Superior Wooden Test Tube Support, 12-Place Entomology & Zoology_Entomology Supplies Wall-mounted Mason's hygrometer with two

Wall-mounted Mason's hygrometer with two identical dual-scale thermometers — one dry and one kept wet via a water reservoir — calculating relative humidity from their paired reading difference

Designed to make electric field lines visible

5-inch plate-and-rod assembly with central mass

showing how inclination shifts from horizontal at the equator to vertical at the poles

Superior Wooden Test Tube Support, 12-Place Entomology & Zoology_Entomology Supplies Wall-mounted Mason's hygrometer with twoTwelve place hardwood test tube rack combining ten 19 mm holes and two 25 mm holes with twelve draining pins for mixed size storage and inverted drying on the bench.