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.
Ever since the mid-19th century with the invention of the siphon-flush toilet â by Joseph Adamson, not, as urban legend has it, the more-famous Thomas Crapper â these handy devices have flushed in pretty much the same way: with a large, satisfying rush of up to 7 gallons of water.