Cwm Idwal By Matt Young December 5, 2011 12:00 MST Photograph by Michael Roberts. Photography contest, Honorable Mention. Cwm Idwal, a hanging valley in North Wales. Mr. Roberts adds, “Darwin’s favourite place. This is looking down into Cwm Idwal in Snowdonia, which Darwin visited several times in the 1820s and in August 1831 just before he received the invite for the Beagle and in 1842 when he was studying glaciation. “In 1831 Darwin studied the rocks, which are mostly Ordovician volcanics, but was a bit confused by them. He was on his own and wrote to Sedgwick for advice. In 1842 (halfway through writing his first draft on “his Theory”) he returned and found clear evidence of glaciation. To the right of the lake (Llyn Idwal) was an ice fall which Darwin called a vomitory. The dark cliffs on the left are Ordovician volcanics, which he thought were basalt.” You may find Mr. Roberts’s article on Darwin’s fieldwork here, but you will not find it cheaply..