NATURAL PHILOSOPHY. 135 



To coloi" a good, dean print, you must, in the first wash on the 

 face, use as much gum as will bring it nearly, although not quite, 

 to the same gloss as the albumen surface ; this wash to be com- 

 posed of — for a i^erson of ordinary complexion — a combination 

 of rose madder and Indian yellow, or Venetian red alone. With 

 these colors judiciously applied, you can produce any comjDlexion, 

 from the highest glow of health to the most sallow ; the shadows 

 to be warm, and in every case glazed even more than the albu- 

 men surface. Sepia, neutral tint, burnt umber, chrome yellow, 

 and ivory black, if projjcrly used, will give that life-like brilliancy 

 which is characteristic of health or decay. 



Should the photograph be clear and well defined, for draperies 

 and carpets use transparent, but, if the picture be deficient from 

 under-develojiment, use opaque. Of transparent colors for such 

 purposes use the following : crimson lake and burnt sienna, Prus- 

 sian blue and Indian yellow. Chrome yellow and Prussian blue 

 also make an excellent wash for draperies, although not purely 

 transparent. 



For backgrounds, which should ever be made to softly recede 

 from the figure, the following colors may be used with much pur- 

 pose : cobalt blue, and a little Chinese white, which give a good 

 efi^ect and altogether a jjleasing result, vignetting it to your own 

 taste with sepia, or other browns. By way of finish, or to relieve 

 an otherwise poor ijroduetion, it is sometimes necessary to make 

 what is termed an introduction ; that is, a side opening in the 

 background, where a neat landscape may be lightly sketclied and 

 colored, comprised of water, land, and sky, or a bit of woodland. 

 These sometimes give a freshness to an otherwise dull picture, or 

 serve to exclude soiue of those hideous backgrounds so much dis- 

 played in cartes generally. But, in putting in draperies,- carpets, 

 plain or pictorial backgrounds, let them ever be subdued, and in 

 quiet harmony with the figure, the head of which should ever be 

 the principal attraction to the eye. — Scott Alexander, in Brit- 

 ish Journal of Photography. 



DESTRUCTION OF PHOTOGRAPHS. 



A suggestion of considerable value to photographers has been 

 made by Dr. Angus Smith, F.R.S. The cause of the destruction 

 of photographs, apparently by the action of time only, is gener- 

 all}' considered to be due in reality to the presence of a minute 

 quantitj^ of hyposulphite of soda remaining in the paper. Hither- 

 to, almost the only plan of getting rid of this agent has been long 

 and continuous washing in cold or hot water. Dr. Smith has sug- 

 gested oxidizing the hyposuli^hite of soda into sulphate of soda 

 (which is likely to be harmless), by means of dilute peroxide of 

 hydrogen. This has been little known to chemists, and even now 

 it is seldom obtained in its pure state ; it is, however, to be had 

 in solution, and in a state sufficiently strong for many important 

 purposes in analysis. Oxides, such as in the case of manganese, 

 Avhich will not fill till more highly oxidized, are, with advantage, 

 treated by it. The lower oxide may remain unobserved in a solu- 



