NOTES ON SCIENCE, MECHANICAL INVENTIONS, ETC.

New Zealand Herald, Volume XXXIV, Issue 10413, 10 April 1897, Page 4 (Supplement)

NOTES ON SCIENCE, MECHANICAL INVENTIONS, ETC.

PHOTOGRAPHY IK COLOURS. If the colour process brought forward by M. Chassagno, of Paris, proves to be genuine it will revolutionise photography. The process is described by Captain Abney (Nature, February 4, 1597) as follows:-" A negative is taken on a gelatiuo plate which has been specially prepared. The plate is developed and fixed in the ordinary way, and the image appears of the same character as if taken on a good density-giving plate. A transparency is next taken on a similar plate from this negative, or a silver print made on specially-prepared albuminised paper, The colouring is of a very simple nature. There are three dyes— a crimsonred, a grass-green, and a very good blue, all in solution, and mixed with some other ingredients besides water. There is ulso what we may call a mordant in the shape of a colourless liquid, containing, I should say, albumen and salt. The last liquid is brushed copiously over tho face of the positive (or tho silver print), and the blue I dye applied, a little at a time. IF tho light be good the blue dye rapidly takes hold of those portions of the surface which represent in monochrome what are blues in tho original. For instance, a china vase will take the blue tint, and the face or hands a faint amount of the same colour. The green dye ie applied in tho same manner, and the greens in the original make- their appearance in the positive, and so with the red. Finally, the print, or positive, presents a picture in colours, underlying which is the dark brown and silver image. It appears as if the image took up selectively these three colours, but. why it takes them up it is hard to see." Captain Abney goes on to remark that if the specially-prepared negative took up the colour the matter would be more intelligible; at present it is a profound mystery. It is pleasing to learn that a patent "has been applied for, and that the veil of secrecy, which at present shrouds the chemical nature of the liquids used, must shortly be withdrawn. BACTERIA AND milk. According to Nature, a aeries of observa tions by various observers has recently been made on the behaviour of different kinds of bacteria in milk. It has been shown that the bacilli of cholera find mill: a medium quito unsuited to their healthy growth ; in fact, at ordinary temperature* tlioy rapidly dio out. The bacillus of anthrax, on the other hand, flourishes wonderfully in raw milk, and is quite unmodilied in its dangerous qualities. The bacillus of diphtheria also finds satisfactory material for growth in raw milk; if, however, tho milk was sterilised by heating for some time conditions very unfavourable for the growth of theao organisms were sot up. It appears that prolongod sterilisation at a high temperature makes milk slightly acid, whoroas in its fresh state it is slightly alkaline. It is apparent that tho chomicnl changes produced by sterilisation, of which the acidity is one expression, produce a food material which is unsuibed to the growth of those noxious bacteria, and the experimenter, Dr. Schottelius, "concludes hU papsr with a warning, now so often repeated, of the danger attending the consumption of milk in a raw, unsterilised condition." COLOUR YEKSDS SCENT. Tho generally received idoa is that tho bright colours of flowers aro tho chief means of guiding insects to them, and many observers litivo performed experiments which seemed to show that this was the case. In tho experiment.", the brightly coloured parts of the (lowers wore removed, and ib was assorted thatinsects.°huwed a preference for the perfect (lowers. Recently, however, Professor F. Plateau, of Ghent, has been investigating the problem, and he is of opinion that most of the previous observers were not sufficiently careful not to handle the flowers and thus interfere with their scent. Ho removed tho brightly coloured corollas of a number of flowers, and found in overy case bub one that the change made no difference to the number of insects which visited them. Tho exception was the snapdragon. Humblo bees frooly hovorod ovor the mutilated flowers, but did not visit them. This sooms to be explained by the fact that humble bees have a peculiar method of entering these flowers, and that tho absence of the corolla puzzled thorn. In another experiment Professor Plateau covered certain flowers with rhubarb leaves, and found that the hidden flowers wore just as freely visited by insects as those which were exposed. These experiments certainly seem to show that tho sense by which insects are guided in their search for flowers is smell rather than sight. COLOUR IN LIMIT. Tho philosophy of colour in light) maybe presented this way: It is noted that tho light from an electric arc, for instance, when seen near at hand, has a distinctively bluish colour, but this samo light, when viewed fremiti distance, appears yellowish, certain of its rays having been absorbed by tho water vapour in the air on its passage to the eye; for a similar reason, the sun is now, by some, considered to be a blue star; his light, which would appear intensely white and rich in blue rays especially, if it could be seon beyond our atmosphere, appears yellowish after ib has passed through that atmosphere and lost some of its most refrangible constituent rays. Tho effect of absorption in producing colour is seen in the fact that powdered bodies generally appear white, a fact accounted for when it is considered that a powder consists of particles arranged at all angles, so that the light falling upon ib moots various surfaces, and is mostly reflected before it has passed below the surface, and thus tho white light meeting ib is nob deprived of some of its constituents by selective absorption, as would bo the case if it penetrated the substance and was then reflected. In this way powdered red glass appears white. COOLING OF THE GLOBE AS A FBIMAIIV OADSE OF EVOLUTION, "According to M. R. Quinton," says Cosmos, " the different modes of reproduction observed in the animal scale— parous, marsupial, viviparous— the immediate consequence of the cooling of the globe. Life appeared on the globe in a high-temperature medium ; it had at the outset for its chemical phenomena the temperature of this surrounding medium. The present representatives of this primitive age are the so-called cold-blooded' animals; these have undergone an adaptation that, now as then, determines an equality between their internal temperature and that of the medium. But there were some who Were not adapted to the fall of temperature which was the occasion of a thermic separation, more and more great between the exterior medium and the animal chemical substance. The first beings were oviparous. Dub in the presence of the separation in temperature this mode of reproduction could not exist any longer, and the animal was obliged to use its own heat to warm its eggs ; honco the successive appearance of the marsupial mode, and then the viviparous mode, and the oviparous with in. cubation. From this theory of the origin of these methods of reproduction M. Quinton thinks that he can deduce that) of (he types of mammals and birds." ■ HUNTING WITH A MIRROR, A taxidermist at North wood, N.Y., says the New York Sun, has been making experiments as to tho effect of light reflected in a bird's eye. A glass seven or eight inches in diameter has been found moat serviceable. Tho antics of blue jays are remarkable when the light strikes them as they sit in the shadow of an evergreen tree. They jump to another branch and try to look into the light, but they have to turn away, as the light dazzles them. Then they fly around the reflector, bub after practice one is able to keep the light) always on them, and the birds nob infrequently come within reach of a man's hand. A ruffled grouse gives a startled look when the light strikes it! Then up ib jumps, and away ib goes. Hawks, too, are usually/ startled or annoyed so that they fly off. Woodpeckers don't seem bo mind ib at all. Rabbits blink and stare at a glass for a while, then go around a stump, and sib up again, as if waiting for the light to play tag with them. BAHOMETRIO CHANGES. A peculiar effect of barometric change is eeeo in the " breathing-ground" of limestone districts. If a well in this kind of toil is covered over eo that only a small hole is left in the top, and a lighted candle ii held, near this hole, quite a strong current of air can sometimes be noticed.': The " breathinga" are irregular, and accompany barometric changes, for the reason that when the pressure on either side of the opening is heavier than that on the other side,' a flow eeta in from the' heavier to the lighter. :; • -■■■ { . - •■ >4j(*-1: