The uniflow type of steam engine uses steam that flows in one direction only in each half of the cylinder. Thermal efficiency is increased by having a temperature gradient along the cylinder. Steam always enters at the hot ends of the cylinder and exhausts through ports at the cooler centre. By this means, the relative heating and cooling of the cylinder walls is reduced.

Jacob Perkins was an American inventor, mechanical engineer and physicist based in the United Kingdom. Born in Newburyport, Massachusetts, Perkins was apprenticed to a goldsmith. He soon made himself known with a variety of useful mechanical inventions and eventually had twenty-one American and nineteen English patents. He is known as the father of the refrigerator. He was elected a Fellow of the American Academy of Arts and Sciences in 1813 and a member of the American Philosophical Society in 1819.