The first telegraph cable was laid under the sea between England and France in 1850. Cables are very much thicker and heavier than telegraph wires. There are a number of reasons for this: one reason is that the salt water of the sea harms ordinary telegraph wires, and so they have to be protected; another is that , because electricity passes easily through water, wires have to be covered to prevent electric signals which are passing through them from escaping and getting lost in the sea; a third reason is that cables have to be very strong or they will break while they are being laid along the bottom of the sea from a ship sailing on the surface.
The first cables that men tried to lay between England and America broke and were lost during storms. At last, after nine years of hard work, the two English speaking nations of Britain and America were joined in 1866 by the electric telegraph under the sea.
Later, all the different parts of the world were joined up by a network of cables. It is as easy to send a message by cable as it is to send an ordinary telegram, and it takes no longer for a message to travel half way round the world than from one town to the next. Every hour of the day and night messages are being flashed underneath the ocean to and from every country in the world.