PLACE.–A small alcove with dark curtains.
The class consists of one member.
SUBJECT.–Thomson’s Mirror Galvanometer.b
The lamp-light falls on blackened walls,c
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.
- aRím: ababcc.
- bProfessor (Sir) William Thomson, inventor of a sensitive device that detects and characterizes an electric current by its intensity and direction.
- cA poem imitating Tennyson’s „The splendour falls on castle walls.”
Professor Chrschtschonovitsch, Ph.D.,
“On the C. G. S.1 system of Units.”
Remarks submitted to the Lecturer by a student.
Prim Doctor of Philosophy
Front academic Heidelberg!
Your sum of vital energy
Is not the millionth of an erg.2
Your liveliest motion might be reckoned
At one-tenth metre3 in a second.
“The air,” you said, in language fine,
Which scientific thought expresses,
“The air–which with a megadyne,4
On each square centimetre presses–
The air, and I may add the ocean,
Are nought but molecules in motion.”
Atoms, you told me, were discrete,
Than you they could not be discreter,
Who know how many Millions meet
Within a cubic millimetre.
They clash together as they fly,
But you!–you cannot tell me why.
And when in tuning my guitar
The interval would not come right,
“This string,” you said, “is strained too far,
’Tis forty dynes,5 at least too tight!”
And then you told me, as I sang,
What overtones were in my clang.6
You gabbled on, but every phrase
Was stiff with scientific shoddy,
The only song you deigned to praise
Was “Gin a body meet a body,”d
„And even there,” you said, “collision
Was not described with due precision.”
“In the invariable plane,”
You told me, “lay the impulsive couple.”7
You seized my hand–you gave me pain,
By torsion of a wrist so supple;
You told me what that wrench would do,–
„’Twould set me twisting round a screw.”8
Were every hair of every tress
(Which you, no doubt, imagine mine),
Drawn towards you with its breaking stress
A stress, say, of a megadyne,
That tension I would sooner suffer
Than meet again with such a duffer!
- 1C. G. S. system–the system of units founded on the centimetre, gramme, and second. See report of Committee on units. Brit. Ass. Report for 1873, 222. p. (Note by Maxwell.)
- 2Erg–the energy communicated by a dyne, acting through a centimetre. (Note by Maxwell.)
- 3Tenth-metre = 1 metre × 10–10. (Note by Maxwell.)
- 4Megadyne = 1 dyne × 106. It is somewhat more than the weight of a kilogramme. (Note by Maxwell.)
- 5Dyne–the force which, acting on a gramme for a second, would give a velocity of a centimetre per second. The weight of a gramme is about 980 dynes. (Note by Maxwell.)
- 6See Sound and Music, by Sedley Taylor, 89. p. (Note by Maxwell.)
- dMaxwell’s homage to Robert Burns’ poem, Comin thro’ the Rye.
- 7See Poinsot, Théorie nouvelle de la rotation des corps. (Note by Maxwell.)
- 8See Prof. Ball on the Theory of Screws. = Phil. Trans. 1873.