Complex sentence: He had no former interest in railways, but saw railways as a profitable investment and in 1835 formed the York & North Midland Railway; by the mid 1840s he was also chairman of the Midland Railway, Newcastle & Berwick and Newcastle & Darlington Railways.
Split into simpler sentences: He had no former interest in railways, but saw railways as a profitable investment. In 1835 he formed the York & North Midland Railway; by the mid 1840s he was also chairman of the Midland Railway, Newcastle & Berwick and Newcastle & Darlington Railways.