A Manual Of Photography

sm J. Herschel’s chrysotype. 59 which quantity must be greater the greater the amount of free acid oresent in the chloride. Under these conditions the gold is precipitated by light as a black powder if the biu-d d« in any bulk, and if merely washed over paper a stain is k^uced,whch, however feeble at first, under a certain dosage of theyM^ oxalate, and free acid, goes on increasing from day -to.day and from week to week, when laid by in the dark, "»à e pe^ a damp atmosphere, till it acquires almost the blackness 0, the unsunned portion of the paper remaining • ^eted or so slightly as to render it almost certain that what little . tie th? kind exists is due to the effect ol casual diapered 1ght incident in the preparation of the paper. I.have before mea specimen of piper so treated in which the effect of thirty seconds’ exposure to sunshine was quite invisible at first «nd which is now of so intense a purple as may weff be ^called black while the unsunned portion has very slight brown. And (which is no - ‘ indicates that in the time of exposure mentioned of effect was attained) other portions of the «amep-ver exposed in graduated progression for longer times, «zJl nun., -, and 3 min., are not in the least perceptible denied darker than the portion on which the light had acted during thirty seconds 0"'‘ if paper prepared as above recommended for the chrysotype, either with the Immonio-citrate or ammonio-tartrate of iron, and impressed, as in that process, with a latent picture be washed with nitrate of silver instead of a solution of gold, a very sp and beautiful picture is developed of great intensity. 11 closure is not instantaneous; a few moments elapse ™thot apparent effect; the dark shades are then fits one, by degrees the details appear, but much more slow ly than U flip case of gold. In two or three minutes, fi"ever,themM mum of distinctness will not fail to be attained The picture may be fixed by the hyposulphite of soda, which alone I båre, can be fully depended on for fixing argentine prepared “The best process for fixing any of the with o-old is as follows:—As soon as the picture is satisfactorily brought out by the auriferous liquid, it is to be rinsed in spring water, which must be three times renewed, letting it remainm the third water five or ten minutes. It is then to be blotted off and dried, after which it is to be washed on both sides wit a somewhat weak solution of hydriodate of potash. If there be any free chloride of gold present in the pores of paper it ^ill be discoloured, the lights passing to a ruddy brown; but they speedily whiten again spontaneously, or at all events on row »