Depends on the aim 11:12 Sep 28, 2009
If the aim is good style rather than a literal translation, then I would suggest that:
"In the 1900's the same amount could be transported in twelve trainloads consisting of thirty wagons, each of which carried the same weight as did one hundred and twenty-five animals."
is the most elegant way of expressing this idea, and I would respectfully suggest that the use of "return journeys" would require a more complex syntactic structure, and would therefore be less elegant. Just my opinion. | 
The translation workplace 
