The results obtained with this apparatus at Evesham, in Gloucestershire, by Mr. Newman, have been most striking. With wheat, increases of from 20 per cent. to nearly 40 per cent. have been obtained, and the electrified wheat is of better quality than unelectrified wheat grown at the same place, and, apart from electrification, under exactly the same conditions. In some instances the electrified wheat was as much as 8 inches higher than the unelectrified wheat. Mr. Newman believes that by electrification land yielding normally from 30 to 40 bushels of wheat per acre can be made to yield 50 or even 60 bushels per acre. With cucumbers under glass increases of 17 per cent. have been obtained, and in the case of strawberries, increases of 36 per cent. with old plants, and 80 per cent. with one-year-old plants. In almost every case electrification has produced a marked increase in the crop, and in the few cases where there has been a decrease the crops were ready earlier than the normal. For instance, in one experiment with broad beans a decrease of 15 per cent. resulted, but the beans were ready for picking five days earlier. In another case a decrease of 11½ per cent. occurred with strawberries, but the fruit was ready for picking some days before the unelectrified fruit, and also was much sweeter. In some of the experiments resulting in a decrease in the yield it is probable that the electrification was overdone, so that the plants were over-stimulated. It seems likely that the best results will be obtained only by adjusting the intensity and the duration of the electrification in accordance with the atmospheric conditions, and also with the nature of the crop, for there is no doubt that plants vary considerably in their electrical requirements. A great deal more experiment is required however to enable this to be done with anything like certainty.
Unlike the farmer, the market gardener has to produce one crop after another throughout the year. To make up for the absence of sufficient sunshine he has to resort to “forcing” in many cases, but unfortunately this process, besides being costly, generally results in the production of a crop of inferior quality. Evidently the work of the market gardener would be greatly facilitated by some artificial substitute for sunshine, to keep his plants growing properly in dull weather. In 1880, Sir William Siemens, knowing that the composition of the light of the electric arc was closely similar to that of sunlight, commenced experiments with an arc lamp in a large greenhouse. His idea was to add to the effects of the solar light by using the arc lamp throughout the night. His first efforts were unsuccessful, and he discovered that this was due to the use of the naked light, which apparently contained rays too powerful for the plants. He then passed the light through glass, which filtered out the more powerful rays, and this arrangement was most successful, the plants responding readily to the artificial light. More scientifically planned experiments were carried out at the London Royal Botanic Gardens in 1907, by Mr. B. H. Thwaite, and these showed that by using the arc lamp for about five hours every night, a great difference between the treated plants and other similar plants grown normally could be produced in less than a month. Other experiments made in the United States with the arc lamp, and also with ordinary electric incandescent lamps, gave similar results, and it was noticed that the improvement was specially marked with cress, lettuce, spinach, and other plants of this nature.
In 1910, Miss E. C. Dudgeon, of Dumfries, commenced a series of experiments with the Cooper-Hewitt mercury vapour lamp. Two greenhouses were employed, one of which was fitted with this lamp. Seeds of various plants were sown in small pots, one pot of each kind being placed in each house. The temperature and other conditions were kept as nearly alike as possible in both houses, and in the experimental house the lamp was kept going for about five hours every night. In every case the seeds in the experimental house germinated several days before those in the other house, and the resulting plants were healthy and robust. Later experiments carried out by Miss Dudgeon with plants were equally successful.
From these experiments it appears that the electric arc, and still more the mercury vapour lamp, are likely to prove of great value to the market gardener. As compared with the arc lamp, the mercury vapour lamp has the great advantage of requiring scarcely any attention, and also it uses less current. Unlike the products of ordinary forcing by heat, the plants grown under the influence of the mercury vapour light are quite sturdy, so that they can be planted out with scarcely any “hardening off.” The crop yields too are larger, and of better quality. The wonderful effects produced by the Cooper-Hewitt lamp are certainly not due to heat, for this lamp emits few heat rays. The results may be due partly to longer hours worked by the plants, but this does not explain the greater accumulation of chlorophyll and stronger development of fibre.
