110 
POPULAR SCIENCE REYIETf. 
lent to three Bunsen elements of a middle size, but their duration is much 
greater. Under the influence of this battery the coil gives sparks of 15 
centimetres. To transmit the electricity to the different lustres a special 
wire is employed for each, but the return current passes through one common 
wire. 
The Fluorescence of Bodies in Castor Oil. — Mr. C. Horner has shown that 
many substances which have no fluorescent properties when dissolved in 
alkaline solutions, or in alum or alcohol, fluoresce very brilliantly when they 
are dissolved in castor oil. 
A New Helio-photometer has been described by M. F. Craveri, in the 
u Moniteur Scientifique,” October 1874. It thus appears in the 11 Chemical 
News ” for November 18 : A box of hard wood, 280 mm. long, 145 
mm. wide, and 200 high, forms a parallelopiped placed upon a pedestal 
in an open situation, where nothing impedes the direct action of the 
sun. The upper surface of the apparatus cannot preserve, during the 
twelve months of the year, a horizontal position, because when the sun 
sinks below the equator in winter its rays would fall too obliquely. It is 
therefore necessary at that season to follow approximately the movement of 
the sun. This result is obtained by gradually inclining the instrument 
towards the south from September to December, and gradually diminishing 
the inclination again till March, when it is replaced in a horizontal position. 
One of the principal sides of the parallelogram represents the door, fixed on 
hinges, and giving access to all the interior. At the side opposite the door 
is fixed a clock, the dial of which is seen through a circular aperture in the 
side. To this clock is adapted a toothed wheel, moved by the drum con- 
taining the spring. This wheel only performs one revolution in twenty-four 
hours. To its axle is fixed by a movable screw a large drum of brass, the 
circumference of which is 520 mm., and the breadth 16 mm. Upon the 
surface of this drum is fixed a slip of paper, as is done with the Morse tele- 
graphs. A few seconds are sufficient for fixing or for removing this band. 
A slit in the box is so arranged that the sun’s rays, shining through it, fall 
upon the band, even when the luminary is very near the visible horizon. 
The bands are prepared with chloride of silver by being steeped first in a 
solution of common salt, and then, shortly before being used, in solution of 
nitrate of silver. 
Magnetic Condensation in Soft Iron . — A paper is published in the 
a Comptes Rendus,” October 19, on this subject. The magnetic condensa- 
tion, first observed and studied by M. Jamin in steel, occurs also in soft iron 
with a very remarkable intensity and persistence. A horse-shoe electro- 
magnet is formed by a cylinder of iron, 4 centimetres in diameter, each 
limb of which is surrounded with a coil of wire of 2 mm. in diameter, and 
150 mm. in length. The armature is a blade of soft iron 2 cm. in thick- 
ness, and 4 in width. When the double coil is traversed by the current of 
a single Bunsen element, feebly charged, the keeper is able to support about 
150 kilos. On interrupting the current the keeper remains strongly 
adhesive, a fact already often observed. It can support as much as 50 
kilos, without detaching itself, but after this rupture every trace of mag- 
netism disappears, and ‘the electro-magnet is not even able to support the 
keeper. We might suppose that cohesion might be partly concerned in the 
