position, &c. would have escaped observation, or would have been passed over as indifferent, had they not been considered as possessing a peculiar value in the defence or refutation of some particular system.'-Pref. p. 16.

In the account we shall give of this work, we shall confine ourselves principally to the matters of fact. To enter into an examination of the author's theoretical opinions, would extend our remarks beyond our limits, unless we were to omit what we have no doubt will be more generally interesting to our readers. The Apennines are an uninterrupted range of mountains, which, branching off from the Maritime Alps, and dividing Italy from north to south, form, as it were, the back-bone of that peninsula. Their geographical termination can easily be determined with sufficient accuracy; but the geologist finds considerable difficulty to fix upon the boundary which separates them from the Alps; for, although they consist principally of secondary rocks, yet, as they approach the primitive country of the Alps, they partake more and more of the nature of the latter: and there is a considerable tract of them where there is a mixture of primitive rocks of different kinds; such as, serpentine, clay slate, greenstone, and granular limestone. These do not present the sharp, broken outlines, the pinnacles and needles, which tower aloft in the Alps, standing like the ruins of great masses which have been broken down and mouldered by the hand of time: Their summits have, in general, a rounded form, a more regular and uniform contour, and their sides a more gentle slope; and although there are many deep gullies hollowed out in the sides of the Apennines, there is no great valley which divides the chain completely across.

The most considerable elevations are, Il Velino, and Il Gran Sasso, which are both in the Abruzzi, and Il Cimone di Fanano, in the territory of Modena. The first of these was found by Von Buch to be 7872 Paris feet above the level of the sea; the second has been estimated, by barometrical measurement, at 9577 feet; and Pini states Il Cimone di Fanano to be 6546 feet above the sea. From the summit of the latter there is a most extensive view, commanding the vast plain of Lombardy, the country around Parma, Reggio, and Modena, a part of Romagna, with the Adriatic in the distance; and, on the other side, a great part of Tuscany, with the whole course of the Arno from its source to its embouchure. The country on the two sides of the Apennines presents considerable difference in geological structure; that next the Adriatic being wholly composed of secondary rocks, with the exception of some insulated masses of serpentine which appear here and there; while, on the

side of the Mediterranean, there is an extensive tract, and chiefly along the shore, of primary and transition rocks, with only occasional patches of secondary strata. On this side, also, have burst forth those innumerable volcanoes which have covered such a vast extent of country with their ashes.

The principal rock of which the north-western part of the Apennines is composed, is a kind of sandstone, known in Tuscany by the names of Macigno and Pietra Serena. It is an aggregate, consisting of grains of quartz, and scales of silvery mica, united by an argillaceous cement. Its colour is most frequently a dark blueish gray; its texture is sometimes coarse-grained, and sometimes so fine, that the component parts cannot be distinguished by the naked eye, It frequently contains small fragments of slate, which appear like black spots; and also angular portions of petrosilex and jasper. It occurs stratified in thick beds, and splits into rhomboidal and polyhedral fragments, and is, in some places, capable of being divided into thin slates, which are used for roofing. In many situations it alternates with a blackish clay-slate, containing minute scales of mica, which give it a silky lustre. M. Brocchi considers these rocks as strictly belonging to the grauwacke and grauwacke-slate of the German mineralogists; and they will be easily recognised as being identical with many of the rocks in Scotland, Wales, and the West of England, which have been described by the same names. The grauwacke of the Apennines also contains beds of limestone; and in the neighbourhood of these beds, the grauwacke is intermixed with calcareous matter. The limestone is of a smoke-gray colour, of a shining and semi-crystalline texture, with a scaly fracture, and contains minute scales of mica and grains of quartz. It also contains animal remains; but they are rare, and they have never been seen by M. Brocchi in the grauwacke, though he has frequently observed portions of bituminized wood in it. Besides these partial and subordinate calcareous beds, there are, in many places, considerable hills entirely composed of this transition limestone. They appear in different parts of the coast, from Genoa to Civita Vecchia; but are nowhere seen between the Apennines and the Adriatic. The Brocatello marble of Siena belongs to this class. With the exception of some slight indications of manganese and pyrites, no metallic substances have been found in the grauwacke of the Apennines. M. Brocchi has not been able to fix, with precision, the southern boundary of this series of rocks; but he believes that it ceases to form any connected chain of hills about the neighbourhood of Cortona. It is not confined to the more elevated and central mountains, but appears also in the lower parts of the Apennines, as may be seen in the hills around Flo

