96 J. D. Dana — Origin of Coral Reefs and Islands. 



The above facts are sufficient to authorize the drawing of the 

 bathymetric lines for 1000, 2000 and 3000 fathoms quite 

 closely about the islands of the Phoenix Group, and to give the 

 areas a northwest-southeast elongation, corresponding with 

 that of the neighboring Pacific islands to the west, as on the 

 accompanying map, Plate II.* 



It follows from the above mentioned facts that the deep-water 

 areas adjoining the Phoenix Group, named provisionally by 

 Petermannf the "Hilgard depths" and the "Miller depths," are 

 parts of one large area 1200 miles broad. The greatest depth 

 obtained in the part of the area southwest of the group (400 

 miles broad) is 3305 fathoms, and in the part northeast, 3448 

 fathoms. 



Again: the soundings of the Tuscarora of 1875 here cited, 

 taken in connection with those of the same vessel in 1874, under 

 Commander George F. Belknap, along a line from the Sandwich 

 Islands westward to Japan (mostly between the parallels of 20° 

 and 25°), suggest the further conclusion : that the deep-sea area of 

 the central equatorial Pacific, in which the Phoenix Islands stand, 

 extends northwestward toward Japan, and that it was crossed by 

 the Tuscarora between 171° E. and 150° E, where were found 

 depths from 3009 to 3273 fathoms (with some alternations of 

 smaller depths that isolated areas may account for). It is also 

 probable that the soundings of the Challenger east of Japan be- 

 tween 153° E. and 143° E. and just northwest of those of the 

 Tuscarora, were within the same deep-sea area. If this be so, a 

 long deep-water area or trough extends from Japan southeast- 



* The line on the map for 1000 fathoms is a simple dotted line ; that for 2000 

 fathoms, ; for 3.000 fathoms, . 



f Geogr. Mittheil., 1877, page 125 and plate 7. The deep areas along the lines 

 of soundings, were named by Petermann on his very valuable bathymetric map 

 of the Pacific simply to facilitate reference. 



The bathymetric lines about the islands, on the accompanying map, Plate 

 II, have an unreasonable degree of regularity. But with no facts to indicate 

 the actual irregularities, none could be reasonably introduced. The trends 

 given them are the same as on Petermann's map. The actual steepness of slope 

 is probably not exaggerated for either of the islands. If similar slopes ex- 

 ist about the smaller islands in other parts of the ocean, the final bathymetric 

 map of the Pacific will have a very different aspect from that presented by the 

 maps hitherto published, and the Central Pacific a much greater mean depth. 

 About Wakes Island, a small atoll in latitude 19° 11', standing alone in the ocean 

 six degrees north of the Ealick Chain, the width of the area enclosed by the 2000 

 fathom line, as drawn on Petermann's bathymetric map, is nearly 100 nautical 

 miles, while, in view of facts at the Phoenix Group, the actual width is probably 

 not over 10 or 15 miles. 



With but four fines of soundings for the part of the great Pacific Ocean, 

 within 35 degrees of the equator, the author of a bathymetric map has to rely 

 chiefly on his judgment or conjecture for the larger part of the surface. There 

 are many great problems in physical, geological and biological science that would 

 be elucidated by the facts which a thorough bathymetric survey of the ocean would 

 afford ; and the work is large and important enough to call for aid from each of 

 the great nations of the world. Thus far, for the Pacific Ocean, the United States 

 is first in the amount of work done. 



