1872.] Electricity. 403 
other impurities upon the articles receiving the coating of nickel. There is added 
to the solution of nickel one or more salts, either single or double, acid or 
neutral, or associate, formed by the union of organic acids, acetic, citric, and 
tartaric, with the alkalies and alkaline earths, ammonia, soda, potash, mag- 
nesia, or alumina. These additions will, it is asserted, counteract the ten- 
dency to decomposition of the solution by action of the electric current. 
These various organic acid salts may be added interchangeably and col- 
lectively, though the inventor prefers to use, in case of the double salts of 
nickel and alkalies and alkaline earths, the organic acid salts which have for 
their bases the alkali or alkaline earth which is associated with the nickel in 
its double salt. Thus, when using a solution of nickel and ammonia, an 
organic acid salt of ammonia is preferred, though the similar salts of soda and 
potash will answer very well. In case of using a solution of a double salt of 
nickel and potash, or a double salt of nickel and soda, an organic acid salt of 
soda and potash is selected. Of the salts which can be used to accomplish 
the effect, the tartrates are preferable. A comparatively small quantity of the 
organic salts is necessary to be added, though more will not change the 
character of the deposit. The following bath is said to work well:—To 
20 gallons of a solution in water of the double sulphate of nickel and ammonia 
of 7° Baumé, add 1 gallon of a solution, of an equal gravity, of neutral 
tartrate of ammonia in water. Mix well, and the bath will be ready after 
standing a few hours. 
Two new electric detonators for mining purposes have been introduced at 
the Royal Arsenal, Woolwich, one for land, the other for marine service. The 
first consists of a tin tuve filled with fulminating mercury, surmounted by a 
spherical head of beech-wood. Through this head, and embedded in gutta- 
percha to insulate them, run the electric wires, separated at their extremities. 
In this separation, and between the fulminating mercury and the wires, a 
small quantity of loose gun-cotton is placed. The passage of an electric 
current generates sufficient heat to ignite the gun-cotton. The second deto- 
nator is a modification of the old platinum wire fuse, and consists, like the 
other, of a tin tube filled with fulminating mercury and with a beech-wood 
head. To the ends of the insulated wires is attached about =s,ths of an inch 
of platinum wire 0°003 inch thick. Some loose gun-cotton is placed around the 
wire, and is ignited when the wire is raised to incandescence by the passage 
of the current. The ignition of the gun-cotton explodes the fulminating 
mercury, which in its turn explodes the powder. 
M. Ruhmkorff has invented a new or rather modified apparatus for the 
generation of ozone. The modes of preparation of this body have been :— 
1. By the decomposition of water by the pile; 2. By means of phosphorus ; 
3. By the action of concentrated sulphuric acid upon barytic oxide; 4. Finally, 
by passinga series of sparks from an electrical machine or from an induction 
coil through oxygen gas. The apparatus of M. Ruhmkorff is founded on this 
last method. It consists of a rectangular wooden case containing several 
horizontal ranges of metal plates, the alternate plates being connected, the one 
set to one terminal and the other set to another terminal, in connection with 
the poies of the battery or machine. These plates being thus arranged as 
a condenser serve to increase the intensity and number of the sparks. 
Tubulures connected with a reservoir of oxygen keep the case supplied, the 
ozone being drawn off by an aspirator. With this apparatus many new 
results have been obtained shortly to be brought to the notice of the scientific 
world. 
The metal cadmium has been found by Dr. Schonn capable of being ren- 
dered, under certain circumstances, indifferent to the aétion of acids. It has 
long been known that iron, if plunged into nitric acid of a certain degree of 
concentration, acquires a peculiar surface condition, rendering it indifferent to 
the action of the strongest acid. Iron which has undergone this surface 
change has been termed passive. It appears, too, that such iron has acquired 
some peculiar physical qualities, since it will form a galvanic circuit with 
ordinary iron; the changed metal behaving electrically negative to the other. 
