Wikipedia tells me that "The Ordnance Survey of Ireland, from its establishment in 1824, used English miles." However, the [1851 Census of Ireland](http://www.histpop.org/ohpr/servlet/PageBrowser?path=Browse/Census%20(by%20date)/1851/Ireland&active=yes&mno=409&tocstate=expandnew&tocseq=500&display=sections&display=tables&display=pagetitles&pageseq=first-nonblank) does not tell me whether they were using English miles or Irish miles. How can we know what definition of mile historical sources such as this were using?
I notice an earlier table states staute acres (IE English). I think it is most likely that all figures are English. That would be usual for state documents.