What is the third quarter of a football game?

Football was introduced to North America in Canada, by the British Army garrison in Montreal, which played a series of games with McGill University. In 1874, McGill invited Harvard to Montreal to play their new game derived from Rugby football in a home and home series. Many of the similarities and differences between the Canadian and American games indeed came out of this original home and home series where each home team set the rules. For instance, Harvard due to lack of campus space did not have a full-sized rugby pitch. Their pitch was only 100 yards long x 50 yards wide with undersized endzones (still the regulation size for American Football). Because of the reduced field, the Harvard team opted for 11 players per side, four less than the regulation 15 of Rugby Union (13 in Rugby League). The number of downs was also increased by Harvard to 4 from 3 set by McGill to generate more offence. Both the Canadian and American games still have some things in common with the two varieties of rugby, especially rugby league, and, because of the similarities, the National Football League has established a formal relationship with the Canadian Football League.