First, let me say that my sparring with Artie over American and British english spelling differences has been totally for fun (on my part, and I believe his as well), but it did inspire me to check further into it. This is what I found. I know answer.com is not to be considered the final word on the subject, so please don't flame me on that point (or any other, for that matter. As if this disclaimer will make any difference!)
from answer.com
The spelling aluminium is the international standard in the sciences (IUPAC).
The American spelling is nonetheless used by many American scientists.
Humphry Davy, the element's discoverer, first proposed the name alumium,
and then later aluminum. The name aluminium was finally adopted to conform
with the -ium ending of metallic elements.[5] Canada uses aluminum
(aluminium on occasion[not in citation given]) and Australia aluminium,
according to their respective dictionaries.[6]
The outer lining of a wheel, which contacts the road or rail and may be metal
or rubber. Canada as US. Tire is the older spelling, but both were used in the
15th and 16th centuries (for a metal tire); tire became the settled spelling in
the 17th century but tyre was revived in the UK in the 19th century for
pneumatic tyres, possibly because it was used in some patent documents,
[126] though many continued to use tire for the iron variety. The Times
newspaper was still using tire as late as 1905. For the verb meaning
"to grow weary" both US and British English use the tire spelling exclusively.
also from answers.com
Historical origins
This section does not cite any references or sources. Please help improve
this article by adding citations to reliable sources. Unsourced material may be
challenged and removed. (June 2009)
In the early 18th century, English spelling was not standardized. Differences became
noticeable after the publishing of influential dictionaries. Current British English
spellings follow, for the most part, those of Samuel Johnson's Dictionary of the English
Language (1755), whereas many American English spellings follow Noah Webster's
An American Dictionary of the English Language of 1828.
Webster was a strong proponent of spelling reform for reasons both philological
and nationalistic. Many spelling changes proposed in the US by Webster himself,
and in the early 20th century by the Simplified Spelling Board, never caught on.
Among the advocates of spelling reform in England, the influences of those who
preferred the Norman (or Anglo-French) spellings of certain words proved decisive.
Subsequent spelling adjustments in the UK had little effect on present-day US
spelling, and vice versa. While in many cases American English deviated in the 19th
century from mainstream British spelling, on the other hand it has also often retained
older forms.
The spelling systems of Commonwealth countries and Ireland, for the most part,
closely resemble the British system. In Canada, however, while most spelling is
"British", many "American" spellings are also used. Additional information on
Canadian and Australian spelling is provided throughout the article.
For more (than I'll bet than you want to know) about the differences between Old English and american English:
http://www.answers.com/topic/american-and-british-english-spelling-differences
