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Reply upon being asked how he made his discoveries, as quoted in "[http://books.google.es/books?id=rYhDAAAAcAAJ&pg=PA3241&dq=I+keep+the+subject+constantly+before+me+and+wait+till+the+first+dawnings+open+little+by+little+into+the+full+light.&hl=es&sa=X&ei=