Sometimes climatic advantages are reinforced by a favorable focal point, which brings the profits of trade to supplement those of agriculture.  This factor of distributing and exporting center has undoubtedly contributed to the prosperity and population of Reunion, Mahe, Mauritius and Zanzibar, as it did formerly to that of ancient Rhodes and modern St. Thomas at the angle of the Antilles.  Barbadoes, by reason of its outpost location to the east of the Windward Isles, is the first to catch incoming vessels from England, and is therefore a focus of steamship lines and a distributing point for the southern archipelago, so that we find here the greatest density of any island in the West Indies.[955] The 9405 inhabitants of Charlotte Amalie on St. Thomas and the 15,000 of Willemsted on Curacao give these also a characteristic insular density.  Samos, blessed with good soil, an excellent position on Aegean maritime routes, and virtual autonomy, supports a population of 300 to the square mile.[956]

Focal location alone can often achieve this density.  Syros, one of the smallest and by nature the most barren of the Cyclades, though well tilled is the great commercial and shipping center of the Aegean, and has in Hermupolis with its 17,700 population by far the largest town of the archipelago.[957] This development has come since Greece achieved its independence.  It reminds us of the distinction and doubtless also population that belonged to Delos in ancient days.  Advantageous commercial location and density of population characterize Kilwauru and Singapore at the east and west extremities of the Malay Archipelago.  The Bahrein Islands, which England has acquired in the Persian Gulf, serve as an emporium of trade with eastern Arabia and have a local wealth in their pearl fisheries.  These facts account for the 68,000 inhabitants dwelling on their 240 square miles (600 square kilometers) of sterile surface.[958]

[Sidenote:  Overflow of island population to the mainland.]

The concentration of population in these favored spots of land with inelastic boundaries, and the tendency of that population to increase under the stimulating, interactive life make the restriction of area soon felt.  For this reason, so many colonies which are started on inshore islets from motives of protection have to be transferred to the mainland to insure a food supply.  A settlement of Huguenots, made in 1535 on an island in the harbor of Rio Janeiro, found its base too small for cultivation, but feared the attack of the hostile Indians and Portuguese on the mainland.  After three years of a struggling existence, it fell a prey to the Portuguese,[959] De Monts’ short-lived colony on an island in the mouth of the St. Croix River in 1604 had an excellent site for defence, but was cut off by the drifting ice in winter from mainland supplies of wood, water and game, while no cultivation was possible in the sandy soil.[960]