From Mr. Newton's letter in the February Number of the GEOLOGICAL MAGAZINE, I am inclined to think that he has somewhat misunderstood my meaning where I referred to the fauna of the Norfolk Forest Bedinmy paper in the December Number. Prof. Hughes had stated in his paper that the bones from the caverns “belong to the newer group of animals found elsewhere in undoubtedly Post-Glæial river deposits.” As Mr. Newton admits “that most of these species have been found in the Pre-Glacial Forest Bed of Norfolk, and it is probable that others of them will yet be found,” it is clear that I was correct in my contention that “a very large proportion of the animals occur in the Norfolk Forest Bed.”

Botallaek Mine.—The dark hornblendic slates of the sea-border of the parish of St. Just are known to many geological tourists. They have been well described by the late Mr. J. A. Phillips,1 who regards them as consisting of altered killas ; and the justice of this conclusion will not I think be questioned by any who have studied the rocks in situ; traces of an original lamellar structure are visible even in hand-specimens. Phillips (op. cit. p. 322) gives the following analyses of the rock, a being from near the surface, and b from a depth of 130 fathoms, or far below the sea-level; while c is the analysis of a typical Cornish killas (from Polgooth Mine, 100 fathoms from surface):—

Considerable attention has been given of late years to the faunas of the rocks in North America considered to be the equivalents of the rocks usually classed as Cambrian in this country, and the facts which have been obtained are particularly interesting to British geologists. Two recent communications by Mr. C. D. Walcott, Palaeontologist to the U. S. Geological Survey, are especially deserving of study in reference to the classification of these rocks, and many facts of importance bearing on the same question are also given in papers by Mr. G. F. Matthew, of St. John's, N.B.

In the northern half of Anglesey occur several intrusions of dark hornblendic rocks, some specimens of which were placed by Henslow in the collection made by him for the Woodwardian Museum. These rocks present a type unusual in Britain, and show some peculiarities which are of considerable interest.

A few years ago Professor Bonney found on the south-west coast of the island some boulders of a rock which he described under the name of Hornblende-picrite. It was subsequently pointed out by Professor Hughes that the probable source of these rocks was to be found in certain intrusive masses near Llanerchymedd, and indeed such boulders are scattered about rather abundantly in that neighbourhood and to the south-west. The rock in question seems, however, to be the common type of the larger eruptive masses in the north of Anglesey, and brief notes on slides cut from selected specimens taken in place may be found not unprofitable. The rocks were noticed and megascopically described in Henslow's Memoir.

When visiting Whitecliff Bay, Isle of Wight, last September, I was so fortunate as to find exposed on the shore at low-water, the whole of the various strata from the Brook Bed of the Bracklesham, to the Bembridge Limestone inclusive. I have visited this locality many times, but have never before seen the Barton Series exposed.

The discovery of diamonds at Kimberley, South Africa, has proved to be a matter, not only of commercial, but of much geological interest. The conditions under which diamonds here occur are unlike those of any other known locality, and are worthy of special attention. The first diamond foundinSouth Africa wasin1867, when a large diamond was picked out of a lot of rolled pebbles gathered in the Orange river. This led to the “river diggings” on the Orange and Vaal rivers, which continue to. the present time.

The following is an attempt to determine a lower limit to the time required for the accumulation of the stratified rocks. It is not supposed to be an accurate estimate, for the data on which it is based are confessedly imperfect; but it is thought that the method employed may be of some little use when more exact determinations can be made of the physical constants involved.

The question of the origin of the Archæan rocks is one of such great interest that it will not be thought unimportant on the one hand to record any facts that may bear upon it, and on the other to examine somewhat severely all the evidence that may be from time to time brought forward on the subject. Among the facts which may be adduced in support of the view that the Archæan rocks are altered sedimentary strata, the occurrence of breccias and conglomerates may well claim a foremost place; and a vast amount of superincumbent theory must rest on a very shaky foundation if there be any doubt whether some of those ancient fragmental beds be true conglomerates or not. The manner of occurrence, the mode of formation, and the character of pseudo-breccias and pseudoconglomerates become therefore questions of first importance.

Until the appearance of the article by Messrs. C. Iieid and G. Sharman in the Geological Magazine for February, 1886, p. 55, no one had ever thrown a doubt on the existence of true Gault in Norfolk.

Introductory.—The writers having had occasion, in company with Mr. Davies, to examine the greater number of the remains of English fossil Emydine and Pleurodiran Chelonia in the collection of the British Museum, with a view both to their rearrangement in the cases and the determination of their affinities, and having in the course of such examination been enabled to add several genera to the British fauna, as well as to make certain emendations in regard to the age and affinity of some of the previously-described forms, have thought it advisable to put their observations on record.

