I know I have seen lists of destinations for kaolin clay that were routed via the Southern (they virtually all originated on the Central of Georgia) but, of course, I cannot find them off hand. Here is a Google drive link to two short documents. The second covers routings off the Central that did not use the Southern not long after the ICC directed the Southern to take over the CofG.
They were part of the internal correspondence, including the Sandersville Railroad and kaolin shippers, as the Southern was trying to handle more of the traffic. Problem was, the kaolin industry was growing very quickly, the Central’s fleet of covered hoppers was old and inadequate and kaolin shippers were moving away from loading bags of product in box cars and into covered hoppers.
Southern ordered a large number of 4,000 cu ft aluminum covered hoppers from Magor. When the railroad asked for a larger capacity covered hopper, Magor developed what became the “Big John” car by essentially stretching that design. My intention was to kit bash one of the ExactRail Big Johns “back” to one of the earlier cars. Although I have a number of Big Johns on the (Asheville) layout, E-R did such a beautiful job on them (with many (!) Magor drawings from the SRHA archives), I just do not have the heart to cut one of them down.
Ike
As info to anyone interested in the Central of Georgia, the archives contain many CofG freight car drawings and documents.