. The microscope and its revelations. hinness ; but even the mostcareful working on the finest-grained stone will leave its surfacecovered with scratches, which not only detract from its appearance,but prevent the details of its internal .structure from being as readilymade out as they can be in a polished section. This polish may beimparted by rubbing the section with putty-powder (peroxide of tin)and water upon a leather strap made by covering the surface of aboard with buff leather, having three or four thicknesses of cloth,flannel, or soft leather beneath it; this operation must be perform
. The microscope and its revelations. hinness ; but even the mostcareful working on the finest-grained stone will leave its surfacecovered with scratches, which not only detract from its appearance,but prevent the details of its internal .structure from being as readilymade out as they can be in a polished section. This polish may beimparted by rubbing the section with putty-powder (peroxide of tin)and water upon a leather strap made by covering the surface of aboard with buff leather, having three or four thicknesses of cloth,flannel, or soft leather beneath it; this operation must be performed011 both sides of the section, until all the marks of the scratches leftby the stone shall have been rubbed out, when the specimen will befit for mounting dry, after having been carefully cleansed from anyadhering particles of putty-powder. Greater facility in the grinding of hard sections. as well as supe-riority of result, is attainable by simple mechanical means. A cutting machine will greatly facilitate the process of preparing. FIG. 411.—Hand machine for cutting hard sections. rock slices. The thickness of each slice must be mainly regulatedby the nature of the rock, the rule being to make it as thin as canbe conveniently cut, so as to save labour in grinding down the thickness of a shilling may be taken as a fair thickness may be still further reduced by cutting and polishinga face of the specimen, cementing that on glass, and then cutting asclose as possible to the cemented surface. The thin slice thus lefton the glass can then be ground down with comparative ease. The first (fig. 411) is a hand machine. The specimen is cementedto the carrier, a, which is movable on the axis, b, and can also berotated in two directions. The object is pressed by the weight, c,against the steel disc, fZ, which i:? revolved by the wheel, e, acting ona smaller-toothed wheel on the axis of d. The second (fig. 412) is intended to be worked by the foot. The p
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectmicrosc, bookyear1901
