lij^lu v.iKf fall upon tlii' film in a dilTusfil tnaniu-r through an aper- 

 ture of lixi'd k'Ugth so llial liius of constant width (exactly juxta- 

 posetl) hut of varying density are produced. A phototnicro(<raph 

 of a variable density picture of the opaciue line test object pre\ iously 

 discussed is shown at J, Fig. IH. Prints maiie from film negatives 

 receivetl in this way, if the structure is chosen fine enough (100 I^iK-s 

 to the inch or more) are closely similar in appearance to original 

 photograpliic prints and may be reproduced through the ordinary 

 half-tone cross-line screen. They may be retouched or subjected to 

 s(K'cial photographic procedures in any way desired. An enlarge- 

 ment of a jX)rtion of a variable density picture is shown in Fig. 15 

 and exam|)les of complete pictures so received are shown in Figs. 

 If.. 17 and 18. 



Klectrically transmitted pictures are, in general, suitable for all 

 purposes for which direct photographic prints are used. Such uses 

 include half-tone reprotluction for magazines and newspapers, lantern 

 slides, display photographs, etc. Among these uses may be men- 

 tionetl, as of some interest, the transmission of the three black and 

 white records used for making three-color printing plates. The 

 frontispiece to this article is an example of a three-color photograph 

 transmitted in the form of three black anfl white records, each corres- 

 ponding to one of the primary colors, from which printing plates 

 were made at the receiving end. 



Some practical details of the procedure follow-ed in the transmission 

 of pictures by the apparatus described may serve to clarify the fore- 

 going description. The picture to be transmitted is usually pro- 

 vided in the form of a negative, which is apt to be on glass and of 

 any one of a numl)er of sizes. F>om this a positive is made on a cellu- 

 loid film of dimensions 5" x 7", which is then placed in the cylindrical 

 film-holding frame at the sending end. Simultaneously an unexposed 

 film is placed on the receiving end. Afijustments of current values 

 for "light" and "dark" conditions are then made, over the line; 

 after which the two cylinders are simultaneously started by a signal 

 from one end. The time of transmission of a 5" x 7" picture is, for 

 a 100 line to the inch picture, about seven minutes. This time is a 

 relatively small part of the total time required from the taking of 

 the picture until it is delivered in the form of a print. Most of this 

 total time is used in the purely photographic operations. When 

 these are reduced to a minimum by using the negative and the send- 

 ing end positive while still wet. and making the prints in a project- 

 tion camera without waiting for the received negative to dry, the 

 overall time is of the order of three-quarters of an hour. 



