ALS : Autograph Letter SignedIrish Geographer. He published "Statistical, Political, and Historical Account of the United States of North America," "Bibliotheca Americana Septentrionalis and "Bibliotheca Americana." Handwritten Autograph Letter Signed on on Development of Boilers and Engines for Early Steam Boats, 1 page, 8 x 10", dated April 15, 1823, Paris. Notes on the explosion of boilers on steam boats, in particular on those low pressure engines which sail on the waters of Ohio and Mississippi. Warden writes in his hand "...The explosion of the boilers in the cases mentioned were with low pressure engines acting with a force of but 4 pounds on every square inch. The high pressure engine of Evans exerts a force of 145 pounds on the square inch. It was in use in Philadelphia before the patent was given to Mr. Gravetich for a similar one whose pressure did not exceed 60 pounds..Evans boiler is rod iron and cylindrical, 30 inches diameter.." He then mentions steam boats with 60 to 75 horsepower. Signed "D.B. Warden". In excellent condition.