▁ ▁draw well s ▁for ▁the ▁extra ction ▁of ▁ch alk ▁for ▁agricult ural ▁uses ▁ ▁For ▁several ▁reasons ▁it ▁is ▁unlikely ▁that ▁they ▁were ▁used ▁as ▁habit ations , ▁although ▁they ▁may ▁have ▁been ▁used ▁occasionally ▁as ▁hiding - p laces . ▁ ▁Sil os , ▁or ▁under ground ▁store h ouses , ▁are ▁well ▁known ▁in ▁the ▁south ▁of ▁Europe ▁and ▁Mor oc co . ▁It ▁has ▁been ▁suggested ▁that ▁the ▁gra in ▁was ▁stored ▁un th resh ed ▁and ▁carefully ▁protected ▁from ▁d amp ▁by ▁st raw . ▁A ▁curious ▁smooth ness ▁of ▁the ▁roof ▁of ▁one ▁of ▁the ▁ch amb ers ▁of ▁the ▁Gra ves end ▁tw in - ch am ber ▁den e hole ▁has ▁been ▁put ▁forward ▁as ▁additional ▁evidence ▁in ▁support ▁of ▁this ▁theory . ▁ ▁Since ▁the ▁ 1 9 5 0 s ▁the ▁theory ▁that ▁they ▁were ▁ancient ▁ch alk ▁mines ▁has ▁gained ▁accept ance . ▁This ▁was ▁formerly ▁thought ▁unlikely ▁as ▁it ▁was ▁reason ed ▁that ▁ch alk ▁could ▁have ▁been ▁obtained ▁out cro pping ▁close ▁by . ▁J . E . L . ▁Ca iger ▁worked ▁in ▁Kent ▁exc av ating , ▁surve ying ▁and ▁research ing ▁den e hol es ▁and ▁concluded ▁that ▁they ▁were ▁exc av ated ▁in ▁pre histor ic , ▁Roman , ▁medieval ▁and ▁even ▁post - med ieval ▁times ▁in ▁order ▁to ▁produce ▁a ▁supply ▁of ▁un p oll uted ▁ch alk ▁to ▁spread ▁on ▁fields ▁for ▁the ▁purposes ▁of ▁mar ling . ▁By ▁exc av ating