If Lamarck allowed his brilliant faculty of generalisation to lead him far astray in his opinions regarding the origin of rocks, he bad formed a saner judgment on the causes that have developed the present terrestrial topography. The first chapter of the “Hydrogéologie ” is devoted to a consideration of the natural results that arise from the circulation of water over the surface of the land. This subject, he remarks, affords less scope than any other for the exercise of the imagination in framing hypotheses, for it can be studied on a basis of facts which are generally familiar. Though the question required to be considered in his treatise and was capable of easy solution, yet it seemed to him to be novel, at least from a general point of view, and to have been previously neglected by physicists and naturalists. He appears to have formed his conclusions regarding it independently, and to have been unaware how far he had been anticipated by previous observers. It is singularthat he makes no allusion to the work of his distinguished fellow-countryman Desmarest, who some thirty years previously had demonstrated, from a prolouged and minute investigation of the volcanic history of Auvergne, that the valleys of that region have been excavated by the streams which flow in them. He does not refer to the enunciation of the same doctrine by De Saussure a few years later in regard to the valleys of the Alps, nor to the clear presentation of similar views by Hutton, whose system had been expounded to French readers by Desmarest. But though he was mistaken in supposing that the doctrine was novel, Lamarck was not surpassed by any of his predecessors in the firmness with which he espoused it, and in the clearness with which he presented it to the world.

When looking through the number of the Quarterly Journal of the Geological Society for August, 1905, I saw the paper by Mr. Richardson on the Rhœtic deposits of Glamorganshire and his figure of Plicatula intusstriata, Emmr. At the first glance it struck me that this fossil was closely allied to a group of bivalves, well known to me as occurring in the Chalk, where it is represented by the genus Dimyodon, Munier-Chalmas.

The author, who has long been engaged on the Palæozoics of West Cornwall, divided the killas extending westward from Gerrans Bay into four groups that formed a natural sequence. Moreover, as they included definite Lower Silurian horizons, as characterized by the fossiliferous quartzite of Carne, these divisions were linked with the Lower Palæozoics. They consist of the Veryan, Portscatho, Falmouth, and Mylor groups. On the latest issues of the old Survey maps the area occupied by the first of these divisions is coloured as Silurian, and the region occupied by the remainder as Devonian. That colouring, however, was not adopted by De la Beche, who surveyed the region, nor was it the result of any subsequent survey of the area. In the original Geological Survey map of Cornwall the killas was separated by De la Beche into two divisions, viz., a grauwacke group and a carbonaceous series. Thus, the former lying below the Culm-measures was undifferentiated for the reason, as explained in his Report, that the progress of geology at that time only warranted the broadest generalizations. He moreover expressed the opinion that the terms Cambrian and Silurian should be restricted to the areas that gave rise to the prolonged researches of Murchison and Sedgwick, and deprecated the extension of that nomenclature to districts that had not received the same detailed investigations. In a later and undated issue of the map the grauwacke group is divided into Devonian and Silurian, presumably by the authority Sir Roderick Murchison. The Devonian colour was not only applied to fossiliferous strata in East and Mid Cornwall, but was extended over the unfossiliferous strata in the west. The Silurian tint, on the other hand, was restricted to a zone that had yielded organic remains. Murchison, however, was of opinion that the older zone extended far beyond those limits into the barren strata coloured as Devonian, and it is evident that the latter tint was adopted as a matter of convenience, as no re-examination of the area seems to have been undertaken. The known Silurian region was confined to the coastal belt between Chapel Point and Gerrans Bay, a boundary connecting those localities admitting of the ready isolation of that zone from the rest of the country. That such a broad generalization, however, was only regarded as provisional may be inferred from the absence of a line on the map between the two divisions. It will be seen, therefore, that the subdivision of the killas, as the result of the recent survey, neither invalidates the map published by De la Beche nor the subsequent conclusions of Murcliison. It has, on the other hand, not only brought their generalizations within more definite limits, but has carried the investigation a step farther by demonstrating the relations between the older and newer Palæozoics of Cornwall.

The collections of Echinoidia described in the following report were made by Messrs. Barron, Beadnell, and Hume during their work for the Egyptian Geological Survey, and were entrusted to me for description by the Director, Captain Lyons, R.E.

Between Crotty's Lough and Coumshingaun a long spur of the Comeraghs juts out eastwards for about a mile and a half with an average height of 1400–1500 feet. On the south side this projecting ridge descends rather steeply to a stream at its base, which heads at a height of over 2,400 feet on the lofty plateau between Coumgorra and Coumshingaun; it runs down the mountain-side in a narrow gully over bare rock and reaches the foot in a series of picturesque waterfalls. No glacial débris occurs in this ravine, but on the lower ground the stream flows over the margin of the moraines belonging to Coumshingaun and runs eastward as the River Ire to join ultimately the Clodiagh.