( ( ( ( ( ( Convex lenses ) ( were ( made ( by ( using ( ( a ( concave-shaped ( grinding tool ) ) ) ( -LRB- ( and ( vice-versa -RRB- ) ) ) ) ) ) ) ) ) , ) and ) ( then ( ( the ( ( roughly shaped ) lens ) ) ( was ( polished ( to ( make ( its ( final shape ) ) ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (NNP Convex) (NNS lenses)) (VP (VBD were) (VP (VBN made) (PP (IN by) (S (VP (VBG using) (NP (NP (DT a) (JJ concave-shaped) (VBG grinding) (NN tool)) (PRN (-LRB- -LRB-) (CC and) (ADJP (JJ vice-versa)) (-RRB- -RRB-))))))))) (, ,) (CC and) (S (ADVP (RB then)) (NP (DT the) (ADJP (RB roughly) (JJ shaped)) (NN lens)) (VP (VBD was) (ADJP (JJ polished) (S (VP (TO to) (VP (VB make) (NP (PRP$ its) (JJ final) (NN shape)))))))) (. .)))
Convex lenses were made by using a concave-shaped grinding tool (and vice-versa),and then the roughly shaped lens was polished to make its final shape.
(ROOT (S (NP (NP (DT The) (NN lens)) (PP (IN of) (NP (DT the) (NN eye)))) (VP (VBZ is) (S (NP (DT a) (-LRB- -LRB-) (NN n) (-RRB- -RRB-) (NN convex)) (VP (VB shape)))) (. .)))