Velocity of Lightning. 



181 



Inter, they indicate a double electrical cause, it may be that of two 

 fluids, or a difference in the equilibrium manifesting itself on both 

 sides at one time. He calculated the rapidity and the duration 

 of the spark by its passage across half a degree of a circle of ten 

 feet radius. The following are the conclusions which he draws : 

 1st, That the velocity of electricity through a copper wire one- 

 fifteenth of an inch thick, exceeds the velocity of light across 

 the planetary spaces; that it was at least 288,000 miles per se- 

 cond. 2d, That in breaking the electrical equilibrium in a wire 

 communicating with a Ley den -bottle at two surfaces, the electri- 

 city appears at the two extremities of the wire at the same mo- 

 ment, and somewhat later at the middle of the circuit. 3d, That 

 the light of electricity, in a state of great intensity, does not last 

 the millionth part of a second. 4th,, That the eye is capable of 

 distinctly perceiving objects which present themselves for this 

 .*hort space of time.— This experiment is most deeply interesting 

 for science; but it requires to be followed up and varied before 

 comparative and positive results can be drawn. The author has 

 .pledged himself to do this, and his additional communications 

 will be expected with much anxiety. We shall only remark, 

 that many questions will demand a separate investigation. For 

 example : — Does the velocity vary with the intensity ? Does it 

 vary with the conductors? Is it the same at all times in the 

 same conductor ? If electricity is propagated in the planetary 

 spaces, is its velocity the same as along material conductors ? — 

 It can scarcely be doubted that, in electricity of feeble intensity, 

 great differences are observed betwixt the velocity of propaga- 

 tion in the first and the following experiments. If we take .a 

 battery which has been for a considerable time in a state of re- 

 pose, the electricity of feeble intensity will with difficulty, and 

 only after a time, overcome the first inertia ; but once overcome, 

 quantities still more feeble will easily pass, either in the same 

 or in an opposite direction. It is in electricity produced by 

 heat that this inequality is most sensible. A similar effect takes 

 .place in the electricity produced by gold leaf. It is not after 

 repose that there is the greatest sensibility, but when their pri- 

 mary inertia has been overcome. This circumstance should not 

 l)e overlooked, either in experiments, or in theoretical conclu- 

 sions respecting the condition of atoms.— -V Institute, 



