THE LITERARY 



OF THE LINN^AN ASSOCIATION OF PENNSYLVANIA COLLEGE. 



Vol. I. DECEMBER, 1844. No. 2. 



ON THE APPLICATION OF THE BICHROMATE OF POTASSA TO PHO- 

 TOGRAPHIC PURPOSES. 



BT SPENCER F. BAIRD, OT CARLISLE, PA. 



Among the Chemical agents used in the various branches of Photo- 

 graphy, the Bichromate of Potassa, recommends itself as being the sim- 

 plest of all, in its practical application to the purpose of copying such 

 objects as can be readily laid flat on paper, and covered with a glass 

 frame. This was first indicated by Mungo Ponton, in the Edinburgh 

 New Pliilosophical Journal, and was copied into Sillinian's .Journal, 

 vol. 37, page 361. The trouble of preparing the paper with this salt, 

 of making the impression, and of fixing it afterwards, is much less than 

 that of any other mode, and the great cheapness of the whole, is such 

 as to put it within the power of any one to experiment in this interest- 

 ing part of the field of Science. It is true that the delicate lines and 

 shades of the Camera image and of fine engravings cannot be distinctly 

 transferred and retained, but to the purpose of copying a coarse print, 

 a piece of music, an embroidering pattern, or a leaf, it is admirably ad- 

 apted, it is for this latter object, that the art has been mostly used by 

 the writer who, last summer copied leaves of nearly all the trees and 

 shrubs of Cumberland County, amounting to nearly two hundred spe- 

 cies. These photographs are as valuable for scientific purposes, as good 

 engravings of the same would be, perhaps more so, as not only is the 

 outline correctly given, but in most cases the fine and delicate nervation, 

 whose arrangement frequently forms a specific character, is distinctly 

 preserved. Thus in tlie course of a few minutes a facsimile of an ob- 

 ject is obtained, which would occupy a skillful artist many hours to 

 draw with even an approximate degree of accuracy. 



The bi-chromate of potash is now readily procured in any of the 

 cities at a very cheap rate, but as under some circumstances it may be 

 more convenient to prepare it, we will give the method indicated in the 

 3 I 



