NOTE. 



The experiments which have been making to apply the different methods of printing perma- 

 nent photographs to illustrations of Natural History, in Nos. VII. and VIII. of the Illustrated 

 Catalogue of the Museum, are now concluded. The readers will be able to judge for themselves 

 how far these new photographic processes, yet in their infancy, can be employed. Similar sub- 

 jects have, as often as possible, been chosen, and nearh' equally divided among the three systems 

 employed. 



When the illustrations were commenced, I coidd not draw upon the experience of others, con- 

 sequently there is considerable inequality in some of the plates. The patentees of the Wood- 

 bury, of the Alberttype, and of the Heliotype processes have not shrunk from repeated attempts, 

 involving loss of time and money, to insure success as far as practicable in the present condition 

 of their patents, which they are constantly endeavoring to perfect. A comparison of the plates 

 of the Hassler Zoological Kesults, and more especially the plates of Part II., with those of 

 Parts III. and IV. of the Revision of the Echini, will show how great the improvements have 

 been, particularly to the Woodburytypes. 



The negatives for the plates have all been taken by Mr. A. Sonrel ; they differ in no essential 

 points from the ordinary negatives made for silver prints. The collodion film of the negative is, 

 in the three processes, used to obtain a second film consisting of gelatine and bichromate of 

 potassa. In the case of the Woodburytype the gelatine film is pressed by hydraulic pressure 

 upon a metal plate, — an alloy of zinc and antimony, — and from the impression produced upon 

 the metal the Woodburytypes are printed on prepared paper, by a small hand-press resembling 

 the printing-press. In the Alberttype the gelatine film is fixed upon a lithographic stone, from 

 which the impressions are then taken with an ordinary lithographic press. The Heliotypes are 

 printed with a common letter-press ; they differ mainly iu the mode of printing from the Albert- 

 types, and, as far as can be judged from the plates accompanying this Report, the proofs are 

 exceedingly unequal. 



The two last methods resemble lithography in their results ; any ordinary plate-paper can be 

 used for the proofs. The Woodburytype, which resembles remarkably an ordinary silver print, 

 and has all its brilliancy and sharpness, must unfortunately be mounted, on account of the 

 peculiar manner of hiking the metal plate from which impressions are taken. This, of course, 

 increases the expense somewhat, and the mounts may eventually scale off ; this risk, however, is 

 very slight. 



The cost of quarto plates, including the paper, mounting, lettering, etc., is fifteen cents per 

 copy for a Woodburytype, and ten cents for an Alberttype or a Heliotype. To this must be 

 added the cost of the negatives. It will be seen that this compares very favorably with the 



