the company's first engine was "locomotion no 1", which opened the stockton and darlington, followed by three more: "hope", "black diamond", and "diligence". their vertical cylinders meant these locomotives rocked excessively and at the hetton colliery railway stephenson had introduced "steam springs" which had proved unsatisfactory. in 1828 he introduced the "experiment" with inclined cylinders, which improved stability, and meant that it could be mounted on springs. originally four wheeled, it was modified for six and another example, "victory", was built. around this time, two locomotives were built for america. the first, a four coupled loco named "america", was ordered by the delaware and hudson railroad. the second, six-coupled and named "whistler", was built for the boston and providence rail road in 1833.