that can hinder us to infer the igneous origin of the former of these rocks, unless the obscure position of the St Wendel pitchstone. Now, were it even proved that this mass forms a short bed, it would only appear as a kind of stream, or a bed-like vein, among sandstones, in the same manner as the basalts are seen in streams or in bed-like veins among calcareous or argillaceous formations, in the Vicentin, Sicily, Auvergne, Scotland, and elsewhere. This observation is equally applicable to the difficulties which M. Beudant finds in the alternations of secondary basalts and sandstones.

It is a matter of fact, that, in Silesia, in Scotland, in France, Germany, &c. such alternations exist; but I have already shown in my Essay, that these alternations are only included in a short space of ground, and that they cannot be observed beyond certain limits. After this, one cannot but be astonished to find M. Beudant asserting that they pervade the whole extent of a formation; whereas the fact is, that they only appear in a formation in the form of more or less extended and unconnected patches. If it be admitted by all geologists, that the face of a hill or a short space has often given rise to the idea of alternations of true basaltic beds with sandstone, what geologist has ever been able to trace a single basaltic bed through a whole local sandstone formation; and where, in the whole annals of science, do we find recorded a single instance of the kind?

Besides, on examining these very alternations, one finds that the number of short beds forming streams or vein-like beds diminishes much, for most of them, after a scrupulous examination, turn out to be only various kinds of veins; for instance, Salisbury Craigs, Lichtenberg district, &c.; and often the short beds have the appearances of those masses elevated at once from below, as at Stirling Castle, Perth, North Berwick Law, Edinburgh*, &c., or the matters have extended themselves to a short distance from the orifice through which they were elevated.

These appearances only present great difficulties of explanation. If we comprehend among these alternations the beds of wacke and of trap-tuffa, we then naturally find it difficult to explain the igneous origin of so many beds of only a few feet in

* See Professor Jameson in Wernerian Memoirs.

thickness alternating with rocks evidently arenaceous, as at the Calton Hill, &c.

But geologists accustomed, like M. Beudant, to distinguish with so much accuracy the immediate products of volcanoes from those which are only results of aqueous destruction and re-aggregation of igneous matters, will find these alternations quite natural; nor will he be at all astonished to find them extending over a great space, although this space will never equal the extent of the common subordinate beds of the sandstone formation; and this phenomenon will only furnish him with an excellent argument for maintaining that these igneous deposits have taken place during the formation of the sandstone deposite, in the same manner as the conchiferous basaltic tuffa of the Veronese, alternating with tertiary beds, shows that basaltic eruptions have happened during that period of time.

Yet M. Beudant finds it extraordinary that these igneous matters should have been able to introduce themselves in such a way among Neptunian arenaceous rocks. This is not a little surprising; for I may venture to predict, that his able description of trachytic districts will soon induce geologists in general to extend with me the igneous domain. It may even be said, that the Wernerian idea of restricting volcanic productions to existing volcanoes only, was much more consistent with sound logic, than to extend the empire of Pluto to the extinct volcanoes and trachytes, and to stop there. In short, the geological thermometer must rise to a degree indicated by Nature, and not by partial views of natural phenomena. I can scarcely believe that M. Beudant should in reality doubt the alternation of basalts with tertiary deposites, for it is a fact too well determined to admit of dispute; and those who believe it, or who have seen it, will see nothing extraordinary in the alternation of older basalts with sandstones.

The geognostical position of porphyries has the greatest relation with that of trachytes; they often form bell-like hillocks or domes, composed of concentric circular layers; as, for example, near Freyberg, Halle, &c. one might fancy himself in front of the Puy of Sarcouy, in Auvergne. In other places, they rise, like certain trachytic districts, into conical and acuminated hills, which are sometimes as striking, on account of their isolated po

sition, as the trachytic mountains; but if the porphyritic masses have been but small, they form only nearly vertical, cylindrical, or wedge-shaped masses, like the submarine basalts of Eisenach, Moravia, Hungary, &c.

Porphyries are situate in hillocks, associated with some kinds of porphyritic streams or protuberances, upon primitive and transition rocks, upon the coal sandstone, upon the todliegende or newer red sandstone, and upon the first floetz limestone. All these formations are traversed by porphyry veins, or cylindrical bodies of the same rock, as is so clearly seen in Scotland, the Erzgebirge, the Alps, &c.; here and there only the veins have accidentally formed short beds or imbedded masses in the Neptunian deposites.

Lastly, porphyries are often connected with sienitic and granitic hills, or immense cylindrical or wedge-shaped granitic masses or districts, and sometimes include more or less considerable portions of older rocks, in some instances elevated, or dislocated, or even altered. Ben-Nevis, the highest mountain in Britain, presents such a connection with sienite; and Dr Macknight's characteristic description of that hill and its neighbourhood testifies most amply its igneous elevation.

