“During the 18th century, it was cheaper to ship a ton of goods the width of the Atlantic than to cart them one hundred miles overland”.
Can anyone point me to a reference that would confirm or refute this?
What kind of “overland” are you talking about? North American? English? Central European?
Sounds like a dreadful misuse of statistics. Compare shipping goods over the Atlantic to carting them over the Rockies, and you get a better perspective. (Not directed at the OP, but at the source.) Methods and routes of getting over or around the Alps is an essential part of European history.
Perhaps it’s a reference to the Suez Canal, which is about 100 miles long and completed in the 19th century. Before it was completed, ships used to sail all the way around Africa (about 5000 miles extra) rather than cart the cargo over 100 miles of land.
p.s. What I just said doesn’t really prove the factoid. It just means that adding 5000 miles to a voyage was cheaper than unloading the cargo, carting it 100 miles and reloading it on a different ship - which also means having to own an extra ship and having 2 extra ports to operate from.