110 MM. Quet and Seguin on the Stratifications 



of which exhibit the phsenomena of luminous strata : the experi- 

 ment also succeeds when the tinfoil is replaced by the hand. 

 The electrophorus is sufficient to charge the tube ; but when the 

 machine is used, the armature of tin and one of the electrodes 

 must be arranged so that the dischai'ge takes place of itself, and 

 thus the appearance of the wave of stratified light is frequently 

 renewed. With a simple winding of metal wire applied on the 

 tube instead of the tin, and communicating with the earth, some 

 strata are produced. 



Action of Conductors on Electric Currents, which produce either 

 stratified or unstratified Light. 



When the current of an induction coil is passed thx'ough a 

 Geissler's tube, by connecting the two extremities of the induced 

 wire with the electi'odes of the tube, stratified light is immedi- 

 ately obtained. But if only single contact be made, and sparks 

 drawn at the other electrode, there is obtained in the place of a 

 stratified wave, a luminous wave without perceptible interruption, 

 whose diameter is less than that of the tube. This stream con- 

 tinues to show itself always at the negative pole : sometimes it 

 extends from one pole to the other; occasionally, besides the 

 continuous wave, luminous strata are seen, which commence at 

 a greater or less distance from the negative electrode and extend 

 to the positive electrode. The length of the part of the tube 

 occupied either by the continuous light or by the stratified light 

 depends on the movement of the hammer, and on the density of 

 the pile, on the force of the induction apparatus, and on the ex- 

 plosive distance from the pole of the tube ; and the two dis- 

 charges may be established at pleasure in the tube. With a 

 feeble pile, and liolding the hammer with the finger, the wave 

 may be made continuous from one end to the other ; by exerting 

 on the hammer sufficient pressure, brilliant stratifications are 

 produced with an almost dark space round the negative pole. 

 Conductors brought near to the tube are not without influence 

 on the two kinds of discharges, which Mr. Grove has already 

 distinguished from one another. 



When the stratified light is produced by the contact of two 

 ends of the induced wire with two ends of the tube, if two fingers 

 be applied to the tube so as to encircle it, or if it be covered with 

 tinfoil communicating with the ground, it is seen that the lumi- 

 nous strata recede from each other in front of the conductor on the 

 side of the positive pole, and at the edge of the conductor a very 

 large dark space is produced. This effect is the more delicate 

 the nearer the conductor is to the positive pole. It depends 

 also on the force of the pile, and on the movement of the ham- 

 mer. By supporting the hammer and using a feeble pile, the 



