Complex sentence: Meanwhile Rethel occupied himself with the production of easel pictures and of drawings; and in 1842 he began a striking series of designs dealing with the "Crossing of the Alps" by Hannibal, in which the weird power which animates his later art becomes first apparent.
Split into simpler sentences: Meanwhile Rethel occupied himself with the production of easel pictures and of drawings. In 1842, he began a striking series of designs dealing with the "Crossing of the Alps" by Hannibal, in which the weird power which animates his later art becomes first apparent.