396 ON THE FORMATION OF THE CHALK STRATA, 



Mr Jameson avoids giving any opinion of his own on the 

 formation of Flint, in any of his works on Mineralogy and Geo- 

 logy. He contents himself with stating, " That the beds of flint, 

 and also the tuberose and other shaped masses found in chalk, 

 appear to have been formed at the same time with the chalk." 

 But he adds, " Werner is of opinion that the tuberose, and 

 many other forms, have been formed by infiltration, and 

 conjectures, that during the depositions of chalk, air was evol- 

 ved, which, in endeavouring to escape, formed irregular cavi- 

 ties, which were afterwards filled up by infiltration with flint," 

 System, vol. i. p. 235. 1820. This opinion was also embraced by 

 Kirwan, which is a little remarkable ; for although it be very 

 probable that Werner never had an opportunity of studying 

 the chalk strata, Kirwan must have seen them frequently, and 

 the most simple inspection of the singular regularity with which 

 the flints are disposed in parallel lines to each other, ought at 

 once to have obliterated any such opinion ; for supposing it 

 possible, had air been evolved, to the extent of one single line 

 of these flints, a vacuity, equal to the whole plane of the rock, 

 or nearly so, must have been formed, and the superincumbent 

 strata as it were suspended, — a position not likely to meet 

 with support even from Werner himself, particularly when it 

 must be conceded, that the vacuity so formed must be multi- 

 plied by the number of lines of flint that occur in the bed of 



chalk. 



Besides, it is difficult to suppose that this discharge of 

 air, from a stratum calculated to extend to the thickness of 600 

 feet should have been confined to certain straight lines. Air, to 

 have been evolved, must first have been generated, and, like the 

 nuclei in amygdaloid, must have pervaded the mass irregularly 

 and indiscriminately, throughout its whole extent. It must be 

 observed too, that it was not till after the air was evolved that 



the 





