MACKIE — THOUGHTS ON DOVER CLIFFS. 



285 



while these parasites lived, grew, and died before they were embedded 

 in the slowly accumulating mud. 



In my former collection, now the property of the town of Folke- 

 stone, there is a fossil oyster — by no means an uncommon example — 

 having a second oyster attached to the inside of one valve. This 

 specimen could neither have been suddenly enveloped nor even em- 

 bedded shortly after death. Decomposition and entire disappearance 

 of the animal must have taken place before the smaller oyster could 

 have fixed its residence. This too must have died, and the connect- 

 ing ligament of its valves have decayed, before the detached valve 

 was worked away ; and both oysters, old and young, embedded to- 

 gether. 



Of all the numerous specimens of the prickly sea-urchin tribe from 

 the Cretaceous rocks, to find one with any of the spines attached is 

 rare, while the test itself is often coated with Serpulse and other para- 

 sitic forms. In such cases also, not only death and the subsequent 

 decomposition of the muscular integument must have happened, but 

 the spine-divested body-shells of the Echinoderms must have remained 

 exposed on the sea-bottom, while these extraneous beings lived out 

 the full periods of their existences. 



The extremely slow formation of the Chalk is further displayed in 

 its microscopic structure. 



Amongst all the wonders which geology has revealed, there is no- 

 thing perhaps more wonderful than that the very substance of solid 

 rocks should be composed of the remains of the minutest animalcules. 

 Yet such the microscope has shown ; and chalk is one of the nume- 

 rous instances. 



Every atom, each individual particle, was once part of a living crea- 

 ture. Thousands of miles of solid rock, hundreds of feet in thickness, 

 form thus a mighty tumulus of fragile invisible beings, — the cemetery 

 of the unseen; beings not suddenly nor violently destroyed, but 

 that naturally sported away their lives above the dead ones of their 

 race, a million of whose carcases scarcely formed a cubic inch of the 

 Cretaceous ocean's mud. 



Beautifully and truly has it been said, that " the majesty of God 

 appeareth not less in small things than in great, and as it exceedeth 

 human sense in the immensity of the Universe, so doth it also in 

 the smallness of the parts thereof." The deposits of the Cretaceous 

 period are very extensive, and are found in Belgium, Holland, Prussia, 

 and over the greatest portion of Europe. A map of the divisional 



