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Sedgwick, Adam (1785-1873). Two autograph letters signed to [James] Marshall. Dent [Yorkshire], Oct. 7, 1857; Trinity College [Cambridge], Oct. 31, 1857. 8pp. total. 186 x 113 mm. Light soiling along folds, but very good. Letters with excellent scientific content from one of the founders of modern geology. Sedgwick was responsible for defining the Devonian and Cambrian ages in the geological time scale, and his immensely popular lecture courses on geology, delivered annually at Cambridge between 1819 and 1870, had an enormous influence on succeeding generations of English geologists. One of his students was Charles Darwin, who began attending Sedgwick's lectures in January 1831 and accompanied Sedgwick on a geological field tour of Wales the following summer. The two men remained friends until Sedgwick's death, even though Sedgwick was never able to accept Darwin's theory of evolution by natural selection. IIn his Oct. 7 letter to Marshall, Sedgwick discusses the geological researches he was then undertaking in England's Lake District: "I mean D.V. to work my way to Ulverston; & on Saturday or possibly Monday to transfer my head quarters to Broughton. I want to connect our work in all quarries on the east side of the road, with the great open quarries in the Ireleth country; which we failed to do. The beds in the great open quarries strike very differently from those you & I saw; yet the strike of the cleavage (?) is unchanged in direction & from end to end almost perpendicular--I think it highly probable that the bed between the Ireleth slate & the Ulverston estuary are nearly all from the flag or flag & grit--And I suspect that some hard gritty ridges I remember to have seen in a part of Cartmell Fell, are but a repetition (by enormous fault) of the Comiston grits. . . ." Sedgwick also notes his intention to "hear Dr. Livingstone's evening lecture"; this is a reference to David Livingstone (1813-73), famous for his exploration of Africa. Sedgwick later provided a preface to Dr. Livingstone's Cambridge Lectures (1858). In his Oct. 31 letter, Sedgwick touches on his precarious health--"On Monday I ought to have begun my course of lectures but on that day I had a severe relapse of vertigo & was obliged to put off my lectures until Friday (yesterday)"--and continues his discussion of his work: "All the rocks from the Ireleth country to the Comiston Ulverston sands are Comiston flag--But in our final traverse we found the hard Comiston grits in the hills S. W. of Penny Bridge--just where they ought to be--I think there is an enormous break down the valley meeting the complicated faults (which come down from the hill a little North of Seathwaite) at an angle.--In short the country from Ireleth Moor inclusive, to the Sand of Ulverston, has had a shove southwards of about five miles!" The recipient of these letters, James Marshall, was an amateur geologist and Fellow of the Geological Society. A friend of both Sedgwick and John Herschel, Marshall was "a keen advocate of scientific education" (Briggs, Victorian Cities [1993], p. 161). Olroyd, Earth, Water, Ice and Fire (2002), p. 20. Dictionary of Scientific Biography. . Seller Inventory # 40858
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