Professor Tait, Loquitur -- June 1877

Will mounted ebonite disc
On smooth unyielding bearing,
When turned about with motion brisk
(Nor excitation sparing),
Affect the primitive repose,
Of + and - in a wire,
So that while either downward flows,
The other upwards shall aspire?
Describe the form and size of coil,
And other things that we may need,
Think not about increase of toil
Involved in work at double speed.
I can no more, my pen is bad,
It catches in the roughened page - -
But answer us and make us glad,
Yet have I still a thousand things to say,
But work of other kinds is pressing - -
So your petitioner will ever pray
That your defense be triple messing.

Answer to Tate: (from Maxwell)

The mounted disc of ebonite
Has whirled before, nor whirled in vain;
Rowland of Troy, that doughty knight,
Convection currents did obtain
In such a disk, of power to wheedle,
From its loved North the subtle needle.

'Twas when Sir Rowland, as a stage
From Troy to Baltimore, took rest
In Berlin, where old Archimage,
Armed him to follow up this quest;
Right glad to find himself possessor
Of the irrepressible professor.

But wouldst thou twirl that disk once more,
Then follow in Childe Rowland's train,
To where in busy Baltimore
He brews the bantlings of his brain;
As he may do who still prefers
One Rowland to two Olivers.

But Rowland, --no, nor Oliver,--
Could get electromotive force,
Which fact and reason both aver,
Has change of some kind as its source,
Out of a disk in swift rotation
Without the least acceleration.

But with your splendid roundabout
Of mighty power, new-hung and greasy,
With galvanometer so stout,
A new research would be as easy;
A test which might perchance disclose,
Which way the electric current flows.

Take then a coil of copper pure,
And fix it on your whirling table;
Place the electrodes firm and sure
As near the axis as you're able,
And soon you'll learn the way to work it,
With galvanometer in circuit.

Not while the coil in spinning sleeps,
On her smooth axis swift and steady;
But when against the stops she sweeps,
To watch the light spot then be ready,
That you may learn from its deflexion
The electric current's true direction.

It may be that it does not move,
Or moves but for some other reason;
Then let it be your boast to prove
(Though some may think it out of season,
And worthy of a fossil Druid),
That there is no Electric Fluid.