20. HEMATITE in the SILURIANS. By J. D. KENDALL, Esq., F.G.S. (Read March 8, 1876.)

In a paper read last session before the Society, I pointed out some of the most important features of the Hæmatite deposits that occur in the Carboniferous Limestone of Cumberland and Lancashire. Amongst other things I showed that the direction of the deposits was invariably parallel to that of the meridional divisional planes by which the rocks are intersected; and as an explanation of that fact I suggested that the hæmatite had probably been deposited in caverns which had been hollowed out by chemical action along the meridional planes, or that the hæmatite had replaced the Limestone along those lines.

The paper also briefly referred to the deposits of hæmatite in the Silurians of the same districts, and went to show that these deposits (which are in the form of veins), like those in the Carboniferous Limestone, were in direction parallel to the divisional planes. There was, however, this difference between these Silurian deposits and those in the Carboniferous Limestone, that whereas all the deposits in the latter were parallel to one another, and had a direction nearly north and south (that is the same as the meridional divisional planes), those in the Silurian had two directions, some being parallel to one set of divisional planes and some to the other.

Since the delivery of that paper I have had an opportunity of examining a Silurian deposit which appears to me to be altogether unlike (as regards the relation between the direction of the deposit and the divisional planes) either those deposits to which I before alluded in the same series of rocks, or those in the Carboniferous Limestone. I therefore deem it may be interesting to the Society if I give an account of my observations on that deposit.

The deposit to which I refer is in the parish of Millom and county of Cumberland, and is now being worked by the WaterBlean Mining Co., their works being known as the Water-Blean Mines.

The geological structure of the district in which the deposit occurs is somewhat as shown in the following plan and section (figs. 1 and 2).

The Silurians are all conformable, and strike about 65° N.E. and S.W., with a dip of about 80° to the N.W. Their order is thus inverted, the Limestone appearing to dip in below the Ash-beds, and the Flags below the Limestone, whereas in reality the Ashbeds underlie the Limestone, which in its turn forms the base of the Flags.

The Limestone is part of that narrow band which stretches through the country in a nearly straight line from Millom to Shap, a distance of about thirty miles. It is in this rock that the hæmatite occurs to which I wish to call attention. The form of the deposit (or,

Fig. 1. Plan of arrangement of Hæmatite deposits, Millom,

Fig. 2. Vertical Section across Hæmatite deposits, Millom, Cumberland, in line a, b, fig. 1.

rather, deposits; for there are several of them) is that of short veins, which vary in width from a few inches to 9 feet. The ore is very hard, and has a high red stain, and where it joins the Limestone appears in most cases to be grown to that rock, as the ore in the Carboniferous Limestone is with it. The direction of the veins is about 65° N.E. and S. W., and they dip at an angle of about 80° to the N.W. The following vertical cross section (fig. 3) will partly show their mode of occurrence.

Fig. 3. Vertical Section of Hematite vein.

A. Glacial drift. B. Limestone. C. Hæmatite. d, d,d. Bed-joints.

The direction and dip of the veins, it will be observed, are exactly the same as the direction and dip of the bed-joints of the Limestone, the strike of both being about 65° N.E. and S.W., and their dip about 80° to the N.W. This is the point which I wish chiefly to place before the Society. In the paper before referred to, as already stated, I pointed out that the hæmatite deposits in the Carboniferous Limestone of Whitehaven and Furness invariably coincide in direction with the meridional divisional planes intersecting that rock, and that the deposits in the Silurian slates at Knockmurton, near Whitehaven, have two directions, which coincide with either one or the other of the divisional planes of those rocks. The Water-Blean deposit, however, appears to me to be different from either of these, the deposition of the ore having taken place along the bed-joints of the rock. In some of the Whitehaven deposits, as at Parkside and Bigrigg Moor, a phenomenon somewhat similar to this is to be seen, as shown in fig. 4, which is a vertical section of the Parkside deposit; but there the strata lie at such a low angle that the ore-deposit is more like a bed than a vein. Their likeness to the Water-Blean deposits, however, is only partial; for, notwithstanding their bed-like appearance, and the fact of their being parallel to the bed-joints of the rocks, the deposits nevertheless have their longest axis parallel to the meridional divisional planes ; and the strike of the rocks does not in any way determine the direction of the deposits, as it does at Water Blean.

