Mysql error.log stays empty

I am replacing the previous server administrator with Ubuntu 10.04.1 LTS.

I have a problem with error logs from mysql. They are empty and they remain empty. :(

I edited /etc/mysql/my.cnf

general_log_file        = /var/log/mysql/mysql.log
general_log             = 1
log_error               = /var/log/mysql/error.log

In any case, nothing is recorded.

rw-rw---- 1 mysql adm      0 2012-04-23 01:09 error.log

What am I missing ...