tufts of “ hair salt,” native sulphate of magnesia, depending like adhe- 
ring snowballs from the roof, and periodicall detaching themselves by 
e 
their own increasing weight. Indeed the more solid alabaster orna- 
ments become at last overgrown, and fall upon the floor of the grotto, 
7, Wy 
Yi 
which was ovina covered with numbers quite entire, besides a haga 
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 solidifying 
gases, &c. received the attention which is due to them in a geological 
point of view? Your much obliged friend, Joun Locke. 
~ Medical College of Ohio, Cincinnati, Oct. 26, 1841. ve 
» 14. Tubular concretions of Iron and Sand from Florida.-—The fol- 
lowing statements respecting the subject ped ab tie head of this ar- 
