Who is attributed with coming up with the most influential scientific innovation of the 18th and 19th centuries

James Watt

Explanation:

James Watt is a Scottish inventor and innovator, lived between January 1736 and August 1819, as a mechanical engineer and a chemist, he worked on Thomas Newcomen's 1712 Newcomen steam engine with his Watt steam engine in 1776.

The innovation was intrumental to the changes brought by the Industrial Revolution in both Great Britain, his native country, and the rest of the world.

Therefore, he is credited with the most influential scientific innovation of the 18th and 19th centuries, due to his development of a steam engine that was efficient enough to power any machine during the period.

He is also credited for the development of concept of horsepower and the SI unit of power, the watt, which was named after him.