After adducing all these facts, which I look upon as of a very superior kind, I might conclude these pages with nearly the same words as Mr Beudant, did I not think them rather too strong; and yet, for the benefit of science, while, at the same time, I have no inclination to diminish the high degree of credit which my opponent so justly deserves, I shall here transcribe his conclusion.

"After all these facts," says M. Beudant," which I look upon as of a very superior kind, I am of opinion that none of the observations which have hitherto been adduced as tending to the adoption of the igneous (I might say aqueous) origin of the felspar and basaltic rocks of the red sandstone, even allowing them all the weight which they have not, could prevail over circumstances of position, so generally diffused in nature, and so well established by the great majority of geologists."

If, after the exposition of similar facts, the igneous (I might say aqueous) origin is still to be admitted for the crystalline rocks subordinate to the coal sandstone or the red sandstone, it VOL. X. NO. 19. JAN. 1824.

F

it must in like manner be admitted, that all the crystalline and arenaceous rocks which constitute the crust of the globe (I might

say

all the crystalline rocks which enter into the composition of the crust of the globe, and even the trachytic and basaltic rocks) are also formed by fire (I might say by water). The fabric of the science will then be overturned, and the science itself rendered subordinate to a favourite system, while error will thus occupy the place of truth.

In the present state of science, and without entertaining any prospective views, it is extremely obvious that the probabilities are much in favour of the hypothesis of an aqueous (I might say igneous) formation. It would tend to diminish, instead of advancing, science; and return it to its infancy, to admit any other opinion, so long as new facts could not be thrown into the balance of probabilities.

The whole of this conclusion applies equally, and à fortiori, to the amygdaloids of the grey-wacke, as well as to the greenstones and the porphyries which accompany them.

ART. XI. Journal of a Tour to the Coast of the Adriatic Sea, and to the Mountains of Carniola, Carinthia, Tyrol, Saltzburg, and Bohemia, undertaken chiefly with a view to the Botany and Entomology of those countries. By Dr DaVID HENRY HOPPE and Dr HENRY HORNSCHUCH. (Continued from vol. ix. p. 353.)

« Hundsberg, April 24.—THE laying out of the beautiful

plants that we last brought home employed us during the whole of yesterday; and, as it also emptied our botanizing boxes, so we determined to replenish these with an abundant stock of Mercurialis ovata, for our collection. Accordingly, we hastened this morning direct to Contobello, and pursued the "buona strada" without much delay, though, as we went, we observed in flower the hairy Lotus corniculatus, and Carex distans, also C. glauca of Scopoli, and C. pracox of Jacquin. We likewise found a singular plant, whose name we cannot at present determine. It is an Apargia. Probably Scopoli has included this species under his A. hispida or hirta; but it

certainly is not the first, and the latter has always appeared to us to be a doubtful plant, which, though mentioned by all authors, is far from being certainly known. Its leaves have the form of all its allied species, but they are narrower, bristly throughout, with the bristles trifid; the stem is much longer and slenderer than in A. hispida; the calyx differently formed; and its yellow petals are red on the outside. Here also grew Hieracium auricula, H. pilosella, and an Ecidium on leaves of an unknown Scorzonera. Globularia vulgaris, and the Astragalus, which we lately found, were plentifully in flower. We now ascended to the top of the mountain to botanize. We saw Thymus Serpyllum var, angustifolium, Thlaspi pracox with an Ecidium, Glechoma hederacea with very hairy leaves, and Thlaspi saxatile. We soon reached a very stony tract, covered with bushes, where many plants just appeared; for instance, Carex alpestris Willdenow, C. Michelii, Paonia officinalis, Convallaria Polygonatum, Hieracium auricula, Orobus vernus, Rhus cotinus, Dictamnus albus, and an umbelliferous plant, new to us, and not yet in flower, with large, much divided, rigid leaves, the segments very narrow, and like those of Athamanta Meum. Lamium maculatum was everywhere in blossom, having spotted leaves; whereas, in our Salzburg specimens of this plant we always find them plain. At last we came to our much admired Mercurialis, which grew plentifully under bushes, on stony ground. Potentilla subacaulis was its neighbour, on grassy hillocks, in open spots. We now ascended nearer to the summit, and then arrived at a delightful place, where the Melittis with white flowers abounded, which Smith* has given as new. Asclepias Vincetoxicum, Orobi, Lathyri, and many other plants, now appeared, when at last one of us, with great enthusiasm, cried out Sesleria tenuifolia, and the other responded, in like manner, Fraxinus Ornus! Euphorbia Characias, which grew plentifully and in great luxuriance, gave us reason to observe that Wulfen's spring had now commenced.

Here we sate ourselves down, to enjoy the delightful view of the Adriatic Sea, to partake of some sweet oranges, which supplied the place of a dinner, and to examine, more attentively,