"We have a priest here from Co. Louth, Dr. Callan, the Professor of Science, and many are afraid he will blow up the College. ....But he is a very holy priest."

These are quotes from a student at Maynooth, Lawrence Johnson, when he wrote to his folks at home on February 21 and April 9, 1855, and they seem to sum up the character of Callan very pithily. It was his coils which enabled him to produce dramatic results, like killing turkeys, and rendering unconscious a later Archbishop of Dublin, William Walsh. Callan's lasting claim to fame is as the inventor of the induction coil in 1836, and Maynooth retains original coils and other apparatus made and used by Callan in his researches. This section of the Catalogue includes Callan's primaries, secondaries and complete induction coils, and also related instruments acquired later by the Museum.
When a soft-iron bar - the "core" - is surrounded by a coil of wire carrying a current, the core becomes magnetised, and the system is called an electromagnet. Callan, with the help of the local blacksmith, James Briody (McLaughlin 1965,58), constructed a large "horse-shoe" electromagnet (068), the coils being wound in different directions on each end of the bent bar, so that they had opposite polarity. When current was passed through the coils, this magnet had an impressive lifting capacity. McLaughlin (1965,70) records that Callan demonstrated the strength of his magnet by challenging a team of "robust young men" to try to separate the keeper [i.e. an iron bar held by magnetism to the poles of the magnet] when the current was on. The team lost. "Then the professor plays a little trick. He cuts the current as the team makes a mighty heave: the magnet is no longer active and the members fall in a heap on the floor, much to the amusement and applause of the on-lookers".
These effects were not new, although the power of his electromagnet was unsurpassed at the time. Callan's original contribution had two parts. To the coil consisting of a small number of turns of thick wire around the core - called the "primary" - he added an unconnected coil consisting of many turns of fine wire - the "secondary". He also constructed a means of interrupting the current to the primary, his "repeater" (102), using the escapement of an old grandfather clock. He found that, when the current was interrupted rapidly in the primary circuit using his repeater, a prodigious charge was produced in the secondary, although it was not connected to the primary. This was the world's first induction coil, completed by 1836 (McLaughlin 1965,72).

Apparatus for showing induced electric currents
Apparatus for showing induced electric currents
Primary Coils
Secondary Coils
Callan Large Electromagnet
Electromagnet
Electromagnet
Callan medium-sized Induction Coil
Callan Great Induction Coil
Callan small-sized Induction Coil
Induction Coil
Induction Coil
Induction Coil
Induction Coil
Induction Coil (Ford Model T)
Induction Coil
Medical Coil
Medical Coil
Medical Coil

Elec./Mag. Page

Other E/magnetic Instr.