( 518 ) 



The (jiuintity of beiizvl lirdiiiidc lias therefore, murli increased 

 l)iit llie proporlion (niJio-piint has kepi fairly well imallered. 



For fiirthei' particulars as to these researches van ukr Laan's 

 original dissertation should be consulted. An article by him on 

 this subject will also appear, shortly, in the "Recueil". 



Amsti'nhiin, Sept. '05. Chemical Laboratory of the University. 



Geology. — "On fragments of rocks from the Ardennes found in 

 the Diluvium of the Netherlands North of the Rhine." By 



Prof. A. WiCHMANN. 



(Communicated in the meeting of November 25, 1905) 



Ever since the 18*'i Century, the attention of geologists has been 

 drawn to the boulders scattered about our heathgrounds and in opposition 

 to the \'arious and oftentimes curious theories started to account for 

 their presence there, A. Vosmakr llieu already expressed the opinion 

 that they had been transported from elsewhere by "A Mighty Flood". M 

 A little later, A. Bruomans ") and after him 8. .T. Brugmans ') pointed 

 to Scandinavia as the original home of these erratics ; but this view, 

 though shared by a few other scientists, was not generally adopted 

 until after the publication of J. F. L. Hausm.\nn's treatise *). It seemed 

 then as if the only question still remaining to he solved, was in what 

 way and by what road this transport had been aifected. Little or 

 no thought was üiven to the possibility that other countries might 

 be also accountable for their origin. 



It was not until 1844 (hat W. C. H. Staring, whilst investigating 

 the nature of these boulders, discovered that at least those composed 

 of sandstone and quartzite, were found as well in the Ardennes, in 

 the districts of Bere, and JMai'k, at the foot of the Harz Mountains 



1) Johannes van Lier. Oudheidkundige brieven, bevattende eene verhandelin.; 

 over de manier van Begraven, en over de Lijicbussen, Wapenen,' Veld- en Eere- 

 teekens der oude Germanen. Uitgegeven.... door A. Vosmaer. 's-Gravenhage 1760, 

 p. XV, 10, 11, 103. 



-) Sermo publicus, de monumentis variarum mutatationum, quas Belgii foederati 

 solum aiiquando passum fuit. Verhandelingen ter nasporinge van de Wetten en 

 Gesteldheid onzes Vaderlands. 1. Groningen 1773, p. 5D4, 508. 



') Lilhologia Groningana. Groningae 17S1. Preface p. 2, 3. 



') Verhandelingen over den oorsprong der Graniet en andere primitieve Rots- 

 blokken, die over de vlakten der Nederlanden en van het Noordelijk Diiitschland 

 verspreid liggen. Natuurk. Verhandelingen der Hollandsciie Maatsch. van Wetensch. 

 XIX. Haarlem 1831, p. 341-349. 



