A SPECIAL exhibit showing the achievements of one of the county's famous sons will be at Callington museum for the next two months. During September and October the museum will have a Trevithick Society exhibition, including a model of the Penydarren, the first steam locomotive. The locomotove was built by Richard Trevithick 200 years ago and was the first high pressure steam engine to haul a load on rails at Merthyr Tydfil, South Wales. The museum is open every Friday, Saturday and Sunday from 10am to 4pm. Group visits are welcome, call A Eade on 382119.