It had not been my intention to publish anything on this subject at present, as I have in preparation a review of the present state of our knowledge of Himalayan geology; but as Col. McMahon has started the subject, and his paper is not exhaustive, I trust the following outline of that part which relates to the gneissose rocks may prove of interest.

Igneous rocks and crystalline schists are often associated with each other in such a manner as to compel the conclusion that either the igneous rocks have been formed out of the schists or the schists out of the igneous rocks. There are other cases in which the two kinds of rock are less intimately related; parallel structure is wanting, the junctions are sharply defined, and there is no evidence of an original mineral gradation. These are examples of the ordinary irregular intrusion of igneous rocks in schists. But there is a third group in which the characters are intermediate. In these rocks, structural parallelism is more or less distinct, and there is often a partial blending of the two kinds of rock at the line of contact; but other indications forbid the belief that the schists have been elaborated out of the associated igneous masses.

At the present time the American geologists, both those of the United States and the Dominion of Canada, are at variance as to the groups the Archæan should be divided into; it is however unnecessary to enter into this controversy, as the strata may be conveniently grouped, as in Selwyn's map (1884), into Norians or Labradorians, excessively coarse gneiss or other granitic rocks; Laurentians, gneisa and granite; and Huronians, schists with subordinate gneiss.

In the Woodwardian Museum is a collection of nearly a thousand rock-specimens made by Professor Henslow to illustrate his “ Geological Description of Anglesea ” (1821, Trans. Camb. Phil. Soc. vol. i. pp. 359–452, plates xv.–xxi.). Specimens of the principal dykes were submitted to the examination of Professor Cordier, and his remarks on them are quoted in Henslow's paper. As Cordier's determinations date from a time when thin slices of rocks were unknown, and but little attention has since been given to the dykes of Anglesey, it is believed that brief notices of some of the typical rocks from localities easity identified may have an interest for British geologists. As regards the mode of occurrence of the dykes and their effects upon the adjacent strata, little can be added to the accurate descriptions of Henslow, written at a time when the igneous origin of dykes was a proposition to be proved.

The two specimens figured below are from the collection of Mr. C. J. Read, of Salisbury, who obtained them from the Upper Chalk (Senonian) of the neighbourhood. Some uncertainty has attached to the exact locality, Mr. Read having told me that he had found them in the Mucronata-Chalk of Clarendon; but he now writes, 18th Jan. 1887—“My belief, on thinking the matter over, is that the right locality is the ‘Devizes Eoad,’ as they were originally marked.” The locality referred to is Old Camp Down lime-pit, three miles N.W. of Salisbury on the Devizes Road.

It has been acknowledged by botanists that the methods generally pursued in determining fossil dicotyledonous plants have been scarcely such as were likely to lead to trustworthy results. Their study has, or should have, two practical aims. The one, that geologists may be able to determine the ages of strata, when they only contain fossil plants, with as much certainty as if they contained the remains of animals. The other, that botanists may be able to trace the evolution of the existing genera of plants from the pala?ontological record under conditions no less favourable than those at the disposal of the zoologist.

The Gelinden Flora, described by Saporta and Marion (Mém. de l'Acad. de Belge, t. 37; and Révision de la Flore Heersienne de Gélinden, ibid., t. 41), has assumed an immense importance owing to the fact that it alone, among Tertiary fossil floras whose age is definitely ascertained on stratigraphical and palæontological grounds, contains certain remarkable types of leaves which are common to it, to the inter-basaltic beds of GlenarminAntrim, and to Atanekerdluk in Greenland. Two of these are long lanceolate leaves, with three or more parallel mid-ribs.

Two Meteorites from France have recently come into my possession from a private source, one of which, though not of a recent fall (1836), has neither been described nor chemically examined, and which I now briefly bring to notice, it being of a most rare type. The other is of a much more recent fall (1875), and is of a much more ordinary character, being similar to many other meteorites of the same class; this stone also appears not to have been described, nor has any notice of it been published. It is somewhat a remarkable coincidence that these two stones should have fallen in the same Department, although at such widely different dates, and from the data and notes I have received from careful inquiries, I now bring forward the following details of these two aerolites.

The section exposing this stratum was discovered during an excursion made last June by Mr. W. Hill, F.G.S., and the author. It occurs in a quarry near West Row Ferry, about two miles west of Mildenhall;here a band of red marly chalk is seen near the entrance, dipping westward at a low angle, hut soon becoming horizontal and running along the whole face of the quarry, till it is cut off by a fault, which brings up lower beds on the southern side.