▁Some ▁are ▁even ▁" hens ", ▁like ▁the ▁Hen ▁of ▁G airs ay . ▁However ▁" h ors es " ▁are ▁fairly ▁rare . ▁Co inc ident ally , ▁the ▁old ▁name ▁of ▁Main land , ▁Or k ney ▁meant ▁" hor se ▁island ". ▁ ▁Geography ▁and ▁ge ology ▁Like ▁most ▁of ▁the ▁other ▁islands ▁of ▁Or k ney , ▁the ▁bed rock ▁is ▁Middle ▁Old ▁red ▁sand stone ▁of ▁R ous ay ▁type ▁of ▁the ▁Dev onian ▁period , ▁but ▁much ▁er oded ▁and ▁t ilt ed . ▁▁ ▁The ▁is let ▁is ▁separated ▁from ▁Cop ins ay ▁by ▁Hor se ▁Sound , ▁and ▁to ▁the ▁south ▁west ▁is ▁Corn ▁Hol m . ▁Main land ▁Or k ney ▁is ▁due ▁west , ▁and ▁Aus ker ry ▁and ▁Str ons ay ▁are ▁much ▁further ▁to ▁the ▁north . ▁The ▁Hor se ▁is ▁the ▁eastern most ▁of ▁the ▁southern ▁Or k ney ▁islands . ▁ ▁The ▁Bl aster ▁H ole ▁is ▁a ▁sea ▁jet , ▁of ▁the ▁type ▁known ▁in ▁the ▁Northern ▁Is les ▁as ▁a ▁gl oup . ▁When ▁a ▁storm ▁blow s ▁in ▁from ▁the ▁east , ▁the ▁apt ly ▁named ▁Bl aster ▁H ole ▁can ▁produce ▁a ▁sp out ▁of ▁nearly ▁ ▁highly , ▁sole ly ▁by ▁wave ▁power . ▁ ▁Use ▁The ▁tiny ▁is let ▁was ▁used ▁for ▁gra zing , ▁and ▁appears ▁never ▁to ▁have ▁been ▁inhab ited ▁( although ▁a ▁number ▁of ▁the ▁smaller ▁islands ▁were ▁often ▁used ▁by ▁cul de e ▁anchor ites ). ▁P igs