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Globular lightning
Feb., 1885.]
Globular Lightening.
143
is one o f the best. I n o r d e r to readily moisten the surface o f the c h a l k c y l i n d e r the vessel u ~, is p r o v i d e d freely with water. T h e lever r t, moves a felt wheel r, against the c h a l k when the latter has become too dry. T h e sound-waves i m p i n g i n g against the t r a n s m i t t e r T, which colltains the o r d i n a r y carbon button, varies the c u r r e n t o f a battery, that p~sses t h r o u g h the p r i m a r y o f an induction coil I , and thus produces positive and negative waves in its secondary coil, which passing over the line cause variations in the adhesion o f a metallic strip to a r o t a t i n g chalk cylinder, s i m i l a r to t h a t shown at a t, a n d g, and therefore cause motions, in its d i a p h r a g m that reproduce the speaker's voice. Since the resistance o f the s p r i n g and the c h a l k are greater when the c h a l k is at rest, t h a n when in nlotion, the c h a l k c y l i n d e r a n d its opl)osing s p r i n g may, i f so desired, be e m p l o y e d as a t r a n s m i t t e r in the place o f the carbon transmitter. CENTRA 1, HIGH SCIIOOL,
I:)ItILADELPHIA,December 15, 1884.
GLOBULAR LIGHTNING.---Gaston Plant6 described, some years ago, under the name of " W a l k i n g electric s p a r k , " a peculiar phenomenon produced by the passage of an electric current of high tension. The appearances are 8o analogous to those of globular lightning, dlat he considers that phenomenon as a slow and partial discharge of the electricity from storm clouds, when t h a t electricity is exceptionally abundant, and when the cloud itself, or the column of strongly electrified damp air, which forms its electrode, so to speak, ahnost reaches the ground, or is only separated from it by a thin layer of insulating air. Under these circumstances the ponderable matter whicl~ is traversed by the electric current collects under the form of a globe of fire. I t is a k i n d of electric egg, without a glass envelope, which is formed by the rarefied and incandescent elements of air and vapor. The globe is not fulminating and dangerous by itself, for a breath is often suWieient to displace it or even cause it momentarily to disappear. Its presence however is formidable, for it brings the electricity from the storm cloud and reveals the chosen path of its escape. I f the layer of air which separates the cloud from the ground is not traversed, the globe of fire may disappear without report. I f a portion of the storm cloud approaches the earth or anotlmr conductor, the lightning m a y strike at a distance at the .same moment that the globe disappears. [f the layer of air is pierced, there i s a flash of l i g h t n i n g accompanied by thunder, which is not due to the amall quantity of electricity enclosed in the globe, but to the sudden discharge of a large portion of the electricity of the cloud.--Comptes Rendus, Aug. 11, 1884. C.
Globular Lightening.
143
is one o f the best. I n o r d e r to readily moisten the surface o f the c h a l k c y l i n d e r the vessel u ~, is p r o v i d e d freely with water. T h e lever r t, moves a felt wheel r, against the c h a l k when the latter has become too dry. T h e sound-waves i m p i n g i n g against the t r a n s m i t t e r T, which colltains the o r d i n a r y carbon button, varies the c u r r e n t o f a battery, that p~sses t h r o u g h the p r i m a r y o f an induction coil I , and thus produces positive and negative waves in its secondary coil, which passing over the line cause variations in the adhesion o f a metallic strip to a r o t a t i n g chalk cylinder, s i m i l a r to t h a t shown at a t, a n d g, and therefore cause motions, in its d i a p h r a g m that reproduce the speaker's voice. Since the resistance o f the s p r i n g and the c h a l k are greater when the c h a l k is at rest, t h a n when in nlotion, the c h a l k c y l i n d e r a n d its opl)osing s p r i n g may, i f so desired, be e m p l o y e d as a t r a n s m i t t e r in the place o f the carbon transmitter. CENTRA 1, HIGH SCIIOOL,
I:)ItILADELPHIA,December 15, 1884.
GLOBULAR LIGHTNING.---Gaston Plant6 described, some years ago, under the name of " W a l k i n g electric s p a r k , " a peculiar phenomenon produced by the passage of an electric current of high tension. The appearances are 8o analogous to those of globular lightning, dlat he considers that phenomenon as a slow and partial discharge of the electricity from storm clouds, when t h a t electricity is exceptionally abundant, and when the cloud itself, or the column of strongly electrified damp air, which forms its electrode, so to speak, ahnost reaches the ground, or is only separated from it by a thin layer of insulating air. Under these circumstances the ponderable matter whicl~ is traversed by the electric current collects under the form of a globe of fire. I t is a k i n d of electric egg, without a glass envelope, which is formed by the rarefied and incandescent elements of air and vapor. The globe is not fulminating and dangerous by itself, for a breath is often suWieient to displace it or even cause it momentarily to disappear. Its presence however is formidable, for it brings the electricity from the storm cloud and reveals the chosen path of its escape. I f the layer of air which separates the cloud from the ground is not traversed, the globe of fire may disappear without report. I f a portion of the storm cloud approaches the earth or anotlmr conductor, the lightning m a y strike at a distance at the .same moment that the globe disappears. [f the layer of air is pierced, there i s a flash of l i g h t n i n g accompanied by thunder, which is not due to the amall quantity of electricity enclosed in the globe, but to the sudden discharge of a large portion of the electricity of the cloud.--Comptes Rendus, Aug. 11, 1884. C.