Archive for July 9, 2019

Father Callan and the Induction Coil

Posted in History, Maynooth, The Universe and Stuff with tags , , , , , on July 9, 2019 by telescoper

Historically speaking, Maynooth is more strongly associated with theology than with science but I thought I’d mention here one famous pioneering physicist, who happened also to be a Roman Catholic priest, who spent his working life in these parts.

Father Nicholas Callan (or, more formally, The Reverend Professor Nicholas Joseph Callan) was born in County Louth in 1799 went to the seminary of St Patrick’s College, Maynooth, in 1816 to train as a priest. During his time as a seminarian Callan studied ‘Natural Philosophy’ and became interested in experiments involving electricity. In 1823 Callan was ordained as a priest, and went to Rome in 1826 to obtain his doctorate in Divinity. At the time Italy was a centre for research into electricity and here Callan became familiar with the work of the Italian physicist Alessandro Volta who had developed the world’s first battery. Callan returned to Maynooth where he was made chair of Natural Philosophy, a post he would hold until his death in 1864.

Callan is most famous for inventing the induction coil (in 1836). By connecting two copper wire coils to a battery and electromagnet and then interrupting the current he was able to generate much larger voltages than could be obtained from batteries alone. His 1837 version that used a clock mechanism to interrupt the current 20 times a second is estimated to have produced 60,000 volts – the largest artificially generated charge at that time. It is said that his induction coil could produce sparks 15″ long, which must have been fun to watch.

Callan’s biggest induction coil, unfinished at the time of his death, can be found in the National Science Museum of Ireland (which is in Maynooth). This was one of the largest in the world at the time. The iron core is 109 cm long. The secondary windings are 53 cm in diameter and consist of about 50 km of iron wire insulated with beeswax. They were made in three separate rings separated by air gaps, so wires carrying large voltage differences would not lie adjacent to each other, reducing the risk of the insulation breaking down. At the left end is a vibrating mercury ‘contact breaker’ in the primary circuit, actuated by the magnetic field in the primary, which interrupted the primary current to generate potentials of over 200,000 volts.

Sadly Callan’s work was forgotten for quite a period after his death – experimental electromagnetism was not a priority for St Patrick’s College at this time – for which reason the invention of the induction coil has often been attributed to Heinrich Ruhmkorff who made his first device (independently) about 15 years after Callan. More recently, however, Callan’s achievements have been more widely recognized and in 2000 the Irish government issued a stamp in his honour.

The Callan Building

Nicholas Callan was laid to rest in the College Cemetery at Maynooth in 1864. The Callan Building (above) on the North Campus of the present-day Maynooth University is named in his honour.


Insects, by John Clare

Posted in Literature with tags , , , on July 9, 2019 by telescoper

These tiny loiterers on the barley’s beard,
And happy units of a numerous herd
Of playfellows, the laughing Summer brings,
Mocking the sunshine in their glittering wings,
How merrily they creep, and run, and fly!
No kin they bear to labour’s drudgery,
Smoothing the velvet of the pale hedge-rose;
And where they fly for dinner no one knows–
The dew-drops feed them not–they love the shine
Of noon, whose sun may bring them golden wine.
All day they’re playing in their Sunday dress–
Till night goes sleep, and they can do no less;
Then, to the heath bell’s silken hood they fly,
And like to princes in their slumbers lie,
Secure from night, and dropping dews, and all,
In silken beds and roomy painted hall.
So merrily they spend their summer day,
Now in the cornfields, now the new-mown hay.
One almost fancies that such happy things,
With coloured hoods and richly burnished wings,
Are fairy folk, in splendid masquerade
Disguised, as if of mortal folk afriad,
Keeping their merry pranks a mystery still,
Lest glaring day should do their secrets ill.

by John Clare (1793-1861)