106 Correspondence of J. Nickles. 
tures at the Faculty of Sciences of Paris, and the Museum of Natural 
History. . In one of these rir elicit made for anatomical demon- 
strations, two persons may see at once the same — ect. e two im- 
“i t whose edges form with the edges of that a right angle. The image 
reversed behind the objective is thus righted by the first prism, so that 
- the qidieutey can direct his needles towards any part of the object with- 
out difficu 
In other dics pas, three or even fou btained through as 
many ocular tubes, by substituting for the OR prism below the ob- 
jective, either three re ecting prisms placed around the optical focus of 
and Milne Edwards and other micrographers say that such instruments 
have been very useful in their demonstrations. 
Aluminium and the Alkaline Metals.—The persevering efforts of M. 
H. Sainte Claire Deville and M. Bunsen, lead us to hope that alumin- 
ium will soon become a useful metal. The last advance has been made 
by means of the pile causing it to act on chlorid of aluminium. _ It is 
an important step ; but still the process is expensive. Deville, not ex- 
pecting to reach a cheaper method by means of the galvanic battery, 
has endeavored to use the old method by sodium, and has sought to re- 
duce the cost of preparing this last metal. He can now prepare this 
metal at a cost of 25 francs the kilogramme ($2 15 cts. the pound avoir- 
dupois.) The following is the process :—Mix together for a thousan 
parts, 
Dried carbonate of soda, 714 parts. 
Carbonate of lime, 108“ 
Pulverized charcoal, bs dee 
Reduce the whole to a paste with oil, and put it into an iron retort, 
like that of a mercury bottle. A musket barrel two decimeters long is ‘ 
fitted to the extremity, to which is adapted one of Donny and Mareska’s i 
receiving vessels. e retort and barrel are heated to redness: the ‘ 
sodium is immediately reduced, volatilizes, and is condensed in the re- 
cipient 
The only peculiarity of this process is the carbonate of lime, which 
serves to prevent the mixture from entering into fusion: it wa s through 
a perusal of the memoir of MM. Donny and Mareska, secmorsing € that 
these chemists recommend the use of crude tartar which contains ‘lime, 
that Deville was induced to study out the reason for this preference ; he 
soon discovered it, and proved that he was right, by adding to the ordi- 
Pee ie: 15 ees cent. of chalk. 
lso prepared metallic chromium, by oe the method 
gees in a preceding number of this Journal, and which depends 
on ;a very high temperature in an ordinary furnace. T 
