Newcomen's engine raises the water entirely by the pressure of the atmosphere ; for the steam is employed merely as the most expeditious method of displacing the air, and then producing a void, into which the atmospherical pressure may impel the first mover of the machine [1].

The Newcomen steam engine was notable for its operation without the need for high or dangerous steam pressures, utilizing only moderate heat. This made it safer compared to the Savery pump. [2]. Unlike Savery’s engine, the power of Newcomen’s engine wasn't limited by the capacity of the boilers and vessels to withstand internal pressure. Instead, it was determined by the size of the boilers and cylinders needed to contain the necessary quantity of ordinary pressure steam, as well as the strength of components like the working lever and chains that transmitted the piston's force to the pump rod.

Additionally, the Newcomen engine offered installation advantages. A Newcomen engine could be placed on the ground above a mine where space was not limited, allowing for larger and more powerful designs. This contrasted with the Savery engine, which had to be installed within the mine, between the groundwater level and the surface, limiting its size and power potential.

Historical records indicate that during Newcomen’s era, technological advancements had not yet reached a level that accommodated steam pressures far above atmospheric pressure. Savery’s engine, for example, needed to withstand at least double atmospheric pressure to elevate water to 20 meters, which led to occasional boiler explosions when pressures were increased, limiting how high water could be pushed. Savery had proposed to employ his devices in stages, but it was impractical to have a more than one Savery fire engine deployed in the same shaft of a mine.

The Newcomen engine, in contrast, could power a chain of mechanical pumps by a common pump rod to move water in stages, offering an advantage over Savery’s design. Nonetheless, this came with its costs. The heavy beam structure of the Newcomen engine caused mechanical losses, and each pump added further inefficiencies. John Farey documented a Newcomen machine with an indicated power of 8.03 HP at the piston, yet effectively delivered only 2.67 HP [3] to lift water from a 54-foot depth, reflecting a 67% loss due to the combined inefficiencies of the machine and pumps. This has led to perceptions that the Newcomen engine was less efficient than Savery’s. This might be true only for some of Savery's pump after another invention of the Newcoman machine was introduced to Savery’s pump.

A critical innovation introduced by Newcomen was the method of internal steam condensation. Savery's engine produced a vacuum by cooling the receiver externally with cold water, which led to significant thermal losses (see losses by cooling a cylinder from the outside) because the receiver had to be reheated with each steam cycle. In contrast, Newcomen utilized an internal jet of cold water to condense steam directly inside the cylinder. This technique allowed most of the cylinder walls to remain near their operating temperature, dramatically reducing thermal losses.

Furthermore, Newcomen’s engine was versatile, applicable to other mechanical purposes beyond water lifting. For example, it could power bellows or pumps to blow air into a furnace or convert the reciprocating motion of its lever into circular motion using a crank and flywheel. However, fifty years passed after the first Newcomen engine was built before such advancements as the crank and flywheel were applied. By contrast, Savery's engine was restricted to raising water and couldn't operate mills without water-wheel intervention.

Newcomen was assisted by John Calley, also spelt John Cawley, a plumber and glass-blower. We do not know what were the contributions of Calley but it was hazard a guess that Newcomen supplied the brains and Calley most of the technical skill [4]. Newcomen and Calley were later described as amateurs which after a great deal of laborious attempts, eventually succeeded in getting the engine to run, but because they lacked the necessary mathematicians or philosophers (=scientific) knowledge to calculate the powers and proportion the parts, they were incredibly lucky to find what they were looking for by accident [5]. This in no way lessens their merits. European patent laws does not require that an inventor intellectually understands his inventions or can explain the underlying physical laws correctly. The only requirement is that an inventor describes his invention so that anyone can rebuild it in a reasonable time. Their ingenuity remains commendable, regardless of how they arrived at their discoveries.