Royal Institution May 20th 1854.
My dear Tom
You have been looking at the subject of billiard balls and will probably be able to enlighten me on a point or two.
Suppose the ball A struck by the cue BC at the point C, the force being thus applied oblique1 to a radius what kind of motion will follow?
Supposing the same ball to be withdrawn from the table and suspended in air, what will be its motion when the same shock as before is imparted to it?
You have seen the ball dancing on a jet of water in the filter maker’s shops2 in London I will give you a sketch of the thing and you will perhaps state to me the precise mechanical forces concerned in the production of the phenomenon.
The ball appears to rest upon the jet in a manner which leaves its centre of gravity unsupported and a quick motion of rotation is imparted to it by the jet. It casts rays of drops on all sides as I have sketched them but a portion of the water actually encircles the ball like a noose. If you place a glass cylinder in the path of a jet the latter is deflected and may be caused to twirl round the cylinder several times, owing to its adhesion to the latter. If the cylinder were moveable it would move – and this in fact is the case with our dancing ball.
Suppose the force acting upon the ball in the direction of the jet AB to be decomposed into two others, one acting in the direction of the radius BC and the other in the direction of the tangent. This latter owing to the adhesion of the water will make the ball revolve, the former will I imagine tend to drive the ball from the jet. Why does it not accomplish this?
My Friday evening lecture3 was given last night and was very successful. The experiments were truly beautiful; and the applause rather exceeded the bounds permitted in the Royal Institution.
I gave my lecture4 to Mrs Faraday to read, and requested Faraday also to read it. He has done so and expressed himself greatly pleased with it. In fact he said he had no expectation of any thing of the kind and that it caused me to stand higher in his estimation than ever I did before. His remarks about means and branch were quite the same as those made by yourself5 and he said it was an error to introduce the word branch into the titles.
Now I have said enough about myself. We are to have Daubeny of Oxford6 to day, and I come on next week.7 My chief troubles for the session will be over at the end of next week and I shall begin to look forward to the time when I can have another game upon the Queenwood playground.
Yours affectionately | John
RI MS JT/1/HTYP/340
LT Typescript Only
oblique: at an angle that is not a right angle (OED).
the filter maker’s shops: not identified.
My Friday evening lecture: the lecture took place on 19 May at the RI (see letter 0910, n. 3).
my lecture: Tyndall’s lecture on education (see letters 0900, n. 6 and 0933).
His remarks about … those made by yourself: Hirst had provided feedback on Tyndall’s lecture in letter 0924.
Daubeny of Oxford: reference to Daubeny’s lecture for the RI series on education published as C. Daubeny, ‘On the Importance of the Study of Chemistry as a Branch of Education for all Classes’, Lectures on Education (London: J. W. Parker & Son, 1854), pp. 117–70.
I come on next week: reference to Tyndall’s lecture for the RI series on education (see n. 4).
Please cite as “Tyndall0932,” in Ɛpsilon: The John Tyndall Collection accessed on