Most of the Irish Crochet patterns I have come across were published in and around 1900. The notation is slightly different to the way modern patterns are written and the phraseology is quite different.
You have to read ahead in these old patterns. They are not linear like modern patterns, quite often there will be an instruction and as you read ahead you will find that it then refers to the stitches you need to make to preceed this instruction ... so save yourself rework and always read ahead to the next obvious row end.
Here is an example taken from a pattern in Priscilla Irish Crochet No 2
"Into last d work 3 t, into next d 3 t, into next d also 3 t, making 9 t in a row. Chain 1, turn; Work 1 d into each of the next 4 t, 3 d into the centre t and 1 d into the next 4 t (always working into the back strand unless otherwise stated); ch 1, turn;"
As you see, the instruction to always work into the back strand comes part way through the narative - where as in modern patterns this instruction would be up front.
You can also see that the pattern is written more as a story than in the more modern row by row way, so it takes a bit more study and reading before you get underway with creating.
The stitch names are also a little different, in some patterns you will see double crochet referred to as "d" and in others "d c", or in some instances as "Plain".
The stitches generally follow the UK notation so you won't see single crochet mentioned.
The translation of UK to US notation is;
Double Crochet = Single Cochet
Half Treble = Half Double
Treble = Double
Double treble = Treble
Trible treble = Double treble