▁Philosoph ical ▁Society ▁and ▁the ▁Ge ological ▁Society ▁of ▁London , ▁he ▁defined ▁the ▁discipline ▁of ▁physical ▁ge ology , ▁making ▁mathematical ▁investig ations ▁dealing ▁with ▁the ▁effects ▁that ▁an ▁elev atory ▁force , ▁acting ▁from ▁below , ▁would ▁produce ▁on ▁a ▁portion ▁of ▁the ▁Earth ' s ▁cr ust , ▁in ▁f iss ures ▁and ▁fault s . ▁In ▁this ▁way ▁he ▁discussed ▁the ▁elev ation ▁and ▁den ud ation ▁of ▁the ▁Lake ▁District , ▁the ▁We al den ▁area , ▁and ▁the ▁Bas ▁B oul onna is . ▁ ▁Hop kins ▁conce ived ▁of ▁a ▁largely ▁solid ▁but ▁dynamic ▁Earth ▁thread ed ▁with ▁cav ities ▁where by ▁hot ▁v ap ours ▁or ▁flu ids ▁could ▁create ▁locally ▁elev atory ▁press ures . ▁Such ▁a ▁model ▁was ▁at ▁odd s ▁with ▁the ▁ideas ▁of ▁Charles ▁Ly ell ▁whose ▁theory ▁was ▁of ▁a ▁" st ead y ▁state " ▁with ▁a ▁largely ▁liquid ▁terrest rial ▁interior , ▁inside ▁a ▁solid ▁cr ust ▁no ▁more ▁than ▁ 1 0 0 ▁miles ▁thick . ▁Hop kins ▁presented ▁a ▁series ▁of ▁papers ▁at ▁the ▁Royal ▁Society ▁between ▁ 1 8 3 8 ▁and ▁ 1 8 4 2 ▁anal ys ing ▁the ▁Earth ' s ▁rotation , ▁including ▁its ▁pre cess ion ▁and ▁nut ation , ▁and ▁using ▁observations ▁to ▁support ▁his ▁theory , ▁cont ending ▁that ▁they ▁were ▁incons istent ▁with ▁a ▁fluid ▁interior . ▁He ▁also ▁interpreted ▁earth qu akes ▁and ▁vol cano es ▁through ▁the ▁same ▁model ▁in ▁an ▁ 1 8 4