248 
Factitious Puzzolana . 
The magnet acts a little on these oxides before calch 
nation, and strongly, or perceptibly, after it. 
The medium weight of a cubic foot is one hundred and 
twenty-five degrees ; that of the Italian puzzolana is but 
ninety- one degrees. 
Analysis by the moist Way . 
I shall not weary the assembly by a detail of the 
manipulations relative to the solvents and re-agents 
which art uses for the decomposition of bodies, and shall 
only say, that silex, iron, alumen, and a small por- 
tion of manganese, are the constituent parts of these 
oxides. 
I repeated these experiments many times, and had 
for a medium result from an hundred pounds, chemical 
weight, 
50 parts of silex, 
31 - — — of iron-; 
16 — — of alumen; 
3 — — of manganese, and loss. 
100 
If this analysis be compared with that of the puzzolana 
of Italy, which contains in 100 parts — 
50 of silex; 
25 of alumen; 
16 of iron; 
3 of lime ; 
6 of loss ; 
100 
their respective properties may be appreciated according 
to the proportions of their integrant parts. 
