ERICSSON, JOHN, designer of the ironclad Monitor. Autograph letter signed ("J. Ericsson") to an unidentified correspondent, n.p., 22 October 1860. 3 pages, 4to, lined paper, small repairs at several fold separations. A detailed technical letter regarding Ericsson's "caloric" engine for naval use: "I will attend to the wheelwright matter...The fact that the engines run away with the work, notwithstanding the small suction, is all sufficient. The leak of the brass lining will entirely take care of itself. The spring of the braces, on the back stroke, only proves heavy suction...Pray tell your men to send the braces to a black smith to put a stout rod in the middle...The 4380 gallons pumped up in 104 minutes by both engines proves each to have run at the rate of 21 gallons per minute...Pray do not give an inch in this matter. Your pumps are big enough to do the work if the pipes are tight...I will send our drawings of bell cranks...after receipt of pillow blocks asked for when plan of connecting rod was furnished. The caloric [engines] have been ready 'ever so long' says Mr. Hunter...The caloric...vessel will be launched Wednesday & the engines are nearly ready..." Ericsson (1803-1889), a Swedish engineer, came to the United States in 1839. He was responsible for important improvements in steam engines, steam-driven locomotives, fire-engines and invented the marine screw or propellor, which made possible his most famous design, the radical ironclad, steam-powered Monitor, whose keel was laid in October 1861.