File:The Quarterly journal of the Geological Society of London (13936963171).jpg

82

 PROF. 
 T. 
 G. 
 BONNET 
 ON 
 TWO 
 TEAVEESES 
 OE 
 TEE 
 

base

 of 
 the 
 hill, 
 crowned 
 by 
 the 
 celebrated 
 forts, 
 is 
 a 
 felspar-acti- 
 

nolite

 rock 
 *, 
 possibly 
 of 
 igneous 
 origin, 
 followed 
 by 
 mica-schist, 
 

and

 a 
 dull 
 green 
 rock 
 banded 
 with 
 epidote, 
 dipping 
 much 
 as 
 before. 
 

The

 rock 
 in 
 this 
 neighbourhood 
 is 
 stronger 
 and 
 less 
 easily 
 weathered 
 

than

 that 
 higher 
 up 
 the 
 valley, 
 and 
 recalled 
 to 
 my 
 mind 
 some 
 of 
 

Fig.

 4, 
 — 
 Diagram 
 of 
 '" 
 stratification-foliation" 
 in 
 Calc-mica-schist 
 

near

 Col 
 cle 
 Sestrie 
 r 
 res. 
 

The

 lines 
 roughly 
 indicate 
 micaceous 
 layers 
 ; 
 the 
 long 
 arrow 
 is 
 parallel 
 with 
 

the

 " 
 cleavage-foliation 
 " 
 of 
 the 
 mass 
 ; 
 the 
 small 
 arrow 
 shows 
 the 
 place 
 

where

 a 
 specimen 
 was 
 taken 
 for 
 examination 
 (p. 
 103). 
 

the

 chloritic 
 and 
 micaceous 
 rocks 
 about 
 Zermatt 
 or 
 near 
 St. 
 Vincent 
 

in

 the 
 Yal 
 d'Aoste 
 f. 
 Below 
 Fenestrelle 
 this 
 change 
 in 
 character 
 

becomes

 yet 
 more 
 marked. 
 The 
 rocks 
 now 
 are 
 more 
 massive, 
 form- 
 

ing

 bolder 
 crags 
 which 
 are 
 no 
 longer 
 masked 
 by 
 a 
 talus 
 of 
 shivery 
 

schist

 ; 
 in 
 short, 
 the 
 same 
 change 
 in 
 the 
 scenery 
 may 
 be 
 observed 
 

 Consists 
 chiefly 
 of 
 epidote, 
 actinolitic 
 hornblende, 
 quartz, 
 felspar 
 and 
 hsema- 
 

tite,

 with 
 some 
 sphene 
 and 
 rutile. 
 The 
 microscopic 
 structure 
 is 
 interesting 
 in 
 

many

 ways, 
 but 
 it 
 is 
 enough 
 for 
 my 
 present 
 purpose 
 to 
 say 
 that 
 subsequent 
 

mineral

 rearrangement 
 has 
 made 
 it 
 difficult 
 to 
 be 
 sure 
 of 
 the 
 original 
 condition 
 

of

 the 
 rock, 
 but 
 I 
 think 
 that 
 it 
 probably 
 was 
 igneous, 
 and 
 that 
 pressure 
 has 
 not 
 

been

 the 
 sole 
 agent 
 of 
 change. 
 

t

 Minerals 
 : 
 quartz, 
 epidote, 
 mica, 
 white 
 and 
 brown, 
 chlorite 
 (probably 
 in 
 

part,

 at 
 least, 
 replacing 
 the 
 latter), 
 garnet 
 (red), 
 a 
 little 
 rutile 
 and 
 a 
 colourless 
 

doubly

 refracting 
 mineral 
 of 
 ill-defined 
 limit 
 and 
 form, 
 probably 
 allied 
 to 
 zoisite 
 

or

 epidote. 
 The 
 rock 
 is 
 distinctly 
 foliated 
 and 
 banded. 
 The 
 constituents, 
 

especially

 the 
 white 
 mica, 
 are 
 fair-sized 
 and 
 well 
 defined, 
 as 
 if 
 freely 
 formed 
 ; 
 so 
 

if

 the 
 foliation 
 results 
 from 
 pressure, 
 a 
 good 
 deal 
 of 
 mineral 
 change 
 has 
 

subsequently

 occurred. 
 The 
 structure 
 is, 
 for 
 a 
 schist, 
 a 
 little 
 abnormal 
 ; 
 possibly 
 

that

 may 
 be 
 connected 
 with 
 the 
 presence 
 of 
 a 
 neighbouring 
 intrusive