the IRB was not a secret society, however they never announced their membership due to British rule in Ireland at that time.The positions such as sargent would not have been allien to Patrick kelly for he was an educated man and a teacher in kilceron conemara.To write poems at this time about freeing Ireland in a hidden manner was not unusual, for w.b. yeats wrote   "no second troy" which is about freeing Ireland. To any other reader it would seem yeats was talking about a women he loved. Austin Clarke wrote the lost heifer refering to ireland.
check it out
http://www.poetryconnection.net/poets/Austin_Clarke/19554   

thanks
aaron