Ottes Magnesium Ribbon Holder
Ottes magnesium ribbon holder.
Darkslide containing step wedge with 21 steps. Phosphorescent plate made luminous by burning magnesium and placed in holder. Plated exposed through wedge under luminous plate for 30 seconds. No.79. L.Warnerke.
Ottes magnesium ribbon holder.
Darkslide containing step wedge with 21 steps. Phosphorescent plate made luminous by burning magnesium and placed in holder. Plated exposed through wedge under luminous plate for 30 seconds. No.79. L.Warnerke.