190 APPLICATION OF PHOTOGENIC DRAWING 



process, although it is to be regretted that this gentleman has 

 not stated more explicitly the proportions in which he uses 

 the ingredients employed in the preparation of his sensitive 

 paper. I have performed a set of experiments on this sub- 

 ject, and can recommend the following proportions as the 

 most effective and economical. 200 grains of common salt 

 are to be dissolved in a pint of water, and sheets of thin blue 

 wove post paper saturated with the solution, which, for this 

 purpose, should be poured into a dish, and, the paper being 

 immersed, the application of the solution to every part should 

 be ensured by the use of a sponge. The paper is then to be 

 removed, drained of its superfluous moisture, and nearly dried 

 by pressure between folds of linen or bibulous paper. 



240 grains of fused nitrate of silver are then to be dissolved 

 in 12 fluid ounces of water, and this solution is to be applied 

 by means of a sponge to one side of each sheet of the previ- 

 ously prepared paper, which side should be marked with a 

 pencil, so that when the paper is fit for use the prepared side 

 may be distinguished. The sheets of paper are then to be 

 hung upon lines in a dark room to dry, and when nearly free 

 from moisture, their marked sides are to be once more sponged 

 over with the solution of silver, and finally dried ; they are 

 then to be cut into pieces of convenient size, and preserved 

 from light, or even too much exposure to air, by being wrap- 

 ped up in several folds of brown paper, and kept in a portfolio. 



The proportions above recommended are sufficient for the 

 preparation of a quire of the kind of paper alluded to ; if 

 more of the salt of silver were used, the paper would indeed 

 become darker by the action of light, but its expense would 

 be proportionally increased : and when prepared in the man- 

 ner directed, it assumes, by less than a minute's exposure to 

 the rays of the sun, a rich mulberry brown tint, of sufficient 

 intensity to define an outline very beautifully, which indeed 

 is all that is required. 



To use this paper, the specimen of which a drawing is re- 

 quired, is removed from the herbarium, placed on a piece of 

 the paper, and kept in situ by a pane of common glass press- 

 ed by weights : a piece of plate glass, however, is preferable, 

 as it is sufficiently heavy to press the plant close to the pa- 

 per. The whole is then placed in the sunshine, and in less 

 than a minute all the uncovered parts of the paper will as- 

 sume a rich brown tint. The paper should then be removed 

 from the direct influence of the sun, and placed in a book un- 

 til the drawing be rendered permanent: the specimen, quite 

 uninjured by the process, may then be replaced in the herba- 

 rium, and the drawing of another be taken, and so on. So 



