Complex sentence: Joseph Damer acquired it in the 18th century and a large building was constructed in 1751, and called the Dorchester House in 1792 after Damer became the Earl of Dorchester.
Split into simpler sentences: Joseph Damer acquired it in the 18th century and a large building was constructed in 1751. It was named Dorchester House in 1792 after Damer became the Earl of Dorchester.