292 THE HISTORY OF SOME DISCOVERIES OF PHOTOGRAPHY. 



world an accomit of the process he had devised for preparing; a sensi- 

 tive paper for photographic drawings. In the memoir read before 

 the Eoyal Society he states : 



In the spring of 1834 I began to put in practice a method which I had devised 

 some time previously for employing to purposes of utility the very curious 

 l)roperty which has been long known to chemists to be possessed by nitrate of 

 silver, namely, its discoloration when exposed to the violet rays of light." 



From this it appears that the English philosopher had pursued his 

 researches ignorant of what had been done by others on the Continent. 

 It is not necessary to enlarge in this place on the merits of the two 

 disco\'eries of Talbot and Daguerre, but it may be well to show the 

 kind of sensitiveness to Avhich Mr. Talbot had arrived at this early 

 period in his preparations, which will be best done l)y a brief extract 

 from his own communication. 



" It is so natural," says this experimentalist, " to associate the 

 idea of labor with great complexity and elaborate detail of execution 

 that one is struck more at seeing the thousand florets of an agrostis 

 depicted with all its capillary branchlets (and so accurately that 

 none of all this multitude shall want its little bivalve calyx, requir- 

 ing to be examined through a lens), than one is by the large and 

 simple leaf of an oak or a chestnut. But in truth the difficulty is in 

 both cases the same. The one of these takes no more time to execute 

 than the other; for the object which would take the most skilful 

 artist days or weeks of labor to trace or to copy is affected by the 

 boundless powers of natural chemistry in the space of a few seconds." 

 And again, " to give some more definite idea of the rapidity of the 

 process, I will state that after various trials the nearest valuation 

 Avhich I could make of the time necessary for obtaining the picture 

 of an object so as to have pretty distinct outlines, Avhen I employed 

 the full sunshine, was half a second." This is to be understood of 

 the paper then used by Mr. Talbot for taking objects by means of 

 the solar microscope. 



In the Philosophical Magazine, Mr. Fox Talbot published the 

 first account of his photogenic experiments. The term was intro- 

 duced by this gentleman, and his experiments can not be better 

 described than in his own words : 



In order to make what may be called ordinary photogenic paper, I select, in 

 the first place, paper of a good firm (luality and smooth surface. I do not know- 

 that anything answers better than superfine writing paper. I dip it into a weak 

 solution of common salt and wipe it dry, by which the salt is uniformly distrib- 

 uted throughout its substance. I then spread the solution of nitrate of silver 

 on one surface only, and dry it at the fire. The solution should not be saturated, 

 but six or eight times diluted with water. When dry the paper is fit for use. 



I have found by experiment that there is a certain proportion between the 



a He no doubt means the chloride. — T. W. S. 



