http://www.txtwriter.com/Onscience/Articles/patsnakes.html
Biology professor George Johnson of Washington University in St. Louis offers a clear scientific explanation of why Ireland doesn’t have any native snakes. He includes a map showing Ireland blanketed by ice 18,000 years ago..
http://www.historychannel.com/exhibits/stpatricksday/history/snake.html
This attractive Web site offers a lot of basic information on St. Patrick, the legends associated with him, the history of St. Patrick Day, Ireland, and the Irish. The explanation of the legend about St. Patrick and snakes is clear and concise with a nice little graphic.