For example, for the Gases under pressure hazard class, the hazard categories are Compressed gas, Liquefied gas, Refrigerated liquefied gas and Dissolved gas. These classes relate to the physical state of the gas when packaged and do not describe the degree of hazard.
1 In 1596, a flush toilet was invented and built for Queen Elizabeth I by her Godson, Sir John Harrington. 2  The first patent for the flushing toilet was issued to Alexander Cummings in 1775. 3  During the 1800s, people realized that poor sanitary conditions caused diseases.
1 With the fall of the Roman empire, the technology was lost.  1596: Sir John Harington is said to have invented 'The Ajax', a flush toilet, for Elizabeth I of England. His design was ridiculed in England, but was adopted in France under the name Angrez. The design had a flush valve to let water out of the tank, and a wash-down design to empty the bowl.