On natural and artificial Puzzolana . 25 i 
rendered it a most important article ; but the difficulty of 
procuring it from Italy while the navigation of the 
seas is interrupted, has made it extremely scarce and 
dear. Attempts have therefore frequently been made 
to procure a substitute for puzzolana, in substances 
which are to be procured in all countries and at a low 
price. 
It seems, therefore, an interesting subject to collect 
the various processes which have been employed for 
adapting different mineral substances to the uses of puz- 
zolana, and with this view' I have draw n up the present 
extract of M. Lepere’s two memoirs, without binding my- 
self to follow his order. 
A substitute for puzzolana may be procured in three 
ways. 1st, By employing the remains of the extinguish- 
ed volcanoes which almost all countries produce. gdly, 
By substituting some other volcanic products for puzzo- 
Jana. 3dly, By giving to certain mineral substances, by 
calcination, all the properties of these volcanic produc- 
tions. 
Messrs. Desmarets and Faujas Saint Fond long ago 
made known some strata of good puzzolana in the volca-. 
noes of Auvergne and Yivarais. I also pointed out this 
substance in the volcanoes which separate Lodeve from 
Bedarieux, in the department of the Herault, and it has 
been employed with success in the construction of bridges 
and other hydraulic buildings. 
W e may also find a substitute for puzzolana in other 
volcanic products, such as basalt, pumice stones careful- 
ly pounded, &c„ 
In 1787 M. Guyton de Morveau sent to M. de Ces~ 
sart, at Cherbourg, some calcined basalts from the extin- 
guished volcano of Brevin, in the department of the Var 
and Loire. The latter proved by conclusive expert- 
