speculate projection survey cover in situ exploration inventory blast mining yield sensors exposure segment diffuse recovery scrape weather concentration compact echo Thesaurus Exercise II Part 1 Thesaurus Exercise II Part 2 erode reduce pulverise density void age heap body fat accummulate penetrate suspension extraction fissure acrete level incline spoil hoist reduce depth sonar calculation marked convention boyancy thickness constant atmosphere envelope unstable concentrated divided altitude conduction magnitude depending elevation reference measuring Thesaurus Exercise II Part 3 sample test indicating vegetation steeper representative measure equal balance quantities cyclical circular surface accurate radius formulas strength force specimen scale Thesaurus Exercise II Part 4