TELEGRAPHING WRITING 87 



or violet ink is usually employed, it is necessary to 

 make a photographic negative, using an ortho- 

 chromatic plate and a yellow contrast filter in 

 front of the camera lens. The writing then 

 appears colourless in the negative, and hence dense 

 " black " in the fish-glue print made from it. Type- 

 written matter has been telegraphed successfully 

 from Paris to London. 



It will thus be seen that a signature for banking 

 purposes could be sent by wire, the signature being 

 written direct in the shellac ink upon a clean sheet 

 of copper or lead foil. This, by the way, must be 

 scrupulously clean, and for the copper a weak solu- 

 tion of potassium cyanide may be used with advan- 

 tage. Another method is to rub the metal with a 

 cloth and some finely -powdered pumice-stone. The 

 telegraphy of signatures for identification purposes 

 may be an important feature of later work. 



The telautograph may be said to have solved the 

 problem of commercial photo -telegraphy, and to 

 have directly stimulated the efforts of others who 

 may have contributed to the development of the 

 work, or who may be now endeavouring to con- 

 tribute to it in the future. 



