing wells, as far as they have fallen under my observation, exhibit, with one exception, no rocks in place, but alternating layers of plastic clay, gravel and sand.* It is somewhat remarkable that in a formation so analogous to the plastic clay formation of London and some other well known localities, no fossil remains have as yet been discovered; we cannot but indulge the hope, however, and have every reason to expect, that they will at no very distant period be met with.t

The only rock which has been found in place and at a considerable depth under the surface, is a variety of clay slate of a light grey colour, dotted with minute points of black;-it is the variety known among mineralogists as whet-slate. Sev

* In the 3d vol. of the Memoirs of the American Academy is a paper on the springs and wells of Boston, by the late Rev. Dr Lathrop, in which the following is given as a section of the southeasterly side of Beacon hill.

7. Grey sand with slate and quartz

fl. in. 0 6

1 6

56445

8. Blue clay with small stones of the same colour and very little variation

63

9. Indurated clay, with larger stones, of the slate kind chiefly; one with ferruginous veins and an incrustation of calcareous matter which effervesces with an acid

10. A mixture of clay and gravel, with smooth stones like those commonly found on the sea shore, and appear as if rubbed against each other

3

2

96 0

This well (which is in the yard of the state house) is 96 feet deep; its bottom is about 7 feet above the level of the sea.

Dr Lathrop speaks of an attempt made at the southwestern part of the peninsula, to dig a well "near the sea." "Having dug about 60 feet in a body of clay without finding water, preparation was made in the asual way for boring, and after passing about 40 feet in the same body of clay, the auger was impeded with stone. A few strokes with a drill'broke through the slate covering, and the water gushed up with such rapidity and force that the workmen with difficulty were saved from death."

A few months since, in repairing an old well (the bottom of which was 32 feet below the surface) near the bead of Elm Street, a stratum of compact yellowish clay was cut through, which continued 30 feet, more or less, intermixed with fine sand and gravel; this was underlaid by a still more compact clay containing small fragments of clay slate.

+ Oyster and clam shells, not however in a fossil state, are often met with in digging wells, and several have lately been found about 50 feet below the surface of Copps' hill.

eral years ago a rock of sienite was to be seen near the western extremity of the common, apparently passing from under Beacon hill. For a considerable time I was inclined to believe that this was the extreme point, or out-going, of a bed of this rock, but repeated examination of the hill has since led me to doubt the correctness of that opinion, and to suspect that this mass was one of those large boulders which are so common in the clay of this vicinity. Not long since I noticed in the clay of Beacon hill a mass of amygdaloid exceeding four feet in diameter, and agreeing in every respect with the rock so abundant at Brighton.

The three hills to which Boston owed its ancient name, and so much of its picturesque beauty, have been in a great measure removed, and great facilities have thus been afforded for studying their geological structure. Copps' hill at the northeastern extremity of the peninsula is composed of hard, compact clay, containing many small boulders of various primitive rocks, and others which can be identified with the strata of the opposite main land, Charlestown.

Beacon hill, originally about 140 feet in height, on the western side of the city, is likewise composed of clay intermixed with quartzose gravel, and boulders of transition rocks, such as are seen in place at Brighton and Brookline.

Fort hill on the southeastern side of the city, rising about 80 feet above the level of the sea, agrees in structure with that portion of the opposite main land known as SouthBoston.

The clay in these three hills is the impure potter's clay, which makes so conspicuous a feature in the geological structure of the low lands of this vicinity, and of which such important use is made in the extensive manufacture of bricks at South-Boston, Charlestown, and several other places. This clay is overlaid by the blue plastic clay and gravel; the lat ter, however, extends but a short distance from the water's edge.

More minute details on the geology of the peninsula will be reserved until better opportunities for examination have occurred; which in the present ardor for improvement cannot be far distant.

