150 ME. GrASSIOT OIST THE STExiTIEICATIOXS IX ELECTEICAE DISCHAE&ES, 
A, carbonic acid vacuum-tube, similar to the sulphur or selenium one (86, 87) , B, va- 
cuum-tube (which shows stratification when discharges are passed); G, a delicate 
Fig. 9. 
galvanometer placed at a sufficient distance to preclude any action on the needle from 
the iron core in the induction coil. If discharges from the induction coil C are now 
made, there will not be a trace of any luminous discharge in A; in B, the stratified 
discharges are reciprocating, and, when tested by a magnet, will be found to divide; 
they are merely discharges from the terminal of the coil to which one of the wires is 
attached, the needle of the galvanometer remains stationary. 
If in this state heat is applied to (CP) the caustic potash in A, in a few seconds the 
stratified discharges will be visible ; the needle of the galvanometer will be deflected, 
and the stratifications in B will at the same time assume the usual appearance of the 
conductive discharge, 
Vacua4uhes ^^repared with Arsenious Acid, Bromine^ Iodine^ PentacMoride of Ajitirnony. 
Bichloride and Bisulphide of Carbon. 
89. Aesenious acid, No. 68.— A few crystals being first introduced Avith some caustic 
potash and chloride of calcium, the arsenious acid being kept separate, the tube was 
charged with carbonic acid gas and exhausted as before (83) ; the discharge at fii’st 
appeared in the form of a wave line of a greenish tinge ; the potash being heated, in a 
ferv days the discharge assumed a tendency to the cloud-like stratifications ; the arse- 
nious acid was then heated, the stratifications immediately narrownd, a biiUiant lumi- 
nous wave discharge passing through them from wire to Aidre ; for about tlmee months 
a gradual change took place, until the discharge again assumed the cloud-like, stratified 
appearance ; on heating the potash, the stratifications suddenly became clear and defined 
Avith a greenish tinge, showing remarkably brilliant bands. 
90. Beomine, No. 69. — The bromine was inserted in a small glass bulb, and placed 
within the vacuum-tube previous to its being charged AAfith cai’bonic acid and exhausted. 
In about ten days the cloud-like stratifications were Aisible, AAdien the glass bulb Avas 
broken ; the tube instantly filled Avith bromine vapour so dense that the discharge Avouid 
not pass. On the following day the potash had absorbed a portion of the vapour, and 
the discharge was visible with very narroAV stratifications; these gradually improved, 
and in tAventy-seven days assumed the cloud-like appearance. On the tAventy -ninth day. 
finding the stratifications becoming indistinct, while the blue tongue at the negath-e 
remained peculiarly fine and extremely sensitive to the magnet, I sealed off that portion 
of the glass tube in which the caustic potash had been placed ; the discharge up to the 
