FIRES IN MINES. 633 
than $200,000, are stated to have been thus sacrificed, and a re- 
port from the Agricultural Bureau at Washington computes 
the annual damage done by this mode of mining at the incredi- 
ble sum of $12,000,000. 
Accidental fires in mines of coal or lignite sometimes lead to 
consequences not only destructive to large quantities of valua- 
ble material, but which may, directly or indirectly, produce 
results important in geography. The coal is occasionally ig- 
nited 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 cir- 
cumstances, a stratum of coal will burn until it is exhausted, 
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 Dutt- 
weiler, 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 communicate a per- 
ceptible degree of heat to the surface, and the author just 
quoted cites cases where this heat has been advantageously 
employed in forcing vegetation. 
Projects of Agricultural Improvements by Duponchel. 
Duponchel’s schemes of agricultural improvement are so 
grandiose in their nature, so vast in their sphere of operation, 
and so important in their possible effects upon immense tracts 
of the earth’s surface, that they must be considered as projects 
of geographical revolution, and they therefore merit more 
than a passing notice. In a memoir already quoted, and in a 
later work,* this engineer proposes to construct artificial tor- 
rents for the purpose of grinding up calcareous rock, by roll- 
ing and attrition along their beds, and thus reducing it into a 
fine slime; and at the same time these torrents are to transport 
* Traité @ Hydraulique et de Géologie Agricoles, 1868. 
