230 SCIENTIFIC AND TECHNICAL LABOURS TO 1860. 



massive iron cores were employed , to* make the 

 tension of the closing and opening currents equal as 

 far as possible. 



With siich inductive writing - telegraphs it was 

 possible by means of a single Daniell battery to tele- 

 graph with certainty at the greatest distance on over- 

 head lines. For underground and submarine lines also 

 the induced electric currents proved highly advantageous, 

 for they made it possible to signal to greater distances 

 and with greater speed. As already mentioned the 

 Sardinia-Malta-Corfu line was fitted in 1857 with our 

 induction writing-telegraphs. For the working also of 

 the first Atlantic cable laid in the following year by 

 the managing electrician, Mr. Whitehouse. induced 



O c? 



currents were made use of, until the destruction of 

 the insulation, which unfortunately occurred soon after 

 the laying, prevented their further employment. Sub- 

 sequently recourse was again generally had on long 

 submarine lines to Thomson's mirror -galvanometer with 

 battery currents. 



For land lines also there was this drawback to 

 the use of short induced currents, that they had to 

 be very powerful to be able to produce the necessary 

 mechanical movements at the end of the line. But 

 since the keeping in condition of very large batteries, 

 such as the working of long lines with uniform current 

 or intermitting battery current requires, was trouble- 

 some and costly, Halske and I tried to transform 

 mechanically battery currents of low tension into uni- 

 form currents of higher tension. We exhibited, at the 



