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phy of the natives, it is both a stone and an ani- 

 mal. It is found in the sand, where it is mo- 

 tionless ; but placed singly on a polished sur- 

 face, for instance on a pewter or earthen plate, 

 it moves when excited by lemon juice. Placed 

 in the eye, the pretended animal turns on itself, 

 and expels every other foreign substance, that 

 has been accidentally introduced. At the new 

 salt works, and at the village of Maniquarez, 

 the stones of the eyes ? were offered us by hun- 

 dreds, and the natives were earnest to show us 

 the experiment of the lemon juice. They wished 

 to put sand into our eyes, in order that we might 

 ourselves try the efficacy of the remedy. It was 

 easy to see, that these stones are thin and po- 

 rous opercula, which have formed part of small 

 univalve shells. Their diameter varies from one 

 to four lines. One of their two surfaces is plane, 

 and the other convex. These calcareous oper- 

 cula effervesce with lemon juice, and put them- 

 selves in motion in proportion as the carbonic 

 acid is disengaged. By the effect of a similar 

 reaction, loaves placed in an oven move some- 

 times in a horizontal plane ; a phenomenon that 

 has given occasion, in Europe, to the popular 

 prejudice of enchanted ovens. The piedras de 

 los ojos, introduced into the eye, act like small 



* They are found in the greatest abundance near the 

 battery at the point of Cape Araya. 



