THE DEPTH AND MARINE DEPOSITS OF THE PACIFIC OCEAN. 23 



tively 40, 65, 58, 72, and 65 per cent of calcium carbonate, and also in one 

 sample containing 33 per cent of calcium carbonate, which might be called 

 a Red Clay. The samples were dredged in stations situated as follows : — 



These deposits have a truly pdagic character, having been formed far fbom 

 land, so that th.e mineral elements contained in them have mostly a volcanic 

 origin. 



Reference to the descriptions will show the widespread distribution 

 of such minerals as volcanic glass,, palagonite, pumice, etc., while augite and 

 felspars have almost certainly the same origin. 



From the foregoing facts it will be seen that when a Globigerina Ooze 

 forms far from land, its nature, when calcareous organisms are not taken 

 into account, is very similar to that of a Red Clay, not only as regards its 

 chemical composition, but also as regards secondary products formed in situ. 

 It may be added that the minute calcareous coccoliths and rhabdolitlis are 

 nearly always represented, but never in large amount, so that they have 

 not been indicated in the descriptions. 



In Red Clay the minerals had to be put down as " traces " in the great 

 majority of the descriptions; the highest percentage observed is one of 4 

 per cent at Station 4658, and even then the 4 per cent is nearly wholly 

 represented by manganese grains. Actual mineral particles, volcanic or 

 continental, never make up an appreciable amount as such, but, of course, 

 if one could devise a means of separating and estimating the very minute 

 particles that pass away in decantation together with the " fine washings," 

 the relative percentages would be widely different. In the present study 

 the mineral particles together with the siliceous organisms were always dried 

 and weighed, and the relative proportions of siliceous organisms and minerals 

 roughly estimated by counting the particles spread on a microscopic slide. 

 When the weight of the residue was so small as to fall within the limits of 

 experimental errors, minerals and siliceous organisms had to be estimated as 

 traces. 



