Other viruses that can cause colds include coronavirus, respiratory syncytial virus, influenza and parainfluenza. Colds cause a lot of people to stay home. The CDC says 22 million school days are lost each year in the U.S. because of them. Some estimates say that Americans have 1 billion colds a year. For more detail, see Common Cold Causes. How a Common Cold Starts. You can catch it from another person who is infected with the virus. This can happen by direct physical contact with someone who has a cold, or by touching a surface contaminated with their germs -- like a computer keyboard, doorknob or spoon --- and then touching your nose or mouth.
The hypocaust system. The hypocaust system (hypocaustum in Latin) was a heating system used in (wealthy) Roman homes and Roman baths, and the closest thing to central heating today. The hypocaust was a system that circulated hot air under the floor and surrounding walls. Hypocaust construction
Under Floor Heating (hypocaust). Rich Roman houses had central heating which was under the floors. This heating system was called a hypocaust. The floors were supported on stacks of tiles (pilae) and hot air was circulated under the floor from a furnace stoked outside the building. Mosaic Floors. Mosaic have been found on the floors of many Roman buildings. Rich Romans decorated the floors of their main rooms with mosaics-tiny coloured stones (tesserae). These were stuck to the floor with mortar, a type of cement. Each mosaic used thousands of pieces to make a pattern. Mosaic floors were a statement of wealth and importance.