In connection with this subject we may call the reader's attention to some facts of considerable interest, which have lately boon studied with much care and success, and have become of such importance as to constitute a distinct branch of inquiry under the name of Ichnology (IxPos, a footstep, and hhos, a discourse).
This department of geological investigation is conversant with the phenomena of footsteps impressed by animals on the strata of the earth.
In 1828 Mr. Duncan's account of tracks and footmarks of animals impressed on sandstone in the quarry of Corn-Cockle Muir, Dumfries shire, appeared in the Transactions of the Royal Society of Edinburgh.' Dr. Buckland caused a living Emys and Mind* Graca to walk on soft sand, clay, and -paste or unbaked pie-crust. He found the correspondence of the footsteps of the latter with the fossil footsteps sufficiently close, allowing for difference of species, to render it highly probable that the fossil footsteps were impressed by Testudo Grcrca.
In Saxony, at the village of Hesslterg, near Hildburghausen, fossil footsteps were, a few years ago, discovered in several quarries of gray Quartzes° Sandstone alternating with bads of Red-Sandstone, nearly of the age of the Red-Sandstone of C9rn-Cockle Muir. Dr. llohnbaurn and Professor Kaup state that those impressions of feet are partly concave and partly in relief; the depressions are described as being upon the upper surfaces of the Sandstone slabs, but the footmarks in relief are only upon the lower surfaces, and cover the depression& In short, the footmarks in relief are natural caste formed in the subjacent footsteps as in moulds'. On one slab, 0 feet long by 5 feet wide, many footsteps of more than one animal and of various sizes occur. The larger impressions, which seem to be those of the hind foot, are generally 8 inches in length and 5 in width, and one was 12 inches long.
The name of Chirotherium was proposed by Professor Kaup as the provisional name for the groat unknown animal that impremesb. the larger footsteps, from a supposed resemblance in the marks of both the fore- and hind-feet to the Impress made by a human hand; and ho thought that they might have been derived from sonic quadruped allied to the Marsupialia. Dr. Sielder, in a 131urnenbach (1834), gave a further account of those footsteps. Fragments of bones were found in the quarries where the footsteps had been impressed, but those fragments were destroyed.
the existence of footprints of this kind soon became more cxten "lively known. In his address to the Oeological Society, in 1840, Dr. Buckland says :—" Further discoveries of the footsteps of airothe rims* and five or six smaller reptiles in the New Red-Sandstone of Cheshire, Warwickshire, and Salop, have been brought before us by Sir P. Egerton, Mr. J. Taylor, jun, Mr. Strickland, and Dr. Ward.
Mr. Cunningham, in a sequel to has paper on the footmarks at Storeton, has described impressions on the same slabs with them, derived from drops of rain that fell upon thin laminas of clay interposed between the beds of sand. The clay impressed with these prints of rain-drops acted as a mould, which transferred the form of every drop to the lower surface of the next bed of sand deposited upon it, so that entire surfaces of several strata in the same quarry are respectively covered with moulds and casts of drops of rain that fell whilst the strata were in process of formation. On the surface of one stratum at Storeton, impressed with largo footmarks of a Chirotherium, tho depth of the boles formed by the rain-drops on different parts of the same footstep has varied with the unequal amount of pressure on the clay and sand, by the salient cnehions aud retiring hollows of the creature's foot ; and from the coastancy of this phenomenon upon an entire series of footmarks in a long continuous track, wo know that this rain fell after the animal had passed. The equable size of the casts of large drops that cover the entire amebas of the slab, except in the parts impressed by the cushions of the feet, record the falling of a shower of heavy drops on the day in which this huge animal had marched along the ancient strand. Hemispherical impressions of small drops, upon another stratum, show it to have been exposed to only a sprinkling of genjle rain that fell at a moment of calm. In one small slab of New Red-Sandstone found by Dr. Ward near Shrewsbury, we have a combination of proofs as to meteoric, hydrostatic, and locomotive phenomena, which occurred at a time incalculably remote, in the atmosphere, the water, and the movements of animals ; and from which we infer, with the certainty of cumulative circumstantial evidence, the direction of the wind, the depth and course of the water, and the quarter towards which the animals were passing : the latter is indicated by the direction of the footsteps which form their tracks; the size and curvatures of the ripple-marks on the sand, now converted to sandstone, show the depth and direction of the current; the oblique impressions of the rain-drops register the point from which the wind was blowing at er about the time when the animals were passing." Soon after this address was delivered, Professor Owen proved the existence of a gigantic Batrachian at the period when the New Red Sandstone was formed, and described three species of Labyrinthodon. He concluded that these creatures produced the fuot-priuts that had been observed, and maintained the following positions :— 1st. Proof from the skeleton that Labyrinthodon had hind extre mities much larger than the anterior extremities.