He worked on the 1851 Exhibition Building, later the Crystal Palace, and he designed the wrought-iron roof of the Birmingham New Street railway station. At the time of its construction it was the largest span roof in existence, at 211 feet.
In 1857, he invented the regenerative hot blast stove known as the Cowper Stove which greatly improved the economy of the hot blast process in the making of steel
Another invention of his was the modern bicycle wheel; a wire-spoke suspension wheel with india-rubber tyre, which is, in principles, the same as that used today.
Cowper took part in founding the Institute of Mechanical Engineers. He was a founding member of the Institution in 1847 and in the following year was elected a member of the council. In 1880-81 he served the office of President
(Grace's Guide and Institution of Mechancal Engineers)