, ▁ 1 9 0 6 ) ▁announced ▁the ▁results ▁of ▁his ▁new ▁experiments ▁on ▁the ▁charge - to - mass ▁ratio , ▁i . e . ▁the ▁velocity ▁dependence ▁of ▁mass . ▁They ▁represented , ▁in ▁his ▁opinion , ▁a ▁clear ▁ref ut ation ▁of ▁the ▁relativ ity ▁principle ▁and ▁the ▁Lor ent z - E in stein - The ory , ▁and ▁a ▁confirm ation ▁of ▁Abraham ' s ▁theory . ▁For ▁some ▁years ▁Kauf mann ' s ▁experiments ▁represented ▁a ▁weight y ▁ob jection ▁against ▁the ▁relativ ity ▁principle , ▁although ▁it ▁was ▁critic ized ▁by ▁Plan ck ▁and ▁Adolf ▁Best el me yer ▁( 1 9 0 6 ). ▁Following ▁Kauf mann ▁other ▁phys ic ists , ▁like ▁Alfred ▁Buch erer ▁( 1 9 0 8 ) ▁and ▁Gün ther ▁Ne umann ▁( 1 9 1 4 ), ▁also ▁exam ined ▁the ▁velocity - dep end ence ▁of ▁mass ▁and ▁this ▁time ▁it ▁was ▁thought ▁that ▁the ▁" L or ent z - E in stein ▁theory " ▁and ▁the ▁relativ ity ▁principle ▁were ▁confirmed , ▁and ▁Abraham ' s ▁theory ▁dis pro ved . ▁However , ▁it ▁was ▁later ▁pointed ▁out ▁that ▁the ▁Kauf mann – B uch erer – Ne umann ▁experiments ▁only ▁showed ▁a ▁qual itative ▁mass ▁increase ▁of ▁moving ▁electrons , ▁but ▁they ▁were ▁not ▁precise ▁enough ▁to ▁distinguish ▁between ▁the ▁models ▁of ▁Lor ent z - E in stein ▁and ▁Abraham . ▁So ▁it ▁continued ▁until ▁ 1 9 4 0 , ▁when ▁experiments