Johann Peter Lange (1802 - 1884), was a German Calvinist theologian. Although he was of peasant origin, he was able to studied theology at Bonn and eventually in 1854 settled at Bonn as professor of theology. There he came to be called the poetical theologian par excellence.
He was a dogmatic writer and his brilliance comes out in his commentaries on the Bible, which are collected here.
This app version of his commentary is cross-linked to the World English Bible.
Note that the files are quite large and may take time to load.