Gerhard Moritz Roentgen (1795–1852) was a Dutch Navy officer, machine building engineer and ship builder.

The invention of the marine compound steam engine is Roentgen's main scientific achievement.

Ludwig's father descended from the artistic cabinet maker family Roentgen from Neuwied on the Rhine.

In 1808 he joined the Dutch naval academy Instituut voor de Marine in Enkhuizen, which he left as midshipman in 1810.

He had a full permit from the British government to visit the navy shipyards, and to draw and model everything.

However, his wife had to come to the Rotterdam Navy Command on 21 May 1821, and promise never to join her husband on a sea trip or on board ship.

The government lacked a true expert, and then gave Roentgen the far wider mission to also gather all possible information about the British iron mining, production, and processing.

[3] Roentgen instructions held that he should primarily focus on how the British iron became so pure by removing other minerals like copper, zinc, arsenic and phosphorus.

This report explained the troubles of the Belgian iron industry: The blast furnaces were too small, and still fired with charcoal instead of coal; the puddle process was used in only one location; Bellows and hammers were underpowered because they still relied on watermills, which did not even work the whole year.

Roentgen advised the government to support the foundation a blast furnace and iron foundry on the English model, see Cockerill.

He got a simultaneous appointment as adviser for machine building at the Department of education, industry and the colonies for 2,000 guilders a year.

He made this report after the king had sent him back to England to investigate the actual application of steam engines.

[9] Roentgen also appreciated that high pressure steam engines would be far more effective, because they would save space and fuel.

He also saw possible improvements in the paddle wheel, but hoped that it could one day be replaced by a more effective means of propulsion.

Of his specific projects, the one to place a steam engine in an existing warship was executed in Vlissingen, but failed.

[15] The invention of the marine compound steam engine is Roentgen's greatest scientific achievement.

Roentgen then decided to re-use the high-pressure steam engine of Agrippina (another failed project).

[16] The core of the invention was the use of a receiver, which enabled the re-use of steam without the cylinders expanding at the same time.

[17] This set Roentgen's machine apart from the earlier Woolf engine, which he had undoubtedly seen in Great Britain.

[17] Roentgen's invention could not be used effectively for sea-going vessels, because it required fresh water to be injected in the condensers.

[18] In the end, Roentgen's invention had little lasting consequences, because of John Penn's elegant version of the oscillating cylinder steam engine.

[20] From 1854 the compound steam engine was successfully applied to ocean-going ships by John Elder, and came in general use.

An 1890 article in the magazine was clear: These old drawings, made between the years 1826 and 1840, prove beyond the shadow of a doubt that compound engines with 70 lb to 80 lb steam were working on the Rhine and Meuse so long back as sixty years ago, and also that many of what are generally supposed to be modern improvements, such as forced draught, hollow shafts, stepped floats, and balanced rudders, were practically applied only a few years later.

[22] In 1822 Roentgen was one of the founders of Van Vollenhoven, Dutilh & Co., a shipping line that built De Nederlander, the first Dutch steamboat, albeit with a British engine.

At first the steam engines for the ships came from John Cockerill & Cie.[24] A more ambitious project of NSM was the idea to establish steamboat lines on the Rhine.

On 26 October 1824 Roentgen then left Rotterdam on board De Zeeuw, the second steamboat of NSM.

The construction of the ocean liner Atlas for the Dutch East Indies was another revolutionary project.

Atlas was launched by the shipyard Hoogendijk in Capelle aan de IJssel on 30 March 1826.

In 1839 Roentgen started the first steam ship for the Dutch East Indies that would actually reach the area.