( ( An ( open-ended ( mercury manometer ) ) ) ( ( was ( used ( to ( measure ( ( the pressure ) ( of ( the ( gas fill ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT An) (JJ open-ended) (NN mercury) (NN manometer)) (VP (VBD was) (VP (VBN used) (S (VP (TO to) (VP (VB measure) (NP (NP (DT the) (NN pressure)) (PP (IN of) (NP (DT the) (NN gas) (NN fill))))))))) (. .)))
An open-ended mercury manometer was used to measure the pressure of the gas fill.
(ROOT (S (NP (NP (DT The) (NN pressure)) (PP (IN of) (NP (NP (DT a) (NN sample)) (PP (IN of) (NP (NN gas)))))) (VP (VBZ is) (VP (VBN measured) (PP (IN with) (NP (DT an) (JJ open-end) (NN manometer))))) (. .)))