Sounds like you are, in reality, trying to segregate networks. If that is the case, why not simply install a 3rd and 4th ... nth network card in e-smith1 and simply assign a different subnet mask to each of them? That way, all persons on each subnet can get out to the internet but are only local to their particular network segment.
If however, you are determined to have 2 or more boxes, I have sucessfully done this too.
SWITCH for better security
or
Internet >> NIC1 Box1 >> NIC2 >> HUB >> NIC1 Box2 >> NIC2 >> LAN2
V
V
LAN1
LAN1 Netmask 255.255.240.0
LAN2 Netmask 255.255.255.0
or
LAN1 Address range 192.168.n.n
LAN2 Address range 10.0.n.n
Looking at the above diagram, it makes more sense to use my original suggestion and simply add extra network cards to the 1st box.