[Trade catalogs on electric mine lighting : miners' safety and carbide lamps and parts, portable acetylene lamps, alkaline lamps, alkaline accumulators; oxygen deficiency indicator ...

The Grier Brothers of Pittsburgh, Pennsylvania began manufacturing carbide mining lamps in 1911. Their finances took a fatal blow in 1922 when the Supreme Court ruled against them for patent ...

Lit by carbide lamps with ore cars accommodated by narrow gauge tracks, the tunnel was considered a marvel of engineering. It was completed in 1904 at a cost of $500,000.