Padhraic Conneally left a comment on my third page about the Rockville Navigation. He made an interesting suggestion that caused me to look at the OSI maps around the Corrib. It seems that there might be another small navigation to the west of Lough Corrib and, because further information would be welcome, I reproduce Padhraic’s comment and my response here.
There is supposed a similar [ie similar to the Rockville] navigation on the Corrib from the old river to Ross lake via Moycullen lake.
I have been up a channel from the old river in a cruiser almost up to the realigned main road but never further. Fr O’Reilly SJ who was a companion of Maurice Semple author of the series of books on the Corrib was reputed to [have] made the trip in a canoe cutting lots of farmers’ barbed wire on the way!
My response:
Looking at it on the OSI maps, the ~1840 (or thereabouts) Historic 6″ map has a quay at the south end of Ross Lake. From there it seems to be possible to get as far as Lough Down, north of Cloghaun. A lot of the channels are straight, suggesting that they’re artificial.
The later ~1900 Historic 25″ then shows another straight channel from Lough Down, through Cloghaun to Moycullen (Ballycuirke) Lough. From the far side of the lake, an artificial-looking channel curves to the Corrib, joining it at this point. So it might be that the system was developed in the early nineteenth century but linked to the Corrib only in the later part of the century. It might have been constructed for drainage, but that wouldn’t stop it being used for navigation as well.
I hadn’t heard of Fr O’Reilly but I do have two of Maurice Semple’s books. I must have a look in them. If anyone else has information about this, it would be very welcome.
If you know anything about this, please leave a Comment below.
Irish waterways history 
Although I love Lough Corriib,with all the nostalgia of a Galway exile,I do not know anyhting about its technical aspects. However,I do recall
Fr. Andrew (Andy) O’Reilly,S.J.,as he tried to teach me Latin in the Jes.
He was a breezy,very practical person, and I do recall that he often went boating on the Corrib with the late Maurice ( who was a dear friend and former neighbour of mine).Fr.O’Reilly was Rector of St.Ignatius College,Galway duuring the 1940s, and continued to teach there until the Sixties. His family set up the Connacht Tribune newspaper in the early 20th century.