Coral Reefs and Islands, 151 



south of it and the other east (the two directions at right 

 angles to one another and the latter not diverging far from 

 the trend of the other islands of the Union group), give the 

 slopes 1:7 and 1:13. Off Danger Island, as Commander 

 Miller's Report states *, the depth of 660 fathoms was obtained 

 half a mile (nautical) off the south-west corner of the reef 

 near south-east island, and 985 fathoms one mile east of the 

 reef — corresponding to slopes 1:1 and 1:0*75. 1: 1 is a 

 steeper slope than occurs even in small dry-made cinder- 

 cones ; and 1 : 0*75 (53° 8') is steeper still. 



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, corre- 

 sponding with that of the neighbouring Pacific islands to the 

 west, as on the accompanying map, Plate I.f 



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

 water areas adjoining the Phoenix group, named provision- 

 ally by Petermann % the " Hilgard depths " and the " Miller 

 depths," are parts of one large area 1200 miles broad. The 



* I am indebted for the soundings about Danger Islands to Commander 

 J. R. Bartlett, Superintendent of the U. S. Hydrographical Bureau. 

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



for 2000 fathoms, ; for 3000 fathoms, . 



X 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 I.) 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 Peterinann's map. The actual 

 steepness of slope is probably not exaggerated for either of the islands. 

 If similar slopes exist 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 Ralick 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 lines 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. 



