50 TOILERS IN THE SEA. 



slight grey colour, due, probably, to the decomposing 

 organic matter, becomes more pronounced, while 

 perfect shells of Globigerina almost entirely disappear, 

 fragments become smaller, and calcareous mud, 

 structureless and in a fine state of division, is in 

 greatly preponderating proportion. One can have 

 no doubt, on examining this sediment, that it is 

 formed in the main by the accumulation and disin- 

 tegration of the shells of Globigerina ; the shells 

 fresh, whole, and living, in the surface layer of the 

 deposit, and in the lower layers dead, and gradually 

 crumbling down by the decomposition of their 

 organic cement, and by the pressure of the layers 

 above ; an animal formation, in fact, being formed 

 very much in the same way as in the accumulation 

 of vegetable matter in a peat-bog ; by life and 

 growth above, and death, retarded decomposition, 

 and compression beneath." x 



The foregoing extract, for which reason we have 

 given it in full, shows some points of remarkable 

 similarity between the Atlantic ooze and deposited 

 chalk. There may be differences in chemical com- 

 position, but, when submitted to microscopical 

 examination the resemblances are so great, or, as 

 Sir Wyville Thomson says, u sufficiently striking to 

 place it beyond a doubt that the chalk of the creta- 



" Depths of the Sea," p. 409. 



