A great than for all the help I received so fast.
My question was :
    every day, the system creates a directory
    /usr/var/adm/syslog.dated/Day-date containing the files
    auth.log  daemon.log kern.log lpr.log  mail.log syslog.log user.log
    but this files are automatically protected with -rw-r-----.
    Is there a way to allow all the users to "read only" one
    or more of this files without changing every day , "by hand" the
    mod ??
And one of the solutions  (which I tried immediately and it works fine)
came from Andrew Gillies <anaru_at_cns.ed.ac.uk> (special thanks to him) 
who suggested :
We direct the syslog information wanted (e.g. mail.debug) to a new
file (e.g. /usr/public/logs/maillog) that is world readable.  This is
done using the syslog.conf file (e.g. adding a line like):
        mail.debug              /usr/public/logs/maillog
ok, yes, this duplicates information, and yes you have to write your
own cron script to do daily/weekly cycles, but that is easy to do..  We
took this approach as it was already working on our SUNs and it seemed
sensible to do the DECs the same - it keeps public logs away from the
system logs.
--------------------------------------------------
Thanks also to :
                Lucio Chiappetti <lucio_at_ifctr.mi.cnr.it>
                Thomas Leitner <tom_at_finwds01.tu-graz.ac.at>
                Daniel Clar <Daniel.Clar_at_supelec.fr>
                boebion_at_celfi.phys.univ-tours.fr
                Stanley Fung<sfung_at_mda.ca>
                "WHITTAKER, Bruce" <bjw_at_ansto.gov.au>
                Kyle_Amon_at_jabil.com
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                                 Jean Schuller
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Received on Tue Nov 05 1996 - 09:42:07 NZDT