Stephen Colwell's The Five Cotton States and New York (1861). It's available at Google Books.
Kettell says that the Northern states are economically dependent on the Southern states. Colwell contents that the five Deep South states are very dependent on New York City economically.
Some have assumed that Colwell was also pro-slavery because his thesis pointed to the interdependence of the two regions, as Kettell's did, but I haven't found anything to support that.
You can find Kettell favorably reviewed in the secessionist DeBow's Review:
x: "Stephen Colwell's The Five Cotton States and New York "
x: Link to Sherman DeBow's review
Thanks, I've added all three links to "favorites" for future reference.
In the mean time, reading the first few paragraphs of Kettell's book shows he's making a full-throated defense of slavery, something which I doubt if anyone here would accept.
And it confirms my suspicion that when referring to "the South", he means all fifteen slave-states, including the four border states, and therein lies one deep flaw in his analysis.
A more accurate analysis would divide "the South" into three general sections: Deep (near 50% slaves), Upper ( about 25% slaves) and Border (less than 10% slaves).
Then we would find that agricultural and other achievements he credits to "the South" come mostly from Border and Upper South states, while the Deep South focused almost entirely on producing cash crops for export.
I also note with concern that Kettell claims: at the time of the Revolutionary War the South wanted to abolish their slavery, but the North wouldn't permit it.
Surely, that is a fantasy worthy of its own "land" in Disney World! ;-)