£204 On natural and artificial Puzzolana. 
One part and three-fourths of well washed siliceous 
sand. 
One part and an eighth of sour lime. 
Two parts of chips from calcareous stone and silex. 
From these and several other experiments (the propor- 
tions of which were varied) it results, that the artificial 
puzzolana constantly exhibited the same effects as the 
best puzzolana of Italy. M. Lepere was an eye-witness 
of all these comparative experiments. 
There can be no doubt, therefore, that wherever there 
are ochrey earths, artificial puzzolana may be made with 
great facility. 
What is called Dutch terrass is in many respects sirah 
larto the artificial puzzolana in question. 
The ashes, or rather scorise, left when coals are burnt, 
may also be applied to the same purpose. M. Guyton 
caused a trial to be made at Cherbourg, and it succeeded 
well. 
M. Gratien Lepere, having been intrusted in 1804 
with constructing the foundation of the new arsenal at 
Cherbourg, began to turn his attention to the best method 
of supplying the puzzolana of Italy. He knew that the 
Swedes had already used a very hard black slate with 
this view, after being twice strongly calcined in a lime- 
kiln. 
M. Lepere thought he perceived a great analogy be- 
tween the Swedish stone and the rocks of Cherbourg, 
particularly those of port Bonaparte, which, when dug 
into, exhibited a black schistus, hard, ferruginous, and 
falling off in scales of various thickness: subsequent 
experiments, however, proved that the slaty schistus of 
Houle, in the environs of Cherbourg, is preferable, and 
that good mortar may be made with the ferruginous schist 
of Haineville, which is inferior, however, to the two 
former. 
