58 IMineralogical Geography of the Environs oj Paris, 



hiviation is composed of sand of all colours, niarle, or even 

 of the mixture of these three substances, impregnated with 

 carbon, which mves it a brown and even black appear- 

 ance. It contains rounded flints ; but what characterizes 

 it more particularly is, the remains of the huge organized 

 bodies wirh which it abounds. It is in this formation that 

 we find large nunks of trees, bones of elephants, of oxen, 

 antelopes, and other large mammiier^. 



It is also to this formation that we may ascribe the ac- 

 cumulation of flints at the bottom of valleys ; and probably 

 also those of Siome plains, such as the Bois de Boulogne, the 

 plain of Nanterre at Chateu, and certain parts of the forest 

 of St. Germain. 



This alluvium is not only found in the bottom of our 

 present valleys, but it has covered valleys or excavations 

 which have been since filled up. We may observe this ar- 

 rangement in the deep cutting made near Scran, for the ca- 

 nal of Ourque. This cutting shows an ancient cavity, filled 

 with the substances which compose the alluvium, and it is 

 in this kind of marshy bottom that we have found bones of 

 elephants and large trunks of trees. 



It is to the existence of these ruins of organized bodies 

 which are not yet entirely decomposed, that we ought to 

 ascribe the dangerous and frequently pestilential emana- 

 tions which are extricated from these soils, when they arc 

 stirred up for the first time since the period of their forma- 

 tion ; for it is the same with this formation, which appears 

 to be so modern, as with all those others which vvc have 

 examined. Although very modern in comparison with the 

 other soils, it is still anterior to any historic jsra ; and we 

 may say, that the alluvium of the old does not in any re- 

 spect resemble that of the present world, since the wood 

 and animals found in them are ei'itirely different, not only 

 from the animals of the countries where they are found de- 

 pobitedj but also from all those hitherto known. 



VII. ^fc- 



