The recent retirement of Professor Albert Jean Gaudry, who for fifty years has been associated with the Jardin des Plantes, gives us an opportunity of presenting our readers with his portrait.

Born in 1827, he started for Cyprus and Greece at the age of 25, on what was destined to prove an epoch-making visit, for while there he obtained satisfactory information about the rich deposit of vertebrata at Pikermi, which he afterwards visited. The results of his labours are embodied in the classic “Animaux fossiles et Géologie de l'Attique” (1862–67), and a new world of vertebrate life was fully opened to zoologists, of which the first glimpse had been obtained by Wagner. But perhaps the best known of Gaudry's writings is his “Enchainements du monde animal dans les temps géologiques” (1878), reprinted in 1895, a work which has had great influence on the younger school of thought (see Geol. Mag., 1878, pp. 221–227, and 1884, pp. 32–40).

Appointed Assistant to Professor Alcide d'Orbigny (the first to hold the Chair of Palaeontology at the Jardin des Plantes) in 1853, while still in Cyprus, he succeeded Edouard Lartet in that Chair in 1872. He was Vice-Secretary of the Geological Society of France in 1852, Secretary in 1854, and President in 1863, 1878, and 1887; while in 1900 he presided over the Meetings of the Eighth International Congress of Geology, held in Paris.

Gaudry's first published works dealt with Starfishes (1852) and the Origin of Flint (1852), but soon afterwards he confined himself to Vertebrate Palaeozoology, with a result that is known to even the most superficial student of the science throughout the world.

Since the publication of the joint paper by Mr. W. H. Hudleston and myself on “Fossils from the Hindu Khoosh,” in which the Devonian age of well-preserved fossils found in the limestone member of a series in Chitral was demonstrated, my attention has been called by Mr. T. H. Holland to the fact that the series in Chitral agrees very closely with the rocks known to the Geological Survey of India as the infra-Trias, and described, for the last time, in Hazara by Mr. C. S. Middlemiss.

The Chitral series consists of three principal formations:— (1) A lower bed of conglomerate with rounded to subangular pebbles, varying greatly in size up to 3¼ inches in diameter, lying in an indurated, fine-grained matrix of slaty grit or arenaceous mudstone. The pebbles consist of limestone, slates, sandstones, and quartzites, with rounded, white quartz-pebbles, which recall the ‘eggs’ of the Blaini conglomerate of the Simla area. (2) A middle band described by my son, who made a hurried visit to the place, as red sandstone; and (3) an upper bed of grey, dark-blue, and creamcoloured fossiliferous limestone.

In Hazara the system of rocks known to the Geological Survey as the infra-Trias, on account of its position unconformably below the Trias, consists in the same way of a lower conglomerate, a middle sandstone series, and an upper limestone formation. These rocks, originally referred to by Wynne and Waagen, were described in fuller detail by Middlemiss in 1896.

According to Middlemiss, the conglomerate is composed of sub-angular pebbles of slates and quartzites, usually of about the size of a cricket ball, but varying from mere pebbles to larger lumps, and set in a fine purple sandy clay or shale.

In the course of my work in the deserts of the Fayûm during the last two years I found that over a certain area to the north of the eastern end of the Birket el Qurun lake flint implements, many of very fine workmanship, were of frequent occurrence. The accompanying Plates illustrate the common and most perfect types (reduced to about one-third).

The objects of this note are three: (1) to call attention to the essential chemical similarity between laterite and bauxite; (2) to offer a theory for the formation of laterite in the moist tropics; (3) to suggest an explanation for its spontaneous dehydration.

(1) Laterite has generally been referred to as a ferruginous clay; but if the term clay is restricted to substances having a basis of hydrous silicate of alumina, this definition is incorrect. The alumina in laterite exists, as it does in bauxite, in the form, of hydrous oxides. Kaolin must thus be removed finally from the list of weathering products; it is formed generally, perhaps exclusively, by the action of subterranean vapours on aluminous silicates. This conclusion necessitates a re-examination of many so-called argillaceous substances; many doubtless include the kaolin already existing in the kaolinized aluminous silicates before they are exposed to the weather. But it is probable that some of the red clays of past geological ages, formed under subaerial conditions, contain free hydrous oxides of alumina; and for those that are shown to contain hydrous silicate of alumina, it would be well to test the possibility of a secondary reunion of aluminic hydrate and free silicic acid.

