Map o ieithoedd Cymru 1850. Allwedd: Gwyrdd: poblogaeth uniaith Gymraeg; pinc: poblogaeth ddwyieithog; gwyn: poblogaeth uniaith Saesneg. (A map of the languages of Wales 1850. Key: Green: monolingual Welsh population; pink: bilingual population; white: monolingual English population.)

Mae'r data wedi'i seilio ar ymchwil gan W.T.R. Pryce - a gyhoeddwyd yn gyntaf yn (Data is based on the research of W.T.R. Pryce. It was first published in):

• Pryce, W.T.R. (1978). "Welsh and English in Wales. 1750-1971: A spatial analysis based on the linguistic affiliation of parochial communities". Bulletin of the Board of Celtic Studies 28: 1-36.
• Pryce, W.T.R. (1978). "Wales as a culture region: Patterns of change 1750-1971". Transactions of the Honourable Society of Cymmrodorion, Session 1978: 229-261., revised and reprinted in: Pryce, W.T.R. (1986) "Wales as a culture region: Patterns of change 1750-1971" in The Welsh and Their Country: Selected Readings in the Social Sciences, Gomer Press ISBN: 9780863832451.

Mae Colin H. Williams yn rhoi trosolwg o ymchwil, dadansoddi a metholdoleg Pryce (Colin H. Williams gives an overview of Pryce's research, analysis and methodology):

• Williams, Colin H. (1990) "The Anglicisation of Wales" in English in Wales: Diversity, Conflict, and Change, Multilingual Matters, pp. 23−30. ISBN: 9781853590313.

Gweithiau academaidd sy'n atgynhyrchu map iaith 1850 Pryce (Academic works republishing Pryce's 1850 language map):

• Pryce, W.T.R. (2000) "Language Zones, Demographic Changes, and the Welsh Culture Area 1800-1911" in Jenkins, Geraint H. , ed. The Welsh Language and its Social Domains, 1801-1911, University of Wales Press, p. 60. ISBN: 9780708316047.

• Jones, David Brian (2013). The influence of religion on the survival of the Welsh language 1801-2011: A tale of two centuries. (Masters). University of Wales, Trinity St David. p. 16.

Nodyn: Mae data ar y Gymraeg cyn gyfnod y cyfrifiad yn bodoli mewn archifdai megis yr eglwys a ffynonellau tebyg. Dyma ffynhonnell W.T.R. Pryce: yr hyn a nodwyd gan glerigwyr y gwahanol gyfnodau am iaith aelodau eu heglwysi. O'r wybodaeth honno, creodd Pryce bedwar map ar gyfer y blynyddoedd: 1750, 1800, 1850 a 1900, gan ddangos dosbarthiad y siaradwyr Cymraeg fel iaith bob dydd, ardaloedd a oedd yn ddwyieithog ac ardaloedd uniaith Saesneg.

Defnyddiodd Pryce symbolau pwynt i ddangos ei ddata parthed yr iaith o fewn yr eglwysi plwy. Rhag gor-gymhlethu'r mapiau, dydw i heb wneud hynny. Yn hytrach dw i wedi canolbwyntio'n unig ar sut roedd y sefyllfa ieithyddol yn lledaenu.

Mae fy mapiau i, felly, wedi eu sefydlu ar fapiau Pryce, ac ailgrgraffiadau o'i fapiau. Drwy gymharu'r rhain, roedd yn bosib gwiro fy mapiau i. Blociau o lwyd a du oedd gan Pryce, a'r symbolau pwynt - sy'n gwneud y weithred o'u dadansoddi nhw yn eitha anodd, yn enwedig gan bobl nad ydynt wedi arfer gyda'r pwnc, data neu fapiau! Oherwydd hyn, penderfynais ddefnyddio lliw. I sicrhau fod y lleoliadau'n gywir defnyddiais feddalwedd gartograffig megis Google Maps, Open Street Map a Bing Maps.

Note: Pre-census data on the Welsh language exists in archives such as the church and similar sources. This is the source of W.T.R. Pryce: what the clergy of the different periods noted about the language of their church members. From that information, Pryce created four maps for the years: 1750, 1800, 1850 and 1900, showing the distribution of Welsh speakers as a daily language, bilingual areas and English only areas.

Pryce also used point symbols to show his data regarding the language within the parish churches. I haven’t, as to not over complicate the maps. Instead I have focused only on how the language situation was spreading.