In order to maintain a constant current, we have from time to time (say once an hour) to interchange the gases, so as to counteract the disturbing influence produced by the transport of the sulphuric acid gas from one side of the diaphragm to the other. This operation can easily be performed automatically by a commutator worked by a clock.

The water produced in the battery by the oxidation of the hydrogen is carried off by the inert gas mixed with the hydrogen, and by the air, of which we use a certain excess for this purpose. This is important, as if the platinum black becomes wet, it loses its absorbing power for the gases almost completely and stops the work of the battery. To avoid this was in fact the great difficulty in designing a powerful gas battery, and all previous constructions which employed the electrolyte as a mobile liquid failed in consequence.

The results obtained by our battery are practically the same whether pure oxygen and hydrogen or air and gases containing 25 per cent. of hydrogen are used; but we found that the latter gases must be practically free from carbonic oxide and hydrocarbons, which both interfere very much with the absorbing power of the platinum black.

We had thus to find a cheap method of eliminating these two gases from the producer gas, and converting them at the same time into their equivalent of hydrogen. The processes hitherto known for this purpose, viz., passing a mixture of such gases with steam over lime (which I mentioned some time ago) or over oxide of iron or manganese, require high temperatures, which render them expensive, and the latter do not effect the reaction to a sufficient extent for our purpose.

We have succeeded in attaining our object at a temperature below that at which the gases leave my producers, viz., at 350° C. to 450° C., by passing the producer gases, still containing a considerable excess of steam, over metallic nickel or cobalt. These metals have the extraordinary property of decomposing almost completely, even at the low temperature named, carbonic oxide into carbon and carbonic acid and hydrocarbons into carbon and hydrogen.

In order to carry the process out with small quantities of nickel and cobalt, we impregnate pumice stone or similar material with a salt of nickel or cobalt, and reduce this by means of hydrogen or producer gas. These pieces of pumice stone are filled into a retort or chamber and the hot gases passed through them. As the reaction produces heat, it is not necessary to heat the chambers or retorts from the outside when the necessary temperature has once been attained. This process has not yet been carried out on a large scale, but the laboratory experiments have been so satisfactory that we have no doubt as to its complete success. It will enable us to obtain gases containing 36 per cent. to 40 per cent. of hydrogen and practically free from carbonic oxide and hydrocarbons from producer gas at a very small cost, and thus to make the latter suitable for the production of electricity by our gas battery. We obtain, as stated before, 50 per cent. of the energy in the hydrogen absorbed in the battery in the form of electricity, while, if the same gas was consumed under steam boilers to make steam, which, as I have shown before, could in this way be raised cheaper than by burning fuel direct, and if this steam was turned into motive power by first-rate steam engines, and the motive power converted into electricity by a dynamo, the yield of electricity would in the most favorable case not exceed 8 per cent. of the energy in the gas.

I hope that this kind of battery will one day enable us to perform chemical operations by electricity on the largest scale, and to press this potent power into the service of the chemical industries.

The statement is frequently made that "Necessity is the mother of invention." If this has been the case in the past, I think it is no longer so in our days, since science has made us acquainted with the correlation of forces, teaching us what amount of energy we utilize and how much we waste in our various methods for attaining certain objects, and indicating to us where and in what direction and how far improvement is possible; and since the increase in our knowledge of the properties of matter enables us to form an opinion beforehand as to the substances we have available for obtaining a desired result.

We can now foresee, in most cases, in what direction progress in technology will move, and in consequence the inventor is now frequently in advance of the wants of his time. He may even create new wants, to my mind a distinct step in the development of human culture. It can then no longer be stated that "Necessity is the mother of invention;" but I think it may truly be said that the steady, methodical investigation of natural phenomena is the father of industrial progress.

Sir Lowthian Bell, Bart., F.R.S., in moving a vote of thanks, said that the meeting had had the privilege of listening to a description of results obtained by a man of exceptional intelligence and learning, supplemented by that devotion of mind which qualified him to pursue his work with great energy and perseverance. The importance of the president's address could not possibly be overrated. At various periods different substances had been put forward as indications of the civilization of the people. He remembered hearing from Dr. Ure that he considered the consumption of sulphuric acid to be the most accurate measure of the civilization of the people.

In course of time sulphuric acid gave way to soap, the consumption of which was probably still regarded as the great exponent of civilization by such of his fellow citizens as had thereby made their name. From what he had heard that morning, however, he should be inclined to make soap yield to ammonia, as sulphuric acid had in its time succumbed to soap. For not only was ammonia of great importance to us as a manufacturing nation, but it almost appeared to be a condition of our existence. England had a large population concentrated on an area so small as to make it almost a matter of apprehension whether the surface could maintain the people upon it.

We were now importing almost as much food as we consumed, and were thus more and more dependent on the foreigner. Under certain conditions this would become a very serious matter, and thus any one who showed how to produce plenty of ammonia at a cheap rate was a benefactor to his country. Mr. Mond's process seemed to come nearer to success than any which had preceded it, and it needed no words from him to induce the meeting to accord a hearty vote of thanks to the president for his admirable paper.

Mr. J. C. Stevenson, M.P., in seconding the motion, said that no paper could be more interesting and valuable to the society than that delivered by the president. It opened out a future for the advancement of chemical industry which almost overcame one by the greatness of its possibilities. Mr. Mond had performed an invaluable service by investigating the various methods proposed for the manufacture of ammonia, and clearing the decks of those processes supposed by their inventors to be valuable, but proved by him to be delusive. It gave him hearty pleasure therefore to second the vote of thanks proposed by Sir Lowthian Bell.

The vote having been put and carried by acclamation, after a brief reply from the president:

The secretary read the report of the scrutators, which showed that 158 ballot papers had been sent in, 154 voting for the proposed list intact, and four substituting other names. The gentlemen nominated in the list issued by the Council were therefore declared elected.

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A paper read at the annual general meeting of the Society of Chemical Industry, London, July 10, 1889.

In his brief report for the year ending May 1, 1889, the director of the Pasteur Institute, Paris, announces the treatment of 1,673 subjects, of whom 6 were seized with rabies during and 4 within a fortnight after the process. But 3 only succumbed after the treatment had been completely carried out, making 1 death in 554, or, including all cases, 1 in 128.