The mounted disk 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, there 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 axle 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.