472 



Profs. Liveing and Dewar 



[Apr. 3, 



the person of Mr. Oscar Doermer, whose assistance was most valuable. 

 We wish, to express our thanks to all these gentlemen for the facilities 

 they so readily granted to us. 



The results obtained with the powerf ul current from the magneto- 

 electric machine did not differ at all in kind from those obtained with 

 the battery, and much less in degree than we had expected. We had 

 really but one day's work with this machine, which we can only 

 regard as a preliminary trial of it, and, in the meantime, until we 

 have the opportunity of a longer series of experiments with it, we 

 communicate the results obtained to the Royal Society. 



I 



CoppprlH ectrode 

 J — 



In some cases we have introduced a current of hydrogen, or of 

 coal-gas, into the crucibles by means of a small lateral opening, or 

 by a perforation through one of the carbon electrodes ; sometimes the 

 perforated carbon was placed vertically, and we examined the light 

 through the perforation (see diagrams). When no such current of 

 gas is introduced, there is frequently a flame of carbonic oxide burning 

 at the mouth of the tube, but the current of hydrogen produces very 

 marked effects. As a rule, it increases the brilliance of the con- 

 tinuous spectrum, and diminishes relatively the apparent intensity of 

 the bright lines, or makes them altogether disappear with the 

 exception of the carbon lines. When this last is the case, the reversed 

 lines are seen simply as black lines on a continuous background. 

 The calcium line with wave-length 4226 is always seen under these 

 circumstances as a more or less broad black band on a continuous 

 background, and when the temperature of the ; crucible has risen 

 sufficiently, the lines with wave-lengths 4434 and 4454, and next that 

 with wave-length 4425, appear as simple black lines. So too do the 

 blue and red lines of lithium, and the barium Tine of wave-length 5535, 



