beach, county of Dorset, England, that stretches 18 miles (29 km) from Bridport to the Isle of Portland. One of the best-known natural features in Britain, it consists of shingle (pebbles), 98.5 percent of which is hard flint or chert rock. From Abbotsbury to Portland (12 miles 【19 km】) the beach is separated from the mainland by a lagoon. The most remarkable feature of the beach is the lateral sorting of the shingle: at the northwestern end it is pea-sized, and at Portland the average diameter of the stones is 2 inches (5 cm).