660 Intelligence and Miscellaneous Articles. 



traces the valley of the Vejtestrands Lake, which belongs to the first 

 of the above series, until it reaches the Hafslo Lake, which lies at 

 a point where the valleys of the two series intersect. The present 

 line of drainage follows a valley of the second series from the lake 

 to the fjord, but a disused outlet from the lake to the fjord is 

 described belonging to the first series. The author, while thinking 

 that the disused outlet is probably the older of the two, gives 

 reasons for believing that both outlets were in use perhaps 

 simultaneously during the latter part of the Glacial Period, when 

 a glacier filled and overflowed the basin of the Hafslo Lake. 



The author describes some giants' kettles and other examples of 

 erosion by water, which for various reasons he believes to date 

 from a time when the glacier extended to the places where they 

 are now found, and it is suggested that they were the work of a 

 river flowing under the ice or between the ice and the rock. 



2. ' On the Genus Aulophyllum.' By Stanley Smith, B. A., M.Sc, 

 F.G.S., Clare College, Cambridge. 



LXVI. Intelligence and Miscellaneous Articles. 



ON THE CURRENT POTENTIAL CURVES OF THE 

 OSCILLATING SPARK. 



To the Editors of the Philosophical Magazine. 



Gentlemen, — 



M. Eoschansky has kindly drawn my attention to a nume- 

 rical error which I have made on p. 719 in the above paper 

 (Phil. Mag., Nov. 19] 2) in estimating the maximum current 

 density which completely ionized air is capable of carrying with 

 the field which exists in the spark. The field in the spark is there 

 wrongly quoted as 10*5 volts per cm., whereas it should be 

 10*5 volts per mm. (Eoschansky, Ann.d.Phys. xxxvi. p. 290, 1911). 

 The corrected estimate for the maximum current density is 



0=600,000 amp./sq. cm., 



instead of the 63,000 there stated. I may add that the argument 

 of the paragraph is not affected, as it is concerned with the order 

 of magnitude only of the quantity, the calculation being of 

 necessity only a rough one. 



I also find that the conclusion of M. Eoschansky, that at high 

 frequencies the spark tends to behave like a pure resistance, which 

 was referred to on p. 713 as being in disagreement with my 

 observations, has been to some extent withdrawn in bis later 

 paper (I. c. p. 305). 



Yours faithfully, 



The University of Sheffield, S. E. MlLNER. 



17th Feb., 1913. 



