Sir FREDERICK BRAMWELL, Vice-President, remarked that a Paper hrr. Coleman.Mr. COLEMAN said he had not much to add to the written contents of the Paper, except to supply an omission with reference to the indicated HP. of the indicator diagrams. The average indicated HP. of the cylinders of cards, Figs. 13, 16, 19, taken during the voyage to Australia and back was 76 ; the average indicated HP.of the air expansion cylinders was 57 ; and the average indicated HP. of the compressors 118. The total driving power was therefore 133 HP. ; the total resistance was 118 HP., and the difference between the two was 15 HP., and indicated the amount of friction, which was about 12 per cent. I n engines for waterworks and 1;ramwell. Downloaded by [ UNIVERSITY OF SOUTH CAROLINA] on [15/09/16]. Copyright © ICE Publishing, all rights reserve Proceedings.] DISCUSSION ON AIR REFRIGERATING MACHINERY. Downloaded by [ UNIVERSITY OF SOUTH CAROLINA] on [15/09/16]. Copyright © ICE Publishing, all rights reserve Proceedings.] DISCUSSION ON AIR REFRIGERATING NACHINERY.
Proceedings.]DISCUSSION ON ELECTRICAL CONDUCTORS. 79Discussion.Nr. BRUNLEES, President, said he thought the discussion might M~. Bmnlees.well be taken in three parts.First, as to the qualities which electrical conductors should possess ; next, as to the manufacture of the conductors, and then, having the elect,ric conductor according to the conditions laid down by men of science, and according to the possibilities of manufacture, on the practical use of the conductor. He would first ask Mr. Preece if he desired to add anything before the discussion commenced.table was empty, a seat that had been filled by one who had taken a prominent part in the discussion of every electrical Paper brought before the Institution. The late SirWilliam Siemens had taken the deepest interest in the subject, and had succeeded very largely in enriching it. Mr. Preece had brought forward many facts to illustrate the improvement effected in electrical conductors during the last quarter of a century, and he hoped that the discussion would elicit other facts, showing how the mechanical and electrical qualities of the various metals had been almost metamorphosed. The chief point that he desired to emphasize was the position that copper was likely to take in the future, and the remarkable mechanical powers that it evinced. He had brought for inspection a number of specimens illustrating the behaviour of metals, and showing how they were produced. In speaking of them in his Paper, he had been compelled frequently to use a term which was familiar in the mouth of every electrician as a household word; but which had not yet become familiar to engineers-the term "resistance." He had spoken throughout the Paper of the resistance of wires, knowing well as an electrician, what the term resistance meant ; but many engineers assumed that it meant mechanical resistance-resistance to tension or to rupture. It was a misfortune that the term had been too freely introduced, and it would have bee2 better if he had spoken entirely in terms of conductivity. If he had said that a copper wire conducted electricity six times better than iron wire of the same dimensions, he should have been better understood than by saying that a piece of wire had one-sixth of the resistance, or six times the resistance, as the case might be. Sir William Thomson had pointed out in that room how it was that conductivity was the exact reverse or reciprocal of resistance, and he went so far as to suggest that there ought to be a standard for conductivity as for exhibition the various instruments that were used to test the metals, and he would show the test upon iron, and if time permitted, upon copper, for he wished the members t o have distinct evidence of the remarkable mechanical qualities of the copper produced at the present day. The copper-wire specimens on the table possessed a breaking strain of 30 tons on the square inch, while the iron used for telegraphic purposes possessed a breaking strain of only 22 tons. Again, there was an impression that copper was very plastic, a...
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