North of the river Wansbeck, the area of workable coal will, probably, depend chiefly on the exact course of the synclinal axis, and the farther it trends seaward, the greater will be the extension of the field in that direction.

It appears, however, to be possible that the easterly rise may not continue indefinitely seaward and that an anticline may be met with, which will still further prolong the extension of the field eastward. In any case, it seems certain that a very large reserve of coal is contained in the undersea area under consideration.

Conclusion. In conclusion, it may be of interest to call attention to the fact that the operations, which have been described above, form a record of the progress which has been made, in this vicinity, in the working of coal lying at moderate depths under the sea. Experience has been gained since 1872, when it was considered necessary to leave unworked a large proportion of a seam with a cover of more than 600 feet, which has gradually admitted of the lowering of the limit to, in some instances, less than 300 feet, and has resulted in the working of large quantities of coal which it was at one time thought would be lost.

The writer hopes that the results of this experience may possibly be of use to others, although, at the same time, he would point out that a careful consideration of the local circumstances is of great value in fixing the conditions under which undersea operations are to be carried on.

Mr. J. G. WEEKS (Bedlington) said that Mr. Forster's paper contained a clear and succinct account of under-sea workings, and it would be a valuable addition to the Transactions, as it dealt with every detail. The paper referred to the thinning out of the clay westward from the sea, until at a line between Bebside and Choppington stations it ran out, and the rock came next to the surface. He (Mr. Weeks) said that the line would run about 4 miles west from the sea-coast. The clay thinned away from 60 or 80 feet to practically nothing, and ordinary sandstone formed the surface with a soil-cover. Mr. Forster did not give the size of the Wansbeck fault; he (Mr. Weeks) had recently proved it, and was somewhat surprised to find that it amounted to 636 feet

at a point between the Bedlington and Ashington collieries, and he had proved it within 200 feet of the workings on either side.

Mr. T. FORSTER BROWN (Cardiff) stated that Mr. Forster's paper appeared to form a complete record of the coal-workings under the sea in Northumberland so far as they had gone. He (Mr. Forster Brown), as the Crown chief mineral inspector, had inspected these workings, from time to time, and he thought it clear that a sound principle to begin with in working longwall in a seam under the sea, unless the depth was exceedingly great, was to have the whole of the space packed thoroughly, so as to avoid any question of endangering the coal, either under the land- or sea-workings. He would be glad if Mr. Forster would explain his grounds for supposing that there might be another anticlinal axis seaward, and beyond that there might be a dip seaward which might extend the coal-area. He entirely agreed with Mr. Forster that after all, in working an unknown area, where they had no surface to guide them, and could only obtain their knowledge and experience by underground operations, it became a question of circumstances, as time went on, how to deal with any particular difficulty that might arise under the sea.

so soon.

Mr. H. M. CADELL (Grange, Bo'ness) said that he was interested to some extent in submarine mining in the Bo'ness coal-field, on the Firth of Forth, although the workings did not extend so far as those described in Mr. Forster's paper. He had previously communicated a paper upon the workings at Bridgeness colliery,* but since that paper was written the Main seam had cropped out towards the west against the sea-bottom at a depth of 500 feet. They did not experience any inconvenience, although they were at first a little alarmed and disappointed at striking the sea-bottom Several glaciated stones fell out, showing that they had got into Boulder-clay. The Firth of Forth was now only about 20 feet deep at that point, and there must have been a deep trough in former times, which had cut off the outcrop of the seams in that direction. Three or four seams were worked in the section, and they all cropped against the bottom of the Boulderelay. The deepest place where this had been reached was 500 feet, and that was only mile below low-water mark. The centre of the Firth of Forth was an old valley eroded prin* Trans. Inst. M. E., 1897, vol. xiv., page 237.

cipally during the Glacial period, and it was not probable that such a thing would be met with in this district, because these deep troughs were only found in places where there had been old river and valley-glaciers. It would be a useful thing at the extreme end of the workings to put a bore upwards to the bottom of the Boulder-clay in order to ascertain its depth, and the hole could be easily plugged. One part of the workings at Bridgeness struck the bottom at a depth of 170 feet, and the Boulder-clay being very strong formed such, an excellent roof that the seam had been worked under it for many feet. A large glacial stone then rolled out and nearly killed a man, and the workings were thereupon stopped. He merely mentioned this as an example of how excellent a roof Boulder-clay could form. If it was possible to prove that the whole of the ground was formed of Boulder-clay, it would be quite safe to work out all the coal. One great advantage of submarine workings was that there was no surface-damage to pay for, and this often meant the difference between profit and loss at many collieries. Of course the farther out they went under the North Sea, the less would be the cost of surface-damage in proportion to the area of the workings. It was not likely that there would be much sand out at sea; the sediment from the shore was carried out as fine mud, and the farther seaward they got the roof should be all the tighter. He would like to know whether there was much water to contend with in the Northumberland workings; under the Firth of Forth, there was not; and down to a depth of 600 feet the water was so small in quantity that it could be dealt with by a Moore hydraulic pump with a ram 8 inches in diameter. bed of overlying clay kept the workings remarkably watertight.

The

Mr. J. B. ATKINSON (H.M. Inspector of Mines, Newcastle-uponTyne) said that there were two points to have in view: -(1) The danger of losing the workings by water, and (2) the danger of loss of life. The first danger would usually declare itself before the second, although that had not always been the case, as was shewn in the accident at the Workington collieries, where there was considerable loss of life from working the undersea coal. There were four factors to consider:-(1) The thickness of the coal-seam; (2) the thickness of the solid strata above the coal; (3) the thickness of the alluvium; and (4) the depth of water. Of these factors, only the thickness of coal and the depth of water were usually