536 J. R. Kih'oe — Lnterite and Bauxite in Germany. 



(fl) The volcanic series near Giessen is divisible into two groups 

 according to Schottler/ viz. : 



a. Basische Basalte, with 40-6 to 46-7 per cent, of silica, sub- 

 divided into basalts with porphyritic and granular structures 

 respectively. The lavas of this stage attain a thickness of 

 about 20 metres. 

 /3. Trappgesteine (anamesites), containing 45-4 to 53-8 per cent. 

 of silica, and reaching some 30 to 40 metres in thickness, 

 perhaps more. 

 ly. A third group is added — jiingere basische Strorabasalte — to be 

 seen near Kloster Arnsburg, etc., referred to by Miinster'' 

 after Schottler. 

 These members of the series are well defined and traceable in the 

 field with precision. Yet at no point has it been found that the 

 junctions are marked by a definite zone of either bauxite or laterite. 

 In my traverses I passed from the Lower Basalt to the Traps, east of 

 "Watzenbom, where the rock is well exposed, without perceiving 

 indications of any such zone. Near Kloster Arnsburg also, where 

 the Upper Basalt rests on the Traps, in the river bank of the Wetter^, 

 only a little bole, tuff, and a very thin seam of white indurated clay 

 marked the junction of the two groups. 



(b) The area is traversed by several post-basalt faults, dislocating 

 the members of this otherwise undisturbed series. One of these, an 

 important 'fossa,' runs southward by Miicka, along the Ohm- and 

 Seen Valley, on each side of which, as shown by Miinster,^ laterites 

 (including ferruginous and aluminous clays with iron-ore and some 

 bauxite) have accumulated to a considerable depth, and to irregular 

 distances up to some 2,500 metres from the fault-line. This observer 

 has shown that the peculiar alteration of the basalt has proceeded 

 from the boundary plains of the component masses — pieces of breccia, 

 exfoliating balls, etc. — towards the centre of each mass, in some 

 cases leaving cores of undecomposed basalt; that the Brauneisenerz 

 — * Stuckerz ' of the miners — accumulates in the boundary joints, and 

 is removed from the adjoining clay by washing ; and that a considerable 

 accumulation of this ore exists beneath the yellow, red, and brown 

 lateritic clay, and in the basalt, some 16 to 18 metres from the surface. 

 The clay is studded here and there with exfoliating lumps of 

 aluminous material, grey and yellow coats alternating around central 

 cores of undecomposed basalt, precisely comparable to those seen in 

 the Antrim lithomarge. Sketches which I have made of these roundish 

 masses in the Grube ' Hoffnung,' near Stockhausen, might serve as 

 illustrations of those to be seen at the Giant's Causeway,* and near 

 Parkmore and Carnlough in Antrim. 



{c) The yellow and red claiy resulting from the disintegration of 

 the basalt is often strongly aluminous, and, as at rothen Hang, to be 

 afterwards referred to, contains lumps of bauxite with basalt structure. 

 At Grube 'Luse,' east of Miicka, these lumps are so numerous as to 



^ Abhandlung der Grossherz. Hessisch. Geol. Landes. zu Darmstadt, Band ir, 

 Heft iii, pp. 331, 451-67. 



2 Op. cit., p. 244. 3 p. 243. 



* See paper by Tate & Holden, Quart. Journ. Geol. Soc, 1870, p. 155. 



