Not only they didn't have the metallurgy, the British didn't have it in 1712, when the Newcomen engine was invented. Some brave souls tried to create engines wi

Not only they didn't have the metallurgy, the British didn't have it in 1712, when the Newcomen engine was invented. Some brave souls tried to create engines with steam under pressure, but ended up blowing up things. So, for almost one hundred years, the steam engine worked on negative pressure. The work was not done by the steam, but rather by the atmosphere when the steam condensed and created a vacuum. James Watt's big innovation was not to allow somehow for more pressure in a cylinder, but to improve the condensation of the steam. So, what was missing in the early Roman empire was not the metallurgy, but the understanding that air has weight, and it's a considerable amount of weight, which can be harnessed to perform work. To us that insight seems trivial, but if you think about it, it could not have come before the scientific method was developed. The Magdeburg experiment [1] that showed that a team of horses cannot separate two hemispheres kept together by the weight of the atmosphere was not only truly brilliant, but it depended fundamentally on a culture of experimentation, culture that simply did not exist on thousand years before. [1] https://en.wikipedia.org/wiki/Magdeburg_hemispheres https://en.wikipedia.org/wiki/Magdeburg_hemispheres