NOTES ON SCIENCE, MECHANICAL INVENTIONS, ETC.

New Zealand Herald, Volume XXIII, Issue 7824, 18 December 1886, Page 4 (Supplement)

NOTES ON SCIENCE, MECHANICAL INVENTIONS, ETC.

TOUGHENED GLASS. VEr.T little is hoard now of tempered or toc»;hened glass for domestic purposes, although, a year or two back, such glass was much advertised snd its praises constantly gong. Wβ uudnretaud that the reason why it las at present disappeared from public notice is that its efficiency doea not last. Wlion fresh from the factory, it can *be dropped from a height oa to the floor and ktiockod »bout with impunity; but some gradual and not understood change occurs in its flonititution, for after a short time it will fly to pieces without any apparent cause. It is said, too, that unscrupulous traders who hava a stoott of the faulty material aro Belling it »* ordinary jjlass. Thoae, therefore, who experience unaccountable breakages, will know to what cause to attribute them. A really unbreakable glass would be auoh a boi>n, that it is to be hoped that farther experiment will goon show how it can be manufactured.

HOW TO SEB ONE'S BRAIX. Pr. Fraser Halle some years ago conimunic*ted a remarkable discovery to the English Mcchauio and World of Sciouoe. Fifty years have elapsed iinoe Purkinje observed that by passing a candle to and fro several times by tho side of the eyo the air iu front was transformed into a kind of screen, on vhich was reflected what was then supposod to be "a magnified image of part of the retina." Sir C. t (then Mr.) Wheat3tone it to be "the shadow of the vascular net-work." Mayo thought it was "»u image of the blood vessels of the retina." Sir Benjamin Brodie, to whom Dr. Halle wrote on the subject, could not identify it ivith any part of the retina, and eaid that it wh to him "really incomprehensible." By niiAns of more careful drawings Dr. Eraser Hallo resumed the exploration, and succeeded in identifying the picture with the representation of the •• anterior lobe of the cerebrum." Tho picture consists, he has long observed, of " red convolutions with dark interspaces, " among which a whitish admixture iu sometimes visible. These, ho says, constitute exactly the imago of folds of the autorior lobo of the brain with the furrows batwoen thorn. The candle should bo moved to &nd fro about four inches below the eye, and three and » quatter inches from the face Wheu tho movement ceases the .ni.lulattons, of course, also cease, and the image disappears. A reddish mist appears tirst, and the image is soon developed aud denned. Night is the best time for it, but it can be seen in a dark place faintly in the daytime.

THE SKVERN* TCTNJsEL. The Severn tunnel, one of the greatest engineering undertakings of modern time*, is uiiislnu, and will be shortly open for passenger traffic, as it has been some weeks for the ■j.uveyance of goods. The total cost of this great work is estimated at two million sterling. The cost has beon greatly augmented by t be unlooked-for difficulties which have cropped up during the progress of the works. Commencing in IS7o, the contractor i.a.l made steady progress for the following si>, years, when a land spring was acciden» tally tapped, and the partially constructed tunnel was Hooded. Again, in ISSI, the seawAter found out a weak place on the Gloucestershire side of the works, and poured ia iu torrents. Once more, in ISSi, the old land spring egaiu tiled the works with water, which had to be pumped out; and "bally, about the same time, a tid&l wavo brought about a great amount of destruction to the works; so we may look npou the completed tunnel not only as a great monument of engineering skill, but as an example of unusual difficulties well grapped with, aud ncaliy overcome.

