296 M. D'Omalius D'Halloy on a 



A sketch of this nature, which I published in 1808, fur- 

 nished M. de Monbret with the idea of engaging me to con- 

 struct a map which should represent the mineral masses of 

 different kinds which cover the surface of France ; he pro- 

 mised at the same time to direct me by his advice, to place 

 at my disposal the numerous materials he had assembled in 

 the course of his studies, and to facilitate the acquisition of 

 new information, both by his correspondence from the Bureau 

 de Statistique, and his personal acquaintance with the most 

 able mineralogists, especially the Engineers of the Mining 

 Corps of France. I eagerly embraced a proposition which 

 so completely entered into my pursuits, and which would 

 place at my disposal an union of mjans superior perhaps to 

 those enjoyed by any naturalist ; but I soon perceived the 

 almost insurmountable difficulties of this work. I observed 

 that independently of those which result fiom the nature of 

 the work, the information with which I was surrounded left 

 immense deficiencies, that many observations which went 

 back to epochs, anterior to the progress geology has latterly 

 made, had become useless, and that far from being able to 

 supply them by my own labours, it would require the whole 

 lives of many laborious men to unite the necessary materials. 

 These obstacles would have made me renounce the enter- 

 prise if I had not felt that this kind of work had better be 

 ill done than not at all, since it may in some manner be said, 

 that error in this case leads us to truth. I also thought that 

 the kind of sacrifice I should make of my self-love for the 

 advantage of science, would entitle me to indulgence. I have 

 then constantly devoted to this work the little time that 

 duties foreign to science left at my disposal, and I have 

 made several tours which, though too rapid to procure me a 

 true acquaintance Avith the countries I passed through, yet 

 furnished me with the means of arranging the observations 

 of others on the same plan. 



Two principal points of view seem equally to lead io the 

 division of a country into physical regions determined by the 

 nature of the soil : in one it is considered geologically, i. e. 

 according to tlic epoch of formation , in the other with re- 