(2) To account for the fact that an aluminous silicate undergoes a more complete disintegration under tropical conditions than under the deep-seated and presumably high-temperature conditions of kaolinization, the writer suggests that laterite is due to the agency of lowly organisms, possibly akin to the so-called nitrifying bacteria.

A Good deal has been written on the permanence of ocean basins, but about the permanence of river valleys I have never noticed any discussion. The causes which tend to maintain the existence of a river valley are indeed obvious and simple; probably this simplicity and obviousness are the very reasons why so little has been said. Yet even if superfluous it may be interesting to bring together some of these causes, such at least as have come into my mind.

What actions can even temporarily obliterate a channel cut into the surface of the land? Submergence followed by re-elevation: what will that effect? During submergence sediment may be deposited. If this be deposited as a mantle of equal thickness over the whole bottom, the surface on re-elevation would have the same shape as before; hills and valleys would reappear of equal relative heights and depths. Probably, however, the amount of sediment would be greater in greater depths: more would be deposited in valleys than over hills. Then on re-elevation the surface would appear with features smoothed down, but not obliterated. Where a valley had been, a valley would again be; less deep, but with a fall in the same direction, tributaries in the same position, and the same catchment basin as before. Rain and rivers would resume their old courses and their old work; the valleys would be the same as before. Imagine even the most improbable case of a sedimentation such as should bury hills and valleys alike; let every feature vanish as a path is hidden beneath a sheet of snow; even then the valley would reassert itself.

We may now examine how far these theoretical conclusions explain and are confirmed by what is seen in nature. First we know that in most formations there are great masses of what is now, or must have been once, fine-grained sediment. These often make up the bulk of the formation. We may quote the Ordovician, Silurian, and Devonian slates, the Keuper, Lias, Oxford and Kimmeridge Clays, the G-ault and London Clay; but we can give no such list of thick masses of marine sandstone. Fine sediment, therefore, has, as a matter of fact, made thicker masses of rock than coarse sediment; but this could not be the case if deposits thinned out seawards, where the fine sediment is carried. Again, it is impossible to imagine a thickness of a thousand feet and more constantly occupying a position near the shore; there is no room for it. If you depress the land, you remove the shore.

A Description of two Rhætic sections forms the subject of this communication. In a county where but one section has been described this is a considerable addition to our knowledge of the series. It is remarkable that the section at Crowle has not been previously noticed; it may be easily examined, and not like the only recorded section in the railway-cutting at Dunhampstead, which is necessarily difficult to obtain access to. The Crowle section is situated at the junction of the road from Oddingley with that from the house marked as “Frisland” on the Geological Survey map. The beds are affected by a fault having a downthrow of about 14 feet.

There is an exceedingly simple method of distinguishing biotite from brown hornblende in thin sections under the microscope, which, so far as I am aware, has not yet been described. As it may possibly be of assistance to beginners, I submit a brief account thereof.

In the Summer of 1901 I found in a pasture, between Oxlow Rake and Cop Round (IX S.E.), some blocks of Toadstone in a bed of clay that has all the characteristics of decomposed Toad-stone. The clay was being dug for puddling a new mere, and the deposit is well known to natives. I traced the outcrop south-west to Starvehouse Mine, and my inference that the clay was decomposed Toadstone was soon verified by the Toadstone itself coming to day-light and replacing the clay. I did nothing more that year, but in the Summer of last year I continued to follow the bed, and have traced it as far as Bushy Heath House (XV N.E.), a distance of about two miles from its starting-point.

The outcrop starts as a clay bed, at the southern end of an enclosure called Old Moor (IX S.E.), at a point about 50 yards south-east of two old mine shafts, and where a spring issues from under the limestone scarp, at a height of 1,400 feet above mean sea-level (by aneroid). Thence it runs in a general south-west direction for half a mile, along a line of five springs at the base of the limestone escarpment, to the north wall of Starvehouse Mine (IX S.E.), which it cuts at an altitude of 1,500 feet.

There is no throw at the Starvehouse lode, and the bed contours round the point of Cop Round and crosses Dick Lane 30 yards from the summit gate (1,510 feet); from there it runs south-east with the dip of the limestone to Moss Rake (IX S.E.), the base passing just above the letter n of Piece Barn on the map. It reaches the lode at 1,350 feet.