( ( If ( we ( follow ( the gradation ) ) ) ) ( , ( we ( ( find ( ( ( ( ( ( that , ) ( of ( ( ( ( ( ( all ( the ( mixed ( corruptible elements ) ) ) ) , ) ( the ( igneous air ) ) ) , ) or ) ( ( the air ) ( we breathe ) ) ) ) ) , ) ( which ( I ( ( called ether ) ( in ( my last ) ) ) ) ) ) , ) ( ( ( ( is really ) ( ( the purest ) ( of substances ) ) ) , ) ( without ( which ( ( no man ) ( can live ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (IN If) (S (NP (PRP we)) (VP (VBP follow) (NP (DT the) (NN gradation))))) (, ,) (NP (PRP we)) (VP (VBP find) (SBAR (S (NP (NP (DT that)) (, ,) (PP (IN of) (NP (NP (NP (PDT all) (DT the) (VBN mixed) (NN corruptible) (NNS elements)) (, ,) (NP (DT the) (JJ igneous) (NN air)) (, ,)) (CC or) (NP (NP (DT the) (NN air)) (SBAR (S (NP (PRP we)) (VP (VB breathe))))))) (, ,) (SBAR (WHNP (WDT which)) (S (NP (PRP I)) (VP (VBD called) (NP (NN ether)) (PP (IN in) (NP (PRP$ my) (JJ last)))))) (, ,)) (VP (VBZ is) (ADVP (RB really)) (NP (NP (DT the) (NN purest)) (PP (IN of) (NP (NNS substances)))) (, ,) (PP (IN without) (SBAR (WHNP (WDT which)) (S (NP (DT no) (NN man)) (VP (MD can) (VP (VB live)))))))))) (. .)))
If we follow the gradation, we find that, of all the mixed corruptible elements, the igneous air, or the air we breathe, which I called ether in my last, is really the purest of substances, without which no man can live.
(ROOT (S (NP (NNP Air)) (VP (MD can) (VP (VB be) (VP (VBN separated) (PP (IN into) (NP (JJ several) (NNS elements)))))) (. .)))