NOTES ON SCIENCE, MECHANICAL INVENTIONS, ETC.

New Zealand Herald, Volume XXXII, Issue 10014, 28 December 1895, Page 4 (Supplement)

NOTES ON SCIENCE, MECHANICAL INVENTIONS, ETC.

DEFECTIVE VISION, A Frenchman, M. Dubois, has ma le aa interesting- eugtjostion us to tlio origin of colour-blindness. This defocl: of vision almost, invariably consists in inability to recognise red. Now a body cooling down from incandescence extends its spectrum towards the red end, or in other words th& white hot or violet coloured body becomes yellow and finally a dull rod as it cools. A few stars such as Sirius are white hot, many others, like our sun, are cooler and therefore yellow, while others aro so cooled down as to shine with a dull red light. Primitive man, according to M. Dubois, lived when tho sun was in either the Sirius or the proSinus stage—that is, when tho sun, which is tho sourcoof all colour, was white hot, and had no red component in its spectrum ; lie had, therefore, no power of recognising red. Colour-blindness, therefore, says M. Dubois, is merely atavism or degeneration to the primitive typo. The objection to this ingenious theory is that we have no reason whatever for suppling that primitive man was contemporary with a wliito hat sun ; further, all white hit. suns that wo linow of have some red at any rato in their spectrum. The intensity of particular components of the spectrum may vary, bub tho components are still there. A LUMINOUS CLOUD. A description of a luminous cloud, observed at Mojanga, Madagascar, on .September 27, by Mr. titration C. Knott, lI.M. Vice Consul, has been forwarded to Nature by Mr. 11. 11. Scott, F.R.S. The phenomenon was seen at B'2o p.m. as a narrow streak of what appeared more like mist than cloud. It came out of a cumulus cloud in the south, a few degrees above the horizon, and extended through the tail of Scorpio across two third'* of the sky, which was quite clear excepting some cumulus on the southern and oastoni horizon. The streak travelled at a rapid rato eastward*, but its base seemed to bo stationary ; as it crossed tho moon, it caused a sort of double coronq. A< the cloud got lowor on the eastern horiz jii, although always maintaining tho same length, some cumulus passed under it, partly obscuring it, and a few minutes later tho streak was lost altogether in the cumulus on the eastern horizon. At the time of the observations the weather was perfectly calm, but soon after this streak had passed, cumulus commenced to ascend from the eastward, and tho sky booh became nearly overcast. NATURE PRINTING. "This proc<Ms,"«iyi I'], M, White,in tlio Photogram, "should commend iisolf to all who Hudy botany and other branches of n.ituial history, inasmuch as it enables faithful and accurata copies of specimens to bo in vie without the aid of a camera. The method of working is as followsWo shall want a printing-frame, a piece of (rood stout glass, free/ from lluvs, cut to lit the frame ; and some gelatino-chlorid paper. Having procured a specimen, such as a spray of maidenhair fern, or a skeleton poplar loaf, we place it in the framo behind tho glass, and over it a piece ol sensitive paper (earo must bo taken to place the Hatter side of the specimen against) the paper); expose the whoie to a bright sun until the background, or uncovered portions of the paper, have darkened as much as they will; then take the resulting negative print, and tono to a goo 1 non-actinic tone, such a3 chocolate; lix in the ordinary mannor, wash and dry as in a print. In printing a positive it is only necessary to place a new piece of paper in tlio frame in contact with the negative print, using the glass as before, and print in bright sunlight The printing, of course, takes a time, owing to the light having to permeate through the paper."

