Complex sentence: Mouchot continued development and increased the scale of his solar experiments, as well as publishing his book on solar energy: "Le Chaleur Solaire et les Applications Industrielles" (1869), coinciding with the unveiling of his largest solar steam engine yet built.
Split into simpler sentences: Mouchot continued development and increased the scale of his solar experiments. The publication of his book on solar energy, "Le Chaleur Solaire et les Applications Industrielles" (1869), coincided with the unveiling of the largest solar steam engine he had yet built.