13O TRAVELS THROUGH 



cryftallifations j which are either femi-tranfp arefl 

 and vitreous, or changed into a clayifli argillaceous 

 fubftance. Even the red pumice-ftones of the 

 alhe, which cover Pompeja, contain fuch cryftal- 

 lifations. 



The more from Naples to Puzzuolo is covered 

 with pumice-ftones, and the fands of that fhorc 

 are filled with a black, fplendent iron fand, drawn 

 by the loadftone ; which is owing to the fea's con- 

 tinual warning and breaking againft the tufo rocks. 

 The fame more offers a great number of worms, 

 called Apbrodit* aculeate, and fome pi/a marina, 

 which are produced by the rolling of the fibrous 

 roots of .the zcftcra marina. 



The loole unpetrifted afhes, which are found in 

 feveral hills about Naples, are known under the 

 name cf terra pozzolana. It is of different co- 

 lours ; that of Vefuvius is commonly black. Mixed 

 with lime it ferves in mafonry, and produces an 

 excellent cement ; which, probably, on account of 

 the .ferruminating iron particles (Cronjied's Mine- 

 ral, publiihed by Brunmch, p. 47.) is fo ftrongly 

 coherent, that it is impenetrable and indifiblublc 

 by water. 'I" hey dig it likewife near Rome, and 

 in other places in Italy; whence, by the way of 

 Civita-vecchia, it is exported to France, Holland, 

 Sweden, and many other countries. The com- 

 mon puzzolana is yeliovvim. brown j an excellcn f 



forr. 



i 



