morganshire. The Iron ore deposits at Llantrissant, which have only of late years attracted marked attention, appear to have been worked at least two centuries since. The name of the principal mine is Mwyndy, and this is derived from the estate in which the mineral is found. The word signifies Ore, therefore Mwyndy House is "Ore House," and around it in all directions we now find Iron slag and remains of the charcoal with which it was once smelted. This Iron ore, which is now worked by two companies only, "The Mwyndy Iron Ore Company," and "The Bute Hematite Company," partakes in its general character of the ordinary conditions of the Brown Hæmatites. Its situation is similar to that of the Whitehaven Red Hæmatite, and it does not appear in this respect to differ from the ferruginous deposits of the Forest of Dean. It occurs at, or rather immediately beyond, the southern outcrop of the Coal Measures of South Wales. Between the coal seams immediately south of the village of Llantrissant and these Iron ore deposits, the Permian rocks occur, these being represented more especially by large masses of Conglomerate. It will be seen by the section given (Fig. 5), that we have conglomerate and shale rocks resting on the limestone formation, which here forms the boundary of the South Wales coal basin. Under the conglomerate and coal measure shale, in which some thin bands of coal occur, the Iron ore is deposited on the upturned edges of the limestone, and in the fissures formed in that rock. It has been thought hitherto that the ore would be found only at the line of inclination of the limestone, but a recent discovery has shown that it suddenly descends into the limestone itself. This vertical mass of ore (Fig. 6) may be found to terminate abruptly, as shown in the Ulverstone section, or it may lead to a limestone cavern which has been filled in with this peroxide of iron. In the immediate neighbourhood of this deposit a small band of argillaceous nodular iron has been discovered.

At Frampton Cotterel, in the Bristol Coal-field we find the Brown Hæmatite occurring in the Pennant Grit, or sandstone bed of the coal-measures. This iron ore deposit has been formed in a great fault, evidently under similar conditions to those which have regulated the deposits already named, in the limestone.

Numerous deposits of Brown Iron ore exist in Cornwall and Devonshire. Near St. Austell in the former county, and near Brixham and Newton Abbot in the latter, these ores are worked with success. The Brown Hæmatites of North Wales and other districts have not as yet attracted much attention. A very remarkable calciferous Brown Hæmatite occurs at Froghall, near Cheadle, in North Staffordshire, which is largely used in the iron works of South Staffordshire. This ore, which occurs in the lower coal measures, may probably be regarded as an altered highly ferruginous limestone.

The Brown Hæmatites of the Oolites must be considered as Hydrous Sesquioxides of Iron; they are in nearly all respects peculiarly distinguished from those ores of which notice has been already taken. The Northamptonshire and Lincolnshire Iron ore deposits especially represent this class; they are continued, with various shades of difference, through the adjoining counties.

The first impression on examining the various beds of Iron ore, which we can now trace from near the Humber to within a few miles of Oxford, will be, that they are the result of deposit from water, as peroxide of Iron, in the same way as we see ferruginous springs depositing as the water is exposed to the air-the Iron which they hold in solution. This hypothesis supposes those beds to be of recent formation. After, however, a careful examination of all the evidences afforded by the fossil remains which exist in those beds, and in other beds above and below the ferruginous ores, no other conclusion can be arrived at, than that they are of very different ages, the result of a recurrence of the same conditions, but all of a marine origin.

Spathose Iron Ores, Sparry Carbonate of Iron.-These ores of Iron have been long selected for the production of the celebrated "steel irons" of Siegen, Styria, and Carinthia, consequently of late years they have been sought after in this country.

Mr. Charles Attwood, to whom we are especially indebted for a knowledge of the Spathose Iron ores of Weardale, notices the same conditions as those found in other districts. They have certainly been all at first deposited as carbonates more or less pure, and have passed into the state of oxides and hydrates, by the joint effects of atmospheric and of aqueous action. Examples of every stage of the transition present themselves in all directions, and there are also met with, from time to time, abundant proofs that whilst the carbonates deposited are more or less rapidly passing into the hydrated condition, a fresh deposit of carbonates is continually going on in the cavernous interstices, and on the roofs and sides of ancient workings. Upon one occasion Mr. Attwood found protruding for six inches from a block of pure and large grained Sparry carbonate of iron, a rod of malleable iron, of about a quarter of an inch in diameter, of which the other end was firmly embedded to about the same depth in the block, which had just before been broken from a mass of it, incrusting the walls and roof of an ancient drift, but which block must have been formed within one or two centuries. Mr. W. W. Smyth remarks, "When we look to the successive introduction of the various minerals which have filled these interesting veins, it is evident that the carbonate of Iron has been one of the latest comers. Many of the specimens exhibit it, investing, as a crystalline incrustation, the previously formed crystals of fluor spar and galena; and the striking manner in which it is

found to coat only those surfaces which face in a peculiar direction, is well worthy of attention in the study of these obscure phenomena." Besides the Spathose ores of Weardale, we have the same ores occurring in great abundance on Exmoor, and they are worked extensively on the Brendon Hills, near Watchet, over a length of nine miles, to Eisen Hill. At Perranzabulæ, on the north coast of Cornwall, a still more remarkable deposit of these ores exists, but at the present time they are but slightly worked. In the northern corner of Perran Bay a lode appears in the cliff, with a width of nearly 100 feet, and it has been traced for some miles inland and worked at several points. Beyond this brief notice, space cannot be given to the further consideration of these most interesting Iron

ores.

The Argillaceous Iron Ores of the Lias.-The Cleveland Iron ore is the finest example we have of this class of ore. The immense extent of this deposit, the value of the Iron works which have arisen amidst the Cleveland Hills, places this district amongst the first of our Iron-producing districts.

This remarkable deposit may be traced by its outcrop for miles along the escarpments of the Cleveland Hills. Above the flat land which extends from Redcar to Middlesborough there crops out a solid stratum, often fifteen feet in thickness, of this Iron-stone. It is a deposit of a green or grey colour, having generally an oolitic structure, and containing numerous well-known fossils of the Marlstone, especially Belemnites and Pecten Equivalis. The plan and section, Figs. 7 and 8, will show the mode of occurrence of this ore. This vast ferruginous deposit is composed, to a great extent, of Carbonate of Protoxide of Iron. We know that such a deposit could not be formed, unless it was precipitated from water charged with Carbonic acid in excess. We have no evidence that such conditions ever prevailed, to the required extent, over this district, when those Iron-stone beds were being formed. Mr. Sorby has drawn attention to the fact that if the Iron-stone be examined it will be seen that it contains, more or less, entire portions of shells. All the indications appear to show that the Cleveland Iron ore was deposited probably as a limestone, containing a large amount of the oxides of Iron and organic matter. By their mutual reaction these would give rise to the bicarbonate of Iron, which in solution, percolating through the limestone, would remove a large part of the carbonate of lime and leave in its place carbonate of Iron.

It is our object in writing this paper, to draw more especial attention than has hitherto been done to the Hæmatites, and the Argillaceous Carbonates of the coal-measures, as related to each other, in their mode of formation.

It will be evident to everyone who carefully studies the conditions of the clay band Iron-stones spread out in beds amongst the seams