And in the impulse of her gladness, she would have clasped his hands; but he looked startled and drew back, as a guilty man might do. Her astonishment took another turn: was it possible that he yielded so readily to her proposal because he wished to make atonement for the past?
He recovered himself instantly, and took her hand.
‘I see, Miss Heathcote, that Mr Shield has told you his version of these unhappy events,’ he said anxiously; ‘and in justice to myself, I must tell you mine.’
ELECTRICITY FOR NOTHING!
We recently received an invitation to witness, in London, a new method of producing electricity for lighting and other purposes ‘free of cost.’ The announcement that anything, with the exception, perhaps, of the air we breathe, can in these days be had for nothing, tempted us without delay to pay a visit to 31 Lombard Street, where, at the offices of Mr H. A. Fergusson, the new system was to be seen at work. Here we found a number of the now familiar incandescent globes dispersed about a large room, together with some small motors for driving sewing-machines, &c., the whole or any number of which could be put into operation by the turn of various switches. These lamps and motors all derived their electrical energy from a primary battery contained in a cupboard. Upon looking into this cupboard, we saw a number of wooden trays, lined with sheet-copper, piled one above the other like a nest of drawers; and we were told that each tray represented one cell of the battery. Further examination showed that the constituents of each cell were a plate of zinc, placed horizontally above a dark layer of oxide of copper in a solution of caustic potash. Coming to the question of cost, or rather of alleged freedom from cost, we learned that the cells were easily charged in the first instance, and that when once charged, would remain without attention for at least a month. During this time the battery would furnish a current. In the process, the copper would be gradually exhausted; but by a simple operation, could be brought back to its pristine state, and would be ready once more for another month’s work. Meanwhile the zinc would gradually be dissolved to form oxide of zinc. Now, one ton of metallic zinc can be transformed in this way to a ton and a quarter of oxide—a valuable white pigment—and as the oxide sells for a greater price than the original zinc, the promoters have some ground for their statement that electricity can be produced by this battery free of cost.
Unfortunately, recent experience of electric-lighting schemes has made the public very cautious in their reception of any new thing of an electrical nature, and there is little doubt that for some time really promising schemes will suffer for the shortcomings of their predecessors. It is, too, by no means the first time that a battery has been brought forward with the intimation that it will pay its own cost by the value of its by-products. But the effect upon the price of such by-products of glutting the market with them, is generally omitted from the calculations. Hitherto, such schemes have proved illusory; though it by no means follows that they must always do so. We have the example of gas manufacture before us, where, by careful working, the cost of the gas could be more than covered by the value of the other products of the coal.
A great deal of valuable information on the subject of primary batteries for electric lighting may be gleaned from a paper recently read before the Society of Arts, London, by Mr Isaac Probert, and which has since been published in that Society’s Journal. (We may here point out that the word ‘primary,’ as applied to batteries, has become necessary in quite recent times, to distinguish those which furnish a direct current from those which, under the name of accumulators, storage or secondary batteries, require charging, in the first instance, from another battery, or dynamo-machine. The current so stored can be afterwards utilised, as convenience may dictate.) This paper records in a lucid manner the numberless attempts which have been made to utilise primary batteries; but, except for experimental purposes, the cost has always proved prohibitive. The unhealthy fumes given by such batteries as those of Grove and Bunsen—which were, until lately, practically the only forms that could be used for electric lighting—also limited their use to situations where the fumes could do no harm. In process of time, Faraday’s grand discovery, that electricity could be generated by a magnet, and the ultimate outcome of that discovery—the introduction of the Gramme machine and its hosts of fellows—gave for a time the coup de grace to battery projects, and for a long time they were heard of no more. But why was this? Let the question be answered by the practical illustration given by Mr Probert, which we must quote—for want of space—in a very condensed form.
Let it be supposed that a house is furnished with one hundred incandescent lamps, the electric energy for which is provided by a dynamo-machine and its necessary companion, a steam-engine. The mechanical energy required for the work is, say, twelve and a half horse-power. This is of course derived from the combustion of so much coal; and if there were such a thing as a perfect engine where no heat was wasted, the amount of fuel required would be very small indeed. But, as a matter of fact, with an ordinary engine the weight of coal required to furnish the power given would be about fifty-six pounds per hour—costing, say, sixpence. Giving the lights a working period of five hours a day all the year round, we have a cost for fuel alone of forty-five pounds. Then we have to take into account the first cost of the machinery, the interest on that cost, annual depreciation, and attendance. We need not dwell on the separate estimate for each item, but may state the total yearly cost of the installation at one hundred and forty-seven pounds, or nearly thirty shillings per lamp.
Now, let us assume that instead of a dynamo-machine and its motor, a galvanic battery is employed, and that the amount of energy furnished is the same as before. In this case, we shall owe our energy to the combustion of zinc in lieu of coal; and instead of obtaining the oxygen for the process from the air, which costs nothing, we must of necessity get it from an acid, which costs a great deal. The total amount of zinc dissolved per hour in the acid, to furnish the current required for our one hundred lamps, will be about thirteen pounds-weight, the cost being nearly three shillings. Added to this sum must be the amount expended on acids, the cost of attendance, prime cost of apparatus, interest, depreciation, &c., bringing up the total annual charge to seven hundred and fifty-nine pounds ten shillings, or seven pounds eleven shillings and eightpence per lamp.
These figures will be both interesting and instructive to many persons who wish to have some idea of the probable cost of changing their old lamps for new ones; but they serve our present purpose in pointing out the reason why the battery current has been superseded for lighting purposes by the far more economical dynamo-machine. Still, it is not every one who requires so many as a hundred lamps; and for smaller installations, an efficient, easily managed, and cheaply working battery would have a wide application. But it must be remembered that electricity can now be had at comparatively little cost to light a dozen lamps or so by employing a small dynamo-machine driven by a gas-engine. Inventors of batteries must, therefore, remember that they have rivals in the field, and that if they would successfully compete with them, they must offer something as cheap and efficient. Hitherto, this something has not appeared. But human nature is sanguine, and the most sanguine of mortals perhaps is one in whom the inventive faculty is highly developed. In spite of previous failures, no fewer than one hundred and fifty patents for primary batteries have been taken out during the past three years. Some of these are acknowledged improvements upon past models. Many batteries now before the public cannot be critically examined, for they employ fluids the nature of which are kept secret. (Of course this objection cannot apply to a patented invention, for one of the conditions of granting protection is that the invention must be so described in the specification that any intelligent workman can understand its nature and construction.) Others cannot be well described without diagrams and technical details of no interest to the majority of our readers.