308 Dr Fleming on the Neptunian Formation 



known to the chemist, and only appear in the results which 

 have taken place. 



The occurrence of flint, in concretions arranged parallel to 

 the seams of stratification in chalk, and the analogous position 

 of menilite in adhesive slate in gypsum, intimate the existence 

 of a condition in which siliceous and calcareous matters have 

 been influenced by similar circumstances. In reference to 

 the chalk-beds, it may be supposed that the substances were 

 deposited in the state of mud, which has been since changed 

 into flint and chalk. That such a process of lapidification 

 has been going on in the bed, is demonstrated by the occur- 

 rence of shells, originally of an imbricated structure and com- 

 pact fracture, now exhibiting the granular structure, or foliat- 

 ed fracture of marble or calcareous spar ; yet retaining dis- 

 tinct traces of the albuminous animal matter. The fusion of 

 the siliceous mud by heat, and its consequent conversion into 

 flint, as has been conjectured to have taken place, by Mr 

 Allan in his valuable paper " On the Formation of the Chalk 

 Strata, and Structure of the Belemnite,"" Edin. Phil. Trans, 

 ix. 416, is a view of the matter, the incorrectness of which is 

 demonstrated by the appearances exhibited. How is it possi- 

 ble to conceive the application of any heat capable of fusing 

 the flint distributed in layers throughout the bed, which would 

 not fuse, at the same time, the far more fusible surrounding 

 chalk ? Yet the chalk in immediate contact with the flint is 

 earthy, and does not exhibit any one of those appearances to 

 be looked for in fused carbonate of lime. It is equally im- 

 possible to conceive the cavity of an echinus filled with flint in 

 fusion, while its thin calcareous, and consequently fusible crust, 

 shall be capable of retaining all the delicate arrangement of its 

 parts, preserving unobliterated, the sutures, the tubercles, and 

 the minute bronchial pores. Mr Allan seems to have been 

 aware of all these objections, but he has been unfortunate in 

 his attempt to obviate them. " But we have," he remarks, 

 " many such anomalies in nature ; the base of many of the 

 trap rocks presents as little the appearance of crystallization 

 as even the softest chalk, and yet it is now admitted, even by 

 the pupils of the Freyberg School, to be of igneous origin," 

 p. 417. I was not a little amused, by thus Avitnessing Mr 



