. On microscopical manipulation : being the subject matter of a course of lectures delivered before the Quekett Microscopical Club, January-April, 1869. found by experi-ence, great risk of misinterpretation. Photography is capable of copying drawings withgreat exactness, and has no fault saving its only a small number are required, it wouldprobably, however, be cheaper than any of theprinting processes. The printing processes proper consist of plate andsurface printing and lithograph3^ Copper and steel plate engraving consist of cuttinglines in a metal plate with a pointed steel tool
. On microscopical manipulation : being the subject matter of a course of lectures delivered before the Quekett Microscopical Club, January-April, 1869. found by experi-ence, great risk of misinterpretation. Photography is capable of copying drawings withgreat exactness, and has no fault saving its only a small number are required, it wouldprobably, however, be cheaper than any of theprinting processes. The printing processes proper consist of plate andsurface printing and lithograph3^ Copper and steel plate engraving consist of cuttinglines in a metal plate with a pointed steel tool ofsquare or rhomboidal sedlion, known as a plate, when finished, is rubbed over with a thickprinting-ink, which is afterwards cleaned off, leavingthe lines full (Fig. 45, B, i). The plate is then passedthrough a powerful rolling-press with a sheet of thick,porous paper over it, which is forced into the lines, andtakes the ink out of them, forming the impression(Fig. 45, B, 2). Instead of excavating the lines with acutting tool, the plate may be covered with a pre- = How to Work with the Microscope, pp. 28—35. ENGRAVED SURFACES. i6:. i68 MICROSCOPICAL MANIPULATION. paration capable of resisting acids\ known as etching-ground. The copper is then laid bare by scratchingthrough the ground with a suitably-mounted nitric acid is poured on the plate, andallowed to corrode the metal. When sufficient depthis obtained, the acid is poured off. Those lineswhich are bitten sufficiently are filled up withvarnish. The process of biting is then repeateduntil the deepest lines are sufficiently process of etching Is a great favourite withartists, and might, no doubt, be turned to account formicroscopical purposes, as it is much easier than usingthe graver, which is a very troublesome tool. Thedisadvantage of plate printing is that the obtainingof impressions is expensive, and the number limited,owing to the rapid wear of the plate ; this latterobjedlion
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectmicroscopy, bookyear1
