Foreign Literature and Science. 395 



size. M. del Nero, delighted to find himself in possession 

 of one of the finest crystals of hyaline quartz, which the 

 country had produced, proceeded to disengage it at the base ; 

 but to his inexpx'essible surprise, he found it elastic and of 

 a pasty consistence, taking any form his hand gave it, but 

 rapidly growing harder, and soon becoming quite solid, and 

 assuming the appearance of calcedony or porcelain. In a 

 moment of vexat/on he threw it among the rubbish, and 

 thus lost a specimen which would have been highly inter- 

 esting to the curious. 



He assured me, (and his assertion was repeated by other 

 witnesses worthy of confidence) that facts of the same na- 

 ture had occurred to them more than once. I made him 

 promise that if another such instance should present, he 

 would impress his seal upon the crystal and send it to me 

 at Florence, with the water which the cavity might contain. 

 Professor Pictet remarked that he saw at Florence in the 

 collection of Dr. Targimi, a rock crystal containing several 

 drops of petroleum in small cavities without communication 

 with each other or with the air. One of them was open- 

 ed to satisfy Sir H. Davy, when at Florence, of the nature 

 of its liquid contents. Bib. Univ. 



40. ji simple but interesting galvanic instrument is descri- 

 bed by Professor De la Rive of Geneva in the Bib. Univ. 

 of December last. A strip of zinc about the sixth of an 

 inch wide, and another of copper are passed through a small 

 cork float, so that the copper shall bend round the end of 

 the zinc and in some measure enclose it. To the upper 

 part of each strip, the extremities of a copper wire, previ- 

 ously covered with silk and rolled into the form of a ring 

 by seven or eight turns upon itself, are to be soldered. The 

 ring should be an inch or an inch and a half in diameter. 

 When this float is placed in a vessel containing acidulated 

 water, the galvanic current is established. If a magnetic 

 bar be then presented to the ring, so that the currents pro- 

 ceed in the same direction, the ring will be attracted and 

 will pass over the bar ; but if the other pole be presented the 

 ring will be repelled ; but at the same time it will seek to 

 take another position by turning half round and will then 

 return to the bar and pass over it. 



Vol. V....N0. If, 51 



