Mesozoic and Ca'nozoic Geology and Paloiontoloyy. 237 



amouDt of calcareous matter, and, under the microscope, a smaller num- 

 ber of foramiuifera. Now calcareous shells of foraminifera were entirely 

 wanting, and the onl}' organisms which could be detected, after wash- 

 ing over and sifting tlie whole of the mud with the greatest care, were 

 three or four tests of foraminifera of the cristellarian series, made up 

 apparently of particles of the same red mud. The shells and spines of 

 surface animals were almost entirely wanting; and this is the more 

 remarkable, as the clay-mud was excessivel3' fine, remaining for days 

 suspended in the water, looking in color and consistence exactly like 

 chocolate, indicating therefore an almost total absence of movement in 

 the water of the sea where it is being deposited. When at length it 

 settles, it forms a perfectl}' smooth red- brown paste, without the least 

 feeling of grittiuess between the fingers, as if it had been levigated 

 with exti'cme care for a process in some refined art. On analysis it is 

 almost pure clay, a silicate of alumina and the sesquioxide of iron, 

 with a small quantity of manganese." 



After a great deal of experience in sea dredging, he says: 



"According to our present experience, the globigerina ooze is 

 limited in the open oceans — such as the Atlantic, the Southern sea, and 

 the Pacific — to water of a certain depth, the extreme limit of the pure 

 characteristic lormation being placed at a depth of somewhere about 

 2,250 fathoms. 



" Crossing from these shallower regions occupied b}' the ooze into 

 deeper soundings, we find universally that the calcareous formation 

 gradually passes into, and is finall\' replaced by an extremely fine pure 

 clay, which occupies, speaking generally, all depths below 2,500 

 fathoms, and consists almost entirely of a silicate of the red oxide of 

 iron and alumina. The clay ic often mixed with other inorganic mat- 

 ter, particularlj" with particles, graduating up to the size of large nod- 

 ules, of peroxide of manganese; and in volcanic regions, or in their 

 neighborhood, with fragments of pumice. The transition is very slow, 

 and extends over several hundred fathoms of increasing depth; the 

 shells gradually lose their sharpness of outline, assume a kind of ' rot- 

 ten' look and a brownish color, and become more and more mixed with 

 a fine amorphous red-brown powder, which increases steadil}'^ in pro- 

 portion until the lime has almost entirelj' disappeared. This brown 

 matter is in the finest possible state of subdivision, so fine that when, 

 after sifting it to separate any organisms it might contain, we put it into 

 jars to settle it remained for days in suspension. 



" We recognize the gray ooze as, in most cases, an intermediate stage 

 between the globigerina ooze and the red clay; we find that on one 



