According to the railroad historian J. Snowden Bell, these locomotives were known as “one-armed Billys,” a term derived from the name of the builder and the single connecting rod on each side. Some of them were in service with light local passenger trains as late as 1857, but by 1839 it had been realized that they could not meet the rapidly increasing requirements of the expanding B & O railroad system. As a result, only the eight “one-armed Billys” were bought by the company, and as early as September 1839 the road introduced on its lines the more advanced 4-4-0, or American-type locomotive—the second stage of transition from the old “grasshoppers” and “crabs.” The replica of the _Lafayette_ has one pair of 42-inch driving wheels, and a leading truck with four 29-inch wheels, although the diameters of the wheels of the original were 48 inches and 30 inches, respectively. It looks somewhat like the Chicago and North Western’s Baldwin-built _Pioneer_, but whereas it was Baldwin’s practice to locate the driving axle behind the firebox, the Norris engine had it located ahead. This feature gave the Norris 4-2-0’s greater adhesion and tractive force. The _Lafayette_ replica, with a wheelbase of 112¾ inches and a weight of 29,200 pounds, has a tractive force of 2,323 pounds. Its cylinders have a 9-inch bore and an 18-inch stroke, and it operates on a steam pressure of 90 pounds per square inch. The replica was built in 1927 for the Fair of the Iron Horse and later appeared at the Chicago World’s Fair in 1933 and 1934, the New York World’s Fair in 1939 and 1940, and the Chicago Railroad Fair in 1948 and 1949. It has also been taken several times to the west coast, where it has been used in the filming of motion pictures. In the fall of 1955 it was used in northern Georgia in a film based on the story of the famous Civil War locomotive _General_ (see p. 84). For many years the replica carried the nameplate _William Galloway_, this name having been given it shortly after it was built, to honor a famous early locomotive engineer of the Baltimore and Ohio. Today, bearing the correct nameplate, the _Lafayette_ is usually to be seen at the B & O Museum in Baltimore. A Rocket in America [Illustration: Figure 50.—_Rocket_, built in 1838 by Braithwaite of London, England, and used by the Philadelphia and Reading Railroad until 1879. Photo was made about 1900.] The second oldest of the three complete British locomotives of the 1825-1849 period extant in North America is the _Rocket_ (figure 50), built in early 1838 for the Philadelphia and Reading Rail Road Co. by Braithwaite[4] of London. It was the first of eight Braithwaite locomotives purchased by that railroad between 1838 and 1841.