Original sentence: The first three stages Needham calls "proto-gunpowders," advocating his view of the evolution of low-nitrate, low carbon proto-gunpowders into modern forms of gunpowder with higher levels of nitrate and carbon in the form of charcoal.. After the third stage (in the 11th century), a formula closer to that of modern gunpowder, with higher levels of saltpeter, takes form
Edited sentence: The first three stages are considered low-nitrate, low-carbon powders and thus specified as "proto-gunpowders," showing the evolution of low-nitrate, low carbon proto-gunpowders into modern forms of gunpowder with higher levels of nitrate and carbon in the form of charcoal.. After the third stage (in the 11th century), a formula closer to that of modern gunpowder, with higher levels of saltpeter, takes form