LUMINOSITY OF FLAMES CONTAINING SALT VAPOURS. 
(Jo 
On the other hand, it was found that when the electric field was strong enough 
to cause a great increase in the current, that is, when an arc discharge began to form, 
then luminous salt vapour appeared between the streak and the negative electrode; 
the negative electrode, if in the flame, emitted a stream of luminous salt vapour. 
The intensity of the luminosity between the streak and the negative electrode was 
much less than in the streak itself. This suggested that, while the luminous molecules 
in the streak were not deflected, positive ions were moving out of the streak towards 
the negative electrode and that these ions could form luminous vapour; these last 
results are in agreement with some of those of Andrade,* who showed that positive 
A * • • • 
ions from a streak when deposited on the negative electrode form luminous vapour. 
This fact was also previously observed by the writer.! 
It was therefore decided to attempt to measure the relative motion of the 
luminous salt vapour and flame gases due to an electric field by a new method 
which seemed to be capable of giving more reliable results than those previously used. 
The flame used was a Bunsen flame formed by burning a mixture of gasolene vapour 
and air from a special burner. ■ 
Fig. 1 shows a vertical section of the burner, and fig. 2 the top of it as seen from 
* ‘Phil. Mag.,’ July, 1912. 
t ‘ Proc. Royal Institution,’ Feb. 12, 1909. 
K 2 
