xvi CONTENTS. 



Chapter XXXVIII. — Mineral Veins. 



Werner's doctrine that mineral veins were fissures filled from above — Veins of 

 segregation — Ordinary metalliferous veins or lodes — Their frequent coincidence 

 with faults — Proofs that they originated in fissures in solid rock — Veins shifting 

 other veins — Polishing of their walls or " slicken-sides " — Shells and pebbles in 

 lodes — Evidence of the successive enlargement and reopening of veins — Tour- 

 net's observations in Auvergne — Dimensions of veins — Why some alternately 

 swell out and contract — Filling of lodes by sublimation from below — Chemical 

 and electrical action — Relative age of the precious metals — Copper and lead 

 veins in Ireland older than Cornish tin — Lead vein in lias, Glamorganshire — 

 Gold in Russia, California, and Australia — Connection of hot springs and min- 

 eral veins — Concluding remarks, ----- page 767 



