intense heat is to originate after the oxidation of the elementary metals has been effected, he has not informed us.

One great objection to the theory of Hutton was his assumption of an internal fire to fuse his stratified masses, when they had accumulated in sufficient quantity to form new continents and islands. The discovery of the metallic bases of the earths, however, seems, in some measure, to supply an explanation of the occurrence of occasional intense heat, without the aid of central fire continually existing, or of materials, combustible in the usual acceptation of the term.

Mr Lyell is of opinion that this hypothesis is as gratuitous and arbitrary as the original igneous fluidity of the globe, propounded by Leibnitz. We humbly think, however, that the metallic theory has facts to support its probability, while the other is a pure hypothesis.

We subjoin the following remarks on the strata round Edinburgh, from our Geology of the district.

"Another subject of inquiry is the relative age of the trap rocks; and to decide this, we think we have sufficient data. From the entire absence of trap debris in the sandstone of the coal measures, and, on the other hand, from the uniform presence of mica there, we are entitled to conclude that granite or gneiss rocks furnished the materials of this extensive deposit ; and that consequently, no trap rocks existed in the vicinity up to the period of the last carboniferous deposit. In the more superficial strata, within a few hundred yards of the surface, we begin to have evidence of trap.

That the trap rocks have been the agents in the elevation of the carboniferous strata, is also evident; for these disrupted strata rest upon the trap; and on the south side of Arthur's Seat, portions of limestone and sandstone still remain, which have been carried upwards.

Another question arises: Are the trap rocks all of one age, or are they of different epochs ? There appear to be two facts which indicate a difference of age of

H

these rocks: First, The different character of the trap placed in juxtaposition, and the marks of disturbance by which the older was affected by the intrusion of the subsequent; Second, The appearance of trap debris, and rounded masses of these rocks imbedded in strata which have been elevated by a subsequent eruption of trap.

If we might form any conjecture, however, from the quantity of this debris accumulated, the period between the first and last eruption of trap must not have been longcertainly a very short period, indeed, compared to the time necessary for the deposition of the coal

strata.

The next inquiry is Were the trap rocks elevated under the water of the ocean, or after the plain of MidLothian became dry land? The facts stated immediately before, will shew that the first eruption of trap; at least, must have been while the waters of the sea still flowed over the spot, and that the ocean continued to flow for some time, by which the trap debris was formed, and many of the large boulders probably carried to the situations where we now find them.

Another fact corroborative of this is, the amygdaloidal state of the vesicular trap of Arthur's Seat and the Pentlands, which must have been owing to a deposit of matter held in solution by a fluid in which they were immersed, subsequent to their eruption in a porous lavalike form.

That dry land, however, almost immediately succeeded the last elevation of the trap rocks, is apparent from the state of the diluvium which lies immediately above, and which appears to have been at once deposited, before the sharp edges of the rocks had time to be worn down,* and which diluvium has ever since remained undisturbed and unmixed with any marine substances which could indicate the presence of an ocean. To this diluvium has

* This is seen at Niddry quarry, and elsewhere.

succeeded, at no long interval, the present soil, with its present vegetables and animals.

The most remarkable and unaccountable circumstance accompanying the last elevation of the trap, seems to have been a total and abrupt change of the whole country. The animals and vegetables that covered the former soil, and stocked the former seas and rivers, appear to have been entirely destroyed, and their remains overwhelmed and buried in the great convulsion of nature. Not only had their destruction and extirpation been complete, but the whole constitution of soil and climate seems to have been so altered, as to preclude the possibility of their again existing, had a remnant even been saved. From all we can ascertain of the structure, both of the animals and vegetables of this early period, they bear a nearer analogy to those of tropical climates than to any that exist in the temperate regions of the globe.

We here in vain look for any thing intermediate between the animals and vegetables of the carboniferous era and those of the present. The same kind of coprolites are found in the alluvial clay as in the low-lying shale; and in the highest beds of the coal measures, the same leaves snd trunks of vegetables are in as great abundance as in the seams 3000 feet lower.

Immediately, too, after this convulsion, the sedimentary deposit of sandstone appears to have ceased. No more vegetable remains, either, have been accumulated in those singularly alternate layers which seemed to mark a periodical overflow of some huge river, or some other unknown modification of transporting currents. Not only had the catastrophe produced a local change, but it had extended to all the region then in connection with this part of the country.

In the alluvium, we have already remarked that many rounded masses or boulder stones are to be found. These consist of fragments of all the rocks in the neigh