▁activities . ▁The ▁first ▁two ▁ships ▁of ▁the ▁Ari ad ne ▁class ▁were ▁built ▁to ▁the ▁same ▁design , ▁but ▁the ▁third ▁vessel , ▁Fre ya , ▁was ▁completed ▁to ▁a ▁modified ▁design ▁with ▁a ▁longer ▁h ull , ▁greater ▁coal ▁storage ▁capacity , ▁and ▁heav ier ▁arm ament . ▁A ▁fourth ▁ship ▁of ▁the ▁class , ▁to ▁have ▁been ▁named ▁Thus nel da , ▁was ▁intended ▁to ▁be ▁built ▁to ▁Fre y as ▁design , ▁but ▁the ▁n avy ▁cancel led ▁this ▁ship ▁and ▁re ordered ▁it ▁as ▁the ▁first ▁Leipzig - class ▁cor v ette . ▁ ▁All ▁three ▁of ▁the ▁ships ▁served ▁extens ively ▁on ▁over se as ▁deploy ments ▁throughout ▁the ▁ 1 8 7 0 s ▁and ▁early ▁ 1 8 8 0 s , ▁primarily ▁in ▁South ▁America , ▁the ▁Mediter rane an ▁Sea , ▁and ▁East ▁Asia . ▁On ▁these ▁voy ages , ▁the ▁ships ▁and ▁their ▁capt ains ▁performed ▁a ▁number ▁of ▁duties , ▁including ▁protect ing ▁German ▁national s ▁during ▁periods ▁of ▁un rest ▁or ▁open ▁war fare ▁in ▁various ▁countries , ▁negoti ating ▁trade ▁agre ements ▁with ▁numerous ▁govern ments , ▁and ▁comb ating ▁pi racy . ▁They ▁were ▁also ▁task ed ▁with ▁conduct ing ▁scientific ▁experiments ▁and ▁surve ys ▁to ▁improve ▁navig ational ▁charts . ▁In ▁the ▁early ▁to ▁mid - 1 8 8 0 s , ▁all ▁three ▁of ▁the ▁ships ▁were ▁converted ▁into ▁training ▁ships ▁for ▁app rent ice ▁se amen , ▁and ▁they ▁went ▁on ▁training ▁cru ises ▁over