rence, at Fiesole, Artimino, Malmantile, &c. The direction and dip of the strata do not appear to follow any constant rule. They are subject to continual variation, and sometimes in the same mountain-as, in Il Cimone di Fanano, they may be seen dipping to different points.

The rocks hitherto mentioned constitute but a small portion of the great chain of the Apennines, and may be considered only as the beginning of it. That which composes the principal part, and which, from its general distribution, may strictly be termed the rock of the Apennines, is a limestone, but quite different in its characters from that already spoken of. It affords very little interest to the mineralogist; and, as soon as he enters its domain, he will traverse vast tracts of country, without any other rock appearing from the foot to the summit of the mountain; and he will pass whole days without meeting a single object to relieve the fatigue and tedium of his journey. Of this limestone are composed the high Apennines of Tuscany and of Romagna, those of Fabriano, Foligno, &c. It extends into the Abruzzi, through Puglia and Basilicata to the extreme point of Otranto: it is not certain whether it stretches into Calabria. Its prevailing colours are, pearl gray, dusky white, and pale flesh red; and sometimes it has a greenish tint. Its fracture is smooth, earthy, and without lustre; the fragments often assume a conchoidal form; and it is frequently traversed by slender veins and filaments of calcareous spar. It contains, in some places, beds of fetid limestone, as at Castellamare in the Bay of Naples, and in the neighbourhood of Salerno. Remains of marine animals are found in it, but not abundantly: casts of the Cornu Ammonis are the most common.

The limestone is identical with that of some of the Alpine mountains which surround the plain of Lombardy, along the territories of Como, Bergamo, Brescia, Verona, &c.: it also quite agrees with that of Dalmatia and Istria. The limestone of Jura, which some, without any apparent reason, have wished to distinguish as a particular formation, is in no respect different from that now described. Reuss has said, that the limestone of the Jura chain never contains flint or jasper; but Bernoulli informs us, that both these substances are found in the mountain of Jura itself. Flint, (or more probably chert), although not very abundant in the Apennines, is found in several places, -as in the mountain opposite the cascade of Tivoli, in those of Caserta, Benevento, &c. Reuss has called the limestone of Jura Höhlenkalk, or cave limestone, from the number of vast caverns existing in the mountains composed of this rock; but these are also of frequent occurrence in Italy,-as at Todi, Orvieto, Foligno, &c. This limestone is very barren, both in metallic and

