that we do not, in fact, at all understand their nature, and that, as these are so little adapted for investigation by the assistance of experiment, there is but little prospect of afterwards acquiring more than a conjectural knowledge of the subject. The prospect is certainly not enticing. We have, however, acknowledged that it is quite natural that a complete and perfectly candid study of facts must often leave us with nothing but what is inexplicable. If it be true that, when every thing is fully explained, there is room for doubting that the strictest attention has been paid to what is matter of fact, the friend of truth will readily be satisfied with his less distinct result.

We now proceed, so far as that can here be done, to treat of the marble which occurs in the oldest rocks, or in formations which contain no organic remains. I say, in so far as that can here be done, because our opinion of the origin of this marble is, after all, entirely dependent on the view we deem it necessary to take of the mode of formation of the principal rocks among which it presents itself.

Here in the North-and, no doubt, the same is the case in other places--what is termed primitive limestone occurs most frequently in gneiss, mica-slate, and hornblende-slate, in masses which, at the first glance, might be thought to have completely the nature of beds, but which, on closer inspection, do not at all correspond entirely with the idea of beds, in so far as we understand by the term bed a particular stratum constituting a member of a series of layers parallel to one another, which were gradually deposited the one upon the other, each for itself in its own period of time. The relations exhibited by these masses of marble are by no means so simple as they would have been, had, for example, a stratum of mica-slate been first formed, then over it a stratum of marble, and again over the last micaslate. It is not only the case that, at the junction of the limestone and the including rock, we find both masses, as it were, mixed with one another, inasmuch as frequently grains of calcspar are disseminated through the slate, and in the same way the constituents of the latter disseminated in the marble, but both rocks frequently invade the boundaries of each other in a bifurcate manner; nay, portions of slate, entirely isolated, are often met with embedded in the marble, while the latter

likewise forms isolated masses in its hanging and lying including strata; the limestone in this instance being usually in very thin stripes between the strata, and the portions of slate likewise being parallel to the planes of stratification of the great slate masses. The individual plates of mica, too, which occur in the manner just stated in the marble near its junction, are parallel to the planes of stratification; and the same is the case with the hornblende crystals which are met with in the marble, when the latter is in contact with hornblende-slate. All this plainly shews that, in fact, no such entirely exclusive process of formation can have produced such a marble; whereas it is clear that the origin of the marble and that of the slate, both as regards the time and the mode of production, have had very much in common with each other. If now we must, in so far as the slates composed of siliceous compounds are concerned, reject the Neptunian theory (and this I regard as absolutely necessary), this must also be done in reference to the marble.* And those who are of opinion that the calc-spar constituting the marble has been formed by carbonate of lime in a state of fusion, or, at least, softened by heat, having been slowly solidified under sufficient pressure, will, in consequence of the above-mentioned relations of the whole mineral combination, doubtless not fail to admit that the silicates and the quartz of the slate are equally the products of fusion; while, on the other side, it will be conceded, that if the non-pyrogenic origin of the including slate can be proved, a pyrogenic origin cannot be assigned to the marble. This result will, I hope, be kept in remembrance afterwards, when we consider the origin of the primitive slates. Those who already, perhaps, think that this marble has been formed by "actions lentes," without heat, will doubtless refer to the analogy of its geognostical relations with those of the masses of marble occurring between uncrystalline strata, which were already discussed.

With respect to the crystalline limestone, an esteemed

I shall not pause here to adduce arguments against the Neptunian hypotheThe many silicates occurring in primitive limestone contradict it, as was vn by Berzelius in his Jahresbericht for 1839.

geologist expresses himself in the following terms :-" This rock occurs in not a few localities under circumstances which are in favour of its having burst forth from the interior of the earth in a melted condition, and that subsequently to the formation of the gneiss and mica-slate. The limestone masses bear completely the stamp of great veins, or of the upfillings of fissures. There are appearances indicative of a violent pushing of the limestone into the surrounding rock. Where the limestone is in contact with the bounding rocks, we find, sometimes on the former, sometimes on the latter, the consequences of powerful rubbings, exhibited in specular or friction surfaces. Farther, the granular limestone includes fragments and large masses of the bounding rock; and lastly, where the former meets other rocks, we find contact products of various descriptions, according to the nature of the different rocks which are in proximity to the limestone."