Most of us are familiar with the yarn about the poultry keeper who fitted all his nests with trap-doors, so that when a hen laid an egg, the trap-door opened under the weight and allowed the egg to fall through into a box lined with hay. The hen then looked round, and finding no egg, at once set to work to lay another. This in turn dropped, another egg was laid, and so on. It is slightly doubtful whether the modern hen could be swindled in this bare-faced manner, but it is certain that she can be deluded into working overtime. The scheme is absurdly simple. Electric lamps are fitted in the fowl-house, and at sunset the light is switched on. The unsuspecting hens, who are just thinking about retiring for the night, come to the conclusion that the day is not yet over, and so they continue to lay. This is not a yarn, but solid fact, and the increase in the egg yield obtained in this way by different poultry keepers ranges from 10 per cent. upwards. Indeed, one poultry expert claims to have obtained an increase of about 40 per cent.
The ease with which a uniform temperature can be maintained by electric heating has been utilized in incubator hatching of chickens. By means of a specially designed electric radiator the incubator is kept at the right temperature throughout the hatching period. When the chickens emerge from the eggs they are transferred to another contrivance called a “brooder,” which also is electrically heated, the heat being decreased gradually day by day until the chicks are sturdy enough to do without it. Even at this stage however the chickens do not always escape from the clutches of electricity. Some rearers have adopted the electric light swindle for the youngsters, switching on the light after the chickens have had a fair amount of slumber, so that they start feeding again. In this way the chickens are persuaded to consume more food in the twenty-four hours, and the resulting gain in weight is said to be considerable. More interesting than this scheme is the method of rearing chickens under the influence of an electric discharge from wires supplied with high-tension current. Comparative tests show that electrified chickens have a smaller mortality and a much greater rate of growth than chickens brought up in the ordinary way. It even is said that the electrified chickens have more kindly dispositions than their unelectrified relatives!
Possibly the high-tension discharge may turn out to be as beneficial to animals as it has been proved to be for plants, but so far there is little reliable evidence on this point, owing to lack of experimenters. A test carried out in the United States with a flock of sheep is worth mention. The flock was divided into two parts, one-half being placed in a field under ordinary conditions, and the other in a field having a system of overhead discharge wires, similar to those used in the Lodge-Newman system. The final result was that the electrified sheep produced more than twice as many lambs as the unelectrified sheep, and also a much greater weight of wool. If further experiments confirm this result, the British farmer will do well to consider the advisability of electrifying his live-stock.
CHAPTER XXIX
SOME RECENT APPLICATIONS OF ELECTRICITY—AN ELECTRIC PIPE LOCATOR
One of the great advantages of living in a town is the abundant supply of gas and water. These necessary substances are conveyed to us along underground pipes, and a large town has miles upon miles of such pipes, extending in all directions and forming a most complex network. Gas and water companies keep a record of these pipes, with the object of finding any pipe quickly when the necessity arises; but in spite of such records pipes are often lost, especially where the whole face of the neighbourhood has changed since the pipes were laid. The finding of a lost pipe by digging is a very troublesome process, and even when the pipe is known to be close at hand, it is quite surprising how many attempts are frequently necessary before it can be located, and its course traced. As may be imagined, this is an expensive business, and often it has been found cheaper to lay a new length of pipe than to find the old one. There is now an electrical method by which pipe locating is made comparatively simple, and unless it is very exceptionally deep down, a pipe never need be abandoned on account of difficulty in tracing it.
The mechanism of an electric pipe locator is not at all complicated, consisting only of an induction coil with battery, and a telephone receiver connected to a coil of a large number of turns of thin copper wire. If a certain section of a pipe is lost, and has to be located, operations are commenced from some fitting known to be connected with it, and from some other fitting which may or may not be connected with the pipe, but which is believed to be so connected. The induction coil is set working, and its secondary terminals are connected one to each of these fittings. If the second fitting is connected with the pipe, then the whole length of the pipe between these two points is traversed by the high-frequency current. The searcher, wearing the head telephone receiver, with the coil hanging down from it so as to be close to the ground, walks to and fro over the ground beneath which the pipe must lie. When he approaches the pipe the current passing through the latter induces a similar current in the suspended coil, and this produces a sort of buzzing or humming sound in the telephone. The nearer he approaches to the pipe the louder is the humming, and it reaches its maximum when he is standing directly over the pipe. In this way the whole course of the pipe can be traced without any digging, even when the pipe is 15 or 20 feet down. The absence of any sounds in the receiver indicates that the second fitting is not on the required pipe line, and other fittings have to be tried until one on this line is found.