IF I may clarify one or two points raised by Mr Davey in his letter dated August 4, regarding Richard Trevithick's locomotive.

Prior to constructing his first railway locomotive, Trevithick had been experimenting with a "steam carriage" which ran on the roads. It was known locally as 'Captain Dick's Puffer'. Trevithick concluded from these trials that a smooth wheel on a flat surface would give sufficient adhesion on any reasonable gradient.

This is the significance of the plaque Mr Davey mentions in Redruth, Cornwall.

Trevithick patented his machine in 1802, with a proviso "that, in certain cases, it may be necessary to make the external periphery of the wheel uneven".

Because of his expertise in constructing mine pumping engines, Trevithick was very much in demand by the fast expanding coal industry and had been appointed engineer at the Pen-y-Darren colliery in Glamorgan.

His first locomotive to run on rails was constructed here, most certainly with smooth wheels and flat rails.

The system Mr Davey describes on the Panama Canal is yet another British invention by Blenkinsop in 1812 for the steeply-graded Middleton Colliery tramway in Leeds, adopted widely in mountainous countries, but only one example in Britain, on the Snowdon Mountain Railway.

This is known as the rack and wheel system (Patent number 3431). This is an interesting period of history and one in which Bolton was a major player.

Brian Liptrot

Winslow Road

Hunger Hill