ASSOCIATED META MORPHIC ROCKS OF THE LAKE-DISTRICT. 5 



the spotted to the mica-schist takes place by the increase of mica and 

 quartz and the disappearance in great part of the andalusite and 

 chiastolite. In the most fully developed mica-schist the whole rock 

 consists of quartz and two micas, brown and white ; but in most 

 cases there are either traces left of the rectangular spots, often very 

 faint, or sometimes even of well-developed crystals of chiastolite or 

 andalusite. Occasionally, also a little hornblende appears to be pre- 

 sent ; but this mineral is by no means a constant or characteristic 

 one in any of the rocks of this metamorphic series. 



In fig. 5 is shown the junction of the granite and schist, the former 

 appearing white in the specimen, and the latter being a dark mica- 

 ceous schist. The junction is well defined, microscopically as well 

 as lithologically, the crystalline particles of mica and quartz in 

 the schist being small as compared with those of the same minerals 

 in the granite. Crystals of felspar in the schist seem also com- 

 paratively rare. In the figure the variously clouded patches are 

 mostly quartz, and some crystals of triclinic felspar occur on the 

 left-hand side : small plates of mica are also present. 



From the above descriptions it will be seen that, the mineral horn- 

 blende being scarce, the old name of hornblende slate is false when 

 applied to the schistose rock ; and I think there can be no question 

 that it is an andalusite schist, probably the equivalent of the German 

 Knotenschiefer. 



III. Chemical Examination. 



Having noticed the appearance and bearing of these rocks in the 

 field, and examined their microscopic structure, we turn to their 

 chemical composition. The following analyses have been made for 

 me by Mr. John Hughes, F.C.S. ; and I prefix an analysis of Welsh 

 slate, after Haughton, to compare with A. 



£*" 



* 





E. 



C. 



X w fl 



QQ 



sis 



Silica 



Alumina 



Lime 



Magnesia 



Potash 



Soda 



Ferrous oxide 



Ferric oxide 



Bisulphide of iron 



Phosphoric acid 



Sulphuric acid 



Carbonic acid 



Loss on ignition, and water 



60-50 

 19-70 

 112 

 220 

 3-18 

 2-20 

 7-83 



3-30 



65-725 

 14-182 

 1176 

 2-342 

 3-261 

 1-981 

 7-306 

 trace 

 trace 

 trace 



•294 

 trace 

 3-733 



54-448 

 23930 

 1-288 

 2-379 

 3-010 

 2-086 

 8-883 

 trace 

 1-801 

 •085 

 trace 

 trace 

 2-090 



53174 

 24-460 

 1-512 

 1-946 

 5-037 

 2-930 

 8-634 

 •246 



•128 

 trace 

 trace 

 1-933 



75223 

 11-140 

 1-624 

 1-081 

 4516 

 3-996 

 1-771 

 trace 



•149 

 trace 

 trace 



•500 



100000 



100 000 



100 000 100 000 



