260 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1910. 



or SO at the receiving apparatus, and the result will be a hopelessly 

 confused mass of overlapping marks. This is well illustrated in plate 

 1, figure 1, Avhere A shows a series of taps passed through a cable 

 of high capacity into the telectrograph receiver ; instead of getting a 

 series of sharp dots or short lines, we get elongated lines ending off 

 in tails. Without the capacity, we get the short lines as shown in 

 the B series. These short, definite lines are again obtained, even 

 when the capacity is present, in series C; but in this case I had 

 shunted on to the receiver Avhat I have termed the line balancer, a 

 modified form of shunt apparatus embodying the principles of wip- 

 ing out residuary currents from the cable in the Avay frequently made 

 use of in duplex telegraphy. 



The use of this apparatus has rendered commercial the old ideas 

 of telegraphing by the electrolj^ic method, and as many as 300 

 sharply defined chemical marks can be recorded in one second by its 

 means. The method of application will be seen if we have the last 

 slide shown again (fig. 1) ; here, shunted on to the line (which is 

 closed by the stylus S._, and the metal drum), is a circuit containing 

 two batteries. B^ and B^, and the two sections of a divided 1,000-ohms 

 resistance. "W^ and Wo. Shunted across the variable contacts of the 

 resistances is a variable condenser K. Bj^ varying the resistances, 

 Wi and W„, we can vary the power of the current used to sweep out 

 the residuary charges in the line; the current can, of course, flow 

 through the chemical paper on the drum, but the pole of the battery 

 Bj, connected to the style, is of opposite sign to that of the line unit 

 connected to it. 



AVhen the leakance on the line is great and evenly distributed, less 

 reverse current from the balancer is necessary, this being quite in ac- 

 cordance with Heaviside's formulae for telephony over lines with 

 capacity and inductance. It is interesting to note, also, that by in- 

 creasing the voltage of the reverse batteries B^ and B^, considerably 

 greater contrast can be obtained in the pictures; the finer the half- 

 tone screen employed in splitting up the photographs into lines, the 

 higher, again, must the voltage of B^ and B, be made. 



I should like to take up a few moments in referring to the actual 

 utility of phototelegraphy. The demand by the public for illustra- 

 tions in their daily papers must be admitted. News is telegraphed in 

 order to expedite its publication, and photographs illustrating this 

 news can therefore be telegraphed advantageousl}^ But where a 

 large installation and establishment, with accumulators, a large in- 

 strument, and an operator to work it are required, the cost of tele- 

 graphing every individual picture becomes quite out of propor- 

 tion to its value. It is therefore desirable to direct special attention 

 to the portable instruments, the first one of whicli is shown for the 

 first time to-night. A photographer going to obtain pictures of some 



