' But these conflicting accounts are reconciled by the
fact that Cooke's electro-magnetic telegraph would not work, and
Wheatstone told him so, because he knew the magnet was not strong enough
when the current had to traverse a long circuit.
Wheatstone subsequently investigated the conditions necessary to obtain
electro-magnetic effects at a long distance. Had he studied the paper
of Professor Henry in SILLIMAN'S JOURNAL for January 1831, he would have
learned that in a long circuit the electro-magnet had to be wound with a
long and fine wire in order to be effective.
As the Cooke and Wheatstone apparatus became perfected, Cooke was busy
with schemes for its introduction. Their joint patent is dated June 12,
1837, and before the end of the month Cooke was introduced to Mr. Robert
Stephenson, and by his address and energy got leave to try the invention
from Euston to Camden Town along the line of the London and Birmingham
Railway. Cooke suspended some thirteen miles of copper, in a shed at
the Euston terminus, and exhibited his needle and his chronometric
telegraph in action to the directors one morning. But the official
trial took place as we have already described in the life of Wheatstone.
The telegraph was soon adopted on the Great Western Railway, and also on
the Blackwall Railway in 1841.
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