TO PROFESSOR LEWIS CAMPBELL.

                                                          Glenlair, Dalbeattie, 19th October 1872.

     . . . Lectures begin 24th. Laboratory rising, I hear, but I have no place to erect my chair, but move about like the    cuckoo, depositing, my notions in the chemical lecture-room 1st term; in the Botanical in Lent, and in Comparative   Anatomy in Easter.

     I am continually engaged in stirring up the Clarendon Press, but they have been tolerably regular for two months. I    find nine sheets in thirteen weeks is their average. Tait gives me great help in detecting absurdities. I am getting   converted to Quaternions, and have put some in my book, in [384] a heretical form, however, for as the Greek   alphabet was used up, I have used German capitals from to Á to stand for Vectors, and, of course,occurs   continually. This letter is called "Nabla," and the investigation a Nablody. You will be glad to hear that the   theory of gases is being experimented on by Profs. Loschmidt and Stefan of Vienna, and that the conductivity of   air and hydrogen are within 2 per cent of the value calculated from my experiments on friction of gases, though the     diffusion of one gas into another is
"in erglanzender ubereinstimmung mit dp/dt schen Theorie."