Parry took a prominent part in the creation of the North Wales Quarrymen's Union in 1874; he was its first secretary, and afterwards ts president for some years. In 1879 he visited slate quarries in the United States at the Union's request. He published several books dealing with the quarrymen's affairs: Caebraichycafn; yr Ymdrafodaeth, 1875; Chwareli a Chwarelwyr, 1896; The Penrhyn Lock-out, 1900-01 — Statement and Appeal, 1901; The Cry of the People, 1906; and edited, with W. J. Williams, the Welsh translation of the evidence on slate quarries and quarrymen submitted to the royal commission on labour (1893).

He wrote much to Yr Herald Cymraeg, Y Genedl Gymreig, the Caernarvon and Denbigh Herald, and the North Wales Observer, on labour problems, leaseholds, Crown lands, Home Rule, county councils, arbitration, etc. He was one of the founders of the newspaper called Y Werin, in 1885, and its first editor for three years. He also wrote for other periodicals — Y Dysgedydd, Y Cronicl, Y Geninen, Cymru (O.M.E.), etc. He published Cofiant Tanymarian, 1886; Cyfrol Jiwbili Capel Bethesda, 1900; Telyn Sankey, 1901; Cofiant Hwfa Môn, 1907; The English Hymnal, 1907; and numerous pamphlets. He d. 1 Sept. 1927, at Bethesda.