The 18th century lasted from 1701 to 1800 in the Gregorian calendar.
However, Western historians may sometimes specifically define the 18th century otherwise for the purposes of their work. For example, the "short" 18th century may be defined as 1715–1789, denoting the period of time between the death of Louis XIV of France and the start of the French Revolution with an emphasis on directly interconnected events. 
To historians who expand the century to include larger historical movements, the "long" 18th century  may run from the Glorious Revolution of 1688 to the battle of Waterloo in 1815 or even later.
During the 18th century, the Enlightenment culminated in the French, Haitian and American revolutions. Philosophy and science increased in prominence. Philosophers were dreaming about a better age without the Christian fundamentalism of earlier centuries. This dream turned into a reality with the French Revolution, although it was later compromised by excess of the terror of Maximilien Robespierre. At first, the monarchies of Europe embraced enlightenment ideals, but with the French revolution they feared losing their power and joined wide coalitions with the counter-revolution.
The Ottoman Empire was undergoing a protracted decline, as it failed to keep up with the technological advances in Europe. The Tulip period symbolized a period of peace and reorientation towards European society, after victory against a burgeoning Russia in 1711. Throughout the century various reforms were introduced with limited success.
Great Britain became a major power worldwide with the defeat of France in the Americas in the 1760s and the conquest of large parts of India. However, Britain lost much of its North American colonies after the American revolution. The industrial revolution started in Britain around the 1750s with the patenting of the steam engine. Despite its modest beginnings in the 18th century, it would radically change human society and the geology of the surface of the earth.
WALES IN THE 19th CENTURY
In the 19th century coal mining and iron working in Wales boomed. Other metal industries in Wales , such as copper, zinc and tin plating thrived in the 19th century. So did slate quarrying. There was also an important woollen industry in Wales.
The population of Wales grew rapidly despite emigration. In 1801 the population of Wales was less than 600,000. By 1851 it was nearly 1.2 million. By 1911 it was over 2 million. Welsh towns grew very quickly but in the early 19th century they were dirty and overcrowded. There were outbreaks of cholera in Wales in 1832, 1848, 1854 and 1866.
There was also unrest in the Welsh countryside. There were riots in the years 1842-1844 known as the Rebecca riots. Men dressed as women and called themselves Daughters of Rebecca. The target of their rage were tollgates. (Many roads in Wales were owned by Turnpike Trusts and you had to pay a toll to use them).
However later in the 19th century things improved. Wages rose and hours of work were cut. Towns became more healthy when sewers were dug.
Furthermore in the 1840s railways were built across Wales. They made it much easier for visitors to reach Wales. Tourism became an important Welsh industry.
At the beginning of the 19th century the British government then decided that radical reform was needed in Ireland. They decided the answer was to abolish the Irish parliament and unite Ireland with Britain. In 1800 they managed to persuade the Irish parliament to agree to the measure. It came into effect in 1801.
In 1803 Robert Emmet (1778-1803) and a small group of followers attempted an uprising in Dublin. They killed the Lord Chief Justice of Ireland and his nephew but the rising was quickly crushed. Emmet was hung, drawn and quartered.
In the early 19th century a movement to remove remaining restrictions on Catholics was led by Daniel O'Connell (1775-1847). In 1823 he founded the Catholic Association. In 1829 their wishes were granted. The Catholic Emancipation Act allowed Catholics to become MPs and to hold public office.
In 1840 O'Connell began a Repeal Association to demand the repeal of the Act of Union. He arranged 'monster meetings' of his supporters. In 1843 he called for one at Clontarf. However the British government banned the meeting. O'Connell cancelled the meeting and his movement collapsed.