126 Progress in Science. (January, 
He went twice as far, and, even then, oxygen and hydrogen did not liquefy, 
but maintained their condition as clear and beautiful gases.” 
ELECTRICITY. 
M. Ruhmkorff in continuing his many experiments on electro-magnetic 
induction has met with some results which he considers worthy of publication. 
When a bundle of iron wires is taken and covered with a very thin copper 
wire destined to convey an intermittent current from a pile, and when on this 
is wound another thin wire to obtain the induced current, if the latter is 
wound on the centre of the bundle where no magnetism is manifested, there 
is obtained an induced current of an intensity more than double that which the 
same quantity of fine wire wound on one of the extremities would give. 
M. Ruhmkorff then constructed an induction coil with an annular core, but only 
obtained a spark of 2°5 m.m. in length. He then cut the ring, when the spark 
increased to a length of 5m.m. Finally, a piece of wood of 5 m.m. in breadth 
was inserted between the severed ends of the annular core, when the-spark 
increased to 15 m.m. In doubling the thickness of the piece of wood, the 
result remained the same. 
M. Th. du Moncel has lately submitted to the Academy of Sciences of Paris 
some results of a series of interesting and valuable experiments on the size of 
the plates of a voltaic couple, relatively to each other, producing the best 
working current. The experiments and the deductions have a great practical 
bearing. The experiments were made with two Bunsen elements. In the one 
the negative electrode was constituted of two plates of carbon plunged into 
nitric acid in the exterior cup; the positive electrode, a single plate of amalga- 
mated zinc was plunged into the porous cup containing acidulated water. In 
the other element two plates of zinc, united at the bottom, replaced the two 
plates of carbon of the first element, while a plate of carbon took the place of 
the zinc. The liquids were the same, and the vases exactly equal in height. 
The plates were freshly amalgamated. The plate of zinc of the first element 
had a submerged surface of 224 square centimetres. The second pile, an 
active surface of zinc of 544 square centimetres. The surfaces of the carbons 
were of corresponding size. The intensities of the currents produced were 
read off from a tangent galvanometer with a ring formed by a copper wire 0°7 
m.m. in diameter, and 1°32 metres in length. The pile with the greatest 
amount of surface of zinc gave a deflection of 78° 5'; the pile with a small 
surface of zinc, 84° 10’. The temperature of the exciting liquids was—for the 
first pile, 29°8°; for the second, 30°2°. The weight of zinc dissolved in the first 
pile was 32 grammes; in the second, 38 grammes. One of the results would 
appear to be that the consumption of zinc with regard to the amount of work 
done is nearly the same in both cases. Therefore, in a pile where the current 
is constantly in circulation, there is the advantage in the point of view of 
economy of expenditure of zinc in the employment of positive electrodes of 
small surface. The experiments also prove that the current gains in intensity 
when the positive eleGtrode is smaller than the negative electrode. These 
experiments accord with those of M. Delaurier, who found that a plate of zinc 
of 9 m.m. in size, furnished at an expense of 115 grammes a deposit of copper 
of ror grammes in 48 hours, while a surface of zinc ten times as large would 
only furnish a continued action for one hour with a work represented by a 
deposit of 5 grammes. The liquids were completely exhausted. A similar 
observation has also been made by M. Ruhmkorff, who found that if the zinc 
plate of a bichromate of potassa pile were plunged to one-fifth of its height in 
the exciting liquid, the couple preserved during six hours an intensity that cor- 
responded with that obtained from the total immersion of the zinc; and in the 
latter case, when the entire plate was covered, the current could not maintain 
a platinum wire at a red-heat for longer than ten minutes. These results are 
strongly in favour of the use of small surfaces of zinc. In practice, where 
generally commercially pure zinc is employed, oxidation goes on continually 
all over the surface of the zinc; economy therefore demands the reduction of 
the surface. 
