i873«] Actinism and Magnetism. 297 



The two last-mentioned processes, in both of which the 

 copies are multiplied by purely mechanical means, afford 

 the most expeditious and economical methods of attaining 

 that end. The copies thus produced, however, are not 

 strictly speaking photographs; while, to an artistic eye, 

 they are inferior in delicacy to those obtained from the 

 primary negative by direct actinic action. Much skill has 

 accordingly been directed towards perfecting the processes 

 by which the latter sort of pictures may be produced. It 

 was first pointed out by Mr. Blair that the best mode of 

 bringing the actinism to exert its effect on the pigmented 

 gelatine, is to make the light act from behind, so as to allow 

 its hardening influence on the gelatine to penetrate to dif- 

 ferent depths, according to the lights and shades of the 

 negative. Hence arose the practice of taking the impres- 

 sions first on paper coated with pigmented gelatine, and 

 thereafter transferring it to white paper coated with simple 

 gelatine. Very good effects were obtained;in this way, but 

 the pictures laboured under the disadvantage of presenting 

 the image reversed as respects right and left. 



To rectify this reversal, recourse was had to the method 

 of double transfer, as practised by the Autotype Company. 

 In this process the picture is first transferred from the black 

 bichromated gelatinised paper to a plate of zinc, and when 

 the picture has been fully developed by washing the plate 

 with luke-warm water, it is transferred from the zinc to 

 white gelatinised paper, on which it appears rectified in 

 position. An improvement on this method was subsequently 

 effected by Mr. Johnston, of the Autotype Company, who 

 discovered that, by coating white gelatinised paper with a 

 film of wax and grease in certain proportions, the image, if 

 first transferred to this paper, may be re-transferred from it to 

 another piece of white paper, prepared with a strong solu- 

 tion of simple gelatine. By this plan, not only is the picture 

 rectified in position, but the pigment, by imbibing a small 

 portion of the wax and grease, becomes assimilated to en- 

 gravers' ink, and adheres firmly to the paper. The brilliancy 

 of the picture is increased by washing it with benzine. For 

 the use of amateurs this last mode of printing in carbon is 

 the best as yet devised, and it reflects great credit on the 

 skill of its inventor. 



In copying portraits, the author has obtained peculiar 

 and striking effects by the following method. The portrait 

 should for this purpose be taken with a dark background — 

 that of the negative being nearly, though not quite, trans- 

 parent. The bichromated black gelatinised paper is to be 



