Notes. 
1879.] 
265 
The lecturer believes the new system of elecftric lighting devised 
by M. Rapieff to be a serious opponent of Jablochkoff’s process. 
The chief advantage of the new system is that the luminating 
point does not change its position, and therefore this system is 
more suitable for the projection of the electric light at a distance. 
This advantage will give increase to the use of the electric light 
for military purposes. 
At a recent meeting of the French Academy of Sciences a 
paper by M. Henri Becquerel, on the “Temporary Magnetic 
Proportions developed by Induction in certain Specimens of 
Nickel and Cobalt,” was read. The specimens of iron used by 
M. Becquerel were taken from the same piece of Swedish soft 
bar iron, of a high degree of purity. By submitting bars of iron 
and nickel, of the same dimensions and shape, to gradually in- 
creasing magnetic influence, it was found that the ratio between 
the coercitive force acquired by the iron and the nickel is a quan- 
tity varying with the intensity of the magnetic force used. This 
ratio begins by being a minimum of about 0-4 ; it then increases 
to 075, and again decreases to a still lower minimum of about 
0-2. A nickel bar becomes saturated much more quickly than a 
similar iron bar; the magnetism of the former remains station- 
ary, while that of the latter goes on increasing. Similar results 
were obtained with a bar of nickel, which was allowed to oscil- 
late over the poles of a powerful magnet. The experiments with 
the bars of cobalt were similar in their results. 
At the same meeting M. Heraud sent in a paper “ On a New 
Voltaic Pile,” in which the exciting liquid is a saturated solution 
of sal-ammoniac, to which one-tenth of liquor ammonia has been 
added, the depolarising substance being mercuric proto-chloride. 
With a closed circuit the ammonic chloride is decomposed, the 
chlorine going to the zinc and the ammonia splitting into ammo- 
nia and hydrogen, which reduces the mercury salt to the metallic 
state, ammonic chloride being once more formed. Each cell is 
hermetically sealed. After being in action for 227 days, a pile of 
9 elements gave an electromotive force equal to 073 per cent of 
the original strength, and at the end of 984 days 0-50 per cent. 
Four kinds of camera lucida were brought before the Royal 
Microscopical Society at their December meeting. Dr. Hoffmann’s 
instrument takes the place of the usual eyepiece. The image of 
the object is viewed by two reflections ; the first by a plate of 
silvered glass ; the second by a plate of transparent glass, through 
which the paper and pencil are viewed directly. The instrument 
has the disadvantage of interfering with the employment of the 
ordinary eyepiece, which has to be removed before the camera 
can be used, and only permits drawings to be made with the 
microscope in either vertical or horizontal positions. 
A somewhat complex arrangement of prisms for the same 
purpose, by M. Pellerin, was also described, but no drawing is 
