I have recently noticed that the spell checker aspell that comes with
Slackware only has a dictionary for US/UK English.
There seems to be different possibilities to install a french dictionary.
First, there is the french dictionary provided by the GNU project for aspell aspell-fr-0.50-3.tar.bz2.
Second, in the past, I was
using the francais-IREQ-1.4.tar.gz dictionary provided by Hydro-Quebec with ispell. The aspell documentation states that ispell
dictionaries can be imported so this might be a second possibility.
Third, the stardict program included the xmlittre dictionary.

I have two questions. First, is the GNU aspell dictionary more complete
than the Hydro-Quebec one or is it the other way round ?

Second, in the case of the two dictionaries being too limited, does anybody know whether a stardict dictionary can be imported
in aspell ? The xmlittre dictionary should have at least all late 19th century words.

Yes, but aspell-fr is available in /extra.

Thanks for that. I have installed the French aspell dictionary. I can also answer my first question.
The aspell-fr dictionary is a merger of the ispell-IREQ dictionary from Hydro-Québec with
a project Gutenberg dictionary. As to StarDict, it has disappeared, apparently because of
copyright issues. The only remaining issue is whether it would be possible to extract the words
from the xmlittre StarDict dictionnary and add them to the French aspell using some Perl or AWK
script.