On a New Method of Constructing Induction Coils. By Robert M. Ferguson Ph.D., F.R.S.S.A., Edinburgh Institution, On a New Current-Interruptor for the Induction Coil. By Robert Description of a New Form of Platometer, invented by Arthur Beverley, Esq., of Dunedin, Otago. Communicated by James Description of a Holophone or Sound Reflector for Fog Signals. Exhibition of a Series of Photographs, illustrating the Land of Egypt, the Great Pyramid, the Second Pyramid, the Third Pyramid. the Sphinx, King Shafre's Tomb, Cliff Tombs, and Moving Figures." By Professor C. Piazzi Smyth, F.R.SS.L. & E., Astronomer Royal for Scotland, Address of the President, Frederick Hallard, Esq. Advocate, on leaving the Chair, delivered at the General Meeting of the Society, held on the 26th November 1866, On the Collection, Removal, and Disposal of the Refuse of the City of Edinburgh. By Charles Macpherson, C.E., Burgh Engineer, Description of a Revolving Apparatus for Washing out Ammonia and other Impurities from Coal Gas, in the process of its Manu- facture, and applicable to the Purification of Air, and for other Sanitary purposes. By John Reid, FR.S.S.A., Engineer and Manager, Edinburgh and Leith Gas Company, Observations on the Construction of the Track of Railways. By W. J. Cockburn Muir, C.E., F.R S.S.A. (With two Plates), Notice as to the Illumination of Beacons at Sea by Electricity communicated through Wires connected with the Shore. By Thomas Stevenson, F.R.S.E., M.I.C.E., Civil Engineer. (With Description of Electrical Apparatus, and Experiments on Mr Stevenson's Proposal to Illuminate Beacons and Buoys; with. Description of a New Contact-Breaker. By W. D. Hart, F.R.S.S.A., Philosophical Instrument Maker, Edinburgh, A Method of Equalising the Illumination of the Image in Land- scape Photography. By G. H. Slight, C.E., Description of a Combined Optical Square and "Line Finder." By James M. Balfour, C.E., F.R.S.S.A., Otago, India Rubber its Manufacture and Applications. By W. Firth, F.R.S S.A, North British Rubber Co (Limited), Edinburgh, Description of an Improved Ball-cock and Nose-cock. By Alexander On the Water Supply of our Towns and Villages. By Stevenson Engineers, Being an abstract of a Discourse delivered at the Conversazione of the Society, held in the Museum of Science and Address by the President, George Robertson, Esq, M. Inst. C.E, F.R.S.E., concluding the Session of 1866-67, at the Meeting, On New Forms of Lighthouse Apparatus. By William Swan, F.R.S E., F.R.S.S.A., Professor of Natural Philosophy in the On a Patent Pot Steam Boiler. By R. W. Thomson, C.E., Some New Arrangements for Lighthouse Illumination. By Thomas Stevenson, F.R.S.E., M.I.C.E. (With Three Plates), Notice of Aseismatic Arrangements, adapted to Structures in Countries subjected to Earthquake Shocks. By David Steven- son, C.E., F.R.S.E., F.R.S.S.A., Notice of a Cheap and Effective Way of Obscuring Window Glass The Science Education Movement: Address by the President, George Robertson, Esq., M. Inst. C.E., F.R.S.E., concluding the Session of 1867-68, delivered at the General Meeting of the So- APPENDIX (A.) Proceedings of the Royal Scottish Society of : TRANSACTIONS OF THE ROYAL SCOTTISH SOCIETY OF ARTS. Remarks on the Sheffield Water-works Failure, and the Report thereon by the Government Engineers. By ROBERT AYTOUN, F.R.S.S.A.* The cause of the failure of the Bradfield embankment is still a complete mystery. The Government engineers have pointed out what they consider to be numerous errors of design and construction, but they have been unable to assign any one thing as the undoubted cause of the disaster; hence the confidence of the public in the numerous reservoirs scattered over the country, which was so much shaken by the disastrous failure of the Bradfield reservoir, has not been restored, and people are apt to fear that the reservoirs are all liable to the same failures, and may occasion the same disastrous loss of life. It is therefore of importance to ventilate the subject as much as possible, with a view to discover the real cause of the failure. According to the Report of the Government engineers, the greatest depth of the embankment was 95 feet, while the waste-weir was within 4 feet 9 inches of that height; the length of the embankment, at the top, was 1254 feet; its greatest width, at the base or valley line, was upwards of 500 feet; the top width of the embankment was 12 feet; the * Read before the Society 28th November 1864, and awarded the special thanks of the Society. VOL. VII. A outer and inner slopes were 24 to 1; the puddle-wall, at the top, was 4 feet wide, and increased in width or thickness by an addition of 13 inches for each foot vertical in depth, making a width or thickness of 16 feet at the ground line. At some points of the works the puddle-trench was said to have been sunk to a depth of 60 feet below the surface. Two lines of plain socket-jointed cast-iron pipes, 18 inches in diameter, 11 inch in thickness, and in 9-feet lengths, were laid obliquely through and beneath the embankment from the north-west to the south-east. These pipes commenced, on the inside, at an in-let bay of masonry, and ended, outside, at the foot of the slope, in a valve-house. The sluice-valves were on the outer ends of the pipes. The safety of such embankments depends, principally, on three things: First, On the puddle or other means taken for insuring the dryness of the outer slope; secondly, On the outer slope, which must have sufficient weight of materials to withstand, by friction, the pressure of the water; and thirdly, On the means provided for carrying off the surplus water of floods. I shall first examine the means provided by puddle and otherwise for insuring the dryness of the outer slope. The embankment across the valley consists of an inner slope, on which the waters of the reservoir repose; an outer slope, looking down the valley; and a nearly vertical wall of puddled clay betwixt them. The use of the inner slope is merely to support the puddle-wall; that of the puddlewall is to keep the outer slope dry; while the outer slope, besides assisting in supporting the puddle, has the sole task of withstanding the pressure of the water in the reservoir; for the due execution of which task it requires to be kept perfectly dry, and free of all leakage from the reservoir. The puddle-wall, moreover, at the bottom and sides, is extended into the rock, until impervious strata are reached, so as to prevent leakage, through porous strata, getting round its edges. It thus appears, so far as we have gone, that no fault can be found with the plan adopted for preventing leakage; and as to the execution, it is allowed on all hands that the ma |