He was professor of Natural Philosophy in Maynooth College from 1826 to his
death in 1864. The previous holder of that chair gave him an interest in
magnetism. In the 1830s and '40s he published papers in Sturgeon's Annals
of Electricity and in the Philosophical Magazine. His 1837
induction coil is preserved in Maynooth; it was working up to the 1890s
and produced a 15-inch spark. One of his earliest inventions was an
electromagnet on an industrial scale which would lift two tons. He also had a
prototype electric motor. The limiting factor was the supply source; this
was before the dynamo was invented. So he worked to improve the performance
of batteries, coming up with an iron-zinc cell, which was manufactured and
marketed by E. M. Clarke in the Strand in London. At the 1857 meeting of the
British Association in Dublin he referred to the work he had done 20 years
earlier, but which had not been recognised at the time.
The definitive paper on Callan by Rev M T Casey was published in the
Proceedings of the Institute of Electrical Engineers in December 1985.
These notes were summarised from the folowing article:
http://www.victorianweb.org/history/ireland/johnston2.html
Page last updated 31 October 2012