I was very glad to see your posting about James Camac. I don't know if there is a connection with my Henry, but it is quite possible! The PRO catalogue in the UK states that a HENRY MCGROTTY born KILLOWEN, Londonderry served in the Rifle Brigade, discharged aged 39, 1810-1822.
My Henry was born 1814 in COLERAINE, Londonderry so it can't be him, but maybe his father???? I don't know Henrys parents names. There was also a HENRY Mcgrotty listed as a shopkeeper in Skagway, Yukon in 1903! maybe there are 2 Henry McGrottys??
There is a JAMES MCGROTTY listed in the Griffiths Valuation of Ireland who held land in COLERAINE, Londonderry somewhere between 1848 and 1864, so who knows? Lots of coincidences, not many Mcgrottys.
Would love to correspond further and share any info.