food supplies like cattle, wheat etc can't be connected.
They are "localized resource"
if it is near the city, the population can work there to get the bonus.
they just provide advantage for local population.
it is therefore important to build city near them (not on them)
horse needs to be connected by road to 1 of your city.
if there is a road that is connected to the capital, AND
ALL city connected to the capital will enjoy the resource too.
They are "non localized resource" important to contruction of high tech stuff!
note that you can ony get a resource IF it is WITHIN your borders.
IF the resource is outside, you will need to use & lose a worker and build a colony.
remember that a conlony doesn't expand your borders, and you will need to guard it
so if they enemy plot a city next to the colony, you will lose the resource and colony!
silk are others help to keep the population happy.
always try as hard as possible to connect as many type for such resources to the capital,
They are "non localized resource" and each type of them make 1 population of the connected city happy
for the same "non localized resource", each civ only need 1 unit,
but capture as many of them as possible to trade with others for profit.
this is just a rough idea.
READ THE MANUAL
