Radium salt Rarefaction fountain Receivers Receiving telegraph station and key Morse type Revolution counter Rheostat with runner Rheostat with double runner Reflector Riess' apparatus for the distribution of the induced electricity Riess' thermometer Righi's oscillator Ring and sphere for cubic expansion Ring and sphere for cubic expansion with stove Roberval balance Rœngten tube

Roget's helix Rumford's differential thermoscope Ruhmkorff. Induction coil Rupert's drops