He managed Cornelius & Co. (later known as Cornelius & Baker) and had great success with his invention of the "solar lamp". At the time, whale-oil was used in lamps but had become very expensive. Cornelius revised a British lamp design which forced additional air into the burner and allowed for the burning of lard rather than whale oil. He applied for and received a U.S. patent for the "solar lamp" in 1843. The lamp proved extremely popular and was sold in the U.S. and Europe. Two large factories in Philadelphia manufactured the lamp. Cornelius also received patents for lighting gaslights with electric sparks. The Cornelius lamp company also created the first kerosene lamp, however cheaper and more efficient versions dominated the market. While Cornelius was still a wealthy man, his once dominate lamp company was overtaken by other companies.