A Manual Of Photography

22 HISTORY OF PHOTOGRAPHY. then attracted so much attention, that M. Biot made them the subject of a communication to the Academy of Sciences in Paris. His remarks are printed in extenso in the Comptes Rendus, from which the following passages are translated, as they bear particularlyon many of the defectswhich stillcontinue to prove an- noyances in the photographicprocess to which they have reference. . Many of the remarks have a peculiar value from the sugges- tions they contain, and they are worthy of record as marking the period when the French were first made acquainted with the processes on paper, as practised in England. Some dispo- sition has been shown on the part of several continental photo- graphers to claim originality for processes published in England many years before their own were devised, and which singularly resemble them. After remarking that many very important physical facts were being developed by the study of photography M. Biot continues:— & F " It is not to be expected that photogenic drawings, made on paper, can ever equal the clearness and fineness of those obtained on level and polished metallic plates. The texture of paper, its superficial roughnesses, the depth of the imbibitions, and the capillary communication established between the various un- equally marked parts of its surface, are so many obstacles to absolute strictness of delineation, as well as to the regular gradation of tints in the camera obscura; and the influence of these obstacles is greater when the chemical operation is slowly carried on. But when there is no pretence or necessity for submitting to the delicacies of art—when it is required, for example, to copy rare manuscripts faithfully—if we have papers which are very susceptible of receiving impressions in the camera obscura, they will suffice perfectly ; particularly when.they present, like those of Mr. Talbot, the facility of immediately procuring copies of the primitive drawing. It will, therefore doubtless be found more commodious, and often even more practicable, to put four or five hundred drawings in a portfolio, than to carry about a similar provision of metallic plates with those indispensable protectors, squares of glass, to cover them. Attempts are being made, at this time, to fix the images pro- duced by the Daguerreotye—perfect prints, it is true, but which are as light as the vapour from which they are produced; and, indeed, to bring a voluminous collection of these fragile products through the accidents incident to long, and sometimes perilous voyages, is a task requiring no ordinary care. But whoever has attentively studied the combination of physical conditions whence these admirable images result, will find it very difficult—I am far from saying impossible,—to fix them without destroying, or at