fatdan:
... further/farther (trying to cover my a$ in case the spelling nit reads this) ....
my bold
As a facilitator of learning in the English language, may I say your spelling is fine. The usage depends on whether you are speaking / writing American or British English but for now I'll assume you are using American English.
In American English when used as adverbs both words can be used interchangeably
e.g.
“How much farther do we have to go?”
“It’s just a mile further.”
“How much further do you want to take this argument?”
“I’ve taken it farther than I want to already.”
However when used as an adjective we are supposed to differentiate between literal distance (farther) and figurative distance (further).
e.g. “My house is the farther of the two.”
“She needs no further introduction.”
For ease of use I advise my students to stick to
literally = farther
figurative = further
However language is an evolving entity and things have, do and likely will change.
I hope you enjoyed the free lesson, (no charge ;-) ) and take it in the light-hearted manner it was intended.