. ▁This ▁min eral ▁was ▁used ▁as ▁a ▁m ord ant ▁to ▁improve ▁the ▁strength ▁and ▁perman ency ▁of ▁colour ▁when ▁d ye ing ▁cloth . ▁This ▁min ing ▁was ▁relatively ▁short ▁lived ▁as ▁a ▁che aper ▁method ▁was ▁developed ▁soon ▁after ▁the ▁bo om ▁in ▁al um ▁min ing . ▁The ▁ru ined ▁rem n ants ▁of ▁the ▁mines ▁can ▁still ▁be ▁seen ▁from ▁the ▁cl iff ▁top ▁when ▁walking ▁the ▁Cleveland ▁Way ▁between ▁Sta ith es ▁and ▁Sk in ning ro ve . ▁To ▁the ▁north - west ▁of ▁the ▁village ▁is ▁B oul by ▁Qu ar ries ▁a ▁Site ▁of ▁Special ▁Scient ific ▁Interest ▁designated ▁due ▁to ▁its ▁ge ological ▁interest . ▁ ▁B oul by ▁is ▁also ▁home ▁to ▁Cleveland ▁Pot ash ▁at ▁B oul by ▁mine ▁- ▁Europe ' s ▁second - deep est ▁mine , ▁where ▁pot ash ▁and ▁rock ▁salt ▁is ▁m ined ▁ ▁under ground . ▁B oul by ▁used ▁to ▁be ▁served ▁by ▁the ▁Whit by ▁Red car ▁and ▁M idd les br ough ▁Union ▁Railway ▁( WR M U ) ▁which ▁ran ▁along ▁the ▁coast line ▁to ▁Whit by ▁Town ▁station ▁where ▁it ▁met ▁the ▁Sc ar borough ▁& ▁Whit by ▁Railway . ▁However ▁the ▁W R M U ▁was ▁closed ▁in ▁ 1 9 5 8 . ▁Today ▁the ▁railway ▁line ▁from ▁Salt burn ▁has ▁been ▁re open ed ▁for ▁goods ▁as ▁far ▁as ▁the ▁mine , ▁and ▁is ▁used ▁for ▁the ▁transport ation ▁of ▁pot ash ▁and ▁rock ▁salt . ▁