WEEKLY EVENING MEETING, Friday, February 3, 1893. SIR FREDERICK ABEL, K.C.B. D.C.L. F.R.S. Vice-President, in the Chair. ALEXANDER SIEMENS, Esq. M. Inst.C.E. M.R.I. Theory and Practice in Electrical Science. (With Experimental Illustrations.) WHEN I was requested to give a Friday evening discourse at this Institution, I felt very much honoured at having an opportunity of speaking to an audience that has listened to so many illustrious men of science. At the same time I felt that instead of selecting a purely scientific subject I should be more likely to interest you if I drew your attention to some illustrations of the way in which science is applied to practice. The tendency of our century, and especially of the latter half, has been to obliterate ancient distinctions, and to break down barriers which formerly were held to be insurmountable. In this respect I need only remind you that at one time, in chemistry, substances were divided into acids and bases, into metals and metalloids, and that until very lately in physics, some gases were classed by themselves as being permanent, and so on. All of these distinctions have been found untenable in the light of modern research, and in a similar manner the strict divisions maintained for a long time between different branches of science have been more and more abolished, so that nowadays anybody who wishes to excel in any one branch of science ought to possess solid knowledge of the principles of all the others. One of the most important barriers broken down by the spirit of our times is that formerly held up between science and practice, and the state of mind in which a learned professor once exclaimed about his own particular branch of science: "Thank goodness, there is no practical application of it possible," is more and more forgotten. Instead of that, endeavours are now made on all sides to turn to practical account all scientific investigations. While quite admitting that it would give much cause for regret if this tendency were developed too far, so as to interfere with the pro gress of purely scientific researches, it cannot be denied that the application of scientific principles has brought about that immense progress which is characteristic of the last half-century. A conspicuous example of the influence of applied science is furnished by the way the use of electricity has been introduced into our daily life, and several causes have contributed to facilitate the scientific treatment of electrical problems. Not the least among these is the circumstance that at first electricity could not be produced at a cheap rate for general commercial uses. Thus it came about that telegraphy, for which weak currents are sufficient, was for a long time the only practical application, and during this period of comparative quiet a number of the most eminent scientific philosophers devoted their time to discover the characteristic features of this great power in nature, and the laws which it obeys. The consequence has been that at the time when the discovery of the dynamo-electric principle made cheap electricity a possible commodity, the laws on which electric currents act were thoroughly understood, and the development of the introduction of electrical appliances could take place on the firm basis of scientific knowledge. The obligations that electrical engineers owe to science they have acknowledged in a practical manner in naming the units by which electricity is measured after the learned men who created the science of electricity. The circumstance that it is possible to reproduce perfectly the exact conditions for which electrical apparatus have been designed, has much facilitated the direct application of laboratory experiments to practical problems. It is, for instance, quite feasible to take a small quantity of ore, to subject it in a laboratory to chemical and electrical treatment, and to judge from the results whether it will be possible to design works for the treatment of such ores in large quantities on the same lines. As far as electricity is concerned it is possible in such cases to predict with absolute accuracy how much energy is wanted in each case to deposit a given quantity of metal in a given time. The electrical engineer is thus enabled to arrive, in a comparatively easy and inexpensive manner, at reliable data, which in other branches of applied science have to be obtained by costly experiments on a large scale. One of the most striking instances of the direct application of scientific researches to practical purposes has been furnished by Dr. John Hopkinson, who explained in his lecture before the Institution of Civil Engineers in the year 1883, how he had been led by mathematical considerations to infer that alternate-current machines could be run in parallel, and what conditions were necessary to secure success. His conclusions were tried shortly afterwards at the South Foreland Lighthouse, and have proved since to be of the utmost value for central electric lighting stations on the alternate-current system. For the sake of historical accuracy I should mention, perhaps, that Dr. John Hopkinson called attention in the following year to a communication to the Royal Society by Mr. Wilde, who had previously demonstrated the possibility of working alternators in parallel; yet the facts just related are an apt illustration of the point I desired to lay before you. While science is a safe guide for the engineer, and will warn him Diagram 1. degree conclusions based on scientific principles alone. As an example, the case of heating by electricity may be cited. The scien of the mistakes and fallacies which ought to be avoided, there are sometimes other considerations which will modify to an important Nail-rod Heating. tific data in connection with this problem are as follows: A kilogram of coal burnt to best advantage will give 8080 calories. The same amount of coal consumed in a boiler will produce steam sufficient for 1 H.P. for 1 hour, and this horse-power can generate electricity at the rate of 660 watts, or about 570 calories, per hour. Assuming that in heating by burning coal, only a quarter of the theoretical effect is attained, and taking the price of coal at 208. per ton, while the cost of a Board of Trade unit of electricity is 8d., it would appear that a farthingsworth of coal will produce as much heat as 22d. worth of electricity. These figures apply to the conditions of life in London, where fuel is abundant and power comparatively expensive; elsewhere, in Norway for instance, fuel may be expensive, and power, in the shape of waterfalls, cheap. Under such altered conditions electricity may with advantage be employed for heating purposes, by producing it with the aid of water-power, and utilising the heat generated by it, in special appliances. One of the most important industries of Norway is the making of horseshoe nails, for which special machines have been constructed, into which a heated rod of iron has to be fed. For this purpose the rod is passed through a charcoal fire, placed close to the nail-making machine, and a great deal of difficulty is experienced in maintaining the rod at an even and suitable temperature. The apparatus placed in front of you is designed to replace these charcoal fires, and its construction is shown by the diagram on the wall. The essential part of it is a hollow carbon, through which a current of electricity is sent, heating the carbon to any desired temperature. In this apparatus, a current of 400 amperes and 5 volts is used, equal to 2 Board of Trade units per hour, which is supplied from a transformer, the primary circuit of which is connected to the high-pressure mains of the London Electric Supply Company. A diagram of the connections shows that the two wires connected to the supply main are led to a commutator on the table, by which the current can either be sent to the transformer of the heating apparatus, or to another one, which will be mentioned later on. In order to prevent loss of heat by radiation, the carbon is placed in a box filled with sand, and the necessary precautions are taken to let the current pass through the carbon only. After the carbon has become white hot, a rod of iron, in passing through it, is rapidly heated, and the temperature it attains depends on the speed at which it is fed forward. It would have been very inconvenient to bring a nail-making machine here. With your permission, I will therefore ask Mr. Williamson, who designed the apparatus, to show us how to make spiral steel springs. By the side of the nail-rod heater stands a similar apparatus for the heating of rivets, which is also illustrated by a diagram, and will be shown in action. It is obvious that such an apparatus can be used in many places |