The only Cashell I have found in my "Tree" is Mary Cashell who married James Clark. Their son Michael was born Ireland 1813 and came to Australia in 1841 with his wife Mary Ann Foran/Forden. They produced 9 children - their first being my Great Grandmother (also Mary Ann) who was born at sea in May 1841 on board the Moffatt. Hoping this may help and please keep in touch if you find a link and/or information.
Ronda Russell