**Heaviside** **in** 1887 **succeeded** **in** **communicating** **by** **telephonic** **speech** **between** **the** **surface** **of** **the** **earth** **and** **the** **subterranean** **galleries** **of** **the** **Broomhill** **collieries**, 350 **feet** **deep**, **by** **laying** **above** **and** **below** **ground** **two** **complete** **metallic** **circuits**, **each** **about** 24 **m**.

**In** 1885 **Preece** **and** **Heaviside** **proved** **by** **experiments** **made** **at** **Newcastle** **that** **if** **two** **completely** **insulated** **circuits** **of** **square** **form**, **each** **side** **being** 440 **yds**., **were** **placed** **a** **quarter** **of** **a** **mile** **apart**, **telephonic** **speech** **was** **conveyed** **from** **one** **to** **the** **other** **by** **induction**, **and** **signals** **could** **be** **perceived** **even** **when** **they** **were** **separated** **by** 1000 **yds**.

**Oliver** **Heaviside** **showed** **mathematically** **that** **uniformly-distributed** **inductance** **in** **a** **telephone** **line** **would** **diminish** **both** **attenuation** **and** **distortion**, **and** **that** **if** **the** **inductance** **were** **great** **enough** **and** **the** **insulation** **resistance** **not** **too** **high** **the** **circuit** **would** **be** **distortionless**, **while** **currents** **of** **all** **frequencies** **would** **be** **equally** **attenuated**.

**Heaviside**); **the** **diffraction** **of** **light** (**E**.

**Oliver** **Heaviside** **after** 1880 **rendered** **much** **assistance** **by** **reducing** **Maxwell'****s** **mathematical** **analysis** **to** **more** **compact** **form** **and** **by** **introducing** **greater** **precision** **into** **terminology** (**see** **his** **Electrical** **Papers**, 1892).

**Heaviside**, **Electromagnetic** **Theory** (**London**, 1893); **O**.