ispell dictionaries

[Kevin Dziulko <dziulko@klaatu.canisius.edu>]

Where can I find information and descriptions about ispell dictionaries?  
Specificlly, I want to set the default dictionary to american.  I also 
want to augment it with a personal dictionary.  I pasted this from the 
readme.w32 file into my .emacs:

;;
;; ispell
;;
(setq ispell-local-dictionary-alist
  '((nil				; default (english.aff)
     "[A-Za-z]" "[^A-Za-z]" "[']" nil ("-B") nil iso-8859-1)
    ("UK-xlg"				; english large version
     "[A-Za-z]" "[^A-Za-z]" "[']" nil ("-B" "-d" "UK-xlg") nil iso-8859-1)
    ("US-xlg"				; american large version
     "[A-Za-z]" "[^A-Za-z]" "[']" nil ("-B" "-d" "US-xlg") nil iso-8859-1)
   )
)
;;

Thanks!!