This immediately suggested to his fertile mind a new source of power, and he labored long to apply it, but without success, until there fell into his hands a book describing the old atmospheric steam engine of Newcomen, and he was at once struck with the fact that steam was only used to produce a vacuum while to him it seemed clear that the elastic power of the steam if applied directly to moving the piston, would be far more efficient.
He soon satisfied himself that he could make steam wagons, but could convince no one else of this possibility."* * Coleman Sellers, "Oliver Evans and His Inventions," "Journal of the Franklin Institute", July, 1886: vol.CXXII, p.

3.
Evans was then living in Delaware, where he was born, and where he later worked out his inventions in flour-milling machinery and invented and put into service the high-pressure steam engine.

He appears to have moved to Philadelphia about 1790, the year of Franklin's death and of the Federal Patent Act; and, as we have seen, the third patent issued by the Government at Philadelphia was granted to him.

About this time he became absorbed in the hard work of writing a book, the "Millwright and Miller's Guide", which he published in 1795, but at a heavy sacrifice to himself in time and money.

A few years later he had an established engine works in Philadelphia and was making steam engines of his own type that performed their work satisfactorily.
The Oruktor Amphibolos, or Amphibious Digger, which came out of his shop in 1804, was a steamdriven machine made to the order of the Philadelphia Board of Health for dredging and cleaning the docks of the city.