T.4KOE FAMILIES. Limiaias calculated that if an annual plant produces two seeds which shall arrive at perfection— though no plant produces so low -and each of these in tarn perfects two, and so on at the same rate, at the end of twenty years the descendant* of the original plant would be a million of individuals. It is reckoned that a single plant of groundsel (jenecio) may produce 6500 seed», one of ciiickweed (Stcllaria) 5000. and one of shepherd's purge (Capsella) 4500 ; but what with, overcrowding, and preying of insects, ar.d other mishaps, usually looked upon as ■' accident*," very few of this enormous progeny ever reach maturity. Again, the Orchis macalata of our hedgerows (Vol. 111., p. SC6) produces so great a quantity of eccds ■.hat were they all to spring up, the earth would soon be covered with this plant ; but in reality the orchis in question is by no means a very common plant compared with other* which eeed much less freely. JTOBHATIOX OF SALT PLAINS. On the tasteru coast ef the Caspian Sea a curious phenomenon is in progress. The Kara Bouhaz is an estuary nearly separated irom the main body of the sea by a bank through which there was an iolet. The evaporation from this gulf is bo great that a current continually sets in from the Caspian ; axid as there is no return current the water of the gulf becomes more and more ealiferous, ■nd a deposit o salt ie in course of formation. In time this gulf will be cut from the Caspian, and will then be dried up and become an extensive salt-bed. HOMEOPATHY IS THE DSITHD STATE 3. Is is stated that, m the United States, there are more than 10,000 hotEcepathic practitioners, and that there are fourteen colleges for educating fitudent3 in homeopathy. The homoeopaths set forth their view* in 143 Boeittiea and twenty journals, and give their valuable services to the public at fifty-one hospitals and forty-eight di»penaarioe. Oar usually well - informed contemporary, the :\ew York Medical Record, appears to accept these figures as at loast approximately correct, though at the came time it expresses the belief that Americans are outgrowing their curione love for tbia worn-out theory. —British Medical Journal. PAPiSR KOOF3. A roof, pronounced superior to that of elate because of its lightness and other advantages, is now made of fibrous pulp. From this material tiles of any shape desired are formed by pressure under machinery, or by any other method which may suggest itself. Pressed into the design wished for, the pulp tiles are partially dried previous to being subjected to a waterproof mixture. After the baking the tiles aro treated to a mixture imparting an enamelled surface ; to this is added a coating of sand, whereby the pulp ia rendered proof against the action of heat and iUme. By the use of different coloured eandfl a variety of tints may be imparted to the tiles, which, after the application of the enamelling mixture and sands, are baked a second time, after whioh they are ready for use. Besides the inherent lightness of , pulp tiles, which obviates the necessity of a heavy frame to support a weighty roof, the pulp tile being tough, and not brittle like elate, is far less liable to be broken from blows, atones thrown upon them, or human fcotstepa. Again, slate tiles cannot be laid compactly together on a roof on account of their brittleneee, which prevents tboir being drawn tightly together by nails. Through ibe fibrous pulp nails may be driven as close home aa. in wood, thereby binding them closely to the bed and together, without any possibility of lateral movement, or boing blown away in a high wind, as slates loosely fastened on roofs eo frequently are, ' MISSELLANBOU3. A strange sight was lately witnessed at Salzburg, in the shape of a vast procession of butterflies, which passed over the city in a south- westerly direction. They seemed to fly in croups, and while preserving one line of direction in flight, the groups revolved round that line. Thie aerial insect army must have numbered millions of individual butterflies. From those which fell to the yround, it was seen that they were of the kind known as willow-spinners. # Dγ Von Bolet says that nitro-glycerme ie very usefal in heart disease, especially where there is no eerious organic change. In angina pectoris the drug glvee relief and •ometimes prodnces a permanent cure ; and he recommends it in preference to camphor or musk where weakness of the heart threatens immediate danger. He. uses a 1 per cent, alcoholic solution, and administers torn one to six drop« throe times a day. , Professor Manassein recommends the watermelon as a cheap but effective substitute for irrapea in the treatment of chronic congestion of the liver, chronic intestinal catarrh, and similar affections. '.',..■ . Uerr L. Lolenche having shown experimentally that the friction of ice and water results in-the positive electrification of we, end consequent negative electrification of water, considers it probable that the friction k cumulus and cirrus clouds may be sumoient i o account for thunderstorms. . o ! \ VAfctronomie records a fall of Innnnoue ; ■ain during a thunderstorm at Sotteville ; that I is to say, the drops on touching the ground ! produced flashes of red and violet light. Similar phenomena have been previously ] recorded.