838 Mr. G. A. Hemsalech and the Comte de Gramont 



on 



of a concentrated solution of magnesium sulphate between 

 poles of magnesium metal. The effect of the well-conducting 

 film upon the various types of lines was found to be the same 

 as that of the non-conducting w T ater film. Experiments were 

 also made with the object of ascertaining whether the spark 

 lines could be excited in the liquid medium itself without the 

 projection of metal vapour from the electrodes. A drop of 

 magnesium sulphate solution was placed between graphite 

 poles, and the arc flash produced in the usual way. The 

 general character of the spectrum thus obtained was found 

 to be similar to that observed when the arc passes between 

 electrodes of magnesium metal through a water film. Thus, 

 for example, in the first phase the spark line X 4481 is sym- 

 metrically widened and the lines of the Rydberg series are 

 winged on the red side. 



The effect of liquid films of various composition has likewise 

 been investigated in the case of zinc and cadmium. The 

 relative behaviour of the spark and arc lines of these elements 

 during the first and second phases is very similar to that 

 shown by the corresponding lines of magnesium. It maybe 

 mentioned in this connexion that a film of alcohol proved 

 equally successful in bringing out the spark lines of cadmium. 

 It thus appears from the whole of our observations that the 

 emission of spark lines in the arc is independent of the nature 

 of the liquid placed between the electrodes. 



§ 3. Effect of high voltage currents. 



In all the experiments described in the preceding paragraph 

 the electric current used for producing the arc was supplied 

 at 80 volts. In a subsequent series of experiments the arc 

 was fed from a 200 volts circuit. The most striking effect 

 of the higher voltage in the case of the water arc between 

 magnesium poles is the remarkable development of the whole 

 second phase emission. This is probably due to the rather 

 intense arc flash which follows the destruction of the liquid 

 film. 



The lines most particularly affected by the higher voltage 

 are those of the Rydberg series and X4481. During the 

 first phase and the early stages of the second the former are 

 strongly winged and hazy, but during the greater part of 

 the second phase they appear as bright and well-defined 

 though not absolutely sharp lines. The lines of the triplet 

 series are symmetrically widened in the film and at the 

 beginning of the arc flash, but afterwards they are narrow 

 and well defined as in an ordinary arc. A most noteworthy 



