•rill'; iiis'i'ouN' oi'' soMi'', i»iS('o\'i'i{ii':s oi' nioiocit \nn . L".>r» 



coiisisls in cK'niiinu' ;iii(l | lol ish in;' llic |t|;ilc to lit it for rcfci \ inn- lli*' 

 s(Misi(i\i' (•()!i(in<^' <>n wliicli (he lij^lii forms llic |ii<(iin-. The second 

 is llic ronnalion of llic scnsili\c iodnrcl of sihcr (imt tlic Imcc of llic 

 liiltlct. Tlic third is tlic ;nljll^^tilll| n\' tlic plnlc in the ciiiiicim ohsciini 

 I'oi' Ihc pnrposc of receiving' Ihc iln|)^cs^^ion. The Toni'lh is the lii-iii;i,' 

 in<i" oiil of Ihc pholof^Tiiphic picliirc, which is iii\ isihic w hen Ihc philc 

 is lidicn iVoni ihc c:iiiiei:i. llic li I'l h ;iimI iiist o|)ci';ilion is lo i'cnio\i> 

 (li(^ scnsilivt' co;ilin<j,', iinti Ihiis |n-c\t'nl lluil sns<'c|)l ihilit v (d" ch.incc 

 iiiidci" linninons inllncnec which woidd otherwise exist and (|iii(kly 

 (lest rov the |)ict lire. 



First o/xi'd/loii. A sniMll |>hi:d of olive oil, sonic iiiicly curded col 

 (on, a iniislin l)ii<i,' ol lincly lc\i^;ilc(l piimicc, :i phiiil of nitric acid, 

 diluted in the proporl ion (d" I |iail of acid to Hi parts (d' water, ar<' 

 rcipiircil lor this operation. 'Hie operator niiisl also proviilc hiinseir 

 with a small spirit lamp and an iron wire frame, upon which Ihc 

 plate is to lie phu'cd w hile liciiii.'' healed oxer the lamp. 



The plate hein^' lirsl po\vdcr<'d oNcr with piiinicc. Iiy shakinii" Ihc 

 l»a<;, a piece of col(<tii dip|>cd into the oli\c oil is then car<d'nlly 

 riililicd o\iM' it with a cont iniioiis circular motion, commciicin^ Irom 

 the center. \\ hen the plate is well polished, il imist lie cleaned hy 

 [)()\vderiii«4' it well oxer with pmnice and then rnliliin^ it with dry 

 <'otton, alwa\s roimdiiii;' and crossiii<^' Ihc st rolv<'s, il iM-iiii^' impossible 

 to ohtaiii a true surface l»y any other motion (d" the hand. Ihc sur- 

 face (d' the plate is now nilthed all o\cr with a pledget of cotton, 

 sli;^hll\ wcIIcmI willi the diliilcil nili'ic acid. h're(|iicnl ly chaiii.'c the 

 cotton and k<'ep riihlHiia Uri kly that the acid may hi' et|iially dif- 

 fiise»l o\cr the sil\t'r. as, if il is pei-iiiilleil to run into drops, it slains 



I he laltle. It will he seen w hen I he 

 acid has hccii propcrl\ dill'iisc(l 

 from t he a ppea ra iwc of a thin lilm 

 e<|iia lly spread over t he : in face. 

 It is then to he clean<>d oil with a 

 little pumice and dry colloii. 



The plate is now placed on the 

 wire frame, the siKcr upward, and 

 the pint lamp held in the hand 

 and iiioNcd ahoiil hclow it, so that 

 the Maine pla\s upon the copper. 

 This is coiitiiiiied for live minnles, 

 when a while coaliii/.^ is forine(l .all 

 over till' iirfacc of the si|\cr; the 

 lamp is then withdi'awn. .V charcoal lire may he ll^ed instead 

 of the lamp. The plate i^ now cooled suddenly \>\ placing il on a 

 mass of iiM'tal or a stone Moor. When peidcclly cold it is a<!,ain 

 polisiied with dry colloii and piimice. Il is necessai'y Ihal acid he 



