1893.] On the Flow in Electric Circuits. 7 



the metal in each case. Lithium chloride gives no continuous 

 spectrum. 



The Volatility of Metals. One of the most interesting facts ascer- 

 tained by this investigation is the volatility of all the metals 

 examined, except platinum, and particularly the extraordinary 

 volatility of manganese, and, to some extent, of the infusible metal 

 iridium. Metal believed to be pure iridium is seen to have dimin- 

 ished after the flame has played upon it for about two hours. 



III. " On the Flow in Electric Circuits of Measurable Induct- 

 ance and Capacity; and on the Dissipation of Energy in 

 such Circuits." By ALFRED W. PORTER, B.Sc., Demon- 

 strator of Physics in University College, London. Com- 

 municated by Professor G. CAREY FOSTER, F.R.S. Received 

 May 4, 1893. 



The arrangement of the apparatus in the experiments here de- 

 scribed was as follows : 



L is a coil of self -inductance L (= 0'42 henry) and of resistance 

 R (= 28 ohms). 



S is a condenser of capacity S (= 5 x 10~ 6 farads), and in the same 

 branch with it is an inductionless resistance, r, the value of which can 

 be varied. 



E is a battery which, when the circuits shown are complete, pro- 

 duces a current through L, and charges the condenser. 



A and B are the two contact pieces of a pendulum interruptor. 

 The two circuits can be broken at these places by the pendulum : the 

 time interval between the two ruptures being regulated by the dis- 

 tance between the contact pieces. 



One centimetre distance apart corresponds to 5*270 thousandths of 

 a second, and, as this distance can be read easily (by a vernier 

 attached) to a tenth of a millimetre, it is possible to measure inter- 

 vals of 



5 hundred-thousandths of a second. 



The method of the experiments is as follows : 



