Grand Lodge of Ireland?

Why does the grand lodge of Ireland have 4 degrees and is it true that the "Ancients" were formed because Irish people in London were "denied admittance to local English lodges" here's the link to the site i learned this: http://www.irishmasons.com.sg/concf/index.php/history

To the best of my knowledge, the Royal Arch Degree existed in Ireland before England. The fourth Degree they speak of is the Past Master's or Installed Master's Degree. Here in Pennsylvania, our Grand Lodge has control over that Degree also. Yes, they weren't admitted into the English Lodges. During that period, there were revisions & changes being made to modernize the ritual & history by the English Grand Lodge,hence they earned the title, Moderns. Being that the Irish followed the old tradition (Antient Freemasonry), I'm sure that English wanted them to covert to their ways. So in order to preserve the Antient ways, they formed their own Grand Lodge.
a little side note, the official title of our Grand Lodge is, The Right Worshipful Grand Lodge of the Most Ancient and Honorable Fraternity of Free and Accepted Masons of Pennsylvania and Masonic Jurisdiction Thereunto Belonging. We are the only Grand Lodge in the U.S. to practice the Antient York ritual. If you haven't seen it yet & you're in Pa., please visit one of our Lodges on a Degree night. We love it have you see it !!!

I had the privilege of sitting in a PA lodge (and yes, it's different), but didn't get to witness a Degree.