They are composed of rock, dust, ice and frozen gases such as carbon monoxide, carbon dioxide, methane, and ammonia. Sometimes called dirty snowballs, recent studies have shown that the ice of a comet is covered by a crust. Comets also contain a variety of organic compounds as well as the gases already mentioned.
It was invented by a carpenter in Bury in 1896 called Brian Gamlin. If you go around the dart board adding up the differences between adjacent numbers – 20 and 1 for example – it would come to 198. The highest possible it could come to is 200, but it’s well organised to reduce the chance of a lucky shot.