[Henry Clifton Sorby, geologist and microscopist.] Autograph Letter Signed to 'My dear Forbes' [the geologist and Alpine explorer James David Forbes?], announcing that he has made discoveries 'at the very foundations of physical and chemical geology'

3pp., 12mo. Bifolium. In good condition, on lightly-aged paper. The letter is addressed to 'My dear Forbes' , and while there is a possibility that it is addressed to David Forbes, the reference to the recipient being 'still in existence' suggests James David Forbes, who had been in bad health since his return from Norway in 1851. It begins: 'Only a few days before receiving your note we had been talking of you and wondering if you really were still in existence, for we had heard nothing of you in any way for so long. However we were very glad to find that you were still on the move, and the more so as there was some hope of seeing you here.' After a reference to a 'previous transgression' of cancelling a dinner engagement, he turns to his own work. 'Since I saw you I have not been idle I assure you, in fact I have learned so much lately that I really do not know to what curious results I shall ultimately be led. The fact I have stirred up so many difficulties that will require such a great amount of research to clear up in a satisfactory manner, that I have fixed to work for some time to come at the very foundations of physical and chemical geology, so as to arrive at data that may be fully relied on.' He 'cannot now attempt to explain' what he is doing, 'but will keep it to talk of here, when I can show you the actual things themselves'. He concludes by attempting to arrange a visit, explaining that he will be 'at home till March, when I intend to start for Cornwall &c'. According to his entry in the Oxford DNB, in the 1850s Sorby developed a technique which he called 'physical analysis', making 'the crucial step of applying the microscope to the method on which the whole science of stereology was later founded'.