The most important and urgent problems posed by the improvement in mine working conditions - those regarding the safety and hygiene of miners - are dealt with. The supervision of mines by the Service des Mines is examined along with possible interventions by the Administration which, in the case of mines and quarries, covers a much broader area than in the case of other industries. Also studied are some major problems of the extractive industry: the recession affecting coal and iron mines, specific hazards in mines, and some aspects (other than hygiene and safety) of improving the mine working conditions.