10 FERGUSON. 



NIN BAY. 



The bay on which the little town of Mandaon is situated consists of 

 three different bodies of water, Nin Bay, Loog Bay, and Port Mandaon. 

 The outer of these, Nin Baj', has regular outlines and shoals oi? very 

 evenly. At its head is a broad line of beach with lowland back of 

 it. The town of Mandaon is at the southeast end of this. The water 

 is very shallow along this beach and at low tide mud flats extend out 

 for a considerable distance. Southwestward, following the long axis 

 of the bay, the water shoals off very reg^ilarly at the rate of about 3 

 meters per kilometer. A line drawn across the entrance of the bay, 

 from Pagbulungan Point to the eastern end of Puro Island, shows a 

 fairly constant depth of about 17 meters and crosses the only shoals in 

 the bay, Nin and Ochoa banks, which show a minimum depth of 3 

 meters. However, on the northwestern and southeastern sides of the 

 bay, the water deepens much more rapidly, depths of over 15 meters 

 being shown on the chart at distances of less than 500 meters from the 

 two points, showing that the present shallowness of the bay is diie to 

 silting up from its head. The sedimentarj^ escarpment already described 

 extends along the northeast shore to Pagbulungan Point. A broken 

 range of basalt hills exists to the southeast of the bay. The range, 

 beginning at Mount Tuitong above Mandaon, extends through the 

 Gapus Hills (elevation, 144 meters), Puro Island (elevation, 162 meters), 

 and Kamasusu Island (elevation, 159 meters), being broken by deep 

 channels between Itfandaon and the Gapus Peninsula, and between Puro 

 and Kamasusu' Islands, a shallow channel being found between Puro 

 Island and the mainland. The basalt is strongly magnetic, so much 

 so that magnetic observations taken in 1895 for the center of Nin Bay 

 showed an eastward declination of 3° 47' instead of the normal eastward 

 declination of less than one degree. 



Loog Bay is south of Nin Bay and connected with it by the two inlets 

 at the ends of Puro Island. Like its northern neighbor it has a north- 

 easterly direction. Its maximum depth is 15 meters at the entrance, 

 and it shoals rather more rapidly toward its head than Nin Bay. The 

 basalt hills of Kamasusu arid Puro Islands on its northern side show 

 their steepest faces in this direction and the deepest part of the bay is 

 close to these islands. The channel between the two is about 400 meters 

 wide and reaches a depth of 17 meters, whereas the channel between 

 Puro and the mainland although slightly wider, has a greatest depth of 

 only 4 meters, a wide bench with a maximum depth of 3 meters joining 

 the island with Gapus Peninsula. The western side of Puro Island 

 is fringed with mangroves and the miidflats extend out for some distance. 

 At the head of Loog Bay is a broad stretch of beach and mud flat, and 

 the mangrove swamp extending south from Port Mandaon forms the 

 greater part of the isthmus. The south shore of the bay is low-lying 



