( 522 ) 



considers tlio zone of (|uarlz sun-ouiiiliiiii' lliese miiieriils lo l>e of' 

 secoiidaiy origin, anil that |H-(>ssni'e (tn Ixttli sides iiad caused caxitics 

 which afterwards lia\e been lillcd np wilh (|uart/,. ') Some time 

 before, A. Daubrék had ah'eady fnrnished a description of trans- 

 formed crystals of pyrites foniid near Rimognes. ') Tiie stnihes of 

 other kinds of I'ocks led to the same conclnsion. ') An analysis iif 

 the pyritiferoiis (piartzites of the Cambrian system affords still l)etter 

 proof of the secondai-y origin of tliis qnartz, because in this case 

 the rock itself is composed of this mineral. When examining specimens, 

 it is easy to observe the sharp contrast between the two formations. 

 Tlie quartz which has formed itself around the pjrite, is clear and 

 transparent, seldom contains enclosui'es, and is built up of 

 fibres which stand perpendicular on the crystals of |)yrite. The 

 same structure is seen in the parts which form the veins. L. dk 

 DoRDOLOT, who has written on the same subject, is inclined to I'egard 

 this (juartz as chalcedony. ■*) 



By the aid of this data it has not been diflicult lo prove that 

 erratics of this kind have been widely dispersed, and it is very 

 ])robable that in the course of time their presence will be signalized 

 from many other places besides those we here indicate. 



1. Province Utrecht: Railway cutting near Rhenen, on the river 

 Lek, Darthuizer Berg, sandpit to the North of Rijsenburg, railway 

 cutting at Maarn, the heath near the pyramid of Austerlitz, near 

 Zeist, Heideboscli near tiie House ter Heide, between the stations 

 de Bilt and Zeist, to the rear of Houderinge near de Bilt, Soester Berg. 



2. Province of North-Holland : Hilversum and the sandy tract lo 

 the North of Larenberg. 



3. Province of Guelders : Heath near Epe, BenneUom near Wage- 

 ningeji. Eerbeek near Dieren, at several places around Eibergen 

 Borculo, Groenlo and Hettenheuvel near Doetichem. 



4. Province of Overiisel : Ileriker Berg near Markelo. 



1) Recherches sur la composition pt la stnietvire ties pliyllaties arilpimais. Bull, 

 du Musée roy. d'hist. nat. de Belgique. 11. Bruxelles 1S83, p. 184— 1H5. 



-) Etudes synthétiques de geologie expérimentale. 1. Paris 1879, p. 443. 



') H. LoRETz. Ueber Transversalschieferung und vcrwandtc Erscheinungen im 

 thiiringischen Schiefergebirge. Jahrbuch der k. preuss. geolog. Landesanstalt fiii' 

 1881. JJerlin 1882, p. 283-289. 



Hans Heusch. Bömmelöen og Karmocn met omgivelser. Kristiania 1888, p. fi9, 70. 



Alfr. Harker. On "Eyes" of Pyrites and other Minerals in Slate. Geolog. 

 Magazine (3) VI. London 1889, p. 396, 397. 



'*') Quelques observations sur les cubes de pyrite des quartzites revinions. Ann. 

 See. geolog. de Belgique. XXXI. Liége 1903—04. Mém. p. 505. 



