ing ▁suit . ▁John ▁L eth bridge ▁had ▁invent ed ▁one ▁in ▁ 1 7 1 5 . ▁ ▁In ▁April ▁ 1 7 2 1 ▁a ▁salv age ▁expedition ▁set ▁out ▁from ▁Sp it head . ▁It ▁compr ised ▁two ▁ships ▁Aud rey ▁( of ▁ 3 8 0 ▁tons ▁( bm ) ▁and ▁ 3 6 ▁guns ), ▁and ▁J olly ▁B atch elor ▁( 2 0 ▁guns ). ▁The ▁British ▁Royal ▁Navy ▁provided ▁the ▁fr ig ate ▁ ▁to ▁protect ▁them ▁from ▁pir ates . ▁The ▁salv ors ▁recovered ▁substantial ▁quantities ▁of ▁silver ▁from ▁V ans itt art ▁using ▁a ▁suit ▁that ▁Jacob ▁R owe ▁had ▁designed ▁and ▁then ▁pat ented ▁in ▁ 1 7 2 0 . ▁When ▁the ▁operations ▁finished ▁on ▁ 2 ▁August , ▁the ▁salv ors ▁had ▁recovered ▁almost ▁ 7 5 K ▁ oun ces ▁of ▁the ▁ 1 4 1 K ▁ oun ces ▁of ▁silver ▁that ▁she ▁had ▁carried , ▁as ▁well ▁as ▁ 8 7 8 ▁sl abs ▁of ▁lead , ▁plus ▁guns ▁and ▁anch ors . ▁ ▁Cit ations ▁and ▁references ▁Cit ations ▁ ▁References ▁Ear le , ▁Peter ▁( 2 0 0 7 ) ▁Tre asure ▁H unt : ▁Sh ip w reck , ▁D iving , ▁and ▁the ▁Qu est ▁for ▁Tre asure ▁in ▁an ▁Age ▁of ▁Hero es . ▁( Mac mill an ). ▁▁ ▁Category : 1 7 1 0 s ▁ships ▁Category : Sh ips ▁built ▁on ▁the ▁River ▁Th ames ▁Category : Sh ips ▁of