1. Biogas contains traces of hydrogen sulfide which is highly corrosive but which can be removed by filtering the gas through steel wool or iron filings

2. When the sheet is vibrated, as if by magic the iron filings bunch up near the magnet’s poles and form into the pattern of the magnetic field.

3. Branly’s detector consisted of a tube filled with iron filings that coalesced, or “Cohered,” when a radio-frequency voltage was applied to the ends of the tube