A WIRELESS METHOD 15 



hien " in four minutes seven seconds," according 

 to a newspaper report, " and the reproduction at 

 EngHien did not show any signs of lines, and might 

 have been made in the studio of a photographer. 1 ' 



An ingenious idea for transmission without wires 

 deserves mention here, and has been patented by 

 the inventor, Francesco de' Bernochi, of Turin. The 

 invention can never be of much practical value, and 

 is, in fact, a retrograde one, carrying us back to the 

 early experiments in wireless telephony by means 



FIG. 3. 



of light waves. The apparatus can be followed by 

 glancing at Fig. 3. Here Ci is a glass cylinder 

 with a transparent photographic film wrapped round 

 it, and light from the lamp L, after passing through 

 a small portion of it, is reflected by a prism on to 

 a selenium cell SS. This is in series with a battery 

 and the primary of a form of induction coil. As 

 light of different intensities falls on the selenium 

 cell, whose resistance alters in proportion, current 

 is induced in the secondary of the coil and influ- 

 ences an arc lamp, on whose circuit it is shunted ; 



