Miscellanies. 207 



tufts of " hair salt," native sulphate of magnesia, depending like adhe- 

 ring snowballs from the roof, and periodically detaching themselves by 

 their own increasing weight. Indeed the more solid alabaster orna- 

 ments become at last overgrown, and fall upon the floor of the grotto, 



which was found covered with numbers quite entire, besides fragments 

 of others broken by the fall. It seems to me that geologically these 

 elaborate works of fairy gnomes may be considered in part the effect 

 of unbalanced pressure, either hydrostatic or solid, modifying chemical 

 and mechanical action. While the arch of the dome sustains the solid 

 mass above, any liquid or semi-liquid would be forced through the 

 pores with a power proportionate to the depth of the cave beneath the 

 surface, counter pressure being removed by the cavernous opening. 

 Have the dynamics of deep pressure, liquefying or perhaps solidifyino- 

 gases, &c. received the attention which is due to them in a geological 

 point of view ? Your much obliged friend, John Locke. 



Medical College of Ohio, Cincinnati, Oct. 26, 1841. 



14. Tubular concretions of Iron and Sand from Florida. — The fol- 

 lowing statements respecting the subject named at the head of this ar- 



