The Compass and Other Magnetic Innovations

Compass and Map
Cultura/Ross Woodhall/ Riser/ Getty images

A compass is an instrument containing a freely suspended magnetic element that displays the direction of the horizontal component of Earth's magnetic field at the point of observation. It's been used to help people navigate for many centuries. Located in the same part of the public imagination as sextants and telescopes, it's actually been in use for a lot longer than the sea voyages that discovered North America. The use of magnetism in inventions doesn't stop there, though; it's found in everything from telecommunications equipment and motors to the food chain.

Discovery

Large deposits of magnetic oxides were found in the district of Magnesia in Asia Minor thousands of years ago; their location led to the mineral receiving the name of magnetite (Fe3O4), which was nicknamed lodestone. In 1600, William Gilbert published "De Magnete," a paper on magnetism that details the use and properties of magnetite.

Ferrites, or magnetic oxides, are stones that attract iron and other metals. These are natural magnets and are not inventions. However, the machines that we make with magnets are inventions.

Magnetic Compass

The magnetic compass is actually an old Chinese invention, probably first made in China during the Qin dynasty (221–206 B.C.). Back then, the Chinese used lodestones (which align themselves in a north-south direction) to construct fortune-telling boards. Eventually, someone noticed that the lodestones were better at pointing out real directions, which led to the creation of the first compasses.

The earliest compasses were designed on a square slab that had markings for the cardinal points and the constellations. The pointing needle was a spoon-shaped lodestone device with a handle that would always point south. Later on, magnetized needles were used as direction pointers instead of the spoon-shaped lodestones. These appeared in the eighth century A.D.—again in China—and between 850 and 1050.

Compasses as Navigational Aids

In the 11th century, compasses' use as navigational devices on ships seemed to have become common. The magnetized-needle compasses used in navigation could be wet (in water), dry (on a pointed shaft), or suspended (on silk thread) and were used by voyagers, such as those traders who traveled to the Middle East, and were used by early navigators to locate the magnetic North Pole or pole star.

Electromagnetism

In 1819, Hans Christian Oersted reported that when an electric current in a wire was applied to a magnetic compass needle, the magnet was affected. This is called electromagnetism. In 1825, British inventor William Sturgeon (1783–1850) displayed the power of the electromagnet by lifting nine pounds with a seven-ounce piece of iron wrapped with wires through which the current of a single-cell battery was sent.

This device laid the foundation for large-scale electronic communications, as it led to the invention of the telegraph. It also resulted in the invention of the electric motor. 

Cow Magnets

U.S. patent #3,005,458 is the first patent issued for a cow magnet. It was issued to Louis Paul Longo, the inventor of the Magnetrol Magnet, for the prevention of hardware disease in cows. If cows happen to consume scrap pieces of metal, such as nails, when they're feeding, the foreign objects can cause internal damage to their digestive tract. Cow magnets keep the metal pieces confined to the cow's first stomach, rather than traveling to the later stomachs or intestines, where the fragments can cause the most damage.