A Manual Of Photography

THE DISCOVERY OE LL. DAGUERRE. 37 Meueing from the centre. When the plate is well polished, 1must be cleaned by powdering it all over with pumice, and then rubbing it with dry cot- » ton, always rounding and crossing the strokes, it bein» impossible to obtain a true sin face by any oilier motion of the hand. ‘ The surface of the plate is now rubbed all over with a pledget of cotton, slightly wetted with the di- luted nitric acid. Frequently change the cotton, and keep rubbing briskly, that the acid may be equally diffused over t16 silver,as, if it is permitted to run into drops, it stains the 1 table. It will be seen when the acid has been properly diffused, from the appearance of a thin him equally spread over the surface. It is then to be cleaned off with a little pumice and dry cotton. 'Ilie plate is now placed on the wire frame—the silver upwards and the spirit lamp held in the hand, and moved about below it’ so that the name plays upon the copper. This is continued for jammutes, when a white coating is formed al1 over the surface the silver ; the lamp is then withdrawn. A charcoal fire may be used instead of the lamp. The plate is now cooled suddenly, oy placing it on a mass of metal, or a stone floor. When per- i^^old, it is again polished with dry cotton and pumice. It the 1 T be again applied two or three times, in the sdirected, the dry pumice being powdered over e plate each time, and polished off gently with dry cotton, re must be taken not to breathe upon the plate, or touch it with the fingers, for the slightest stain upon the surface will be a defect in the drawing. It is indispen- sable that the last operation with the acid be performed immediately before it is in- tended for use. Let,every particle of dust be removed, by cleaning all the edges, and the back also, with cotton. After the first polishing, the plate c is fixed on a board by means of four fillets, b b b b, of plated copper. To each of these are soldered two small projecting pieces, which hold the tablet near the corners ; and the whole is retained in a proper position by means of screws, as represented at d d D d. 1