GELLIDEG (GELLI-DEG), a hamlet, in the parish and newly-created borough of MERTHYR-TYDVIL, hundred of CAERPHILLY, county of GLAMORGAN, SOUTH WALES, 3 miles (N. E.) from Merthyr-TydviL The population is returned with the parish. It is situated on the right bank of the Tiff Vawr, and is principally inhabited by the workmen employed at Merthyr-Tydvil. The Cardiff canal passes along its eastern boundary, close to, and parallel with, the TAY Vawr river; and there are some well-wooded enclosures scattered over its surface.