FIRES IN MINES. 607 



wliicli it is necessary to remove to reach the gold-bearing strata, or 

 which themselves contain deposits of the precious mineral.* Naked 

 hills and fertile soils are alike washed away by the artificial torrent, 

 and the material removed — vegetable mould, sand, gravel, pebbles 

 and gold-dust — is carried down by the current and often spread 

 over ground lying quite out of the reach of natural inundations, 

 and burying it to the depth sometimes of twenty-five feet. An 

 orchard valued at $60,000, and another estimated at not less than 

 $200,000, are stated to have been thus sacrificed, and a report 

 from the Agricultural Bureau at "Washington computes the an- 

 nual damage done by this mode of mining at the incredible sum 

 of $12,000,000. 



Accidental fires in mines of coal or hgnite sometimes lead to 

 consequences not only destructive to large quantities of valuable 

 material, but which may, directly or indirectly, produce results 

 important in geography. The coal is occasionally ignited by the 

 miners' lights or other fires used by them, and certain kinds of 

 this mineral, if long exposed to air in deserted galleries, may be 

 spontaneously kindled. Under favorable circumstances, a stratum 

 of coal will burn until it is exliausted, and a cavity may be burnt 

 out in a few months which human labor could not excavate in 

 many years. Wittwer informs us that a coal mine at St. Etienne 

 in Dauphiny has been burning ever since the fourteenth century, 

 and that a mine near Duttweiler, another near Epterode, and a 

 third at Zwickau, have been on fire for two hundred years. Such 

 conflagrations not only produce cavities in the earth, but com- 

 municate a perceptible degree of heat to the surface, and the 

 author just quoted cites cases where this heat has been advantage- 

 ously employed in forcing vegetation. 



Projects of Agricultwral Improvements ly Duponchd, 



Duponchel's schemes of agricultural improvement are so 

 grandiose in their nature, so vast in their sphere of operation, 



* The water is sometimes driven through iron tubes under a hydrostatic 

 pressxire of several himdred feet, with a force which cuts away rock of con- 

 siderable solidity almost as easDy as hard earth. In this way of using water, 

 the cutting force might, doubtless, be greatly augmented by introducing sand 

 or gravel into the current. 



