The writer is indebted to Mr. W. O. Wood, Mining Agent and Director of the South Hetton Coal Company, Limited, for permission to record the details of this large plant, and also to Mr. E. Raffle, Chief Mechanical Engineer, South Hetton, and Mr. J. Plummer, Resident Engineer at Murton Colliery, for their assistance in preparing this paper, the successful working of this large plant having been greatly due to the energy and to the careful attention to detail of these two latter gentlemen. Messrs. D. Selby Bigge & Company, of Newcastle-upon-Tyne, were the electrical engineers.

Mr. W. C. Mountain (Gateshead-upon-Tyne) said that Mr. Wood's paper was one of those very practical ones which went to show how an apparently old-fashioned, out-of-date colliery could be brought up to something like modern conditions. It would be even more satisfactory if the author could give the figures of what the consumption of the colliery was in the old days, and the saving that had been effected by the introduction of electricity, as the whole matter turned largely on the commercial aspect of the case rather than on the scientific side. He did not know whether he was asking for more data than Mr. Wood was prepared to give, but such figures would certainly be interesting, and add greatly to the value of the paper.

With regard to the conversion of the haulages, the paper showed in a very practical way how existing steam could be converted into electrically-driven haulages. Mr. Wood had described the larger as liquid and the smaller as metallic controllers. Personally, he thought that where liquid controllers could be used, and where there was water to cool the liquid, they got a cheaper controller, and altogether an apparatus which required less attention than a metallic controller, where there was a large number of fingers always requiring dressing up and refitting. The auxiliary motor arrangement seemed to him to be very neat. In some mines where endless-rope haulage was in use, a combination of such a device to speed up the haulage would be valuable. Many mine-owners said that if an endless rope were installed, the men could not be run in; but where one had an apparatus of that kind, endless-rope haulage could be utilized and made to serve the purpose. He noticed that three-throw pumps had been adopted, which seemed to him to be the only satisfactory kind to use, considering the small quantity of water and the high head. Rope-driving had also been adopted, which he personally thought was very necessary, as it took all vibration off the motors, increased very considerably their life, and reduced the cost of upkeep.

Mr. H. W. Clothier (Wallsend, Northumberland), speaking of the metallic controllers described in the paper, said that they made a very satisfactory job, but, unfortunately, they were too expensive to manufacture in competition with liquid resistances, and so he considered that there was not much prospect of more of them being made. He thought, however, that some photographs of them would be of interest, if only historically.

Fig. 27 showed the controller with all tanks and covers removed. There was only one hand-wheel for the complete operations, including switching in and out and the control of the speed and direction of the motor. The dial seen at the back of the hand-wheel indicated the "on," "off," and "intermediate" steps, the indicator moving clockwise for one direction, or anti-clockwise for the reverse, to correspond with the direction of the hand-wheel.

The drum of the multiplying controller was seen on the left and the high-tension change-over quick-break stator switch on the right. Convenient arrangements were made for lowering the oil-tanks, thus providing an easy means of inspecting the various contacts.

It should be noted that although there were only ten cable connections per phase to the resistance (Fig. 28), thanks to the multiplying arrangement twenty-four different speeds were obtained in either direction. A wire resistance 4 was subsequently added to give an additional speed for slowly taking up the slack rope; the cable-connections to this resistance did not complicate the controller, but merely connected the main and multiplying resistances together.

Fig. 29 showed the mechanism of the controller and the gear which interlocked it with the high-tension switch. It should be noted that the motors had two-phase rotors and three-phase stators.

Fig. 30 showed the details of the high-tension switch-contacts and operating-gear. It also showed the iron cover over the terminals of the controller and the bushes for the low-tension leads to the rotor and resistance.

Fig. 31 showed one section of the grid resistances enclosed in a ventilated cover.

Mr. Wood, replying, said that there had been a large saving in coal-consumption at Murton Colliery since the introduction of electricity. With regard to the commercial outlay, he thought that if a return of 15 to 20 per cent. could be got on the money spent, it was not a bad investment. He would be very pleased to take out the actual cost per ton-mile on the electrical haulage system.

The President (Mr. T. E. Forster) said that the figures promised by the author would be of great interest. He moved a vote of thanks to Mr. Wood for his paper.

The vote of thanks was cordially adopted.