Cascade Standby Configuration in 9.2.4

Greetings!

I am setting up cascade standby (primary->slave1->slave2)

Everything is working as expected but I am not sure why it is working though....

Primary: archive = on and archive_command is enabled to send logs to slave1
I can see in pg_log that logs are being rsynced to slave1

Slave1: archive = on (I am not sure what this does in case of standby) archive_command is enabled to send logs to slave2
Problem: I don't see logs going to slave2 though

Slave2:archive and archive_command are commented out

I don't see anywhere logs being shipped from slave1 to slave2 but when I stop slave2 and do some activity on primary and later restart slave2 I see the data in slave2. This means somehow logs are getting to slave2 and eventually streaming is catching up....

Can you tell what I am missing here????

Thanks for reading this.
Murthy