t 
ON THE HEAVY CALCINED MAGNESIA. 131 
genee concerning the new processes employed, nor concern- 
ing the products obtained, we cannot form any opinion in 
this regard. 
The examination of the memoir and sample sent by M. 
Hardy, and of which we have just given a report, shows 
that, notwithstanding exceptional and unfavorable circum- 
stances of temperature, the quality of the opium is sustain- 
ed and even improved ; it is therefore permitted to us to 
hope that better results may yet be obtained in the ordina- 
ry conditions, by continuing with the same care these inte- 
resting agricultural experiments. 
Everything leads us to believe that we may thus be able 
to obtain the important result of furnishing the medical art 
with an agent whose useful properties will be guaranteed 
by the uniformity of its composition. 
The efforts to be made in order to obtain so high an ob- 
ject appear to us very worthy of being encouraged by the 
approbation of the Academy. — London Chemist. 
ART. XXXVI.-^ON THE HEAVY CALCINED MAGNESIA. 
By M. J. Dalpias, 
For half a century, Messrs, Henry, of Manchester, have 
prepared a heavy calcined magnesia ; the consumption of 
which is immense, notwithstanding its very high price. 
For a long time, these gentlemen alone possessed the se- 
cret of manufacturing this kind of magnesia ; but for se- 
veral years, two or three other English manufacturers ap- 
peared to have discovered their process. Thus, the heavy 
calcined magnesia of Mr. Howard of London, is perfectly 
similar to that of Henry's ; its density is the same, it is at 