Crossing the arm of the sea that flows on the northwest and southwest, and which separates Boston from Charlestown and Cambridge, we observe the clay extending from the water's edge, along the low lands and on the borders. of the rivers, to the distance, in some places, of between two

and three miles; in others it is soon lost beneath the beds of gravel and mud. In the town of Charlestown the land gradually rises from the water's edge towards the northwest forming the two eminences so well known under the names of Bunker's and Breed's hills; the former being 113 feet, and the latter 87 feet above the sea. These eminences are composed, as far as can yet be seen, of quartzose gravel intermixed with clay; the only rocks met with upon them are rolled masses of greenstone, hornblende slate, sienite, and granite. In the greenstone, epidote occurs in crystals of considerable size, with white quartz, and some calcareous spar.

From the foot of Breed's hill the land continues for a short distance nearly level, when it gradually rises, until at Winter hill it attains the elevation of 124 feet. This hill is composed of clay slate passing on the north into hornblende slate. These rocks are distinctly stratified, and the strata dip towards the north under an angle of from 15° to 20°. They contain beds and veins of greenstone, which in some places is very compact, in others soft and friable, especially where sulphuretted iron is present in the rock. From the abundance of the clay slate and its fissile character, it has been by many considered indicative of coal, and considerable expense has at various times been incurred in fruitless searches for that substance. From careful and repeated examination of this hill in every direction, I have been unable to discover in it any characteristic members of the coal formation. The rocks which accompany coal are of a peculiar character, and taken collectively constitute a series to which geologists have given the name coal formation. To those who have paid much attention to geology an enumeration of these rocks will be unnecessary, but as some of our readers have probably never looked into a geological treatise, or examined a coal formation, and as it is well known that in this part of our country coal is an important desideratum, it may be useful briefly to notice some of the principal rocks and minerals associated with this sub

stance.

Coal is generally found connected with a sandstone, composed of particles of quartz, variously mixed with grains of feldspar and scales of mica, and these constituent parts are of

It is in contemplation to erect on Bunker's hill a majestic monument in commemoration of the events of the 17th of June, 1775. Should there be no bed of rock beneath the comparatively loose materials of which, as far as can now be seen, this hill is composed, it is deserving of serious consideration whether a foundation sufficiently firm for such a structure can be anticipated.

ten so large as to entitle the rock to the name of Breccia, or Conglomerate.

Three varieties of slate are met with in coal fields, viz. bituminous shale, slate-clay, and flinty slate. The shale is more or less impregnated with bituminous matter, has a deep brown, nearly a black colour, and a distinct slaty fracture. It usually contains impressions of reeds and ferns.

The slate-clay is of a grey colour, having an earthy aspect, it sometimes contains scales of mica, and quartz; like the shale, it often presents vegetable impressions. When this slate-clay contains a large proportion of siliceous earth, it is hard, and becomes the flinty slate.

Limestone is also found in this formation, and its colour is various; it generally contains petrifactions: this rock is, however, not always present.

Carbonate and hydrate of iron are common in the coal formations of Scotland and England, and from them is obtained the principal part of the iron produced in Great Britain. Greenstone and porphyry, of peculiar characters, are often met with constituting veins and beds.

It has been remarked that in some districts beds of coal are contained in the slate, which, as it recedes from the coal, becomes coarser until it passes into sandstone; in other cases, and perhaps more commonly, the sandstone is beneath the coal, and the slate above it. Sometimes the coal is covered with limestone, at others it rests upon it.

In Scotland, according to Prof. Jameson, and as I have myself observed, the predominating and characteristic members of the formation are those already enumerated; the same is true with some little variation in regard to the coal fields of England, France, and Germany.

There is but one extensive section of the strata of Winter hill, and this as we shall presently have occasion to notice more particularly, is through slate. But the structure of the surrounding country and the indisputable characters of the slate are strong facts against the existence of coal in this place. The slate has often a high lustre and dark colour, being at the same time easily divisible into thin lamina; these circumstances have caused it to be confounded by those who have not attended to mineralogy, with the shale and slate-clay of the coal formation. But they are readily distinguishable by the streak, hardness, and other characters. The clay slate gives a greyish white streak, the shale a shining brown streak; the slate-clay is much softer than clay.