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XVI. On the influence of Iodine in rendering several Argentine Compounds, spread 
on Paper, sensitive to Light, and on a new Method of producing, with greater 
distinctness, the Photographic Image. By Mr. Robert Hunt. Communicated 
by Sir J. F. W. Herschel, Bart., K.H. V.P.R.S. 8$c. 8$c. 
Received May 13, — Read June 18, 1840. 
The magical perfection of the designs delineated by light on the prepared tablets of 
M. Daguerre, and the extreme sensitiveness of his photographic material, render the 
discovery of inappreciable value to art and science. It appeared to me unfortunate, 
that a process which promised to improve our perceptions of the beautiful, and which 
placed in the hands of the scientific observer an instrument of wonderful delicacy, 
should have its utility circumscribed by its expense and inconvenience. 
Had the art of engraving the Daguerreotype tablets, or any other mode of multiply- 
ing copies of the original designs been discovered, nothing further would have been 
desired ; but as it was, it appeared to be of the greatest importance, that means 
should be sought for of using some lighter and less expensive material. 
Even M. Arago, when speaking on the Report of the Commission on Daguerre’s 
pension, remarks, “ It had unquestionably been preferable, for the convenience of 
travellers, and also on the score of economy, could paper have been here employed.” 
It will, without doubt, occur to all, that the original photographic processes dis- 
covered by Mr. Fox Talbot, and published by that gentleman some time prior to 
the disclosure of Daguerre’s secret, were on paper ; and, though compelled to admit 
the superior beauty, the infinite minuteness of detail, and the charm of the aerial 
effect, in the pictures drawn on the polished tablets, yet, it must be allowed, the 
great end of the art being the multiplication of an indefinite number of fac-similes of 
original drawings, we can only expect to arrive at it by following in the steps of our 
talented countryman, whose recent productions, with the sight of some of which I 
have been favoured by the extreme kindness of Sir John Herschel, are of the richest 
promise. To Mr. Talbot, therefore, we must concede the high merit of being the 
discoverer of the photographic processes, which will, probably, ultimately turn out 
the most convenient and most extensively useful. 
By a careful examination of the means employed to give the required sensitiveness 
to the silver surface, particularly the application of heat, and the subsequent rubbing 
with nitric acid, which performs a more important part than merely polishing, I 
was convinced of the possibility of covering paper with a preparation on which the 
iodine and mercury might operate as they are found to do upon the plate of metal. 
