India Company transferred their headquarters there from Surat. In 1737 the island was captured by the Marathas, all of the Portuguese northern province of Konkan except Damaon, Diu& Silvassa, was frequently invaded by the Maratha navy and army in 1739, Marquis de Pombal formally ceded Greater Bombay to the Peshva ruler of the Maratha Empire in the 1750s. The British occupied Salsette in 1774, and it was formally ceded to the East India Company in the 1782 Treaty of Salbai. In 1782, William Hornby, then Governor of Bombay Province, initiated the project of connecting the islets of Bombay. By 1845 the seven southern islands had been connected to form South Mumbai, with an area of 435 km². Railway viaducts and causeways were built in the 19th century to connect Bombay Island to the mainland via Salsette. The channels separating Mumbai from Salsette and Trombay were bridged by the Sion Causeway in 1803. Accessibility considerably increased after construction of this causeway. Mahim and Bandra were connected by the Mahim Causeway in 1845. These railway lines and roads encouraged wealthier merchants to build villas on Salsette. By 1901, the population of Salsette had increased to 146,993 and the area began to be referred to as Greater Bombay. Geography Salsette is dominated by a central mass of hills surrounded by tidal flats. A number of much smaller islands lay on its western flank. These included Bandra, Khar Danda, Juhu (an old linear sand bar rising above sea level by just a metre or two), Versova, Marve Island, Dharavi Island and Rai Murdhe, all with a knoll core and fringing wave-cut platforms and sandy beaches. These islands seem to have remained separate until as late as 1808. At the time of writing of the old Gazetteer of Thana in 1882, these islands could be reached during low tides by walking across the tidal inlets in between, except for the island of Dharavi in present-day Gorai (not to be confused with the slum near Mahim), which had to be reached by a boat. These are no longer separate, being joined to Salsette via reclamation. The highest point is the conical peak of Kanheri (467 metres) in Borivali National Park on the northern reaches of the island. This national park is the world's biggest within city limits. Geology The island is at the confluence of a number of fault lines. This makes the area earthquake-prone, up