File:The Quarterly journal of the Geological Society of London (13937463002).jpg

VICTORIA

 PARK, 
 WHITEINCH, 
 NEAR 
 GLASGOW. 
 629 
 

tionably

 belongs 
 to 
 the 
 whin-vein, 
 indicates 
 that 
 there 
 is 
 a 
 difference 
 

in

 the 
 chemical 
 composition 
 of 
 the 
 two 
 bands, 
 the 
 deep 
 colour 
 of 
 the 
 

glass

 in 
 contact 
 with 
 the 
 shale 
 being 
 probably 
 due 
 to 
 the 
 presence 
 of 
 

metallic

 oxides 
 in 
 the 
 latter 
 rock. 
 If 
 this 
 be 
 so, 
 the 
 dark-colonred 
 

glass

 results 
 from 
 the 
 fusion 
 of 
 the 
 shale. 
 It 
 may 
 be 
 that 
 this 
 

is

 merely 
 the 
 outermost 
 glassy 
 selvage 
 of 
 the 
 whin 
 -vein, 
 tinted 
 

more

 or 
 less 
 by 
 metallic 
 oxides 
 derived 
 from 
 a 
 very 
 slight 
 in- 
 

cipient

 fusion 
 of 
 the 
 shale. 
 Assuming, 
 for 
 the 
 moment, 
 that 
 this 
 

is

 the 
 case, 
 we 
 have 
 to 
 account 
 for 
 the 
 well-defined 
 sinuous 
 line 
 of 
 

demarcation

 between 
 the 
 coloured 
 and 
 colourless 
 bands 
 of 
 glass, 
 and 
 

regarding

 these 
 two 
 bands 
 as 
 viscous 
 matter 
 of 
 different 
 densities, 
 

the

 existence 
 of 
 such 
 a 
 line, 
 the 
 trace 
 of 
 an 
 undulating 
 separation- 
 

surface,

 in 
 a 
 rapidly 
 cooling 
 magma 
 is 
 precisely 
 what 
 one 
 would 
 

expect.

 A 
 more 
 perfect 
 incorporation 
 of 
 the 
 two 
 glasses 
 would 
 have 
 

resulted

 in 
 a 
 lowering 
 of 
 tint 
 and 
 in 
 the 
 abolition 
 of 
 any 
 such 
 line 
 

of

 demarcation. 
 The 
 colourless 
 glass 
 may 
 therefore 
 be 
 regarded 
 

as

 the 
 tachylyte 
 of 
 the 
 whin- 
 vein, 
 while 
 the 
 darker 
 band 
 I 
 propose 
 

to

 distinguish 
 by 
 the 
 term 
 shale-glass. 
 

As

 already 
 pointed 
 out 
 by 
 Messrs. 
 J. 
 Young 
 and 
 D. 
 Corse 
 Glen, 
 

a

 considerable 
 variation 
 in 
 texture 
 and 
 colour 
 is 
 met 
 with 
 in 
 the 
 

material

 constituting 
 the 
 intrusive 
 veins 
 at 
 Whiteinch, 
 and, 
 to 
 quote 
 

their

 own 
 words, 
 " 
 Where 
 thinner 
 sheets 
 and 
 veins 
 derived 
 from 
 the 
 

main

 mass 
 are 
 found 
 to 
 be 
 intrusive 
 in 
 higher 
 or 
 lower 
 levels 
 of 
 the 
 

strata

 in 
 the 
 same 
 locality, 
 as 
 in 
 the 
 quarry 
 at 
 Victoria 
 Park, 
 the 
 

rock

 is 
 generally 
 seen 
 to 
 pass 
 from 
 its 
 normal 
 dark 
 colour 
 into 
 

different

 shades 
 of 
 light 
 grey 
 and 
 greyish 
 white, 
 the 
 alteration 
 being 
 

evidently

 due 
 to 
 its 
 contact 
 with 
 the 
 sedimentary 
 rock 
 and 
 to 
 rapid 
 

cooling,

 especially 
 along 
 the 
 lines 
 of 
 contact 
 " 
 *. 
 

Mr.

 Young 
 has 
 kindly 
 forwarded 
 small 
 specimens 
 of 
 the 
 veins 
 at 
 

Victoria

 Park, 
 showing 
 these 
 variations, 
 and 
 I 
 have 
 examined 
 

sections

 made 
 from 
 those 
 which 
 appeared 
 most 
 typical, 
 with 
 the 
 

result

 that 
 I 
 find 
 the 
 dark, 
 coarsely 
 crystalline 
 dolerite 
 to 
 consist 
 of 
 

felspars

 which, 
 from 
 their 
 extinction 
 -angles, 
 appear 
 to 
 be 
 labradorite, 
 

but

 which 
 are, 
 for 
 the 
 most 
 part, 
 in 
 too 
 advanced 
 a 
 stage 
 of 
 

alteration

 to 
 admit 
 of 
 any 
 optical 
 determination. 
 Olivine 
 and 
 

ilmenite

 are 
 also 
 plentiful 
 — 
 the 
 former 
 mineral 
 often 
 showing 
 

alteration

 into 
 serpentine 
 or 
 calcite, 
 while 
 the 
 ilmenite 
 has 
 been, 
 in 
 

great

 part, 
 converted 
 into 
 leucoxene. 
 Apatite 
 is 
 also 
 plentiful 
 in 
 

the

 form 
 of 
 slender 
 hexagonal 
 prisms. 
 A 
 considerable 
 amount 
 of 
 

green

 to 
 brownish-green 
 chlorite 
 is 
 also 
 present, 
 occasionally 
 form- 
 

ing

 fringes, 
 composed 
 of 
 fan-shaped 
 aggregates 
 of 
 plates, 
 around 
 the 
 

walls

 of 
 vesicles, 
 the 
 central 
 portion 
 of 
 the 
 vesicle 
 being 
 frequently 
 

filled

 with 
 calcite. 
 In 
 addition 
 to 
 the 
 minerals 
 mentioned, 
 the 
 

section

 shows 
 a 
 few 
 small 
 crystals 
 of 
 a 
 dark-brown 
 magnesian 
 mica, 
 

and

 here 
 and 
 there 
 a 
 speck 
 of 
 pyrites. 
 

Another

 specimen 
 from 
 the 
 same 
 locality, 
 but 
 of 
 a 
 totally 
 different 
 

character

 from 
 the 
 preceding, 
 is 
 very 
 fine-grained 
 in 
 texture, 
 and 
 of 
 

a

 pale 
 bluish-grey, 
 passing 
 into 
 a 
 buff 
 colour. 
 In 
 a 
 section 
 taken 
 

 Trans. 
 Geol. 
 Soc. 
 Glasgow,