OCEAlSrOGEAPHY OF THE PACIFIC. 9 



being replaced b}^ another, the temperatures are again recorded at the 

 normal of 35° and above. 



Of the 188 temperatures taken at depths from 3,000 to 4,000 fathoms, 

 10 have been excluded from the computation of averages, for the 

 reasons given above. They are the following: Stations 239 (52°), 244 

 (38°), 251 (38°.9), 257 (60°), 312 (38°.4), 422 (37°. 8), 489 (40°.2), 501 

 (37°.4), 790 (32°), 809 (22°. 9). 



Three temperature observations were made between 4,000 and 5,000 

 fathoms, and two at depths of 5,070 and 5,101 fathoms respectively, 

 all in the abyss southward and eastward of Guam. 



The obvious inference from the above computation is that the tem- 

 perature of that part of the Pacific Ocean covered by this survey falls 

 rather rapidly from the surface to about 600 fathoms, then very slowly 

 to about 2,500 fathoms, where the normal temperature varies but 

 slightly from 35° F. Below 2,500 fathoms there appears to be a 

 slight rise of a fraction of a degree. But it is open to question if 

 this apparent rise may not be due to the effect of the enormous pres- 

 sure of three to five tons to the square inch, at these great depths, 

 upon the instruments. 



CHARACTER OF BOTTOM. 



The character of the bottom indicated on the record by abbrevia- 

 tions, refers onl}^ to the gross appearances of the material recovered 

 in the sounding cup, when fresh from the water. Translated into the 

 terms of the usual scientific classification, the brown mud ('"''br, m.") 

 of the record is generally the red clay of the oceanographer, or rarel}^ 

 volcanic mud from deep water. With few exceptions what is desig- 

 nated coral sand ("co. s.") is globigerina ooze. The rock (R. or r.) 

 has, in every case examined, proved to be fragments of pumice or 

 manganese- iron concretions; the black specks also are almost always 

 particles of manganese iron. Except in the immediate vicinity of a 

 shore, gravel (G. or gvl.) is, in this part of the ocean at least, 

 coarse volcanic debris which has been distributed by wind or wave all 

 over the sea, and has finally found its way to the bottom. The sand 

 (S. or s.) so often noted consists of finer mineral particles from the 

 same source as above-mentioned, except near the shores of islands. 



Other abbreviations than those just given, used in the columns for 

 character of bottom, refer to color, size, etc.^ — bk = black; br = brown; 

 dk — dark; gy = gray; It — light; rd=red; wh = white; y. oryl=yellow; 

 crs = coarse; fn = fine; hrd = hard; rky = rocky. 



