276 Progress in Science. (April, 
magnet, 14 inches in length, placed, in one series, with its edge towards the 
small compass on which its directive power is estimated, and another series 
with its flat side towards the small compass; also a galvanic coil, 13°4 inches 
in length, animated by a battery of three cells, and in the same coil, with the 
insertion of a soft iron coil. In the field of experiment the earth’s magnetism 
was sensibly neutralised by external large magnets. The observations with 
the small compass were taken in thirty marked stations in one oval ring sur- 
rounding the magnet, and in thirty-eight stations of another oval ring outside 
the first one. The following specific points are remarked:—At a constant 
distance from the steel the greatest force exerted by a magnet is not the 
longitudinal force at the end, but the transverse force near the end. In going 
round the magnet there are six maxima and six minima of force. The law of 
attraction of the core of a galvanic coil is not very different from that of a 
magnet. The force produced by the core within the coil {s very much greater 
than that produced by the coil alone. In some positions of the small compass 
it is about forty times as great, and in some about one hundred and seventy 
times as great. The law of force at different parts of the coil differs greatly 
from that at corresponding parts of the magnet or core. In the coil it is pro- 
portionally far greater at the end, and its direction is different. Near the end 
of the magnet or core the directions of force converge to a point within it 
distant from the end by about one-twelfth of its length. Near the end of the 
coil the direGtions of force converge to a point as exactly as possible at the 
centre of the end of the coil. 
M. Becquerel, in a paper ‘‘ On the Chemical Effects of Caloric in the Action 
of Powerful Electric Discharges,” states that the reduction of oxides of silver, 
lead, tin, and copper, can be effected by mixing these substances with charcoal 
dust in U-shaped tubes, and exposing them to the heat derived from the dis- 
charge of a powerful induction apparatus; the oxides of nickel, cobalt, iron, 
and chromium, mixed with charcoal powder and powdered sugar, and put ina 
platinum crucible, are also reduced. Silica and alum are fused, and small 
crystals are sometimes found in the fused mass. 
In spite of the labours of Faraday and of L. Foucault, and in spite of the 
excellent arguments of these two great physicists in favour of the condudtibility 
of liquids without electrolysis, this conductibility is not generally admitted. 
M. Favre has endeavoured to elucidate the subject, and has sought to show 
that, under some circumstances, the electrolysis of a liquid traversed by an 
eleG&tric current is impossible. He placed in circuit with a single Daniell’s 
cell an electrolytic cell of sulphate of copper: after a quarter of an hour there 
was a deposit of copper in the pile, but on the negative plate of the voltameter 
there was found neither the metal nor its oxide. On the porous cup of the 
element there was also copper deposited. With the voltameter out of circuit 
and the circuit of the element open, copper was deposited on the porous cup 
only. And by several carefully considered experiments M. Favre shows that the 
volume of gas disengaged in the voltameter is by no means equivalent to the 
reduction and oxidation of the materials of the pile, thus proving that a portion 
of the current must have traversed the liquid without electrolytic effect. He 
finds, also, that three Smee’s cells are needed to decompose sulphuric acid; 
it requires, it would seem, a force corresponding to 45,000 calories in order to 
electrolyse the acid. 
Sir W. Thomson gives the following law for rendering galvanometers 
sensitive with a minimum of wire. The curve forming the transverse section 
of the coil is expressed by— 
eta ( x iF en 
a 
x being the abscissze from the zero point, passing through the magnet; y, the 
ordinates; and a, a constant. 
Prof. Osborne Reynolds, from some experiments on the electro-dynamic 
effe& the induction of statical electricity causes in a moving body, has been 
‘led to the consideration of the induction of the sun as a probable cause of 
