Complex sentence: About this time, the discoveries of Charles Darwin began to exercise a fascination over him, and finding them little understood in Denmark, he translated into Danish "The Origin of Species" and "The Descent of Man".
Split into simpler sentences: About this time, the discoveries of Charles Darwin began to exercise a fascination over him. When he realized that the work of Darwin was not well known in Denmark, he translated into Danish "The Origin of Species" and "The Descent of Man".