AND STRUCTURE OF THE BELEMNITE, 397 



the infiltration took place, so that it is not only a vacuity, but 

 a vacuum, that is required for the operation. 



Another hypothesis, equally destitute of philosophic induc- 

 tion, has been proposed to account for the formation of flints ; 

 and because they present an outer crust, although perfectly si- 

 liceous, as white and as opake as the chalk they were lodged in, 

 some speculators have not hesitated to urge the probability of a 

 transmutation ; and Bakewell, (Introd. p. 171. 1813.) gravely 

 tells us, " that as it is a common belief among working miners, 

 that lime and flint are changed into each other, we should not 

 hastily reject the opinions of practical men, but examine whe- 

 ther their opinions be opposed to facts only, or to theories." 

 As well might we listen to the fancies of the practical men at 

 the diamond-mines of Mallevully, who insist that the precious 

 gem is actually generated among the turned-over rubbish ; an 

 idea which, had it been entitled to more attention than the 

 transmutation of the precious metal, must have been traced 

 and determined long ere now. 



On the subject of transmutation, however, Parkinson, vol. L 

 p. 322, observes, " In the present advanced state of chemistry, 

 it is unnecessary to dwell on the opinion which has been en- 

 tertained by M. Patrin, M. de Carosi and others, that chalk 

 undergoes a conversion into flint, except for the sake of re- 

 marking, that all those apparent transmutations which have 

 given rise to this opinion, are easily explained, by supposing a 

 partial introduction of a siliceous fluid in various quantities, 

 into porous calcareous earth." And after a good deal of argu- 

 ment on the subject of this formation, he arrives at the follow- 

 ing supposition, vol. i. p. 328. " Whether it be believed that 

 these several bodies owe their existence to fire or water, it will, 

 I conceive, be equally admitted, that they have been formed 



in 



