230 Sir Norman Lockyer. 



Using an E.M.F. of 100 volts, the following values of the current 

 were obtained (1 = 10~ 5 ampere) : — 



Temperature 300° 400° 500° 600° 700° 800° 



Current 0*2 1-9 5'1 5-4 5-5 5-5 



Temperature 900° 1000° 1100° 1200° 1300° 



Current 5 -5 5*3 6*8 8*2 9*2 



Thus the current has a maximum value near 900° C, and rises very 

 rapidly near 1150°. Similar results were obtained with other salts. 



The energy required to ionize 1 gramme molecular weight of KI at 

 about 300° C. was estimated to be 15,000 calories in the same way as 

 was done for air. 



The maximum current carried by the salt vapour (at 1300° with 

 800 volts) was found to be nearly equal to that required to electrolyse 

 the same amount of salt in a solution. 



This fact must be regarded as considerable evidence in favour of 

 the view that the ions are of the same nature in the two cases. 



" Further Observations on Nova Persei, No. 2." By Sir Norman 

 Lockyer, K.C.B., F.RS. Eeceived and Eead March 28, 

 1901. 



In continuation of two previous papers, I now bring the observations 

 of the Nova made at Kensington to midnight of March 25. Since the 

 last paper* of March 7th, estimates of the magnitude of the Nova 

 have been made on ten evenings, visual observations of the spectrum on 

 eight evenings, and photographs of the spectrum on four evenings up to 

 the evening of the 25th. * 



In consequence of the greater faintness of the Nova, the 6-inch 

 prismatic camera has not been utilised, but the 10-inch refractor to 

 which it is attached has been used for eye observations of the spectrum 

 with a McClean spectroscope. 



With the 30-inch reflector four photographs have been secured on 

 the evenings of the 6th, 10th, 24th, and 25th by Dr. Lockyer, and with 

 the 9-inch prismatic reflector seven photographs on the nights of 10th, 

 21st, and 25th by Messrs. Butler and Hodgson. 



Change of Brightness. 



Since March 5th the magnitude of the star has been gradually 

 decreasing, but between the nights of the 24th and 25th the light of 



* Supra, p. 142. 



