▁from ▁Arm agh ▁ 2 0 ▁minutes ▁after ▁the ▁exc urs ion . ▁ ▁The ▁train ▁was ▁sc rew - cou ple d ; ▁each ▁carriage ▁was ▁first ▁couple d ▁by ▁a ▁loose ▁chain ▁and ▁hook ▁coupling ▁to ▁the ▁next ; ▁the ▁s lack ▁on ▁this ▁was ▁then ▁taken ▁up ▁by ▁a ▁turn bu ck le ▁sc rew ▁arrangement , ▁until ▁the ▁buff ers ▁of ▁the ▁two ▁carri ages ▁were ▁touch ing . ▁To ▁un cou ple , ▁there ▁needed ▁to ▁be ▁some ▁s lack ▁in ▁the ▁coupling ; ▁as ▁the ▁train ▁had ▁stopped ▁all ▁the ▁cou pl ings ▁were ▁under ▁t ension . ▁Once ▁the ▁vac u um ▁bra ke ▁connection ▁to ▁the ▁rear ▁portion ▁was ▁broken , ▁any ▁attempt ▁to ▁introduce ▁s lack ▁into ▁the ▁coupling ▁between ▁the ▁two ▁port ions ▁would ▁be ▁defeated ▁by ▁the ▁rear ▁portion ▁sett ling ▁back ▁to ▁rest ▁its ▁weight ▁upon ▁the ▁rear ▁van ▁bra kes . ▁To ▁assist ▁un cou pling ▁the ▁front ▁van ▁guard ▁therefore ▁sc ot ched ▁one ▁of ▁the ▁whe els ▁of ▁the ▁sixth ▁vehicle , ▁that ▁is , ▁the ▁front ▁vehicle ▁of ▁the ▁rear ▁portion ▁being ▁det ached . ▁Lo osen ing ▁the ▁turn bu ck le ▁thus ▁transferred ▁the ▁weight ▁of ▁the ▁rear ▁portion ▁to ▁the ▁sc ot ch ▁on ▁the ▁sixth ▁vehicle , ▁rather ▁than ▁to ▁the ▁rear ▁van ▁bra kes . ▁The ▁cou pl ings ▁to ▁the ▁rear ▁of ▁the ▁sixth ▁vehicle ▁remained ▁under ▁t ension , ▁and ▁the ▁s lack ▁introduced ▁remained ▁in ▁the ▁coupling ▁between ▁the