In a little seen diary, now kept in the Archives of Bangor University, there is this short note entered after one of the preaching services conducted by the diarist, Edward Cefni Jones, then of Blaenau Ffestiniog, ‘A great revival – many came to the fellowship.’ (‘Coming to’ or ‘staying for’ the fellowship was synonymous with becoming a Christian in those days.) The chapel he was preaching at was Hebron – a Welsh Baptist church in the town of Dowlais near Merthyr Tydfil in industrial south Wales. And the date? 5th September 1904 – nearly two months before Evan Roberts’ prayer meeting at Moriah. Indeed, according to a letter in the Welsh Baptist weekly, Seren Cymru, in December of that year, the revival had already sparked in Hebron a week before Cefni Jones was there for the church’s anniversary services, under the leadership of the church’s minister, W. C. Thomas.
http://www.dyfedwynroberts.org.uk/index/who-started-the-welsh-revival-of-1904-05-