Copy letter from Herbert Rix, to Joseph Goold 'Dear Sir, I am sending (inclosed) an invitation to you to exhibit again your very interesting Twin Elliptic Pendulum. We do not usually pay the costs of exhibits, but in the present instance the Treasurer thinks that, as your apparatus is rather heavy, we ought to pay the expense of its carriage; and if you will let me know what that amounts to, I shall be pleased to do so. I am, yours truly, H Rix Asst. Sec. R.S. [Assistant Secretary, Royal Society]'. 24 May 1894