I hope this will be useful to other newbies.

If you're on a lan with a bunch of different physical segments, it is
not enough to simply enter your default gateway in /etc/mygate. I hope
someone knowledgeable will correct me if I am wrong, but it is as if you
have to specifically tell a machine to use a gateway when it _looks_
like there is no need to use a gateway.

Perhaps it is not the most elegant way, but it works to use the 'route
add' command. I'm not sure what is the standard place to enter it, but I
stuck it in /etc/rc. An entry referencing the proxy external to my own
firewall has allowed me to connect with it.

Sincere thanks to the two people who did their best to help me.

henry nelson