96 



itself, I never found any; but, in some basalts very near 

 it, on the west side, I have met with it: these had fal- 

 len from an upper stratum. 



A most respectable correspondent, to whom I com- 

 municated this fact, as new in natural history, tells 

 me, he suspects, the water- passed in by percolation. 

 Determined to pay all attention to any thing, suggested 

 from such high authority, I took my friend, Mr. Joy, to 

 the spot, where I used to find the water in the greatest 

 abundance (Ballylagan). We broke several stones, and, 

 where we found water, observed, that, at first, it wet the 

 whole fracture evenly; but, as it evaporated gradually, 

 the wet was confined to cracks, diverging from the little 

 cavity that had contained the Avater. These, therefore, 

 we at fii-st supposed, must have been the passages, 

 through which the water had made its way: but, on 

 attentively examining the cracks, we perceived, that, as 

 they radiated from the cavity, they diminished in breadth, 

 and finally terminated in the solid stone; of course, that 

 the water had not come in by them. 



Another fact seems conclusive against percolation. I 

 never found, in our basalt, any cavities, but those which 

 contained water, or which bore evident marks of having 

 been once filled with it. We have, therefore, this alter- 

 native: 



Either the water first made its way through the com- 

 pact tissue of the basalt, then collected, and dilated it- 

 self with such force, as to form rounded cavities, often 



larger 



