62 



MISS C. A. EAISIN ON CERTAIN 



[Feb. 1 90 1, 



streaks. A patch seen on one joint-face is doubtless the section of 

 a nodular mass ; it measures about 56 x 36 inches, is nearly circular 

 above, but projecting at the side as shown in the diagram, and 

 shaped rather like a sprouting bulb Ij'ing on its side (fig. 1). The 

 layers of the sedimentary rock directly above are slightly arched, 

 and divided by small joints into lath-like structures. The 'nodule* 

 and the surrounding mass are cut by vertical joints ; and other joints 

 mostly occupied by quartz-veins, tailing off below, occur between 

 this ' nodule ' and the next. The rock is spotted along certain 

 lines, and seems indurated, weathering into ridges and furrows near 

 to the nodule. This has an outer zone, about 1 to 2 inches thick, 

 pale grey, crowded with sheaves and tufts of green hornblende 

 without orientation. The next zone, brown, speckled, crowded with 



Fig. 1. — Craglet about 6 feet high, showing a nodular patch luhich 

 measures 3 x nearly 5 feet : north-east of Bastogne, hy the 

 road to Longwilly. 



[The margin of the nodule, about 1 to 2 inches broad, is grey, the interior 

 being black from abundant carbon. The nodule throughout is rich in 

 hornblende-tufts, which, however, are seen more clearly in the greyer 

 outer zone, and are specially well developed in two small included bands.] 



hornblende, has a fairly sharp boundary which can be traced across 

 the stratification. The central area is dark, even blackish, and is 

 dusty and crumbles easily. Further, a harder band (about | inch 

 thick) projects into the 'nodule' from one side; it is black, and 

 crowded with crystals of hornblende ; another enclosed band some- 

 what lenticular, about | inch thick, is of a pale greyish colour. 



On examining the sedimentary rock under the microscope, it is 

 found to vary from a compact quartz-grit to an imperfect slate, 

 sometimes crowded with filmy microliths. Grains of corundum (?) 

 occur, possibly tourmaline ; and biotite (sometimes bleached) is found 

 not infrequently either in patches, or in flakes which may represent 

 original fragments with subsequent enlargement. The secondary 

 modifications, although all somewhat slight, do not always increase 

 nearer to the nodule. The difi'erences may be partly due to the 

 original nature of the layers ; but the hand-specimens are all fine- 



