The value of graphite was soon realized, mainly because it could be used to line the moulds for cannonballs. The mines were taken over by the Crown and guarded. When sufficient stocks of graphite had been accumulated, the mines were flooded to prevent theft until more was required. Graphite had to be smuggled out for use in pencils. Because graphite is soft, it requires some form of holder. Graphite sticks were at first wrapped in string or in sheepskin for stability. The news of the usefulness of these early pencils spread far and wide, attracting the attention of artists all over the known world.
England continued to have a monopoly on the production of pencils until a method of reconstituting the graphite powder was found. The distinctively square English pencils continued to be made with sticks cut from natural graphite into the 1860s. The town of Keswick, near the original findings of block graphite, has a pencil museum.
The first attempt to manufacture graphite sticks from powdered graphite was in Nuremberg, Germany, in 1662. It used a mixture of graphite, sulphur, and antimony.
Residual graphite from a pencil stick is not poisonous, and graphite is harmless if consumed.
The Italians first thought of wooden holders. In 1560, an Italian couple named Simonio and Lyndiana Bernacotti created the first blueprints for the modern carpentry pencil to mark their carpentry pieces. Their version was instead a flat, oval, more compact type of pencil. They did this at first by hollowing out a stick of juniper wood. Shortly thereafter, a superior technique was discovered: two wooden halves were carved, a graphite stick inserted, and the two halves then glued together–essentially the same method in use to this day.
English and German pencils were not available to the French during the Napoleonic Wars. France was under naval blockade imposed by Great Britain and could not import the pure graphite sticks from the British Grey Knotts mines – the only known source in the world for solid graphite. France was also unable to import the inferior German graphite pencil substitute. It took the efforts of an officer in Napoleon's army to change this. In 1795, Nicholas Jacques Conté discovered a method of mixing powdered graphite with clay and forming the mixture into rods that were then fired in a kiln. By varying the ratio of graphite to clay, the hardness of the graphite rod could also be varied. This method of manufacture, which had been earlier discovered by the Austrian Joseph Hardtmuth of Koh-I-Noor in 1790, remains in use.
In England, pencils continued to be made from whole sawn graphite. Henry Bessemer's first successful invention (1838) was a method of compressing graphite powder into solid graphite thus allowing the waste from sawing to be reused.
American colonists imported pencils from Europe until after the American Revolution. Benjamin Franklin advertised pencils for sale in his "Pennsylvania Gazette" in 1729, and George Washington used a three-inch pencil when he surveyed the Ohio Territory in 1762. It is said that William Munroe, a cabinetmaker in Concord, Massachusetts, made the first American wood pencils in 1812. This was not the only pencil-making occurring in Concord. Henry David Thoreau discovered how to make a good pencil out of inferior graphite using clay as the binder; this invention was prompted by his father's pencil factory in Concord, which employed graphite found in New Hampshire in 1821 by Charles Dunbar.
On 30 March 1858, Hymen Lipman received the first patent for attaching an eraser to the end of a pencil. In 1862 Lipman sold his patent to Joseph Reckendorfer for $100,000, who went to sue the pencil manufacturer Faber-Castell for infringement. In 1875, the Supreme Court of the United States ruled against Reckendorfer declaring the patent invalid.
The metal band used to mate the eraser with pencil is called a ferrule.
The first attempt to manufacture graphite sticks from powdered graphite was in Nuremberg, Germany in 1662. They used a mixture of graphite, sulfur and antimony. Though usable, they were not as good as the English pencils.
English and German pencils were not available to the French during the Napoleonic wars. It took the efforts of an officer in Napoleon's army to change this. In 1795 Nicholas Jacques Conté discovered a method of mixing powdered graphite with clay and forming the mixture into rods which were then fired in a kiln. By varying the ratio of graphite to clay, the hardness of the graphite rod could also be varied (the more clay, the harder the pencil, and the lighter the color of the mark). This method of making pencils is still used today.
Today, pencils are made industrially by mixing finely ground graphite and clay powders, adding water, forming long spaghetti-like strings, and firing them in a kiln. The resulting strings are dipped in oil or molten wax which seeps into the tiny holes of the material, resulting in smoother writing. A juniper or incense-cedar plank with several long parallel grooves is cut to make something called a slate, and the graphite/clay strings are inserted into the grooves. Another grooved plank is glued on top, and the whole thing is then cut into individual pencils, which are then varnished or painted.
A few common brands of colored pencils (among other items) are Crayola, RoseArt and Cra-Z-Art.
Logic
Logic is the study of reasoning. The rules of logic let philosophers make valid logical deductions about the world. Logic helps people decide whether something is true or false.
Logic is often written in syllogisms, which are one type of logical proof. A syllogism is made from a collection of statements used to logically prove the final statement, called the conclusion. One popular example of a logical syllogism was written by the Classical Greek philosopher Aristotle:
The conclusion is the final statement. This syllogism connects the first two statements to make a logical deduction: Socrates is mortal.
The syllogism is made from three logical statements or propositions. These statements are short sentences describing a small step in a logical argument. The small statements make up the argument, the same way atoms make up molecules. When logic is correct, the statements are said to "follow" from each other.
Statements have a truth value, meaning they can be proved to be true "or" false, but not both. Illogical statements or mistakes in logic are called logical fallacies.
Logical statements can be written in a special type of short hand writing, which includes the symbols of the symbolic logic. These symbols are used to describe logical reasoning in an abstract way. For example:
Here is the previous syllogism written in symbolic logic.
By replacing the English words with letters, one can make the syllogism even simpler.
Similar to mathematical symbols for operations like addition and subtraction, symbolic logic separates abstract logic from the English-language meaning of the original statements. With these abstract symbols, people can study pure logic without the use of a specific written language.
The syllogism is now written in the most abstract and simple way possible. Any distracting elements, such as English language words, have been removed. Anyone who understands logical symbolism can understand this argument.
A logical proof is a list of statements put in a specific order to prove a logical point. Each statement in the proof is either an assumption made for the sake of argument, or has been proven to follow from earlier statements in the proof. All proofs must start with some assumptions, such as "humans exist" in the above syllogism. A proof shows that one statement, the conclusion, follows from the starting assumptions. With a proof, we can prove that "Aristotle is mortal" logically follows from "Aristotle is a man" and "All men are mortal".