The direction of the Water-Blean deposit is exactly the same as the strike of the rocks in which it occurs, and altogether different from the directions of either of the divisional planes.

Fig, 4. Vertical section of Hæmatite vein in Carboniferous Limestone at Purkside.

A question which here naturally suggests itself is, Why was not the ore deposited along the meridional divisional planes of the Limestone at Water Blean, in the same way that it is in the Carboniferous Limestone of Furness and Whitehaven? To answer that question it appears to me to be necessary to state that the bed-joints in the Limestone at Water Blean are much more persistent than the divisional planes are, the latter being very irregular in direction, and not by any means so strong and open as the bed-joints. We should therefore naturally expect the carbonated water to act most powerfully on the bed-joints, as it, in my opinion, for the same reason, has done on the meridional, in preference to the transverse divisional planes in the Carboniferous Limestone of the district of Whitehaven and Furness.

DISCUSSION.

Mr. FORBES considered that this paper was equivalent to a withdrawal on the part of the author of the opinions expressed in his former paper. Mr. Forbes maintained that the direction of the vein-like deposits is due to their being formed in preexisting fissures, into which the hæmatite has been injected. When hæmatite is found in caverns it has been washed in by water.

Prof. HUGHES thought that the only rule as to the mode of occurrence of these deposits was dependent on the direction of the joints and bedding, pointing out that in the Mountain Limestone it was determined chiefly by the joints, while in the highly inclined Coniston Limestone the ore was found along the Limestone bands, which were separated by impervious shales.

Mr. WARINGTON W. SMYTH remarked that this is a problem in the investigation of which great caution is necessary. In some localities undoubtedly the veins of hæmatite have a general direction; and in many cases there is a considerable coincidence of the veins of hæmatite with joints.

21. OBSERVATIONS on the UNEQUAL DISTRIBUTION of DRIFT on OPPOSITE SIDES of the PENNINE CHAIN, in the country about the SOURCE of the RIVER CALDER, with Suggestions as to the CAUSES which led to that RESULT, together with some Notices on the HIGH-LEVEL DRIFT in the UPPER PART of the VALLEY of the RIVER IRWELL. By JOHN AITKEN, Esq., F.G.S. (Read June 23, 1875.)

[Abridged.]

FOR many years past the attention of geologists has been more or less directed to the fact that a marked difference exists in the distribution of drift on opposite sides of the Pennine chain, a difference amounting in some instances to an entire absence of that material on the easterly slopes for many miles from the watershed of the country, and over a considerable portion of its length, notwithstanding that these deposits overspread the great plains of Lancashire and Cheshire. in great force, and are found mounting up upon the flanks of those hills on their western sides to very considerable elevations, approaching closely in some cases to the culminating ridge, and in others, where the chain is crossed by intersecting valleys, to some hundreds of feet in excess of the summit-level of these gorges. It would further appear from facts hereafter to be adduced, that although some of these cross valleys attain to only very moderate altitudes, no communication existed during the glacial period of such a character as to permit of the passage of a body of land ice from one side of the chain to the other. Whilst, however, these phenomena have not wholly escaped the notice of those observers who have, more particularly of late years, directed their attention to the surface accumulations of the northern counties of England, allusion having been made to the subject by Messrs. Binney, Tiddeman, Green, Foster, Dakyns, Goodchild, and others, yet no serious attempt has, I believe, so far been made to grapple fully with the subject by any of those who have hitherto given attention to it.

The subject has long perplexed me, amongst other observers; and it is only after a lengthened consideration that I have ventured to suggest a theory which, whilst offering an explanation of the phenomena, does no violence to any of the well-established principles of physical or geological science. My object, then, in presenting the present communication is to show that the whole of these phenomena are explicable on the supposition that, during the flow of the great ice-sheet over this region, these intersecting channels were sealed and blocked up so effectually as to completely cut off all communication between the eastern and western sides of the chain, and that the only agency fully meeting the requirements of this supposition is that of ice or snow so consolidated and fixed in the sinuous channels as to remain stationary and inert while the great mass of glacial ice, in two sheets separated by the more elevated portions