When Kelvin looked through the eyepiece he saw what was undoubtedly the phenomenon that Maxwell had described, but in addition there was the image of a little man dancing about in the field of view. Maxwell had achieved this by the addition of a zoetrope, a device in which he was much interested and for which he had drawn the animated diagrams. Kelvin could not help asking: ‘What is the little man there for?’ ‘Have another look, Thomson,’ said Maxwell ‘and you should see’. Kelvin had another look but was no wiser. ‘Tell me Maxwell’, he said impatiently, ‘what is he there for?…’ ‘Just for fun, Thomson’.

PLACE – A small alcove with dark curtains.

The Class consists of one member.

SUBJECT – Thomson's Mirror Galvanometer.

The lamp-light falls on blackened walls,

And streams through narrow perforations,

The long beam trails o'er pasteboard scales,

With slow-decaying oscillations.

Flow, current, flow, set the quick light-spot flying,

Flow current, answer light-spot, flashing, quivering, dying,

O look! how queer! how thin and clear,

And thinner, clearer, sharper growing

The gliding fire! with central wire,

The fine degrees distinctly showing.

Swing, magnet, swing, advancing and receding,

Swing magnet! Answer dearest, What's your final reading?

O love! you fail to read the scale

Correct to tenths of a division.

To mirror heaven those eyes were given,

And not for methods of precision.

Break contact, break, set the free light-spot flying;

Break contact, rest thee, magnet, swinging, creeping, dying.