First he wrapped a coil of wire around an ion core. Then he wrapped another wire coil over the first one. Each coil increased the strength of the electromagnet. As he was working, Henry had a big problem with wrapping the wires over each other. Whenever the wires touched, electrons would jump from one wire to the other.
Electrons always take any short cuts they can find.
Any bare wires touching each other meant s hort circuits. Henry learned that it was necessary to insulate the wires. So, they were wrapped in cotton or silk to keep the electrons in. Electromagnets were used by Samuel Morse when he developed his telegraph. Morse's telegraph was used to send long distance messages over wires up until 1874.