the breadth of the arms of the cross, as Mr. Davis had replied to this point, except to state that one of the advantages claimed for this sight was that the ghost-image could be made of shapes and forms which would not be possible if it were a material object: that is to say, the lines may be broken lines, or dotted lines, or rings hanging apparently in space, forms which it would be hardly possible to produce, except with a virtual image. Personally, he favoured the cross with a blank centre, which Prof. Louis had been kind enough to suggest, and which he had been using for some time with gun-sights.

With regard to the suggestion that an error was introduced in the measurements obtained by the plane-table, by reason of the instrument reading off "an intercept proportional to the hypothenuse of the vertical triangle of which the staff forms the perpendicular, the measurement really required being the base and not the hypothenuse," this would be perfectly true and correct for many of the instruments which had been used for subtense work; but when Prof. Louis had an opportunity of inspecting one of his (Sir Howard Grubb's) instruments he would see that this matter had not been overlooked. It was true that a staff, held upon an eminence would subtend a smaller angle to the observer than if placed vertically under it in the horizontal plane: (1) Because it was placed at a greater distance, as the crow flies, and (2) because the staff was not at right angles to the direction in which it was viewed. But in his graphometer, so long as the planetable was kept level, and the zero of the scale corresponded with the horizon (as it should do) that portion of the scale which was used to calibrate that staff subtended a less angle to the optical centre of the collimating-lens for the very same reasons, namely: (1) It was at a greater distance from the optical centre than the centre of the scale; and (2) it was inclined at an angle to the direction in which it was viewed, and this was in exactly the same proportion as the staff itself, consequently the result obtained was correct.

Of course, he (Sir Howard Grubb) was referring to moderate angles. If the angle at which the staff was to be viewed was very great, and the scale required to be so long that the end of it was sensibly out of focus with the collimating-lens, the above remarks would not be strictly true, and correct observations would not be possible except at the optical centre of the lens.

He (Sir Howard Grubb) would add that in making surveys with his graphometer, he did not propose that the subtense method should be used for all observations, at least where considerable accuracy was required. He would commence by chaining a line and laying down his large triangles from each end of that line, using the graphometer only as an angle-measurer; and then he would put in his secondary triangles and off-sets by the subtense method. By this means, fairly accurate surveys could be made and that very rapidly.

DISCUSSION OF MR. W. R. COOPER'S PAPER ON "ELECTRIC TRACTION ON ROADS AND MINERAL RAILWAYS."*

Mr. JOHN MCLAREN (Leeds) wrote that the question of electric traction at mines was very ably dealt with in the paper, but the use of electricity as a propelling agent for vehicles on common roads was hedged about with so many practical difficulties, that he was afraid it would be a long time before electric could come into serious competition with steam and petroleumengines. The question of moving heavy loads on common roads by mechanical means had been engaging the attention of some of the best mechanical engineers in the country, and, although no absolutely satisfactory solution had yet been obtained, most of the practical difficulties had been overcome, and the matter was now in a fairly satisfactory position. Engineers were waiting for a good storage-battery; and as soon as this was discovered, there would no doubt be an immense development of electrically-driven road-motors, both for light and heavy work.

MIDLAND INSTITUTE OF MINING, CIVIL AND
MECHANICAL ENGINEERS.

GENERAL MEETING,

HELD AT THE ROYAL VICTORIA STATION HOTEL, SHEFFIELD,
NOVEMBER 8TH, 1902.

MR. H. B. NASH, PRESIDENT, IN THE CHAIR.

The minutes of the previous General Meeting were read and confirmed.

The following gentlemen were elected, having been previously nominated:

MEMBERS

Mr. WALTER BAXTER, Colliery Manager, Silverwood Colliery, Thrybergh, Rotherham.

Mr. ALBERT VICTOR KOCHS, Colliery Engineer, Forster's Buildings, High Street, Sheffield.

Mr. ALFRED NORMAN ROUTLEDGE, Mine Surveyor, Cross Green House,

Knowesthorpe, Leeds.

Mr. RICHARD SUTCLIFFE, Mining Engineer, Horbury, Wakefield.

ASSOCIATE

Mr. WILLIAM LEEBETTER, Chargeman-deputy, 35, Cliffe View, Denaby Main, Rotherham.

The PRESIDENT delivered the following Address:-

PRESIDENTIAL ADDRESS.

BY H. B. NASH.

I have to thank the members for the honour which they have conferred upon me in making me their President for the ensuing year. I sincerely trust that, during my term of office, the work of the Institute will at any rate equal that of my worthy predecessors, and assisted as I shall be by so able a Council, I feel sure that no effort will be spared either on their part or my own to attain these results.

The President's address can of necessity only deal in a general way with such subjects as are most to the front at the moment, and I purpose reviewing briefly the great changes that have taken place in our own immediate districts of South and West Yorkshire during the past forty years; and then giving expression to my views as to the future development of this valuable coal-field, feeling thankful that it is customary for the members to accept without criticism the remarks embraced in the President's address.

THE PAST.

It was my good fortune to make my first practical acquaintance with the coal-trade when it was at the height of its prosperity, in 1873. Anything black would sell, and 10,000 tons of slack, which had been used for ballasting the empty-wagon sidings, was filled and sold at about 13s. per ton at the pits with which I was then connected, and ripping-dirt was sent out of the pit to replace it.

Prior to 1865, few pits had been sunk to a depth of 900 feet, and outputs of 500 tons per day from one shaft were considered large. Egg-ended boilers ranging from 20 to 36 feet in length, and from 4 feet to 6 feet in diameter, working at pressures varying from 40 to 50 pounds to the square inch, were in general

ease.

seen.

use. Fixed-bar screens, making only two sorts of coal (large and slack), were the only screens necessary, and coke-making was a small industry. The life of the colliery-salesman in those days, with only three classes of coal to sell, was one of comparative Railway-wagons were generally of 6 tons capacity, fitted with dead buffers. Shafts were usually sunk from 9 to 10 feet in diameter, single-decked cages were universal, and winding from upeast-shafts was practically unknown. Winding-engines, with the engineman holding a pair of handles like wheelbarrowshafts, handling every stroke of the engine, were commonly to be Pumping-engines were worked on the lift-principle, with heavy columns of pipes in the shafts, and huge spears and beams at most of the pits. Cast-iron tubbing, for keeping back the water, was only coming into use at new sinkings. Ventilation, generally, was effected by large furnaces, and candles were used in all but the most fiery pits, but Davy or Clanny safety-lamps were used in those parts which were considered most dangerous. The system of working was chiefly bord-and-pillar, and dip-workings were only practicable where steam could be carried to the coal-face to actuate the pumps, often with most disastrous results to the roof. Plans were made up when the manager could find time to attend to them, with the inevitable results that inundations from old disused workings were of frequent occurrence. A royalty of 500 acres was a large take, and the majority were of much smaller area.

In 1856, the tons of coal raised in Yorkshire were 9,083,265; and 12 years later, in 1868, the output had only increased by 700,000 tons, proving that it had been practically stationary. In the latter year, the number of working collieries was 441, the number of men employed 37,000, and the mineral raised per person employed was 262 tons.

THE PRESENT.

But the prosperous times of 1872 to 1874 gave an immense impetus to the development of the coal-field, resulting in the sinking of deeper shafts of larger diameter, competent to deal with increased daily outputs. This was followed by the introduction of Lancashire boilers working at pressures of between 60 and 80 pounds per square inch, thereby enabling the speed of winding to be considerably accelerated.