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bituminous substances. Some slight indications of fossil coal have been found here and there in the lower parts of the Apennines; and at Castro and Trisulti, in the Campagna di Roma, mountain pitch has been collected from it in small quantity. The distinct stratification of this rock, its opacity and dullearthy aspect, and its occurring always above the rocks already mentioned, and never covered, except by the alluvial deposits, evidently fix its place among what are usually termed the secondary rocks. It is not confined to the principal chain of the Apennines, but extends also into the lower country, forming here and there detached hills. In the plain of Tuscany, (if that term can be plied to so undulating a surface), it covers in many places the grauwacke and other older rocks; but in general only a small part of the limestone strata are seen, as they are covered either by volcanic matter, as in the Agro Romano and Campania, or by sand and marl, as in Tuscany, in the territory of Bologna, in Romagna, in the Abruzzi, &c. This is not the case, however, in Puglia Pietrosa; for there, the bare limestone strata extend to the sea-shore, and are only occasionally concealed by a scanty coat of vegetable soil, or by a kind of shelly tufa; so that in planting the small trees which are cultivated there, such as the olive, the vine, and the carob-tree, they are obliged to break with mallets and iron bars the solid stony crust, in order to come at an intermediate layer of ochreous clay, where the roots may spread. In Tuscany, there are a great many hills of limestone, which are quite detached from the main body of the Apennines; but it is remarkable, that in Romagna, throughout the whole of that long tract which extends from Bologna to Macerata, and even to Fermo, on the confines of Abruzzo, the only calcareous hill which is distinctly separated from the Apennines, is that in the neighbourhood of Ancona, forming a promontory on the sea-shore. In Puglia Pietrosa, however, there is a long continued chain of low hills, (Le Murgie), which are separated from the Apennines by the plain of Capitanata, though they differ in no respect from them in the nature of the rock of which they are composed.

From what has been said, the primitive rocks cannot be supposed to exist very abundantly in the Apennines; and in fact they are only found at the two extremities of the great chain of these mountains, and are wholly wanting in the intermediate space. At both extremities there are found granite, clay-slate, mica-slate, and cristalline limestone. Granite is very abundant in Calabria, and it is also sometimes found in Liguria; as Spadoni observed it in the neighbourhood of Sarzana, and Viviani in some other part of the Riviera di Levante. Mica-slate occurs in Eastern Liguria, and at Massa di Carrara; but it may

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also be considered as extending further south towards the Mediterranean, as gneiss, which is only a modification of it, appears in the mountains of Montieri, Gerfalco, and Prata, in the Maremma Sanese. But these places are far distant from the calcareous Apennines; near which, in the opinion of M. Brocchi, not one of these rocks is to be found.

The primitive rock which chiefly predominates is serpentine. It forms, according to Viviani, the nucleus of all the Apennines in Eastern Liguria, where it is covered by transition limestone, as at Pignone, and in the neighbourhood of Spezia; and by clayslate, greenstone and grauwacke, at Chiavari, Lavagra, and Levanto. This rock is found at a considerable height in the Maritime, Grætian, and Pennine Alps; from whence it descends into Liguria with a continually decreasing level, until it no longer appears above the surface of the ground. Thus, while it constitutes the chief mass of many mountains in Liguria, which make a part of the principal chain of the Apennines, in Tuscany, on the contrary, it only composes hills of moderate elevation. The part of Tuscany where it occurs most abundantly, is near Impruneta, where it occupies almost the whole district between the Ema and the Greve; from whence it seems to extend a considerable way, as it is met with at Borgo San Stefano, in the neighbourhood of Anghiari, and in the territory of Gubbio. It forms the principal mass of the hills of Monte Nero, Valle Benedetta, and Sambuca, near Leghorn. In the territory of Volterra, it is seen between Montecatino and Miemo; also at Riparbella, near Bibona; and in the neighbourhood of Orbitello, which M. Brocchi considers to be the most southern point of its appearance along the coast of the Tyrrhene Sea.

It generally appears in detached masses, more or less extensive, which are separated from each other by intervals of several miles; but there is every reason to believe, that they are the more prominent parts of one general mass, which has been partially covered by other materials; these are in general grauwacke, galestro, (a kind of coarse-grained grauwacke-slate, containing a great deal of calcareous matter), secondary limestone, grey marl, and siliceo-calcareous sand. M. Brocchi considers it highly probable, that the serpentine is not only the primitive rock on which the secondary formations in the plain of Tuscany rest, but that it extends under the Apennines to the opposite side of the Peninsula; as he observed it in several places on the eastern side of these mountains. He saw it at Varana, about fifteen miles from Modena, and five from Sassuolo, where it rises in the form of an insulated rock, surrounded by calcareous sand, having solid beds of limestone interstratified. But the most considerable group he observed was