Prof. R. Bunsen's Spectral- Analytical Researches. 429 



that effects of such magnitude can only be hoped for by paying 

 strict attention to the easily observed rule of never allowing the 

 pairs to remain in contact with the liquid one moment longer 

 than the conditions of the experiment absolutely require. 



In fig. 2 is shown the special disposition of the battery for 

 spark-production. The apparatus consists of four pairs fastened 

 to the frame a, which are immersed in and withdrawn from the 

 liquid in the glass cells by means of the handle b. The pivots 

 e, e of the frame a slide in the grooves c, c of the larger stand ; 

 the pin / prevents the elements from sinking beneath this fixed 

 point into the liquid. In order to allow of easy removal and 

 replacement from the liquid, the movable part of the apparatus 

 is nearly counterbalanced by the weight g. The zinc plates are 

 soldered to the thin copper plate h, against the other platinized 

 end of which the coal rod is pressed by means of a screw-clamp. 



The amalgamation of the zinc plate is renewed by bringing 

 the amalgamation-vessel (fig. 3) containing the requisite amount 

 of mercury and dilute sulphuric acid under the plate, and gently 

 raising the vessel until the plate touches the bottom ; the mer- 

 cury which flows out is caught in a small tray, with which the 

 glass cylinder is closed when the battery is not in use. The 

 pole-wires of the battery, i, i, of a somewhat spiral form, conduct 

 the primary current, a branch of which puts the current-inter- 

 ruptor into action, to a RuhmkorfPs apparatus furnished with an 

 induction-coil about 0*2 metre in diameter and 0*5 metre in 

 length. The current herein induced is conducted to a spark- 

 apparatus (fig. 4) standing before the slit of a spectroscope : w is 

 a three-necked flask which serves as a support; the induced cur- 

 rent passes from the small mercury-cup a through the fine wire 

 b to the carbon point c, which is supported on a platinum wire ; 

 thence it passes as a spark to the other carbon point c , and 

 so to the second mercury-cup a v which is in connexion with the 

 other end of the induction-coil. The platinum wires supporting 

 the carbon points are sealed into glass tubes, which again so pass 

 into holes bored in the corks d, d as to be easily turned on their 

 axes ; the corks themselves are supported on glass rods so that 

 they may be moved up and down or turned upon their axes. 

 These various movements allow of the quick and exact disposi- 

 tion of the carbou points before the slit of the spectroscope. The 

 observation of the spark-spectra is carried out as follows : — The 

 eye being in "proper position, the battery is brought into activity 

 by the left hand, w T hile the spark-apparatus, the carbon points 

 of which have been once for all set at the proper height, is so 

 adjusted by the right hand that the spectrum coincides with the 

 scale in the telescope. The spark, rendered more vivid by means 



