Confirmation of cipher?

[Jack Brennan]

Hello,

When one signs a message GnuGPG will add "Hash:SHA1" or your preferred 
hash at the start of the message.

However a similar line of text isn't available with an encrypted text 
block. Is the reason for this to hide as much
information as possible from a possible attacker?

Is there any way to confidently identify the encryption algorithm used 
with a GPG encrypted text block?

Many thanks

Jack Brennan.