Pièce 52 - James David Forbes to William Whewell

5 pp

Edinburgh - JDF is 'surprised with your astronomers [James Challis] speculations about the comet'. JDF is convinced it is a comet - especially since so many astronomers independently around Europe saw it more-or-less in the same orbit: 'But it is like Challis's old crotchet on the undulatory theory'. JDF is going to write up his European travels [Travels through the Alps of Savoy and other parts of the Pennine Chain with Observations on the Phenomena of Glaciers, 1843]. Adam Sedgwick expressed himself favourably to JDF regarding the glacier priority dispute between JDF and Louis Agassiz [see JDF to WW, 23 May 1842]. JDF thinks Hopkins [William Hopkins] comments may be interesting, but no more than the idea 'that the heat of the earth keeps the ice constantly detached from the sides and bottom except at the surface in winter'. All this will not move glaciers: 'it is essentially plastic and semi fluid, and this semifluidity is I am persuaded the main and almost the sole cause of its motion as I shall attempt to demonstrate in my book'.