Harold Hayward Clark

1876

• Electric lights for use about oil and gas wells
• Electric switches for use in gaseous mines
• Electrical symbols for mine maps
• Ignition of gas by miniature electric lamps with tungsten filaments
• Ignition of gas by standard incandescent lamps
• Ignition of mine gases by the filaments of incandescent lamps
• Permissible electric lamps for miners
• Permissible explosion-proof electric motors for mines
• Portable electric mine lamps
• Safety electric switches for mines
• Shot firing in coal mines by electricity controlled from outside
• Suggested safety rules for installing and using electrical equipment in bituminous coal mines