2Q0 
The Jablochkoff Candle : [April, 
in the solar envelope and produce the alteration of sun-spots 
and terrestrial magnetism which is known to accompany 
such planetary motions. And, lastly, the authors point out 
that the known lagging of changes in terrestrial magnetism 
behind variations in the sun-spots would be explained if the 
great pressure to which the iron in the earth’s interior is 
subjected produces, as is very probable, considerable coercitive 
force, forsuch coercitive force would necessarily cause changes 
in the magnetic intensity to lag behind the disturbances 
in the earth’s electric charge produced by alterations in the 
static induction of the sun and planets. 
V. THE JABLOCHKOFF CANDLE; 
ITS PRACTICAL RESULTS IN LONDON. 
By Charles W. Quin. 
f T is now nearly three-quarters of a century since Davy 
first exhibited to an astonished and delighted audience, 
at the Royal Institution, a voltaic arc, of no less than 
4 inches in length, playing between the terminals of the 
great 2000-plate battery with which he obtained illuminating 
and heating effects exceeding anything of the kind which 
had been heard of up to that time. For many years the 
most brilliant of terrestrial lights received no practical ap- 
plication, owing to its defects being numerous and apparently 
insurmountable. As to its adaptation to the wants of every- 
day life no really serious move was made in the right direc- 
tion until within the last few years, up to which period it 
had only been used for lighthouses, building works carried 
on at night, a few factories, and some startling theatrical 
effects at the Paris and Vienna Operas, the efforts to apply 
it to street-lighting and other general purposes being 
sporadic and generally unsuccessful. Many of its original 
defects have long since disappeared, but much still remains 
to be done. The rapid waste of the charcoal terminals was 
obviated by Foucault in 1842 by the use of hard gas-retort 
carbon. The gradual weakening and ultimate cessation of 
the current, and the proportional diminution and final ex- 
tinction of the light, were got rid of by the inventors of the 
different forms of constant batteries. The unequal wearing 
away of the two poles, and the consequent flickering and 
frequent extinction of the light, were almost entirely 
triumphed over in 1846 by Staite, who invented the first 
regulator or electric lamp. The enormous expense caused 
