( 528 ) 



"liave been picked up near Hnissels ')". K. iAIartin ') and J. Lorié') 

 in fact assign tlieni also to tliat locality; they forget, however, that 

 no strata of nnmmulitic limestone are known to exist tiiere "). Their 

 origin lies much farther South. In 'J 863 J. Gosself,t had ah-eady 

 indicated the original source of these "silex a Nummnlites", of which 

 a few years later he published a description '). They are dispersed 

 in large cpiantities in the arrondissement of Avesnes, in the department 

 du Nord, more especially in the environs of Trelon ') where, on 

 account of their hardness, they are frequently used for the paving 

 of roads. 



Since then numerous fragments of this rock have also been found 

 in Belgium, specially on the plateau situated between the Meuse and 

 the Sambre, e. g. around Silenrieux, Sivry, Clermont, etc., as well 

 as in parts lying further West '). 



The second question which we have to examine, is the period at 

 which these rocky fragments from the Ardennes have been trans- 

 ported to districts at present situated North of the Rhine. The view 

 expressed by Staring that this transport has taken place before the 

 deposition of Scandinavian erratics, seems at present also satisfactorily 

 established, for those carried by the Meuse. In the railway cuttings 

 at Maarn and Rhenen, I'ocks of diverse origin lie together in friendly 



1) De Bodem van Nederland. II. Haarlem iSiiÜ, p. 89. 



2) Niedeilandische und Nordwestdeutsclie Sedimentaigeschiebe. Leiden 1878, p. 37. 

 *) Les metamorphoses de I'Escaut et de la Meuse. Bull. Soc. beige de Geologie, 



IX. 1895 Bruxelles 1895—96, Mém. p. 60. 



*) E. VAN DEN Broeck. A propos de Torigine des Nummuiiles laevigata du gravier 

 de base du Laekénien. Bull. Soc. beige de Geologie. XVI. 1902. p. 580. 



S) De I'exlension des couidies a Nummulites laevigata dans le nord de la France. 

 Bull. Soc, géolog. de la France (3) II. 1873—74. Paris 1874, p. 51-58. See also 

 Ann. Soc. géol. du Nord. 1. 1870-74. Lille, p. 36. 



*) Gompte-rendu de rexcursion du 7 Septembre [1874] a Tiélon 1. c. p. 681. 

 Leriche. L'Eocéne des environs de Trelon. Ann. Soc. géol. du Nord. XXXII. Lille 

 1903. p. 179. 



'') Michel Mourlon. Sur les anias de sable et les blocs de gres dissiminés a la 

 surface des collines famenniennes dans TEntre-Sambre-et-Meuse. Bull. Acad. roy. 

 de Belgique (3) VII. Bruxelles 1884, p. 301-303. 



A. RuTOT. Sur I'age de gres dc Fayut. Bull. Soc. beige de Geologie I, 1887, 

 p. 47. 



L. Bayet. Premiéi'e note sur quelques depots lertiaii-cs de FEnlre-Sambi-e-et-Meuse. 

 Bull. Soc. beige de Geologie X, 1896. Bruxelles 1897-99 p. 139-140. 



G. Velge. De I'exlension des sables eocenes laek^niens a travers la Hesbaye et la 

 Haute Belgique. Ann. Soc. géolog. de Belgique, XXV, 1897—98. Liége, p. GLXV. 



A. Bkiart. Notice descriptive des terrains lerliaires el crétacés de Entre-Sambre- 

 et-Meuse. Ann. Soc. géolog. de Belgique XV. 1887 — 88, p. 17, 



