Opisometer Geology this concave glass mirror at

this concave glass mirror at 100mm focal length runs at f/1 for vivid real-image demos and converging-reflection work

Used to draw electrons from glass and ebonite rods during rubbing

sized to read one step up from the 0-1A meter when student circuits draw past the lower meter's full-scale deflection

Single large transparent plate filled with iron-rod plotting compasses

supplying a duplicate-value option for paired-bench experiments on capacitor energy storage

Opisometer Geology this concave glass mirror atOpisometer with a knurled wheel on a threaded spindle, rolling along curved lines on maps, charts, and drawings to convert winding distance into straight line length for geography coursework.