250 
On natural and artificial Puzzolana . 
brown-red colour equal to that of commerce, and applied 
it to use successfully.* 
NO. 49. 
Report made to the Institute on two Memoirs of M. 
Ghatxen Lepere, on natural and artificial Puzzolana. 
By M. CHAPTAL.f 
EVERY person is acquainted with the purposes to 
which puzzolana is applied in buildings under water. 
The property possessed by this volcanic substance of 
speedily becoming hard when mixed with sour lime, in 
the composition of cements for hydraulic purposes, has 
* This paper has been abridged in its introduction, in the details relative to 
negociations with the Constituent Assembly, and in some other points a little ir- 
relevant to the puzzolana; but all matters directly tending to illustrate its na- 
ture and properties have been carefully copied. 
M. Dodun’s discovery may be of some use to this country, as there are in 
many parts of it large masses of iron-stone, and some is found in the vicinity of 
most coal-mines. 
It has been long known that iron ochres have the same property of forming 
puzzolana with lime, when properly roasted, and this circumstance is mentioned 
at large in Chaptal’s Chemistry, A patent has also been obtained in this country 
for the application of iron pyrites to the same purpose, the right to which was 
purchased long ago by Mr. Samuel Wyat. But the novelty of M. Dodun’s dis- 
covery is, that poor iron-stone is equally fit for this use, as the other substances 
mentioned, which is of the more importance as it is very plentiful, and may of- 
ten be procured in situations where the others cannot. 
It may not be amiss to mention here, that basalt treated in the same manner, 
has the same property as the puzzolana : the whinstone, of which the ovoidal 
paving-stones consist mostly, is of this kind ; and it is found in great abundance 
in these countries, in different forms.-— B. 
*** It may not be amiss to ascertain by experiment, whether the slag of the 
blacksmith’s forge, which contains a considerable proportion of oxided iron, will 
not, with a due proportion of lime and sand, form a factitious puzzolana, equal to 
any we obtain from abroad. If this should be the case, as, from some few slight 
experiments I am disposed to believe, we shall always have, in every situation, 
ample materials for this important matter — Coxe. 
t filloch, vol. 34, p 178. i'rom the Annates de Chimie 3 tome 64, p. 2 73. 
