Article snapshot taken from Wikipedia with creative commons attribution-sharealike license.
Give it a read and then ask your questions in the chat.
We can research this topic together.
The Eagle class were sixteen 4-4-0STbroad gauge locomotives operated on the South Devon Railway (SDR), Cornwall Railway (CR) and associated adjacent railways. They were designed for passenger trains on this steep and sharply curved line but were also used on goods trains when required.
They were ordered by Evans, Walker and Gooch who were contracted to operate the locomotives for both the railways. Daniel Gooch designed them as a development of his earlier Comet class. They had slightly smaller wheels but larger tanks containing 1,100 gallons, a 37.5% increase. They were built by Slaughter, Grüning and Company.
The locomotives were bought by the SDR on 1 July 1866 after which they were operated as a combined fleet over both the SDR and CR, but they continued to be accounted to their original owner. On 1 February 1876 the South Devon Railway was amalgamated with the Great Western Railway, the locomotives were given numbers by their new owners but continued to carry their names too.
Pollux (SG 592 of 1865); GWR no. 2120; withdrawn 1892
Named after the Greek mythological character, Pollux, it had originally been intended to be named Tamar after the River Tamar.
Castor (SG 593 of 1865) GWR no. 2121; withdrawn 1882
Named after the Greek mythological character' Castor, it had originally intended to be named Fal after the River Fal.
References
Beck, Keith & Copsey, John (1990). The Great Western in South Devon. Didcot: Wild Swan Publications. ISBN0-906867-90-8.
Gregory, R. H. (1982). The South Devon Railway. Salisbury: The Oakwood Press. ISBN0-85361-286-2.
Reed, P. J. T. (February 1953). White, D. E. (ed.). The Locomotives of the Great Western Railway, Part 2: Broad Gauge. Kenilworth: RCTS. ISBN0-901115-32-0.