Figure 1. — Original boiler, now in 

 Notionol Museum, of experimental 

 locomotive built in 1 825 by Col. John 

 Stevens. 



Of this original locomotive only the boiler 

 and safety valve remain. They are on exhibi- 

 tion at the National Museum (USNM 

 180029), where they were deposited in 1888 

 by the Stevens Institute of Technology. The 

 boiler (figure 1) contains 20 wrought-iron 

 tubes, each a little over 1 inch in outside di- 

 ameter, set closely together in a circle and 

 originally surrounding a circular grate, now 

 missing. It is 4 feet high, including the headers, 

 and 1 foot across, and was formerly enclosed 

 by a jacket of thin sheet iron topped by a con- 

 ical hood on which rested the smokestack. 



Wood used as fuel was dropped onto the grate through a 

 door in the hood, and water was put into the boiler through 

 a pipe in the bottom header. Steam was taken from a 1-inch 

 pipe in the top header. The boiler when new is reported to 

 have sustained with safety a steam pressure of 550 pounds 

 per square inch. The design of the boiler was patented by 

 Stevens on April 1 1, 1803. 



The safety valve (figure 2) is of simple design. It con- 

 sists of a lever 10 inches long from which a 4-pound lead ball 

 about 2^2 inches in diameter is suspended. Beneath the lever, 

 and about 1 inch in from the fulcrum, is a disk valve con- 

 trolled by the weight of the ball, which hangs by a stirrup 

 that can be moved to any of several notches, so that it can be 

 set for different pressures at which the valve will open. 



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