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CHAP. CCLIII. To File, or Silver the Looking-Glass.
THE Glass is not perfected, till it be Silvered; for without that, it is impossible it should di∣stinctly shew the opposite Objects; 'tis the Filing or Silvering therefore which gives it its just Perfe∣ction.
For this you must have a firm well smooth'd Ta∣ble, much greater than the Glass, whereon spread one or more Sheets of very fine Tin, let them be as thin as Paper, and so prepared, as not to have any Rumple, Furrow, or Spot, else the Glass will be spoil'd: Over these Sheets spread good Mercury quite covering them with it; when the Mercury has soaked in well, place the Glass thereon, and it will stick to them; then turn it, and spread Sheets o•• Paper on the Filing; press it gently, smoothing an•• stroaking it with your Hands, to take off the Super∣fluous Mercury; then dry it in the Sun, or by a sof•• Fire, and it will become perfect.
But because 'tis not so easie to file the Large Glas∣ses as the small, you must have recourse to a Table for the purpose, with a Diamond-Cut rising Border, to keep the Sides of the Glass firm, whereon yo•• must lay it, with the Backside, (which is to be filed) upwards; then lay on the Sheeted Tin very smooth and closely; over these the Mercury,to dissolve them•• then with the Sheets of Paper cover all, and 〈◊〉〈◊〉 smooth, and run it over with your Hands to take a∣way the Surplus of the Mercury, and so dry it 〈◊〉〈◊〉 before.