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known until now where red deep-sea clay of mesozoic age is 
found unmodified as a true clay. Up to this day fossil red deep-sea 
clay in an equally unaltered state of preservation, has been found 
only in one place, viz. the island of Barbados. But here it occurs in 
much younger deposits, viz. in the so-called “oceanic beds” of miocene 
age. Harrison ') describes it as “clays having a peculiarly greasy feel, 
ranging in colour from a dark chocolate-red through various shades 
of red and pink to yellow and greyish white”. 
There is some difference in properties between the varieties 
of the clay of Noil Tobee. The pale red variety displays most 
distinctly the properties of a true clay and is also fractured least by 
joints showing slickensides; it no doubt represents the purest and 
least modified form in which the deep-sea clay here occurs. This 
explains why ‘only this pale red variety has been used by me as a 
material for an analysis as well as for microscopic examination. 
The brown varieties have undergone a more marked modification ; 
they are harder and very much fractured by minor polished fault- 
planes. 
An analysis of a sample of pure, pale red deep-sea clay of Noil 
Tobee, carried out by Prof. H. ter Meuren at Delft, shows its 
chemical composition to be as follows: 
SiO, 57.6 
TiO, 0.6 
Al,O, Foe 
Fe,O, (is 
MnO, trace 
CaO 1:2 
MgO 1.4 
K,O trace 
Na,O 2.3 
H,O below 110° 6.2 10.2 
H,O above 110° 4.0 
99.6 
Trace of Sulphate. 
In order to compare this composition with that of recent deep-sea 
clay and that of the miocene deep-sea clay of Barbados, the results 
of the analyses have to be brought first into intercomparable form 
In the analyses of the numerous samples of recent red deep-sea 
clay, collected by the Challenger-expedition, Brazier has not taken 
into account the salts which had been dissolved in the seawater 
1) A. J. JuKES BROWNE and I. B. Harrison. Lit. 3 p. 189. 
