( Thus ( , ( ( although ( ( the ( balanced ( mass-for-mass equations ) ) ) ( appear ( to ( be ( quite logical ) ) ) ) ) ) ( , ( they ( ( ( can not ) ( be ( used ( to ( ( explain ( ( ( ( the origin ) ( of myrmekite ) ) , ) ( at least ) ) ) ( in ( some rocks ) ) ) ) ) ) ) . ) ) ) ) ) )
(ROOT (S (ADVP (RB Thus)) (, ,) (SBAR (IN although) (S (NP (DT the) (JJ balanced) (JJ mass-for-mass) (NNS equations)) (VP (VBP appear) (S (VP (TO to) (VP (VB be) (ADJP (RB quite) (JJ logical)))))))) (, ,) (NP (PRP they)) (VP (MD can) (RB not) (VP (VB be) (VP (VBN used) (S (VP (TO to) (VP (VB explain) (NP (NP (DT the) (NN origin)) (PP (IN of) (NP (NN myrmekite))) (, ,) (ADVP (IN at) (JJS least))) (PP (IN in) (NP (DT some) (NNS rocks))))))))) (. .)))
Thus, although the balanced mass-for-mass equations appear to be quite logical, they cannot be used to explain the origin of myrmekite, at least in some rocks.
(ROOT (S (NP (DT A) (NN student)) (VP (MD should) (VP (VB use) (NP (DT a) (NN balance) (S (VP (TO to) (VP (VB compare) (NP (NP (DT the) (NNS masses)) (PP (IN of) (NP (CD two) (JJ small) (NNS rocks)))))))))) (. .)))