GUAHAN. Almost the whole of this island is fringed by reefs, which extend in most parts about a third of a mile from the land. Even where the reefs are most extensive, the water within them is shallow. In several parts there is a navigable channel for boats and canoes within the reefs. In Freycinet's "Hydrog. Mem." there is an account of these reefs, and in the "Atlas," a map on a large scale; coloured red.--ROTA. "L'ile est presque entierement entouree des recifs" (page 212, Freycinet's "Hydrog. Mem."). These reefs project about a quarter of a mile from the shore; coloured red.--TINIAN. THE EASTERN coast is precipitous, and is without reefs; but the western side is fringed like the last island; coloured red.--SAYPAN. The N.E. coast, and likewise the western shores appear to be fringed; but there is a great, irregular, horn-like reef projecting far from this side; coloured red.--FARALLON DE MEDINILLA, appears so regularly and closely fringed in Freycinet's charts, that I have ventured to colour it red, although nothing is said about reefs in the "Hydrographical Memoir." The several islands which form the northern part of the group are volcanic (with the exception perhaps of Torres, which resembles in form the madreporitic island of Medinilla), and appear to be without reefs.--MANGS, however, is described (by Freycinet, page 219, "Hydrog.") from some Spanish charts, as formed of small islands placed "au milieu des nombreux recifs;" and as these reefs in the general chart of the group do not project so much as a mile; and as there is no appearance from a double line, of the existence of deep water within, I have ventured, although with much hesitation, to colour them red. Respecting FOLGER and MARSHALL Islands which lie some way east of the Marianas, I can find out nothing, excepting that they are probably low. Krusenstern says this of Marshall Island; and Folger Island is written with small letters in D'Urville's chart; uncoloured.
BONIN OR ARZOBISPO GROUP.
PEEL Island has been examined by Captain Beechey, to whose kindness I am much indebted for giving me information regarding it: "At Port Lloyd there is a great deal of coral; and the inner harbour is entirely formed by coral-reefs, which extend outside the port along the coast." Captain Beechey, in another part of his letter to me, alludes to the reefs fringing the island in all directions; but at the same time it must be observed that the surf washes the volcanic rocks of the coast in the greater part of its circumference. I do not know whether the other islands of the Archipelago are fringed; I have coloured Peel Island red.--GRAMPUS Island to the eastward, does not appear (Meare's "Voyage," page 95) to have any reefs, nor does ROSARIO Island (from Lutke's chart), which lies to the westward. Respecting the few other islands in this part of the sea, namely the SULPHUR Islands, with an active volcano, and those lying between Bonin and Japan (which are situated near the extreme limit in latitude, at which reefs are formed), I have not been able to find any clear account.
WEST END OF NEW GUINEA.
PORT DORY. From the charts in the "Voyage of the 'Coquille'," it would appear that the coast in this part is fringed by coral-reefs; M. Lesson, however, remarks that the coral is sickly; coloured red.--WAIGIOU. A considerable portion of the northern shores of these islands is seen in the charts (on a large scale) in Freycinet's "Atlas" to be fringed by coral-reefs. Forrest (page 21, "Voyage to New Guinea") alludes to the coral-reefs lining the heads of Piapis Bay; and Horsburgh (volume ii., page 599, 4th edition), speaking of the islands in Dampier Strait, says "sharp coral-rocks line their shores;" coloured red.--In the sea north of these islands, we have GUEDES (or FREEWILL, or ST. DAVID'S), which from the chart given in the 4to edition of Carteret's "Voyage," must be an atoll. Krusenstern says the islets are very low; coloured blue.--CARTERET'S SHOALS, in 2 deg 53' N., are described as circular, with stony points showing all round, with deeper water in the middle; coloured blue.--AIOU; the plan of this group, given in the "Atlas of the Voyage of the 'Astrolabe'," shows that it is an atoll; and, from a chart in Forrest's "Voyage," it appears that there is twelve fathoms within the circular reef; coloured blue.--The S.W. coast of New Guinea appears to be low, muddy, and devoid of reefs.