W. Lindgren — Auriferous Veins of California. 201 



case of the brush discharge although we may be dealing with 

 very small values of self induction and small values of time, 

 we have on the other hand great values of R. I believe 

 therefore that the brush discharge is reduced to the case of 

 one throb which is analogous to the pilot spark in disruptive 

 discharges. In regard to the Aurora, it may be urged that 

 the resistance of the rarified air is not enormous. In answer 

 to this, it can be said that the phenomenon of the Northern 

 light can be best reproduced by intercalating a tube of rarefied 

 air with some megohms of a water resistance between the 

 terminals of a suitable transformer. The supposition that the 

 Xorthern light is produced by the action of extremely rapid 

 electrical oscillations on molecules of rarefied air is not borne 

 out by the theory of transient currents and experiment shows 

 that the phenomenon of the waving and apparent stratifica- 

 tion observed at times in the Aurora is due to the re-distribu- 

 tion of the lines of force which is produced by suitable earths 

 in the shape of regions of cloud and moisture. 



The comparatively small resistance of the electric spark in 

 air noticed by many observers is due I believe to the perma- 

 nence of path, for this path is intensely heated and is practi- 

 cally a charred hole in the air. When this path no longer 

 becomes such a hole and the heated air rises and is dissipated, 

 the oscillations of the electric spark become rapidly damped, 

 and we have the phenomenon of the glow at each of the 

 spark terminals without the disruptive discharge ; that is, we 

 perceive what is termed a brush discharge. The lines of force 

 crowding from one terminal seek through the air of the room 

 the other terminal, and in passing through rarefied air the 

 energy along the lines of force is manifested by molecular 

 actions which are apparently protean in form. I see therefore 

 no evidence for believing in the rapid oscillation of the 

 Aurora. 



Jefferson Physical Laboratory, Cambridge, Mass. 



Aet. XXX. — The Auriferous Veins of Meadow Lake, Cali- 

 fornia ; by Waldemar Lindgren. 



General type. — Fissure vei?is containing auriferous sul- 

 phides and arsenides with gangue of tourmaline, quartz and 

 ejpidote in granitic and diabasic rocks. 



By far the larger part of the veins of the gold belt of 

 California have a gangue of quartz alone or quartz with some 



