102 PBESIDENT*S /IDDEESS. 



tliere can be uo room for doubt ; but it would seem that iu this 

 case the progress has been extremely slow, and that it has been 

 brought about almost in the absence of those causes, such as 

 minor and local oscillations of the crust of the earth producing 

 barriers and affecting climate, on which we are most inclined to 

 depend for the modification of Faunae "'^' Again he boldly writes, 

 " There seems much reason for belieyiug that the great ocean 

 depressions of the present time have persisted through all the 

 later geological periods, back probably as far as the Permian age, 

 and perhaps much farther. If this be so, the length of time 

 during which the vast area occupied by the abyssal fauna has 

 maintained its continuity, and probably great uniformity in es- 

 sential conditions, is incalculable ; that is to say, it cannot in 

 the present state of our knowledge be reduced even approxi- 

 mately to astronomical time."f 



{d) Radiolarian Oo^e. — In certain portions of the greatest 

 depths, where an ordinary red clay might have been expected to 

 occur, deposits are found in which microscopic siliceous organisms 

 play an important part, and the bottom takes its character, not 

 in this case from the Eoraminifera of the surface for these are 

 decomposed before or soon after they reach the bottom, but from 

 the siliceous skeletons of still more minute beings upon which 

 the water has no chemical action. Thus in certain parts of the 

 West and Mid Pacific, between latitudes 10° S. and 20° Is^., an 

 ooze is being formed, which consists mainly of the remains of 

 Eadiolaria. This deposit was found at eight stations, including 

 the deepest sounding which was taken during the voyage of the 

 ^ Challenger^ at a depth of over five miles. | The number of 

 exquisite forms of Polycystina and Acanthystina in this deposit 

 is astonishing, and they equal in beauty and variety the forms iu 

 the well-known Padiolarian fossil deposit in Barbadoes, of which 

 the counterpart has now been found in a recent state. 



(e) Biatomacean Oor,e. — This ooze may be considered to take, 

 in the Antarctic Circle, the place of the Biloculina Ooze of the 



* Keport Scientific Eesults ChaUmger, Vol. I., p. 50. 

 t Voyage of ' Challenger' in the North Atlantic, Vol. II., p. 332. 

 I Sounding 247, 23rd March. 187.5, 4,475 fathoms, Lat. llo 24' N. 



