THE HISTORY OF SOINIE DTS(X)VEEIES OF 

 ITlOTOCniAPHY." 



By RoREKT Hunt. 



A. Heliograph Y — I'iie Puockss of Monsieur Niepce. 



Monsieur Niepce was tlie first iiKjiiirer who appears to have pro- 

 duced j)ei"ni!ineiit ])ictiires by the influence of the sun's rays. This 

 process — lieliogra])liy — is in many respects peculiar', which renders it 

 necessary, although his preparation was only acted on by an exposure 

 of many hours to full sunshine, to give a jiarficular account of it; 

 the more so, as some points of considerable interest require further 

 elucidation. 



The substance employed by Monsieur Niepce was asplialtum, or 

 bitumen of Jiidea. He thus directs its preparation : '' I about half 

 fill a wineglass with this pulverized bitumen; I pour upon it, drop 

 by drop, the essential oil of lavender '' until the bitumen is completely 

 saturated. I afterwards add as nnich more of the essential oil as 

 causes the whole to stand about three lines above the mixture, which 

 is then covered and submitted to a gentle heat until the essential oil is 

 fully impregnated with the coloring nuitter of the bitumen. If this 

 varnish is not of the required consistency it must be allowed to evap- 

 orate sloAvly, without heat, in a shallow dish, care being taking to 

 protect it fron.i moisture, by which it is injured, and at last decom- 

 posed. In Avinter or during rainy weather the precaution is doubly 

 necessary. A tablet of plated silver or well cleaned and warm glass 

 is to be highly polished, on which a thin coating of the varnish is to 

 be applied cold, with a light roll of very soft skin. This will impart 

 to it a fine vermilion color and cov(m- it with a vei'v thin and e([ual 

 coating. The plate is then j^laced upon heated iron, which is Avrapped 

 around with sevci-al folds of jjaper, from which by this method all 

 moisture had been previously expelled. When the varnish has ceased 

 to simmer the plate is withdrawn from the heat and left to cool and 



a Revised by T. W. Siiiillie. U. S. National Museum, from Chapters II-IV of 

 A Manual of Photography, by Robert Hunt. Fourth (Mlition. London .md 

 Glasgow, 1854. Octavo, pp. ^^2i^. 



6 The English oil of lavender is too expensive for this iinr])()so. An article 

 sold as the French oil of lavender, redrawn, is very muoli cheai)or and answers 

 iu every respect as well, if not better. 



287 



