How to verify if a reboot was due to power outage?

How to verify if a reboot was due to power outage?

We've had problems with tripping a breaker and I think we just did it again, but I need to confirm that 1 of our boxes rebooted due to a power outage and not for another mundane reason.
I have gleaned the following information from the logs, but wonder if there's something more telling:
Approx time of restart:
May 19 19:54:57 atlas07

$ last
davidpar pts/0        10.1.2.12        Sun May 19 19:54   still logged in
reboot   system boot  3.5.0-30-generic Sun May 19 19:44 - 20:19  (00:34)
davidpar pts/0        10.1.2.83        Tue May 14 04:14 - 04:21  (00:06)
...


$ tail -n 500 syslog
<cut>
May 19 19:44:58 atlas07 ntpdate[1489]: adjust time server 91.189.94.4 offset 0.000047 sec
May 19 19:45:04 atlas07 CRON[1492]: (root) CMD (command -v debian-sa1 > /dev/null && debian-sa1 1 1)
May 19 19:54:57 atlas07 dbus[1012]: [system] Activating service name='org.freedesktop.ConsoleKit' (using servicehelper)
May 19 19:54:57 atlas07 dbus[1012]: [system] Activating service name='org.freedesktop.PolicyKit1' (using servicehelper)
May 19 19:54:57 atlas07 polkitd[1565]: started daemon version 0.104 using authority implementation `local' version `0.104'
<cut>