( 530 ) 



to 36 M. cub, weighing from 10600 to 95400 K.G. '). He believed 

 tlicm to belong to the landenian stafje of the eocene system. His 

 opinion, that they covered the plateau of the Ardennes (where 

 Ch. Barrois was the first to discover similar masses '), to a height 

 of 672 M., has been much contested. E. van den Broeck classed these 

 sandstones first among the triassic system '), afterward referred them 

 to the oligocene system''), and finally suggested they might either be 

 oligocene, miocene or pliocene, but certainly not eocene*), (i. Dewalqi'e 

 pronounced them to be miocene °), whilst O. van Ertborn sought 

 their origin in the pliocene system '), more especially in the diestian 

 group "), but was of opinion that they must be regarded as the 

 remains of a "delta caillouteux" '). M. Mourlon, on the contrary, 

 held that they had been formed in the vicinity of their present place 

 of deposit, by the fusion of the "sable de Moll" ^''), an opinion 

 which cannot be maintained, because similar blocks are present in 

 the diluvium of Maastricht where no trace of this sand exists ''). 



J. GossELET compares these rocks with the fresliwater-quartzites of the 

 diluvium of tiie Rhine and, with reason, thinks that they belong 

 to the oligocene system '''). At all events it is universally admitted 

 that the Ardennes have been covered by extensive layers of tertiary 



1) Description sommaire des bloes colossaux ele gres blanc crlstalllns proveriant 



de l'étage landénien supérieur en différents points de la Gampine limbour- 



geoise. Ann. Soc. géolog. de Belglque XIV. 188(J— 87. Liége 1887. Mém. p. 117 — 130. 



-) Sur l'étendue du système tertiaire inférieur dans les Ardennes. Ann. Soc. 

 géol. du Nord. VI. Lille 1879, p. 371. 



3) Ann Soc. roy. malacolog. de Belgique XVI. Bruxelles 1880. Buil. p. LXXIV. 



*) Note préliminaire sur Ie niveau sLraligrapliicjue de la Belgique et de la region 

 d'origine de certains des bloes de gres quartzeux de la Moyenne et de la Basse- 

 Belgique. Buil. Soc. beige de Geologie IX. 1895. Bruxelles Proc. verb, p. 94—99. 



•') Les gres erraliques du sud du Dénier et dans la region de Heurgk. Buil. 

 Soc. beige de Geologie XV. 1001. Bruxelles 1902. Proc. verb. p. 628. 



<^) Ann. Soc. géolog. de Belgique. XIV. 1880—87. Liége 1887. Buil. p. 18. 



7) Le Quaternaire dans Ie sud de la Belgicpic. Buil. Soc. beige de Géolog. XV. 

 1901. Proc. verb. p. G62. 



f*) Quelques mots au sujet des divers niveaux gréseux du tertiaire supérieur 

 dans le nord de la Belgique. 1. c. p. G32. 



») Contribution a l'Étude des Élages nipélien, buldérien, diestien el poederlien, 

 1. c. XVI. 1902. Mém. p. Ü5. 



10) Gompie rendu de rexcursion géologi(iue en Gampiiie les 23, 2-i et 25 sep- 

 tembre. 1. c. Xlll. ISO'.l. Mém. p. 205, 213, 214. 



11) Alph. KiiEXS. Note siu- los ruches crislallines 1. c. PI. XIU. 



12) L'Ardenne. Paris 1888, p. 833. 