ELECTRIC I'KOITLMON Fill'. STEAMSHIPS. The recent alliance betweeon the Baldwin Locomotive Works and tlio VVestinvjhon«e Klectric and Manufacturing Company lias (according to a San Francisco paper) started a great ileal of talk, "eligible and otherwise, about the substitution of electricity for •team on railroads. The idea that (ho same change might beeffectod advantageously on tho treat vessels which cross the 0:0111 was suggested to C. H. Cramp, who replied that no conspicuous shipbuilder would think of such a tiling for a moment. It was more economical to apply the power of the engine on a ileaui'hip directly to the service than to convert it tirsc into electricity and then me tho latter to do the work. This was a tiling which any electrical engineer could lure told the enquirer. Small launches can be propelled by electric power which has previously been stored in accumulators on I in-l and transferred to the boats but the supply of energy is sufficient to last only a few hours, and then the exhausted battery is lifted out to be freshly charged, and new cells are put in its placo. An ocean-going ve«?el cannot return to port evory three or four hours, and, as at present constructed, a storage battery capacious enough to hold the electricity which would be required in taking an ordinary steamship from hare to Honolulu would weigh more than the whole ship. This phase of the subjoct was nor. discussed by Mr. Cramp, who considered only the idea of generating the current 011 shipboard, but to both BChomes would equally apply his emphatic statement : " l'lie application of electricity to the propulsion of ocean steamships is practicably impossible.* A SUBMARINE BOAT. A new kind of submarine boat, the work of a French inventor, is propelled by a screw, which also servos the purpose of a rudder, the shaft being jointed to enable of its being moved right or left. Tho horsepower is extremoly small (one or two), this, it is said, being sufficient) under water, where there is no wavetnaking, to give seven or eight kno;s. The motive power is supplied by an electrical battery, accumulator? being tabooed on account of tho fumes in case of any breakdown. The boat may be rowed backwards or forwards by a pair of fin-like arrangements to the tore, When the boat is in harbour the dome emerges. When this is closed and the boat sets out 011 the war-path, water is lot into compartments in tlio loiver part of the boat, which gradually sinks. By means of mirrors submarine observations can be taken of events above water. One novel and ingenious arrangement is for sending up despatches to the surf ice in bottlos. METALS AND MINERALS, Profosior-Skidmore, of Philadelphia, in a course of laboratory lessons to supervising principals and teachers of tho Philadelphia public schools, took up the subject of niotals cooently. In the course of his lecture he raado some interesting remarks in regard to the distinction between minerals and metals. It is not possible, he observed, to define exactly what a metal is, yet there is little liability of misfcako in distinguishing a metal from a non-metal. The metallic properties of lustre, toughness, fusibility, opaqueness, conductivity, and rust may be I possessed separately by non-metals, but they are not associated as they are with metals. Most metals may be bent, twisted, drawn, and hammered to an extent far beyond what any mineral not a metal could •ndure. Taking up tho mattor of tho rusts of different metals, ho showed by a series of interesting experiments, that sodium, potassium, lithium, and, in a lesser degree, calcium, strontium, and barium, rust instantly when exposed to moist air, their white rusts quickly dissolving in water and forming alkalies. Other experiments demonstrated the fact that another group of metals, in which are zinc, lead, magnesium and antimony, have white rusts which are nob soluble in water. These rusts form a thin adhering coaling, which only half conceals the metal, and gives to it a dull, tarnished appearance. It was shown that at higher temperatures than tho ordinary, and especially if the metals are finely divided, the chomical energy of rusting is so great that the metals burn with a vivid light and emit a dense white smoke. The permanency of these rus's and their protective character are utilised in white points, Professor Skidmore then directel attention to a third group of metals, which includes those which have dark or coloured rusts, as with copper, iron, and silver. A series of experiments followed to show how those rusts were formed, and tho changes which iron undergoes in-appearance in the tempering process were carefully noted. Attention was directed, finally, to tho fourth group 01 metals, which never rust. These are gold and platinum, and it was! noted that they are alto tho metals which are found as metals in tho earth, and nob as ores from which the metal musb be" manufactured, In the caso of tho other metals it is an advantage that thoy are found in the rust or ore condition, as they can be manufactured much more eaiily than they could bo cui from ledges of tho pur« .metal.