Testing syphon recorder (Photo A2)
|After an eventful childhood in Britain and on the continent
the family fled from their Paris home to avoid one revolution and
promptly, in Genoa, found themselves in the middle of another) Jenkin, on
completing his studies at the University of Genoa, was apprenticed at the works of
William Fairbairn in Manchester to learn the practical details of
In 1859 he was at the Submarine Telegraph Works of Newell & Co. at
Birkenhead when he began a working correspondence with Thomson that was to
last for the rest of his life. Their co-operation was chiefly on the
design and testing of equipment for telegraphy, for which it was important
- not least for the profitability of a line - to transmit signals as
accurately and as quickly as possible. Jenkin supplied one prerequisite
when he gave the first true measurement of the specific inductive capacity
of gutta percha, the insulating material used in submarine cables. Thomson
designed the mirror galvanometer, a machine which converted electrical
impulses transmitted through a cable into signals of light read on a
scale, allowing the smallest possible current to be used - for which Clerk
Maxwell provided a characteristic paean:
The lamp-light falls on blackened walls,
And streams though narrow perforations,
The long beam trails o'er pasteboard scales,
With slow decaying oscillations.
Flow, current! flow! set the quick light-spot flying!
Flow, current! answer, light spot! flashing, quivering, dying.
Thomson subsequently patented, in 1867, the highly important syphon recorder, which recorded signals on tape as they were received.
Thomson and Jenkin soon became - to their great profit - consulting
engineers to most of the international cable-laying ventures of the time.
Both their early experiments and their later commercial dealings are
documented in the letters from Jenkin to Thomson, numbering almost a
hundred, in the Kelvin Papers.