56 BULLETIN 119, U. S. NATIONAL MUSEUM. 



solidity with tlie greatest portability ; possessing unlimited power with a won- 

 derful pliancy to accommodate to a varying resistance. It may, indeed, be 

 called the Steam Engine. Cat. No. 180,739 U.S.N.M. 



Print of Trevithick's Second Road Locomotive, London, England, 1803. 

 Wood cut from the " Memorial Edition of the Life of Richard Trevi- 

 thick, E. and F. N. Spon, London, England, 1803." Presented by Trevi- 

 thick's granddaughter through Colonel Davis of London. 



This locomotive was built at Tuckingmill, in Cornwall, and dif- 

 fered from its predecessor in having a horizontal cylinder in place 

 of a vertical one and at the same time being of lighter construction. 

 It was tried in Cornwall and then sent to London, where it ran for 

 some time daily through the streets, sometimes at the speed of eight 

 or nine miles an hour. 



The engine had three wheels, the two driving wheels about eight 

 feet in diameter, with a small steering wheel in front. The engine 

 and boiler were between the driving wheels, the exhaust steam 

 escaping up the chimney enabling the small boiler to make sufficient 

 steam. The continual trials and their subsequent cost drained the 

 pockets of the inventor and the steam carriage was sold for what it 

 would bring. The engine portion became a hoop-iron rolling-mill 

 engine. Cat. No. 180,741 U.S.N.M. 



Model of Traction Engine. Patented by Cassius M. Miller, 1880. TJ, S. 

 Patent, No. 227441. Transferred from United States Patent Office. 



The tractor is steam driven, in which a combined vertical and 

 horizontal boiler supported by springs from both the front and rear 

 axles form the truck. The rear carrying wheels are driven from 

 a countershaft supported by studs upon the rear axle and provided 

 with a fast and loose pinion to engage with gear wheels on the trac- 

 tion wheels. The countershaft and axle are fixed with respect to 

 each other to preserve the working contact of the gear wheels and 

 pinions, but the boiler has an independent movement on the springs, 

 which are applied to the studs. The countershaft, likewise, carries 

 differential gearing to compensate for the unequal travel of the trac- 

 tion wheels when the machine turns to one side or the other. This 

 differential gear is driven by a chain belt running over a sprocket 

 wheel on the engine shaft and to a similar wheel from the main 

 wheel of the differential gear. Cat. No. 251,277 U.S.N.M. 



Model of Steam Traction Engine Patented by John C. Praul, 1879. TJ. S. 

 Patent No. 221354.' Transferred from United States Patent Office. 



The propelling forces of this tractor are two pairs of vibrating 

 levers or walking legs. These legs are of right-angular shape and 

 connected at their apices by links or parallel bars attached overhead; 



