Science.

Alexandra Herald and Central Otago Gazette, Issue 348, 8 January 1903, Page 7

Science.

QUESTIONS. * are Borne bodies, as glass, ,A \t/\KI fc ra E&pnrent, and others, as stone, not ? The explana • tion is to be found in the fact that the continuous. medium of space permeates jboth" transparent bodies, such as glass, anS liabt-abortive bodies, such as stone; ano|f this? in .roan, a considerable degree (o wing; to a the molecular constitution of bodies) that waves progressing tb rough the rare medium—luciform waves —are but little impeded in their motions while traversing the solid. This applies to the passage of common white lightwaves through glass and other such 'transparent' substances. But if it should happen (as in tinted glass) that some of the atomic particles, of which the 'solid' molecular framework is built up, have periods of vibration synchronical, or nearly so, with the periods "of light waves, those waves those constituents of white light—will be suppressed, communicating the energy of their motion to the molecules sympathetically excited. Thus it is that the selective extinction of light takes place in substances which are transparent but coloured. And the only difference which can be admitted in the case of an opaque substauee like stone or coal is that, instead of a few, all of the constituent rays of white light are suppressed—none of the visually effective rays are transmitted. Other (longer) ether-waves, not appreciable to our eyes, ace,, however, convoyed through almost any thickneas of stone or coal; and to actinism (very short etherwaves), on the other hand, many visually trazssparent bodies are opaque. Thus (excepting only in the case of. metals): both transparency and opacity are relative terms, the applications of which are determined by the peculiarities' of :our sense of vision, and not by the extend to which energy is fey yradietipn through the sub&fcaiices (as glasa 'or stone) referred to. * """'* How many. specimen slides for tho microscope wOuld be requisite to a complete 'study of human anatomy ? The microscopic peculiarities of the human frame are of unknown altitudes, since, according to a bigh authority, t>s many as 800,000,000 distinct-specimens' might be cut from it by meaas of a microtome. The total bulk assumed in this estimate, of flesh, fat, and bone, is 4,000 cubic inches. And the dimensions;, of .tho microscope? specimens referred t6 are one tenth fit ah ind&.eaeh' way ialaurface, and one tWotHcusan^th; iofjjan; thickness.: -.-...- »->•- -- - ■•-•■