162 ANNUAL OF SCIENTIFIC DISCOVERY. 



DAGUERREOTYPES WITHOUT MERCURY. 



M. NATTERER, of Vienna, has discovered a process for obtaining 

 proofs on iodized plates with the chloride of sulphur, without the use 

 of mercury. A plate of silver is iodized in the usual manner, and 

 then placed on the top of a vessel 6 or 8 inches high, having at the 

 bottom, in a small cup, a few drops of chloride of sulphur ; it should 

 remain exposed to the action of the vapor until the sombre yellow 

 color is changed to a red, after which it is brought to a focus in the 

 camera, where it is left for a time, depending upon the luminous 

 strength of the focus of the objective. (With the objectives of Voigt- 

 lander, not less than ten seconds and not more than two minutes.) 

 The plate is then taken out and examined in the camera by the light 

 of a candle. It often occurs that no trace of the image is as yet per- 

 ceptible, but if the plate is heated by placing over a spirit lamp the 

 unprepared side, or if left for some time in the dark, or, lastly, if 

 exposed only for a few seconds to a weak dimmed light, the positive 

 picture then appears with all its shades. Of these three modes of 

 bringing out the image, the second is superior to the others. 



ENGRAVED PHOTOGRAPHS. 



THE idea of the prospective advantages of bringing the photographic 

 process into immediate connection Avith the engraver's art, and the 

 probable chance of fitting it for the part of the engraver's draftsman, 

 in actually pencilling out the lines for the wood engraver, the etching 

 needle or the burin, has been often discussed. The London Practical 

 Mechanic's Magazine for May, contains two wood engravings, 

 engraved from photographic designs taken upon a collodion film, 

 which was subsequently transferred to wood. The design of the 

 picture was thus, as it were, pencilled upon the block by the action of 

 light. This result has been accomplished by Mr. Urie, of London, in 

 the following manner : The picture is first obtained upon a collodion 

 film upon glass in the usual manner. The film is then carefully 

 detached, and laid upon the prepared wooden block. The engraver 

 then engraves through the film, as if he were treating an actual draw- 

 ing upon the wood surface. It is obvious that the whole process, more 

 especially the transfer of the pictorial film from its original foundation 

 to the block, is a matter involving extreme nicety of manipulation. 

 The operator proceeds by floating off the film in water, by placing the 

 glass plate horizontally therein, and with the picture upwards, assisting 

 the dislodgment of the film, when necessary by a slight mechanical 

 action. Then, the wood block, having its surface previously prepared 

 with the white of an egg and lamp-black, the darkening being 

 necessary to throw out the picture from its translucent ground - - the 

 film is carefully laid upon the block ; the white of an egg having suf- 

 ficiently adhesive power to hold it firmly down. At first, the very 

 obvious difficulty of the peeling off, or disintegration of the film, 

 opposed the efforts of the engraver in his subsequent treatment of the 



