Please find below a timeline for the building of the Neath Canal and all it's branches.
Resources and References:
The History of the Vale of Neath, D. Rhys Philips (facsimile edition),  chapter XIV ~   Roads, Canals, Railways Bridges, Inns  
Neath and District, A Symposium, Edited by Elis Jenkins, pages 239 – 24.
The Canals of the Welsh Valleys, and their tramroads ~ D.D. & J.M Gladwin 1991.