Complex sentence: Later improvements, such as a midden closet built in Nottingham, used a brick-raised seat above a concave receptacle, to direct excreta toward the centre of the pit--which was lined with cement to prevent leakage into the surrounding soil.
Split into simpler sentences: Later improvements, such as a midden closet built in Nottingham, used a brick-raised seat above a concave receptacle, to direct excreta toward the centre of the pit. The pit was lined with cement to prevent leakage into the surrounding soil.