[ 178 ] ■ 



XXV. Report made to the Listitufs on two Memoirs qf 

 jV/. Gkatien LEPJiiiK, Eriginser of the Imperial Roads 

 and Bridges, on natxiral and artijicial Puzzolano. Bij 



■ M. Chaptal*. 



JCiVERY person is acquainted with the purposes to which' 

 puzzolano is applied in buildings under water. The pro- 

 perty po,>sessed by this volcanic substance of speedily be- 

 coming hard when mixed with sour lime, in the compo- 

 sition of cements for hydraulic purposes, has rendered it a 

 most important article ; but the difficulty of procurmg it 

 from Iialy while the navigation of the seas is interrupted, 

 has made it exlreviisriy scarce and dear. Attempts have 

 therefore frequently been made to procure a substitute for 

 puzzolano, in substances which are to be procured in all 

 coiuitries and at a low price. 



It seems, therefore, an interesting subject to collect the 

 various processes which have been employed for adapting 

 difierent mineral sul)S!ancts to the uses of puzzolano, and 

 with this view I have drawn up the present extract of 

 M. Lepere's two memoirs, without binding myself to follow 

 his order, 



A substitute for puzzolano may be procured in three 

 ways. 1st, By employing the remams of the extinguished 

 volcanoes which almost all countries produce. 2dly, By 

 substituting some other volcanic products for puzzolano. 

 Sdly, By giving to certain mineral substances, by calcina- 

 tion, all the properties of these volcanic productions, 



Messrs. Desmarets and Faujas St. Fond long ago made 

 known some strata of good puzzolano in the volcanoes of 

 Auvergne and Vivarais, 1 also pointed out this substance 

 in the volcanoes which separate Lodeve from Bedarieux, in 

 the departn)ent of the Hcrault, and it has been employed 

 with success in the construction of bridges and other hy- 

 draulic buildings. 



We may also find a substitute for puzzolano in other 

 volcanic products, such as basalt, pumice stones carefully 

 pounded, &c. 



In 17S7 M. Guyton de Morveau sent to M. de Cessart, 

 at Cherbourg, some calcined l)asalts from the extinguished 

 volcano of Drevin, in the department of the Var and 

 Loire. The latter proved by conclusive experiments, that 

 they might be employed with great advantage in buildings 

 under water. 



The Dutch terrass is a kind of pumice stone brought 



* Viom /Inmdes tie Chimic, tome Ixiv p. 273, 



froi"n 



