Actually, Wendell, the difference between Rugby football and Association Football (what we call Soccer, from the abbreviation: Assoc.) WAS a big thing, big enough that there was a definitive schism between schools that decided to play football that didn’t include carrying the ball and those that did (most prominently, Rugby School, hence, the name). The main differences were over how much touching of the ball was allowed and how a player was ‘tackled’ (that is, his progress stopped so that he was forced to yield up the ball to other players). Each ‘public’ school had its different rules, as did both Cambridge and Oxford.
The following website: http://www.innotts.co.uk/~soccerstats/histrule.htm shows three sets of rules in existence in 1863. One set is the Cambridge Rules, another the rules from Uppingham School, and the third the rules of the Sheffield Football Club. In contrast to these rules would be the rules of Rugby school, which allowed both ‘hacking’ (tripping the carrier) and carrying the ball forward.
On October 26, 1863, representatives of eleven clubs in the London area met to try and unify their rules. The result was the birth of the Football Association (website is http://www.the-fa.org ). The original rules for the FA are shown at the prior website; notice that players were still allowed to take a mark (catch the ball, make a mark on the ground, and place the ball there to take a ‘free’ kick). The FA runs soccer in England to this day, having merged with the Sheffield rules clubs in 1878 to create the game we see today.
Rugby, by the way, is theorized to have started totally by accident. The primary difference in Rugby football was the fact that a player could carry a ball forward. Legend has it that one William Webb Ellis did so out of frustration one day in 1823, and although against the rules at the time, this maneouver was incorporated into the rules at his school (Rugby School). The main characteristic of Rugby continues to this day to be the ability to carry the ball forward, but not pass it forward.
Note that in Australia, the ‘mark’ is still taken, though the ball no longer must be placed on the ground in order to kick it. Aussie Rules Football was codified in 1858, mostly to eliminate the ‘violence’ of the Rugby game (oh yes, those Aussie games are SOOOOO tame).
Which brings us to American, or Gridiron football. The history of the American game is capsulized here: http://www.optonline.com/comptons/ceo/01709_A.html . You will note that the rules did not sharply vary from the rules of soccer and rugby until the introduction of the forward pass in the early 20th Century. Although Walter Camp at Yale helped stylize American football with the introduction of kicking the ball back to the quarterback and the introduction to the American game of downs in 1882, both of these innovations were already in place in Rugby football to some degree (an American scrimmage is really a scrum without the two sides touching). The forward pass was adopted in part to avoid the problems associated with massed players running down the field (the famous ‘flying wedge’) which type of play was also outlawed at the same time.
In short, therefore, the schism between football that consisted of kicking and football that consisted of carrying occurred by the mid-1800’s, and was cemented by 1863. In America, the schism wasn’t ever clear; the slow adoption of Yale rules during the latter part of the 19th Century eventually resulted in soccer-like football dissapearing, only to recur in the formation of actual soccer clubs, playing the game that England had adopted and was spreading throughout the world.