NOME IV. TUFO. 



427 



perfectly resists the corrosive action of marine 

 salt. 



" There are in Vivarais, Velay, as well as in 

 Auvergne, as good mines of puzzolana as those 

 of Italy ; and yet we still use the puzzolana of the 

 environs of Naples : which shows that much time 

 is necessary to change the customs of men, even 

 in the most simple things. 



" The trass of the environs of Andernach, on 

 the left bank of the Rhine, is a kind of puzzolana 

 formed of small fragments of pumice, and several 

 species of lavas, more or less altered and agglu- 

 tinated in the manner of volcanic tufos*. Trass 

 is transported by water as far as Dort, to be re- 

 duced to powder in stamping mills worked by the 

 wind. Trass, thus pulverised, circulates through- 

 out Holland ; and is used with the greatest suc- 

 cess for all constructions in masonry, in a country 

 where water is every where found in digging the 

 earth: the Dutch also supply England with 

 trass." 



* " I have given the description of the quarries of trass in the 

 .first number of Annales du Museum, vol. i." 



