760 Transactions of the American Institute. 



paper, is perfectly permanent if kept with ordinary care. A print 

 placed in an album or portfolio, or laid within the leaves of a book, 

 and left in an atmosphere no damper, or otherwise more contami- 

 nated than that of an inhabited room, ought to last indefinitely. If it 

 does not, the fault is with the maker of the print and not with the 

 process. Seven years ago he printed some silver positives by different 

 processes, cut them in pieces, and toned these pieces in various ways, 

 which he recounts, and then subdivided them and treated them with 

 various destructive agents. All of these specimens so treated, as well as 

 the originals for comparison, were fastened into a note-book, and the 

 mode of production and after treatment carefully registered. After 

 an interval of between seven and eight years the originals — that is 

 to say, the portions of the prints which were not subjected to any 

 destructive agency — are fitted to give useful information as to their 

 resisting powers to time. Not a single specimen produced by any 

 of the ordinary methods of printing and toning has faded. He 

 therefore concludes that when prints, made by the methods described, 

 after a longer or shorter interval give indications of perishing, there 

 has been a grave want of care on the part of the printer. That fault 

 lies, as every photographer knows, in the employing of hyposulphite 

 that has been previously used ; in fixing too many prints in a given 

 quantity of hyposulphite, and in insufficient and badly managed 

 washing. The wrong that has been done to photography by a neglect 

 of these simple precautions has been incalculable. Even at the 

 present day no one feels any certainty that a purchased photograph 

 will last more than a year or two. There should be some way of 

 reaching and punishing those who impose on the public with half- 

 washed, sulphur-toned prints. 



* 

 VIII. Russian Sheet-ikon. 



Dr. John Percy, in his pamphlet on the manufacture of Russian 

 sheet-iron, recently published at London, has collected several descrip- 

 tions of the process employed by the Russians in manufacturing the 

 sheet-iron of high polish which is extensively used for stoves and 

 pipes in this country. The ores used in the Russian iron-works are 

 magnetic oxide of iron, red and brown hoematite, and carbonate of 

 iron, which are reduced by means of charcoal. The puddled bars 

 are rolled into sheets and cleaned with a wet broom of green fir 

 leaves. Powdered charcoal is then spread between the sheets, three 

 of which are placed together, reheated, and passed through the rolls. 

 This process of heating and rolling is repeated several times, after 



