On the production of Crystals. 43 



No remains which can be satisfactorily referred to the 

 Reptilia, have been discovered in the crag. 



The remains of fish are very abundantly dispersed through- 

 out the red and mammiferous crag, but are far less numerous 

 in the coralline. Occurring only as detached bones, it is not 

 very easy to arrive at any very satisfactory results in their 

 examination. Their distribution throughout the three depo- 

 sits is as follows. — 



Mammiferous Crag. — Bones of the genus Platax, in im- 

 mense numbers ; several species of the genus Rata ; ver- 

 tebra of genera totally new to Agassiz. 

 Red Crag. — Teeth of Carcharias, several species, including 

 C. Megalodon of Agassiz ; palates of Myliobatis ; teeth 

 of Lanina, Notidanis, Galeus. 

 Coralline Crag. Genera undetermined. 



Art. XI. Remarks on the production of Crystals. By John 

 Morris, Esq. 



The origin of the various combinations of the metallic and 

 earthy bodies familiar to the geologist, in the primary and se- 

 condary rocks, will become more elucidated in proportion as 

 the chemist investigates their composition. Nature, though 

 silent has not been inactive, during the long succession of 

 ages intervening since their deposition. Mechanical action 

 is evident in the consolidation of shales and clays by pressure 

 — in the conversion of sand into sandstone — in the hardening 

 of calcareous marls — the deposition of chert, &c. There is 

 also extensive evidence of chemical action ; from an attentive 

 examination of the contents of our secondary strata, . I have 

 been led to the opinion of the animal origin of some of the 

 sulphur ; we find it combined in the state of sulphuret and 

 sulphate, through all the argillaceous deposits — in the clay 

 slate — lias marls and clays — the Oxford and Kimmeridge 

 clays — in the gault and London clay, and sparingly in the 

 oolites and chalk ; — the two latter contain a smaller propor- 

 tion of iron scattered through their substance, whilst in the 

 former, it not only exists in great quantities, but in a finely 

 divided state. The abundance of fossil remains in these for- 

 mations, especially of the testaceous tribes, is well known, 

 and it is probable that many of the animals were entombed 

 with their shelly covering ; the decomposition of all this ani- 

 mal matter has produced quantities of sulphuretted hydrogen, 

 which, in a nascent state, may have united with the particles 

 of iron, and converted them into a sulphuret, or at certain 



