I had now corresponded for several years with a little circle of geological friends, and had described in my letters, and in some instances had attempted to figure in them, my newly-found fossils. A letter which I wrote early in 1838 to Dr. Malcolmson, then at Paris, and which contained a rude drawing of the Pterichthys, was submitted to Agassiz, and the curiosity of the naturalist was excited. He examined the figure, rather, however, with interest than surprise, and read the accompanying description, not in the least inclined to scepticism by the singularity of its details. He had looked on too many wonders of a similar cast to believe that he had exhausted them, or to evince any astonishment that Geology should be found to contain one wonder more. Some months after, I sent a restored drawing of the same fossil to the Elgin Scientific Society. I must state, however, that the restoration was by no means complete. The paddle-like arms were placed further below the shoulders than in any actual species; and I had transferred, by mistake, to the creature's upper side, some of the plates of the Coccosteus. Still the type was unequivocally that of the Pterichthys. The secretary of the Society, Mr. Patrick Duff, an excellent geologist, to whose labors, in an upper formation of the Old Red Sandstone, I shall have afterwards occasion to refer, questioned, as he well might, some of the details of the figure, and we corresponded for several weeks regarding it, somewhat in the style of Jonathan Oldbuck and his antiquarian friend, who succeeded in settling the meaning of two whole words, in an antique inscription, in little more than two years. Most of the other members looked upon the entire drawing, so strange did the appearance seem, as embodying a fiction of the same class with those embodied in the pictured griffins and unicorns of mythologic Zoölogy; and, in amusing themselves with it, they bestowed on its betailed and bepaddled figure, as if in anticipation of Agassiz, the name of the draughtsman. Not many months after, however, a bona fide Pterichthys turned up in one of the newly discovered beds of Nairnshire, and the Association ceased to joke, and began to wonder. T merely mention the circumstance in connection with a right challenged, at the late meeting of the British Association at Glasgow, by a gentleman of Elgin, to be regarded as the original discoverer of the Pterichthys. I am, of course, far from supposing that the discovery was not actually made, but regret that it should have been kept so close a secret at a time when it might have stood the other discoverer of the creature in such stead.
The exact place of the ichthyolites in the system was still to fix. I was spending a day, early in the winter of 1839, among the nearly vertical strata that lean against the Northern Sutor. The section there presented is washed by the tide for nearly three hundred yards from where it rests on the granitic gneiss; and each succeeding stratum in the ascending order may be as clearly traced as the alternate white and black squares in a marble pavement. First there is a bed of conglomerate two hundred and fifteen feet in thickness, "identical in structure," say Professor Sedgwick and Mr. Murchison, u with the older red conglomerates of Cumberland and the Island of Arran,[AJ] and which cannot be distinguished from those conglomerates which lean against the southern flank of the Grampians, and on which Dunnottar Castle is built. Immediately above the conglomerate there is a hundred and fourteen feet more of coarse sandstone strata, of a reddish yellow hue, with occasionally a few pebbles enclosed, and then twenty-seven feet additional of limestone and stratified clay. There are no breaks, no faults, no thinning out of strata—all the beds lie parallel, showing regular deposition. I had passed over the section twenty times before, and had carefully examined the limestone and the clay, but in vain. On this occasion, however, I was more fortunate. I struck off a fragment. It contained a vegetable impression of the same character with those of the ichthyolite beds; and after an hour's diligent search, I had turned out from the heart of the stratum plates and scales enough to fill a shelf in a museum—the helmet-like snout of an Osteolepis, the thorn-like spine of a Cheiracanthus, and a Coccosteus well nigh entire. I had at length, after a search of nearly ten years, found the true place of the ichthyolite bed. The reader may smile, but I hope the smile will be a good-natured one; a simple pleasure may be not the less sincere on account of its simplicity; and "little things are great to little men." I passed over and over the strata, and found there could be no mistake. The place of the fossil fish in the scale is little more than a hundred feet above the top, and not much more than a hundred yards above the base of the great conglomerate; and there lie over it in this section about five hundred feet of soft, arenaceous stone, with here and there alternating bands of limestone and beds of clay studded with nodules—all belonging to the inferior Old Red Sandstone.