Regarding the preceding quotation I must remark, that what I have said of the mode of occurrence of the marble, may very easily be made analogous to the appearances described by the author. When the strata of the slate are much undulated and contorted (as may every where be observed, both when the marble is present and when it is absent), the whole phenomenon acquires a complicated aspect, and the isolated portions of slate embedded in the marble may easily be thought to resemble actual fragments, which, it may be imagined, were violently torn from the hanging or lying sides. The minerals disseminated in the limestone at its junction with the slate, and which are the same as those of which the slate is composed, may readily be taken for "contact products;" that is, for products of quite a different act of formation from that which gave rise to the mineral species of the slates. As to the marks of rubbing and sliding, they prove nothing for the view expressed, as they can scarcely have been produced in any other way than by the action of perfectly compact masses on one another; and they are met with in all places and in all kinds of rocks where separations have occurred, and where the separated part has been subjected to a sliding or other movement.

VOL. XXXVI. NO. LXXII.-APRIL 1844.

2 A

That, however, granular limestone can occur as the upfilling of fissures, that sometimes it contains true fragments of the including rock, and in the vicinity of the latter is accompanied by peculiar mineral products, is willingly conceded; but, as I hope to make apparent afterwards, all this is no proof of the pyrogenic origin of marble. The chief object I had in view in quoting the passage, was to direct attention to the pernicious consequences of the mode of proceeding at present followed by so many geologists. I may be forgiven for not being able to help thinking that we really have here an example of the manner in which the science may be deprived of that impartial observation and delineation of facts so perfectly indispensable for its advancement; and this either because the observer had previously a particular opinion as to what must and should be found, and thus was led quite involuntarily to construct rather than to observe and remark directly, or because the describer was unwilling to represent facts which, perhaps, he could not at once satisfactorily account for to himself and others. As, in the description which has been quoted, the occurrence of the limestone as the upfilling of fissures, is alone mentioned, we are thus only informed of the very rarest case met with; while the usual mode of occurrence of the marble in the crystalline slates, and precisely that which constitutes the general rule, is altogether omitted. As I speak here from my own observation, I believe that my distrust will be thought natural, and that, therefore, no disapprobation is to be expected even from the respected author himself, on account of my candid expression of opinion.

(To be continued.)

Notices of Earthquake-shocks felt in Foreign countries, in Britain, &c. By DAVID MILNE, Esq., F.R.S.E., M.W.S., F.G.S., &c. Communicated by the Author.

(Continued from page 86.)

This comparison is facilitated in regard to one portion of the continent, by there having been a regular register kept of the

shocks from the 19th December 1838 to the 8th March 1840. The shocks so registered, were felt at St Jean de Maurienne, in Savoy, a place where the sun comes to the meridian about 40 earlier than at Comrie. As the time of each shock is given in hours and minutes in this register, means are at once afforded, for judging whether the shocks at St Jean de Maurienne and at Comrie corresponded in point of time.

The following are the results of this comparison :-(1.) The two Registers run together for five months, viz. from October 1839 to March 1840. (2.) During that period, 130 shocks were felt at Comrie, and 58 at St Jean de Maurienne. (3.) At Comrie, the most violent and the greatest number of shocks occurred in October 1839, whilst at St Jean de Maurienne, December 1839 was the month, during the above period, in which they were most frequent and severe. (4.) Whilst at Comrie there were, during the above period, about 61 days on which shocks occurred, at St Jean de Maurienne there were only 22 days. (5.) During the above five months, when shocks were occurring so frequently at both places, there were only eleven days on which shocks were felt at both, within the same space of twenty-four hours. (6.) So far from any of the shocks, on these days, having happened at St Jean de Maurienne about 40′ before they were felt at Comrie, no shocks occurred at the two places nearer one another than 3 hours; and no regularity of intervals between the shocks of the two places, is discoverable.

These results shew conclusively, that the shocks of earthquake at St Jean de Maurienne, have no correspondence or connection, in regard to the period of their occurrence, with those at Comrie. Indeed, the circumstance stated in the report on these earthquakes, that the shocks caused by them were not in general felt to extend into Piedmont, prove that, just as at Comrie, the origin of them cannot be very deeply seated. But what is thus proved of earthquakes in Savoy, viz. that they have no connection with those occurring in Great Britain, will be found to hold equally good of earthquakes occurring in other parts of the world. Some trouble has been taken to collect notices of suc, and a number have been collected