The Corliss-engined fan at Seghill colliery has now been running for 10 years, and the following particulars may be of interest.

Engine. — The valve-gear of the engine has required neither repairs not adjustment : two of the trip-gear steel-plates h ave been turned round, as the edges were slightly worn and occasionally failed to open the valves ; but this did not affect the speed of the engine. Two sets of piston-rings have been put in, one of them only a few weeks ago, and one set of plates for the metallic packing of the piston-rod has been replaced. The cylinder is hardly worn.

The engine has worked absolutely satisfactorily, and apparently will continue to do so for many years without overhauling and the continuous work through day and night is equal to 30 years work at the rate of one shift a day.

Ventilation. — The following measurements of the air have been made so as to compare what the fan is now doing, with what it was doing when tested in 1893, and also to show the improvement in the airways in the pit.

Tests have also been made to show the effect of cleading the fan-drift, so as to turn the air into the inlet-opening of the fan and to lessen the air-eddies ; and also of cleading the fan-race, at the end where the fan runs downward into it.

If the airways had remained in the same condition as they were in 1893, it would have required 2.42 inches of water-gauge to produce 131,004 cubic feet. of air per minute instead of 0.96 inch, and 5.81 inches of water-gauge for 208,170 cubic feet of air per minute instead of 2.17 inches of water-gauge.

The increase in the volume of air and the decrease in the water-gauge is due to improvements in the shafts and airways, namely: The John (downcast) shaft has been widened from a diameter of 8½ feet to 12 feet, for a length of 300 feet to the Yard seam, the wooden guides have been replaced by steel-rail guides, longer cages are used, and a steam-pipe, 10 inches in diameter, has been taken out of this shaft for a length of 456 feet.

In the Engine (downcast) shaft, 11½ feet in diameter, the brattice-division has been removed from top to bottom for a length of 456 feet, and 4 cages and wooden guides have been replaced by 2 big cages and steel-rail guides.

The return and intake airways have also been improved, and in some cases doubled, and larger openings have been made into the upcast shaft, which is 11 feet in diameter.

In 1893, there were 10 main splits of air, with a total length of 96,000 feet, and in 1902, there were 12 main splits with a length of 163,000 feet.

Mr. T. H. Bailey (Birmingham) said that the members were indebted to Mr. Leach for going so minutely into the particulars which were contained in the tables accompanying his paper, as they enabled others to see some of the mistakes and difficulties under which Mr. Leach had been labouring. He asked what was the area of the shaft, of the fan-drift, and of the opening from the shaft into the fan-drift.

Mr. C. L. Watson (New Tredegar) said that at the Powell Duffryn collieries, South Wales, several fans, dealing with very large quantities of air and mostly of the Walker-Guibal type, were in use, driven by Corliss-valved engines. The engines in each case were compound condensing, and very good results had been obtained from the Corliss valves. All the newer engines, including the winding-engines at their new colliery at Bargoed, which were compound with four cylinders, were being fitted with Corliss valves and expansion-gear.

Mr. J. A. G. Ross (Newcastle-upon-Tyne) said that the advantage of the Corliss valve was that it was very susceptible; it was so delicate that the governor acting upon it cut off steam in proportion to the work done, and if at any instant there was a sudden demand for work they could instantly raise full steam. A Corliss engine was erected at the Elswick engine-works, about 30 years ago, and it had always worked satisfactorily. The Corliss valve worked economically and with little friction : and the trip-gear was delicate, and worked with the slightest movement.

The Chairman (Mr. J. S. Dixon) remarked that he had no doubt that the enlargement in the airways had been of considerable advantage. The old theory of ventilation was summed up in the words "big airways."

Mr. C. C. Leach said that the paper was really a continuation of one read when the fan was started some years ago.¹ The fan-drift had an area of 191 square feet, and the openings into the shaft were as large as they could be made.

Mr. C. H. Innes (Newcastle-upon-Tyne) wrote that he had read with much interest Mr. Leach's paper on the Seghill fan : the tests had evidently been made with care, and were of scientific as well as practical value. The accuracy of the tests was shown by the fact that in each pair of tests, A, B and C, the equivalent orifice was practically constant, and the discharge in cubic feet per minute was very nearly proportional to the revolutions : for example, in the two tests A, it was 3,509 by revolutions, and 3,489 by revolutions. The water-gauge was also very nearly proportional to the square of the revolutions, thus in test A it was revolutions squared divided by 1,568 and revolutions squared divided by 1,600. Under these circumstances, he (Mr. Innes) thought it a great pity that details were omitted that should, where possible, be given to every fan-test. In the first place, the leading dimensions of the fan should be given, the diameter of the wheel, the diameter and number of inlets, the breadths at the internal and the external radii, and the angles made by the vanes with the tangents at the inner and outer circumferences ; the dimensions of the diffuser, if any, and the sections of the volute by 4 planes at right angles, the first being taken by a plane passing through the axis of 90 degrees from the beak of the volute ; and a drawing of the fan should also have been given. The position of the water-gauge should also be stated, and whether its end was turned like that of a Pitot tube, in a direction opposite to that of the air-current, or whether it was placed at right angles to it. Messrs. Heenan & Gilbert's tests with a fan, published some years ago,² showed the importance of the tip given to the water-gauge. The manner of measuring the discharge should be fully explained and illustrated by a drawing, showing how the fan-drift or the top of the chimney was divided into suitable areas. It should also be stated whether the fan was driven direct or otherwise. Had Mr. Leach supplied this information it would have increased the value of the tests. It was strange that the mechanical efficiencies at 60 revolutions were on the average so very little better than those at 40. The efficiency of an engine increased with the mean pressure, while that of the fan remained constant for a given equivalent orifice, so that the combined efficiency should increase.

The Chairman (Mr. J. S. Dixon) moved a vote of thanks to Mr. Leach for his valuable paper.

Mr. Bailey seconded the resolution, which was cordially appinoved.

1 Trans. Inst. M.E., 1893, vol. vi., page 48.

2 Minutes of Proceedings of the Institution of Civil Engineers, 1896, vol. cxxiii., pages 272-294.