[AJ] Different in one respect from the conglomerates of Arran. It abounds in rolled fragments of granite, whereas in those of Arran there occur no pebbles of this rock. Arran has now its granite in abundance; the northern locality has none; though, when the conglomerates of the Lower Old Red Sandstone were in the course of forming, the case was exactly the reverse.
The enormous depth of the Old Red Sandstone of England has been divided by Mr. Murchison into three members, or formations—the division adopted in his Elements by Mr. Lyell, as quoted in an early chapter. These are, the lowest, or Tilestone formation, the middle, or Cornstone formation, and the uppermost, or Quartzose conglomerate formation. The terms are derived from mineralogical characters, and inadequate as designations, therefore, like that of the Old Red Sandstone itself, which, in many of its deposits, is not sandstone, and is not red. But they serve to express great natural divisions. Now the Tilestone member of England represents, as I have already stated, this Lower Old Red Sandstone formation of Scotland; but its extent of vertical development, compared with that of the other two members of the system, is strikingly different in the two countries. The Tilestones compose the least of the three divisions in England; their representative in Scotland forms by much the greatest of the three; and there seems to be zoölogical as well as lithological evidence that its formation must have occupied no brief period. The same genera occur in its upper as in its lower beds, but the species appear to be different. I shall briefly state the evidence of this very curious fact.
The seat of Sir William Gordon Camming, of Altyre, is in the neighborhood of one of the Morayshire deposits discovered by Mr. Malcolmson; and for the greater part of the last two years Lady Gordon Gumming has been engaged in making a collection of its peculiar fossils, which already fills an entire apartment. The object of her Ladyship was the illustration of the Geology of the district, and all she sought in it on her own behalf was congenial employment for a singularly elegant and comprehensive mind. But her labors have rendered her a benefactor to science. Her collection was visited, shortly after the late meeting of the British Association in Glasgow, by Agassiz and Dr. Buckland; and great was the surprise and delight of the philosophers to find that the whole was new to Geology. All the species, amounting to eleven, and at least one of the genera, that of the Glyptolepis, were different from any Agassiz had ever seen or described before. The deposit so successfully explored by her Ladyship occurs high in the lower formation. Agassiz, shortly after, in comparing the collection of Dr. Traill (a collection formed at Orkney) with that of the writer, (a collection made at Cromarty,) was struck by the specific identity of the specimens. In the instances in which the genera agreed, he found that the species agreed also, though the ichthyolites of both differed specifically from the ichthyolites of Caithness, which occur chiefly in the upper beds of the formation, and from those also of Lady Cumming of Altyre, which occur, as I have said, at the top. And in examining into the cause, it was found that the two collections, though furnished by localities more than a hundred miles apart, were yet derived, if I may so express myself, from the same low platform, both alike representing the fossiliferous base of the system, and both removed but by a single stage from the great unfossiliferous conglomerate below. Thus there seem to be what may be termed two stories of being in this lower formation—stories in which the groups, though generically identical, are specifically dissimilar.[AK]
[AK] Since this period, however, several species identical with those of Cromarty have been found in the Morayshire deposits.
[CHAPTER VIII.]
Upper Formations of the Old Red Sandstone.—Room, enough for each and to spare.—Middle, or Cornstone Formation.—The Cephalaspis its most characteristic Organism.—Description.—The Den of Balruddery richer in the Fossils of this middle Formation than any other Locality yet discovered.—Various Contemporaries of the Cephalaspis.—Vegetable Impressions.—Gigantic Crustacean.—Seraphim.—Ichthyodorulites.—Sketch of the Geology of Forfarshire.—Its older Deposits of the Cornstone Formation.—The Quarries of Carmylie.—Their Vegetable and Animal Remains.—The Upper Formation.—Wide Extent of the Fauna and Flora of the earlier Formations.—Probable Cause.