of Light Radiations emitted by Iron Vapour. 5 



circuit of a small plate condenser, which is connected to the 

 secondary of an ordinary 20,000 volts transformer. An 

 adjustable impedance coil in series with the primary pre- 

 vents arcing. A shower of sparks will then pass between E 2 

 and the surface of the solution, and minute drops in the form 

 of a spray are projected all round. 



Air is now allowed to enter through tube A, and on its 

 passage through the jar becomes charged with the spray. 

 The heavier drops fall back to the bottom of the jar, but the 

 lighter particles are carried along with the air and pass 

 through the outlet tube B into a series of collectors, in which 

 the material undergoes a process of refining. These col- 

 lectors form an important addition both to the Gouy and the 

 electric sprayer, for it is essential that only the very finest 

 particles should reach the flames. I have in the main fol- 

 lowed de Watte ville's plan, both with regard to the shape 

 and order of these collectors ; his paper should therefore be 

 consulted for details. Finally, the air carrying the spray is 

 mixed with the coal-gas and the mixture then passed into the 

 burner. Pressure gauges in both the air and coal-gas circuit 

 complete the arrangement. For high temperature flames, 

 which are fed with oxygen, the sprayer is inserted in the 

 oxygen circuit. 



Relative merits of the Gouy and electric sprayers and the Spark 

 Method. — Although the character of the spectrum is always the 

 same whichever method is used, the three methods do not 

 always give equally good results, in so far as brilliancy and 

 completeness of spectrum are concerned. Thus the spark 

 method will not yield such well-developed spectra in the case 

 of the air-coal gas flame as the sprayers ; this I believe is due 

 to the fact that the oxides given by the spark do not volatilize 

 so easily at the low temperature of the air-coal gas flame. 

 In this case, therefore, one of the sprayer methods should 

 be employed, as it allows the use of the more volatile 

 salts. 



For the high-temperature flames the spark method is, 

 however, to be preferred, being cleaner and more economical, 

 and giving results so far unattained by any other method. 



The electric sprayer gives good results all round, and 

 would probably reach the standard of either of the two other 

 methods if worked with resonance sparks. 



Burners. — These form the most important item in the 

 instrumental equipment, and special attention was paid to 

 them from the outset. The new results obtained in this 

 research are largely, if not entirely, attributable to the com- 

 plete change of plan adopted in their construction. They 



