Gruber and Dorville report crossing the Yellow River two times in their trip trough China, however they do not mention how or where they cross it.
The Yellow River is often so big that it resembles a lake and, after having stood by its shores, we can imagine how hard it could have been to cross it especially if with horses and carriages along!!!!
In 1661, at the time when the Jesuits travelled, there were no bridges built as the first bridge ever to be built was in 1900 by the Germans. They must have therefore cross it trough the water.
Our best guess therefore is that, the second time they had to cross, they crossed in the city of Lanzhou. Lanzhou in fact is the only city in China crossed by the Yellow River, and therefore maybe had better facilities to help the Jesuit go to the other side compared to other wild parts of the river.
Today, the problem does not subsist anymore as Chinese have now built numerous bridges and dams to control the river, which before, because of its power, was equated to a goddess, Mother River.
