Breandán wrote:
Gumbi wrote:
Hah! Caithfidh gurbh bréag a bhí ann leis an bhfreagra a thug mo mhúinteoir dom bliain ó shin

Is féidir an dá cheann acu a fháil ar an idirlíon.
Is féidir an dá cheann acu a bheith "ceart" freisin. Just because one is right doesn't necessarily mean that the other is wrong.

Absolutely. Of course, to say that the other is not necessarily wrong isn't to suggest it's necessarily right! Actually, I think I was taught
ar muin na muice too. Bloody teachers.
About 'set phrases' - I think the rule is better explained by saying that where
ar doesn't mean physically on top of something, there is no lenition. Such phrases usually describe a state of being:
ar bís, ar siúl, ar buile....
Ar mhuin na muice is metaphorical (and describes a state of happiness) but does refer to being on top of something, so it's debatable. FWIW Dinneen agrees with Gumbi.
Now back to the story.
Tús na seachtaine a bhí ann. Bhí mé ar mhuin na muice mar bhí saoire na Cásca ann. Sos ó chúrsaí scoile agus uaireanta fada staidéir ar feadh tamaill. Chuaigh mé trasna na sráide chuig teach mo charad atá ar imeall na cathrach. Sheas mé os comhair a thí in aice an gheata. Chuir tafann a ghadhair eagla an domhain orm. Rith mé i dtreo an dorais ar luas lasrach. Chuir sé fáilte Uí Cheallaigh romham ach níor thuig sé fáth mo bhuartha. Bhí sé ag stealladh báistí faoin am seo, mar sin rug sé leis a scáth fearthainne. Ar aghaidh linn gan a thuilleadh moille chuig stad an bhus.