. The Iron and steel magazine. 3IO The Iron and Steel Magazine iron, it being very seldom that higher or lower magnificationsare found necessary. When examining a specimen of metal under the microscopeit is absolutely necessary to bring the polished surface in a planeexactly perpendicular to the axis of the instrument, and unlesssome special device be used for holding the sample in this posi-tion, this means that the polished surface and the oppositeside must be exactly parallel, so that when the sample rests uponthe stage of the microscope, the upper surface will be in theproper position. The
. The Iron and steel magazine. 3IO The Iron and Steel Magazine iron, it being very seldom that higher or lower magnificationsare found necessary. When examining a specimen of metal under the microscopeit is absolutely necessary to bring the polished surface in a planeexactly perpendicular to the axis of the instrument, and unlesssome special device be used for holding the sample in this posi-tion, this means that the polished surface and the oppositeside must be exactly parallel, so that when the sample rests uponthe stage of the microscope, the upper surface will be in theproper position. The difficulty and labor implied by the cuttingof two exactly parallel surfaces will be readily appreciated. Toobviate this necessity, the special specimen holder illustrated inFig. 2 will be found most effective. A rubber band holds the. Fhj. 2 The Iuuuihy Specimen firmly in the holder, however irregular in shape, and acover glass may be inserted between it and the object so as tofulfill the requirements called for by the correction of the ob-jectives. The holder is then placed on the stage where it canbe clipped like any ordinary microscopic slide. (See Fig. i.) Illumination of the Sample. — Metallic samples are absolutelyopaque objects and, unlike the ordinary transparent slides ofother microscopists, cannot be illuminated by transmitted light;that is, by light sent from below the stage through the light, that is, light thrown from above upon thespecimen, must of necessity be used. This light may be reflectedobliquely upon the specimen, directly from the source of light orwith the assistance of a mirror or of a condenser, or it may be AIciaIIoi:^rapliy Applied to Foundry Practice 311 reflected vertically upon the sample by the lenses themselves ofthe objective by means of a device known as a verti
Size: 1748px × 1429px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bo, bookcentury1800, bookdecade1890, booksubjectiron, bookyear1898
