ON THE GEOLOer OF BARBADOS. 



187 



mass. To this category belong a large number of the ' Challenger' 

 soundings which are entered in the Station List either as red clay 

 or Glohigerina ooze .... Probably such mixed radiolarian ooze 

 is very widely distributed in the depths of the ocean, as for example 

 (Pacific stations quoted), also in the South Atlantic (Stations 324, 

 'd2b, 331, 332), and in the tropical Atlantic (Stations 348-352)." ' 



It would seem from this that the classification of the Atlantic 

 Oceanic Deposits requires some revision, and we hope that Dr. John 

 Murray wiU take some note of this point in his forthcoming Eeport 

 on Deep-sea Deposits.^ 



Analyses of some of the mixed radiolarian marls of Barbados are 

 given in the following table : — 



Loss on ignition 



Quartz 



Colloid silica 



Clay 



Iron peroxide and alumina 



Manganese peroxide 



Calcium phosphate , 



Calcium sulphate 



Calcium carbonate 



Lime 



Alkalies and loss in analysis 





Lower Beds. 





Upper Beds. 



1- 



4= &o 



m . 



5§ 



o ^ 



>5 



o 



II 



o^ 



^'^ 



.2 — 





A'^ 





O 



> 



f^ 



o 



O 



O 



3-21 



2-89 



2-lb 



1-72 



4-69 



3^82 



•44 



-02 



-04 



•25 



•05 



•29 



22-22 



19-53 



13^83 



16-73 



18-77 



17-17 



20-20 



15-02 



4-29 



7-67 



21-53 



7-47 



4-49 



3-67 



1-44 



2-78 



3-77 



3^70 



•35 



•06 



2-51 



•81 



•54 



•44 



•51 



•16 



•51 



•68 



•18 



•33 







•40 



•51 



trace 



trace 



46-25 



55^23 



73-33 



67-15 



46-81 



63^64 



1-84 



1-71 



•03 



•82 



2-04 



2^55 



■75 



1^44 



•67 



101 



1-53 



•64 







•27 



•20 





•09 







100-26 



10000 



100-00 



10013 



100^00 



100-05 



(c) The Radiolarian or Siliceous Rocks. — These, which are of great 

 thickness, occur in the middle portion of the Oceanic Deposits ; 

 they contain far less calcium carbonate than the two preceding 

 groups, and, as a rule, much larger quantities of clay. They con- 

 sist essentially of mixtures of clay and of colloid silica in the 

 form of skeletons of radiolaria, of diatomaceae, and of sponge- 

 spicules, organisms which in places constitute by far the greater 

 part of the bulk of the rock. Certain of the beds also contain con- 

 siderable quantities of calcium carbonate, generally present in a 



^ ' Challenger ' Eeports, vol. xviii. pt. i. p. clvii. 



'^ [Dr. Murray informs us that he cannot accept Prof. Haeckel's classification 

 of oozes; but we think the discrepancy between them would be greatly dimi- 

 nished if Dr. Murray had taken account of the fragments of siliceous organisms 

 separately instead of including them under the bead of ' fine washings.' We 

 note that the deposits at Stations 270, 271, 246, and 284, described in the 

 'Challenger' Report as Glohigerina -ooze, appear to be very similar in character 

 and composition to this group of Barbados rocks, and they all come from about 

 2000 fathoms.— J. B. H. & A. J. J.-B., Feb. 16th, 1892.] 



