File:The Quarterly journal of the Geological Society of London (13937049251).jpg

TERTIARY

 VOLCANOES 
 OP 
 THE 
 WESTERN 
 ISLES 
 OF 
 SCOTLAND. 
 187 
 

12.

 The 
 Tertiary 
 Volcanoes 
 of 
 the 
 Western 
 Isles 
 of 
 Scotland. 
 

By

 Professor 
 John 
 W. 
 Judd, 
 F.R.S., 
 F.G.S. 
 (Eead 
 January 
 9, 
 

1889.)

Contents.

 Page 
 

I.

 Introduction 
 187 
 

II.

 Views 
 WHICH 
 WERE 
 maintained 
 previous 
 to 
 1874 
 188 
 

III.

 Conclusions 
 announced 
 in 
 1874, 
 which 
 have 
 been 
 confirmed 
 by 
 

subsequent

 Observations 
 190 
 

A.

 The 
 Relations 
 between 
 the 
 Plutonic 
 and 
 the 
 Volcanic 
 Rocks 
 of 
 

the

 Western 
 Isles 
 of 
 Scotland 
 191 
 

B.

 The 
 Existence 
 of 
 five 
 Great 
 Centres 
 of 
 Eruption, 
 with 
 many 
 minor 
 

and

 scattered 
 Vents 
 in 
 the 
 Western 
 Isles 
 of 
 Scotland 
 192 
 

C.

 The 
 Subaerial 
 Origin 
 of 
 the 
 Lavas 
 and 
 Tuffs, 
 and 
 the 
 Tertiary 
 Age 
 

of

 both 
 the 
 Plutonic 
 and 
 the 
 Volcanic 
 Rocks 
 194 
 

IV.

 Conclusions 
 announced 
 in 
 . 
 874, 
 which 
 are 
 Disputed 
 in 
 a 
 recent 
 

Memoir

 by 
 Dr. 
 A. 
 G-eikie 
 196 
 

A.

 The 
 General 
 Order 
 in 
 which 
 the 
 several 
 Varieties 
 of 
 Igneous 
 Rocks 
 

were

 erupted 
 in 
 the 
 District 
 196 
 

B.

 The 
 Existence 
 in 
 the 
 District 
 of 
 great 
 Volcanoes, 
 which 
 have 
 

been

 dissected 
 by 
 Denudation 
 201 
 

V.

 The 
 Alternative 
 Theory 
 op 
 " 
 Fissure-Eruptions 
 " 
 206 
 

A.

 Can 
 great 
 Basaltic 
 Plateaux 
 be 
 formed 
 by 
 ordinary 
 Volcanic 
 

Action?

 ;. 
 206 
 

B.

 The 
 Age 
 of 
 the 
 Basic 
 Dykes 
 of 
 North 
 Britain 
 209 
 

C.

 Insufficiency 
 of 
 these 
 Dyke-fissures 
 as 
 Sources 
 of 
 the 
 Plateau-basalts 
 210 
 

D.

 Arguments 
 drawn 
 from 
 the 
 Lava-fields 
 of 
 the 
 Western 
 Territories 
 

of

 the 
 United 
 States 
 212 
 

VI.

 Conclusion 
 215 
 

I.

 Introduction. 
 

In

 the 
 year 
 1874 
 I 
 communicated 
 to 
 this 
 Society 
 the 
 results 
 of 
 

my

 studies 
 concerning 
 the 
 Tertiary 
 and 
 Older 
 Volcanic 
 rocks 
 of 
 

Western

 Scotland, 
 and 
 their 
 relations 
 to 
 the 
 Secondary 
 strata 
 with 
 

which

 they 
 are 
 so 
 intimately 
 associated 
 *. 
 The 
 very 
 generous 
 

manner

 in 
 which 
 the 
 memoir 
 dealing 
 with 
 those 
 subjects 
 was 
 

received

 by 
 this 
 Society 
 — 
 and 
 especially 
 by 
 those 
 who 
 were 
 at 
 that 
 

time

 the 
 leaders 
 of 
 geological 
 thought 
 in 
 this 
 country 
 — 
 can 
 never 
 

be

 forgotten 
 by 
 me. 
 Such 
 a 
 reception 
 lays 
 upon 
 the 
 author 
 of 
 a 
 

memoir

 certain 
 very 
 obvious 
 responsibilities. 
 In 
 the 
 event 
 of 
 serious 
 

and

 fatal 
 errors 
 being 
 indicated 
 in 
 his 
 observations 
 or 
 reasoning, 
 it 
 

is

 clearly 
 his 
 duty 
 to 
 come 
 forward 
 and 
 frankly 
 withdraw 
 the 
 state- 
 

ments

 to 
 which 
 this 
 Society 
 has 
 given 
 such 
 wide 
 currency. 
 It 
 is 
 

equally

 incumbent 
 upon 
 him, 
 should 
 his 
 premises 
 and 
 conclusions 
 

be

 openly 
 challenged 
 on 
 what 
 seem 
 to 
 him 
 to 
 be 
 insufficient 
 grounds, 
 

to

 undertake 
 the 
 task 
 of 
 re-examining 
 and, 
 if 
 necessary, 
 of 
 defending 
 

his

 views. 
 

It

 may 
 not 
 perhaps 
 be 
 out 
 of 
 place 
 to 
 remark 
 that 
 my 
 work 
 in 
 

Scotland,

 to 
 which 
 were 
 devoted 
 .five 
 years 
 of 
 heavy 
 labour 
 and 
 

careful

 research, 
 was 
 one 
 that 
 taxed 
 to 
 the 
 full 
 the 
 powers 
 of 
 a 
 

private

 individual. 
 It 
 involved 
 the 
 examination 
 of 
 the 
 physical 
 

relations

 and 
 the 
 discussion 
 of 
 the 
 palseontological 
 characteristics 
 of 
 

the

 whole 
 of 
 the 
 rocks 
 of 
 the 
 Highlands 
 between 
 the 
 Old 
 Red 
 Sand- 
 

 Quart. 
 Journ. 
 Geol. 
 Soc. 
 vol. 
 xxx. 
 (1874), 
 pp.