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MARCI25, 1880.1 THE PHOTOGRAPHIC NEWS. 145 Ue Ahotographic Ucs, Earc 25, 1880. PHOTOGRAPH! IN AND OUT OF THE STUDIO. The ELECTRIC Light and Vegetation—The London Water Supply—Microscopic Measurement of Bromide of Silver in Gelatine Emulsion—Photography and Elections. The Electric Light and Vegetation.—We have never done with the electric light now-a-days : horticulture is next to reap a benefit from it. Dr. Siemens read a paper to the Royal Society, in which he proved that by turning night into day in his conservatory, he was able to aid the growth of various early vegetables, including beans, peas, mus tard, and potatoes, whilst the blooming of flowers was absolutely exemplified before the scientific senate by his exhibiting a pot of tulips in bud, and after forty minutes’ exposure to light showing them in full bloom. Whether this action is due to the light, or to the presence of an elec tric current in their vicinity, it seems, isopento doubt, for in India it is affirmed—and with some reason, apparently — that a thunderstorm is necessary to cause bamboos to shoot well. As regards the growth of plants when above the ground, it has over and over again been shown that the yellow and blue rays have a marked influence in causing the formation of chlorophyll, on which, in a measure, the growth of plants depend, and by the electric light we have these rays supplied in abundance. The con clusion that is drawn by the author of the paper coin cides with that of Dr. Schubeler, of Christiana, who experi mented on plants in an Arctic summer. This shrewd and observant philosopher stated that under the influence of continuous light, plants are able to grow continuously and develop more brilliant flowers, and larger and more aromatic fruit, than under the alternation of light and darkness. The formation of sugar, on which the ripeness of the fruit depends, is simply caused by the elevation of temperature. What the influence of the light may be on seeds below the surface of the soil is an open question, and is not decided by Dr. Siemens at present. The electric light has, we believe, also been utilized in the study of vegetable physiology. It is well known that in certain plants (exotics principally) the leaves stand well out from the stem during daylight, but gradually droop as the light declines. Drawings have been made of these nocturnal positions, but photographs have also been considered necessary to verify the accuracy of the drawing. To do this, an electric light has been used to illuminate the plants when they were well asleep, and with the best of results. In some negatives we have seen, the light has been turned on just a trifle too long, and before the exposure was finished, the plants begin to awake, and the leaves commenced ascending to their proper daylight position, the consequence being a slight blurring or indistinctness of the image. The London Water Supply.—It is a mercy to us poor ratepayers that Parliament is dissolved without having passed Mr. Cross’s little Bill (it would have been a big one, by-the-bye, for us to pay), by which we were to have obtained pure water in the future; the future being—well, we won’t say how long hence. Now, of all people in the world who should be benefited by a pure supply it is the photographer, since so much is dependent on it in his operations. We Londoners, however, have not much to grumble at; the water is tolerably pure after it leaves the filter beds of the different companies’ reservoirs, much more so than is generally believed. London water is infinitely better than most well water, even when the latter is stated to be chemically pure. We know of one instance where a succession of families, all inhabiting a certain house, drank the well water, and the majority of them died from typhoid fever. The well water was analysed and found excellent, and yet a microscopic examination of a slight sedi ment there was, showed the scales of fish fibre and a few more organic substances quite undetectable by chemical means. The presence of these minute forms show that sewage leaked into the well very slowly and in a very dilute form, and yet the poison left by one family was sufficiently virulent to poison the next. In another case a well-known photographer was suddenly afflicted with spots in his plate— spots of a circular form, darkening on the metallic image after he had fixed his plate. These plagues appeared sud denly, and nothing would move them. An examination of the water used for washing showed at once what was the cause. The well water contained a certain amount of iron in solution, and the chloride of sodium and other salts soaked into the water from an adjoining cess pool, owing to an overflow caused by heavy rains. Perchloride of iron was formed, and after washing the cyanide away, used for fixing, it speedily attacked the least resisting parts of the image, forming chloride of silver, and naturally these darked by exposure to the light. .Nature had here shown the photographer how he might । reduce the intensity of his negatives, but, instead of taking the hint, he blamed his bath, his developing solution, and cyanide, and never thought of the water. Even if Mr. Cross’s Bill does not pass, we are never likely to get water so impure as that. No doubt, water drinkers in London swallow thousands of animalcule of all sorts, but usually they are of the most harmless descrip tion, and they don’t affect the sensitive plates or developed images. We can well rest content with the rates we pay now, and, we may add, the water. The only improve ment that we can suggest is that there should be two sup plies, one for drinking, carefully filtered by the very best means before it reaches the houses ; and the other, in its natural state, for the ordinary purposes of the house. It seems a waste of money andlabour to filter, as is done now, all the water which is used for ordinary domestic purposes. Microscopic Measurement of Bromide oj Silver in Gelatine Emulsion.—The indefatigable Dr. D. J. M. Eder has had recourse to the microscope to tell us rather more than we knew before regarding the sizes of the bromide of silver particles which are to be found in gelatine emulsions. The extreme minuteness of the particles can be judged when it is stated that the limits are somewhere about 1-30,00oth and 1-10,000th of an inch, according to the length of time that the gelatine has been cooked ; the longer the cooking, the coarser being the particles. No doubt the Doctor measured these in his microscopic micrometer, and with all that accuracy which distinguishes his country men. It is not every one who has a microscope, however, who has the necessary delicate measuring apparatus; and, perhaps, a rough method of approximately ascertaining the size of these minute forms may be acceptable. Tie your forefinger rather tightly round with your handkerchief so as to cause the blood to be forced to its top, and take a fine needle and give it a small prick. A drop of blood will immediately exude, which can be spread by the needle point on the same strip of microscopic glass as that on which the object to be examined has been previously placed. On examining this drop of blood with a quarter inch objective and a tolerably low power of eyepiece, the blood corpuscles can be readily seen. The corpuscles look like small jelly-fish floating about in a fluid, and their longest diameter is about 1-3,200th of an inch. By keeping in the mind the apparent size of these small bodies, and then examining (say) the particle of bromide of silver, a very fair approximation to the size of the latter can be arrived at. Perhaps one point requires caution—and that is, not to come within the clutches of the law, and to avoid this it is as well to prick your finger in private, and get the blood on the plate before any one sees you. According to the literal wording of the Act which prohibits vivisection, such a maltreatment of your own finger, or of any one else’s, renders you subject to penalties which are almost too terrible to enumerate. Pholoyraphy and Elections.—A very clever application of photography to electioning purposes is being made in some electoral districts and towns. It consists of presenting a carte photograph of the candidate to each elector, on which