As most people know, the 18th Century actually refers to the period of time from 1701 to 1800 on the Gregorian Calender. The "short" 18th Century refers to the period of time between 1715 and 1789, between the death of Louis XIV of France and the start of the French Revolution, while the "long" 18th Century may bracket as much as from 1689 (the "Glorious Revolution" in Britain) to 1815 (the battle of Waterloo).
Chronologically, notable inventions of the 1700s are as follows:
1709: The pianoforte, known today as the "piano", was built by the Italian Bartolomeo Cristofori. An updated version of the harpsichord and clavichord, it was the first keyboard instrument capable of playing both softly and loudly, depending on the force o the key pressed.
1712: The steam engine was invented and built by Thomas Newcomen, an Englishman working near a mine that constantly filled with water. The Newcomen steam engine is often seen as the herald of the Industrial Revolution.
1717: The diving bell, an underwater viewing and breathing apparatus, was first tested by Edmond Halley to a depth of 55 feet in the Thames river.
1730s: The sextant, a navigational tool for ships, was developed by John Hadley of England and Thomas Godfrey of America.
1736: Europeans discover rubber in South America. It does not receive the name "rubber" until 1770.
1740s: Benjamin Huntsman first develops modern steel.
1745: The world's first electrical capacitor is invented by Edward von Kleist (the device is called the Leyden Jar).
1751-1785: The first and subsequent publishing of the French "Encyclopedie, ou Dictionnaire de Raisonne des Sciences, des Arts, et des Metiers" (lit: "Encyclopedia, or the systematic Dictionary of Science, Art, and Crafts")
1755: The first publishing of "Dictionary", by Samuel Johnson. Though not the *first* English dictionary, it is by far the most complete and sets the footprint for all dictionaries to follow.
1764: The Spinning Jenny (or Spinning Ginny), a device allowing a single worker to produce eight spools of yarn simultaneously, is created by James Hargreaves in England. Most historians consider this the start of the Industrial Revolution.
1765: James Watt (for whom the Watt is named) improves the original design of the steam engine.