"We may test other solutions by arranging the following circuit, including a source of current, the substance to be tested, and some instrument to detect the passage of the current." -Brownlee 1907

Conductivity Test

"We may test other solutions by arranging the following circuit, including a source of current, the…

Germination test of different ears of corn.

Germination test

Germination test of different ears of corn.

"Testing the insulation resistance of a motor or generator from its winding to ground." —Croft 1920

Measure Insulation Resistance of Motor

"Testing the insulation resistance of a motor or generator from its winding to ground." —Croft…

A man sitting at a desk, with a boy standing in front, with his eyes closed.

Man at desk and boy

A man sitting at a desk, with a boy standing in front, with his eyes closed.

A woman mixing milk with acid to test it, using a rotary motion with the bottle not pointed towards her face.

Mixing milk

A woman mixing milk with acid to test it, using a rotary motion with the bottle not pointed towards…

A woman putting milk into a test bottle. The pipette is held at an angle with the test bottle and its point against the inside of the neck.

Testing milk

A woman putting milk into a test bottle. The pipette is held at an angle with the test bottle and its…

"A proof-plane may be made by cementing a bronze cent or a disk of gilt paper to a thin insulating handle, as a glass tube or a vulcanite rod. Slide the disk of the proof-plane along the surface of the electrified body to be tested, and quickly bring it into contact with the knob of the gold-leaf electroscope, the leaves of which will diverge." — Avery, 1895

Hand with proof-plane

"A proof-plane may be made by cementing a bronze cent or a disk of gilt paper to a thin insulating handle,…

Sea-stars are Echinoderms. The order Ophiuroides is closely related to starfishes. The arms of sea stars however, differ from those of starfishes in not containing any prolongations from the stomach.

Sea-star

Sea-stars are Echinoderms. The order Ophiuroides is closely related to starfishes. The arms of sea stars…

Sea-urchins are Echinoderms. Their shell is mainly composed of calcareous plates.

Sea-urchin

Sea-urchins are Echinoderms. Their shell is mainly composed of calcareous plates.

"Tenacity is that property of matter by virtue of which some bodies resist a force tending to pull their particles asunder Its measure is the ratio between the breaking weight and the area of the cross section of the body broken. It varies with different substances, with the form of the body, with the temperature, and with the duration of the pull." -Avery 1895

Testing for Tenacity

"Tenacity is that property of matter by virtue of which some bodies resist a force tending to pull their…

A test tube

Test tube

A test tube

"The Actual Size of the Test Type, which shiykd be seen by the Normal Eye at a distance of Twenty Feet." — Blaisedell, 1904

Test type

"The Actual Size of the Test Type, which shiykd be seen by the Normal Eye at a distance of Twenty Feet."…

A handy testing set.

Testing Set

A handy testing set.

This illustration shows a vacuum boiler in which liquid to become glue is boiled by steam, as well as a man testing the liquid in the manufacturing process.

Vacuum Boiler, Testing the Liquid (Glue)

This illustration shows a vacuum boiler in which liquid to become glue is boiled by steam, as well as…

A portable combination volt-ammeter for testing.

Volt-Ammeter

A portable combination volt-ammeter for testing.