86 On the Geographical Extent of [Feb. 



so much of what was valuable was obscured by what was 

 repulsive, and the patriot will regret that so much public spirit 

 and integrity was rendered useless by excessive zeal and undue 

 attachment to speculative principles. 



Article II. 



Memoir on the Geographical Extent of the Strata of the Environs 

 of Paris. By J. J. Omalius d'Halloy.* 



The learned examinations of MM. Cuvier and Brongniart 

 have attracted the general attention to the strata of the environs 

 of Paris. This is not to be wondered at, as they contain so 

 great a quantity of the remains of organized beings that they 

 present a vast field to the researches of true philosophical geo- 

 logy ; which, drawing its conclusions from the knowledge of the 

 organic remains buried in the earth, can alone give us certain 

 means of comparing distant strata, and which will, perhaps, 

 one day throw some light on the different catastrophes that 

 have changed the surface of the globe, as it has already given 

 indications of the nature of the liquids in which some of those 

 phenomena have taken place. 



The extent of the Paris basin, and the plan of MM. Cuvier 

 and Brongniart, having prevented them from determining the 

 whole of the limits of this district, I have thought that a 

 detailed examination of those limits would be interesting, and I 

 have undertaken several journeys for that purpose, of which I 

 now offer the result. I should, however, observe, that a part of 

 this labour has been already performed by M. Desmarest, sen.f 

 who has carefully traced the limits of the chalk of Champagne. 

 I have also derived much assistance from the mineralogical atlas 

 of M. Monnet, and two memoirs of MM. de Tristan and Bigot de 

 Morogues, for some other parts. 



The different formations which compose the strata of the 

 environs of Paris, considered in their mass, and without includ- 

 ing some insulated portions, occupy a surface of about 174 

 square myriameters, J in the form of an irregular polygon, longest 

 in the direction from north to south. The greater axis may be 

 considered a line of 30 myriameters § drawn from Laon to 

 Blois. The outline of this polygon passes near the towns of 

 Laon, La Fere, Noyon, Clermont, Beaumont, Gisors, Mantes, 

 Houdan, Chartres, Chateaudun, Vendome, Blois, Orleans, 

 Cosne, Montargis, Nemours, Nugent-sur-Seine, Sezarme, Eper- 

 nay> and Rheims. Throughout all this extent the Paris strata 



* From the Annalosdes Mines, vol. i. 



+ Dictionnaire de Oeographie Physique; part of theEncyclopedie Methndique. 



t 7,100 sq. miles, English. ^ 3*8,091 English yards. 



