own limited period, and the whole taken together yield a consecutive record. But while we find them merely scattered over the later formations in which they occur, and that very sparingly, in the Silurian System we find them congregated in such vast crowds, that their remains enter largely into the composition of many of the rocks which compose it. The Trilobite is the distinguishing organism of the group, marrying, if I may so express myself, its upper and lower beds; and what the Trilobite is to the Silurian formations, the Pterichthys seems to be to the formations of the Old Red Sandstone, with this difference, that, so far as is yet known, it is restricted to this system alone, occurring in neither the Silurian System below, nor in the Coal Measures above.

I am but imperfectly acquainted with the localities in which the upper beds of the Old Red Sandstone underlie the lower beds of the Coal Measures, or where any gradation of character appears. The upper yellow sandstone belt is extensively developed in Moray, but it contains no trace of carbonaceous matter in even its higher strata, and no other remains than those of the Holoptychius and its cotemporaries. The system in the north of Scotland differs as much from the carboniferous group in its upper as in its lower rocks ; and a similar difference has been remarked in Fife, where the groupes appear in contact a few miles to the west of St Andrews. In England, in repeated instances, the junction, as shown by Mr Murchison, in singularly instructive sections, is well marked, the carboniferous limestones resting conformably on the

pper Old Red Sandstone. No other system inter

_ouse,

osed between them; and it is corroborative of the ct, that in Russia, scales of the Megalichthys, a fish f the Coal Measures, were found by Mr Murchison 1 an upper bed of the Old Red Sandstone, mingled ith those of the Holoptychius; and that in Burdie-a lower bed of the Coal Measures,—scales of he Holoptychius have been found mingled with those f the Megalichthys. Both ichthyolites cross, as it vere, the borders of their respective formations; the one witnessed the closing twilight of the more ancient ystem, the other the dawn of the system which succeeded it. They were cotemporaries for a time, somewhat in the manner that Shem was cotemporary with Isaac.

There is a Rabbinical tradition that the sons of Tubal Cain, taught by a prophet of the coming deluge, and unwilling that their father's arts should be lost in it to posterity, erected two obelisks of brass, on which they inscribed a record of his discoveries, and that thus the learning of the family survived the cataclysm. The flood subsided, and the obelisks, sculptured from pinacle to base, were found fast fixed in the rock. Now the twin pyramids of the Old Red Sandstone, with their party-coloured bars and their thickly-crowded inscriptions, belong to a period immensely more remote than that of the columns of the antediluvians, and they bear a more certain record. I have, perhaps, dwelt too long on their various compartments; but the Artist by whom they have been erected, and who has preserved in them so wonderful a chronicle of his earlier

works, has willed surely that they should be read, and I have perused but a small portion of the whole. Years must pass ere the entire record can be deciphered; but of all its curiously-inscribed sentences the result will prove the same,-they will be all found to testify of the Infinite Mind.

CHAPTER X.

Speculations in the Old Red Sandstone, and their Character. George, first Earl of Cromarty.-His Sagacity as a Naturalist at fault in one instance.-Sets himself to dig for Coal in the Lower Old Red Sandstone.-Discovers a fine Artesian Well.-Value of Geological Knowledge in an economic view. Scarce a Secondary Formation in the Kingdom in which Coal has not been sought for.-Mineral Springs of the Old Red Sandstone.-Strathpeffer.-Its Peculiarities whence derived.-Chalybeate Springs of Easter Ross and the Black Isle.-Petrifying Springs.-Building-Stone and Lime of the Old Red Sandstone.-Its various Soils.

THERE has been much money lost, and a good deal won, in speculations connected with the Old Red Sandstone. The speculations in which money has been won have consorted, if I may so speak, with the character of the system, and those in which money has been lost have not. Instead, however, of producing a formal chapter on the economic uses to which its various deposits have been applied, or the unfortunate undertakings which an acquaintance with its geology would have prevented, I shall throw together, as they occur to me, a few simple facts illustrative of both. George, first Earl of Cromarty, seems, like his namesake and cotemporary, the too celebrated Sir George

M-Kenzie of Roseavoch, to have been a man of an eminently active and inquiring mind. He found leisure, in the course of a very busy life, to write several historical dissertations of great research, and a very elaborate Synopsis Apocalyptica. He is the author, too, of an exceedingly curious letter on the "Second Sight," addressed to the philosophic Boyle, which contains a large amount of amusing and extraordinary fact; and his description of the formation of a peatmoss in the central Highlands of Ross-shire has been quoted by almost every naturalist who, since the days of the sagacious nobleman, has written on the formation of peat. His life was extended to extreme old age; and as his literary ardour remained undiminished till the last, some of his writings were produced at a period when most other men are sunk in the incurious indifferency and languor of old age. And among these later productions are his remarks on peat. He relates, that when a very young man, he had marked, in passing on a journey through the central Highlands of Ross-shire, a wood of very ancient trees,—doddered and moss-grown, and evidently passing into a state of death through the last stages of decay. He had been led by business into the same district many years after, when in middle life, and found that the wood had entirely disappeared, and that the heathy hollow which it had covered was now occupied by a green and stagnant morass, unvaried in its tame and level extent by either bush or tree. In his old age, he again visited the locality, and saw the green surface roughened with dingy-coloured hollows, and several Highlanders engaged in it in cutting peat in a stratum several feet in