TO C. HOCKIN, Esq.

                                                             Glenlair, Dalbeattie, September 7th 1864.

     . . . I have been doing several electrical problems. I have got a theory of "electric absorption," i.e. residual charge,    etc., and I very much want determinations of the specific induction, electric resistance, and absorption of good    dielectrics, such as glass, shell-lac, gutta-percha, ebonite, sulphur, etc.

     I have also cleared the electromagnetic theory of light from all unwarrantable assumption, so that we may safely   determine the velocity of light by measuring the attraction between bodies kept at a given difference of potential,   the value of which is known in electromagnetic measure.

I hope there will be resistance coils at the British Association.