Pièce 77 - James David Forbes to William Whewell

4 pp

Eastwhyne, nr. Dunkheld - would like to see WW's correspondent's letter on the phenomena of moving mud at Malta. JDF has been reading the work of Collin, a French engineer: 'He has given geometrical sections of sliding banks of railway cuttings and the like, which have given way under quasi-hydrostatic pressure, which have the most perfect analogy with glacier-forms, and the mere inspection of which suffice to show that I had rightly seized at first the remarkable peculiarity of viscous motion which, so far as I know had not before been mentioned, namely, the upward thrust of the particles producing the swollen surface'. JDF gives a diagram of their paths. Due to the importance of viscous motion to engineers, JDF has undertaken to produce plastic models - 'making quantitative measures of the movements, lateral as well as forward, of certain points on the surface'. Louis Agassiz has published a large book 'with a beautiful map of his glacier'. On the whole JDF believes most people will find the text dry reading. Agassiz confirms in every particular, down to the minutest detail, JDF's theory without acknowledging him: 'I am persuaded that no impartial person can regard it otherwise than as setting the seal to the adoption of my theory'.