WCP2099

[1]¹

Nov^r.24^th /[18]67

Dear M^r Wallace,

My time is just now so wholly occupied — I am delivering nine lectures a week at University College,² as fast as I can prepare them — that I am unable to give to your two problems the consideration which they require.

I can give you only impressions; but mathematically [2] considered[?] ^speaking impressions are of little no value.

If a tube, in which the pressure of air were ^slightly greater than an atmosphere, were closed at one end with a perfectly elastic ^{[one world illeg.]} membrane such as you describe;³ the latter would (I believe) assume the form of a segment of a spherical surface.

If the membrane were inelastic (that is to say if it yielded to the slightest pressure and had no power of restitution) I imagine it would [3] also assume a spherical form until ^when the slight difference between ^the external and internal pressures become vanished.

The curvature in this case would, however, be greater than in the first; that is to say the radius of the spherical surface with which the membrane would coincide, would be less in this case than in the first.

Pray regard these as impressions merely; I give expression to them only because I wish you to understand that your questions interest me and that I should be only too glad if my time [4] would permit me to send you more trustworthy solution.

Ever yours faithfully | T. Archer Hirst [signature]