torque amplifier
... that Vannevar Bush's use of the torque amplifier solved a problem with the ball-and-disk integrator that Lord Kelvin found when he first thought of the differential analyser over 40 years earlier?
... that <a href="./Vannevar_Bush" id="mwEWU" rel="mw:WikiLink" title="Vannevar Bush">Vannevar Bush</a>'s use of the <b id="mwEWY"><a href="./Torque_amplifier" id="mwEWc" rel="mw:WikiLink" title="Torque amplifier">torque amplifier</a></b> solved a problem with the <a href="./Ball-and-disk_integrator" id="mwEWg" rel="mw:WikiLink" title="Ball-and-disk integrator">ball-and-disk integrator</a> that <a href="./Lord_Kelvin" id="mwEWk" rel="mw:WikiLink" title="Lord Kelvin">Lord Kelvin</a> found when he first thought of the <a href="./Differential_analyser" id="mwEWo" rel="mw:WikiLink" title="Differential analyser">differential analyser</a> over 40 years earlier?