I have found on a coastguard website a reference to the 1891 Census mentioning a John Harris, aged 68, retired officer, living in Flushing, which I believe is near Penryn.
That would mean that he was born in 1823, which is about the right timescale to have a daughter, my great grandmother Laura, who was born about 1860. Laura's father moved to Ireland and worked as a coastguard and when he retired he returned to Cornwall.
If this John Harris was Laura's father and was working in Ireland at the time, he would not appear on the 1871 Census
and probably not the previous one for Cornwall.
Would anyone know how I could find more information on this John Harris ?
Leslie