SCIENTIFIC.

Otago Witness, Issue 1805, 25 June 1886, Page 27

SCIENTIFIC.

— The exceedingly delicate coloured photographs on glass, says an engineering paper, which have come into fashion somewhat of late, are produced by fixing a paper photograph upon a cushioned-shaped glass with transparent cement, and when it is dry rubbing away two-thirds of the thickness of the photograph with sandpaper. The thin film left is then rendered transparent by soaking in melted paraffin wax, after which transparent colours are applied, which appear softened down when looked at from the front. The background and heavier portions of the picture are then painted in body colour upon the face of another cushionshaped piece of glass, which is afterwards fixed behind the first one. An improvement in this process has recently been made by Mrs Nelson Decker, daughter of the late C. F. Varley, F.R.S., and the first of the young membeis of his family to have produced a scientific, novelty. She lias just discovered that the second sheet of glass may bo abolished, a better artistic effect produced, and the picture rendered more permanent by being protected trorn the action of the air and deleterious gases by being wholly embedded in paraffin. She does this by quickly dipping the photograph in paraffin a second time after the transparent colours have been applied, and painting the heavier colours upon the back of this second coat. A third layer of paraffin is then applied, and the background painted upon that ; tho third coat may be finally protected by yut another layer of paraftm. Some practice is necessary to acquire the knack of doing this efficiently. Tt must be done quickly enough not to remelt previous lavciv, :md' the plate must, after eack dipping, be quickly tilted on end in such a manner that the parnflin does not run into, ridges and thickened lines, but i'mms an even coating. --•A very valuable scientific discovery, which ha? just been made by Herr Ernest

Freund, a student in the chemical laboratory of Professor Strieker, at the Vienna University, has been announced. Herr Freund has discovered that the coagulation of blood, after it has been drawn from the veins, can be prevented by simply pouring it into a clean glass, or other receptacle, of which tho sides have been, coated with a thin film of oil. When the vessel has been nearly tilled another layer of oil has to be poured on the bop of it, to prevent contact with any substance to which the blood might adhere. The coagulation of blood within a quarter of an hour after its effusion has proved a great obstacle to scientific experiments with microorganisms, and all the means hitherto tried bo prevent coagulation, including that to which Dr, Haycraft, of Edinburgh, has attached his name, have been more or less unsatisfactory, because they altered the chemical composition of the blood. By Hcrr Freund's process, however, the decomposition of the blood is arrested. Experiments have been made with vaseline, almond oil, and olive oil, and all have been equally successful. The only requisite is that the oil should be perfectly clear, so that there shall be no centre of coagulation by any hard particle of foreign matter. — A contemporary philosophises upon the interesting possibilities in regard to future astronomical discoveries by means of photography, substantially as follows : Photography differs from all other pictures in being an absolutely faithful reproduction of everything within its range. The piercing rays of the sun are absolutely impartial, reflecting the exact apparent form and size of everything within range of the camera. This evident fact suggests an interesting thought. If the sensitive plate could be made of such exceeding fine quality as to print accurately the smallest objects conveyed to it by the rays of light, the simple process of magnifying it would enable us to print copies so large that it would be equivalent to multiplying many times, the power of the largest telescope. The present limit to the magnifying power of telescopes is the obscurity of the glass which has to be, very thick, in high powers ; but if the magnified object is photographed, and the photograph is of fine enough quality to be itself magnified, what wondrous results might not be obtained ! ' An object on the moon the size of a small hill can be plainly seen now ; with this improvement tho houses and people (if there were any) could bo plainly seen. The mysteries of Mars' varied surface, the belts of Jupiter and the extraordinary rings of Saturn, we may hope, will be understood in the near future— a future blight with the scintillations of man's genius which is fairly overturning the world and bringing us into closer harmony with the infinite universe, and fairly opening our ears to the " music of the spheres." — A new. kind of refrigerator has been devised, and is on sale in New York. The principle on which it acts is old enough, but the application of that principle is simple and interesting. An iron pipe two feet long and three and a half inches in diameter U filled with liquefied ammonia. To a stopcock at one end of this pipe is fitted a smaller pipe, which ultimately forms a coil within a cylinder about ten inches high and as many in diameter. This cylinder is made of wood and lined with hair-felt. The action of the apparatus is as follows : When the stopcock is turned on, the liquid ammonia rushes out in the form of gas, and absorbs so much heat that the temperature of surrounding bodies is immediately lowered. Any vessel placed within the coil inside the box can actually be lowered in temperature to sixty degrees of frost in a few minutes.