5 Sep. 1898.

10 New Inn W.C.
London

Dear Prof. Sommerfeld

I beg to thank you for Heft II of your very interesting work - Ueber die Theorie des Kreisels. In acknowledging Heft II am afraid I wrote to Prof. Klein only. I felt much /2/ flattered at the kind way in which you mention, on p. 199, the stereoscopic views drawn by Mr. Dewar. But I think it ought to be mentioned that, after a little practice, it is soon possible to dispense with the Steroscope, and to obtain the solid effect with the unassisted eyes. /3/ I am sorry I have no other cards than the one I am sending of the Rosette curves (as in your fig. 33); but those contained on pp. 587, ... will serve to practice the eyes. I hope you will receive also the copy of my Elliptic Functions, which I have requested Macmillan to send.

Yours sincerely
A.G. Greenhill