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
The Manufacture of Swords. By the time of the Roman Republic (c.509 44BC), the use of steel in the manufacture of swords was well advanced and Roman swordsmiths smelted iron ore and carbon in a bloomery furnace (the predecessor of the blast furnace).he Pilum. Around 2m (6.5ft) in length, the main heavy spear or javelin used by the Roman Army was the pilum. It consisted of a socketed iron shank with a triangular head. The pilum weighed in at around 3 4kg (6.6 8.8lb); later versions produced during the Empire (27BC AD476) were lighter.