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THE  NINETEENTH 

CENTURY  SERIES 


EDITOR  : 

JUSTIN  MCCARTHY. 
ASSOCIATE  EDITORS  : 
W.  P.  TRENT,  LL.D. 
T.  G.  MARQUIS. 
CHARLES  G.  D.  ROBERTS. 

REV.  W.  H.  WITH  ROW;,  D.D. 


PROGRESS  OF  SCIENCE 
IN  THE  CENTURY 


BY 
J.  ARTHUR  THOMSON,  M.A., 

Regius  Professor  of  Natural  History  in  the  University  of  Aberdeen  ;  Author  oj 

"  The  Study  of  Animal  Life,"  "  The  Science  of  Life,"   "  Outlines  of 

Zoology"  etc;  Joint-Author  of  u  The  Evolution  of  Sex." 


THE   LINSCOTT   PUBLISHING   COMPANY 

TORONTO  AND  PHILADELPHIA 
LONDON :  47  Paternoster  Row 

VV.    &    R.    CHAMBERS,    LIMITED 

EDINBURGH  :  339  High  Street 
1906 


Entered,  according  to  Act  of  Congress,  in  the  Year  One  Thousand  Nine 
Hundred  and  Three,  by  the  Bradley-Garretson  Co.,  Limited,  in  the  Office 
of  the  Librarian  of  Congress,  at  Washington. 


Entered,  according  to  Act  of  Parliament  of  Canada,  in  the  Year  One 
Thousand  Nine  Hundred  and  Three,  by  the  Bradley-Garretson  Co.,  Limited, 
in  the  Office  of  the  Minister  of  Agriculture. 


All  Rights  Reserved. 

$  R  A  jf 


To  discuss  in  a  single  volume  the  progress  of  sci- 
ence in  the  nineteenth  century  has  been  no  easy  task, 
and  the  author  craves  the  reader's  indulgence.  It 
must  be  remembered  that  the  book  does  not  pretend 
to  be  a  history  of  nineteenth  century  science;  it 
is  designed  simply  as  an  introduction  to  many  histo- 
ries— some  still  unwritten.  It  is  not  a  consecutive 
story  of  the  marvellous  progress  of  knowledge  which 
the  century  witnessed ;  it  is  simply  a  record  of  some 
of  the  great  scientific  events.  Many  famous  names 
and  many  important  discoveries  have  been  left  un- 
mentioned,  for  any  attempt  at  exhaustiveness  would 
have  made  a  volume  of  this  size  a  mere  catalogue.  On 
the  other  hand,  there  has  been  a  serious  attempt  to 
discuss  the  great  theme  so  as  to  give  prominence  to 
the  salient  steps  of  progress.  To  have  attempted  this 
in  an  easy-going  mood  would  have  been  irreverent  to 
the  past  and  insulting  to  the  serious  reader ;  therefore 
no  apology  is  offered  for  the  difficulty  of  some  of  the 
pages,  nor  does  it  seem  necessary  to  apologise  for  the 
numerous  quotations  from  expert  authorities, — they 
help  to  give  personal  reality  to  some  of  the  pages, 
and  they  were  needed  as  acknowledgments  of  the 
author's  indebtedness.  J.  A.  T. 

USIVEBSITY  OF  ABERDEEN,  SEPTESCBEB,  1902. 

Note. — The  reader  will  understand  that  the  absence  of  any  reference 
to  radium  and  its  marvellous  properties  is  due  to  the  fact  that  the  book 
was  printed  before  the  discovery  had  been  made.  In  the  same  way  it 
will  be  obvious  why  Sir  Oliver  Lodge  and  Sir  William  Kamsay  are  not 
duly  entitled,  and  why  some  great  men  of  science  no  longer  with  us. 
such  as  Gegenbaur,  Spencer,  and  Zittel,  are  referred  to  in  the  present 
tense. 


CONTENTS. 


BOOK  ONE. 

INTRODUCTORY. 


CHAPTER  I. 

THE  SCIENTIFIC  MOOD. 

PACT 

The  Meaning  of  Science. — A  Contrast  of  Moods. — Charac- 
teristics of  the  Scientific  Mood — (a)  A  Passion  for  Facts 
— (b)  Cautiousness — (c)  Clearness  of  Vision — (d)  Sense  of 
Inter-Relations. — The  Aim  of  Science. — Scientific  Method..  1 

CHAPTER  II. 

THE  UNITY  OF  SCIENCE. 

Classification  of  the  Sciences. — The  Correlation  of  Knowledge. 
— Need  for  Criticism  of  Scientific  Work. — Unity  of  Life. 
— Unity  of  Science. — Unity  of  Nature 25 

CHAPTER  III. 

PROGRESSIVENESS  OF  SCIENCE. 

The  First  Condition  of  Scientific  Progress. — The  Fact  of  Pro- 
gress.— Its  Necessity. — Scientific  Conclusions  of  the  First 
Magnitude. —Factors  in  Further  Progress. — Justification 
of  Science. — Science  and  Practical  Utility 41 


viii  CONTENTS. 

BOOK  TWO. 

MATTER  AND  ENERGY. 


CHAPTER  IV. 

A  CENTURY  OF  CHEMISTRY. 

PAOB 

Search  for  the  Elements. — Theory  of  Combustion  and 
the  Conservation  of  Matter. — The  Atomic  Theory. — De- 
velopment of  the  Atomic  Theory.  —  Development  of 
Organic  Chemistry. — The  Periodic  Law. — Co-operation  of 
Chemistry  and  Physics. — The  Circulation  of  Matter. — 
Chemical  Affinity 70 


CHAPTER  V. 

THE  PROGRESS  OF  PHYSICS. 

Introductory. — The  Newtonian  Foundation. — Conservation 
of  Energy. — Heat  as  a  Mode  of  Action. — Kinetic  Theory 
of  Gases.  —  Undulatory  Theory  of  Light.  —  Theory 
of  Electricity.  —  Theories  of  Matter.  —  Theory  of  the 
Ether ..  131 


CHAPTER  VI. 

ADVANCE  OF  ASTRONOMY. 

From  Copernicus  to  Newton. — Applications  of  the  Gravita- 
tion-Formula.—The  Study  of  the  Stars.— Extension  and 
Intensifying  of  Observation.  —  Physical  and  Chemical 
Problems. — Spectrum  Analysis. — The  Evolution-Idea  in 
Astronomy 179 


CONTENTS.  IX 

CHAPTER  VIL 

GROWTH  OF  GEOLOGY. 

PAQE 

Cataclysmal,  Uniformitarian,  Evolutionary.  —  Foundation- 
Stones  of  Geology.  —  The  Evolution-Idea  in  Geology. — 
Age  of  the  Earth.  —  Reading  the  Rock-Record. — Prob- 
lems of  Earth-Sculpture. — Recognition  of  Ice  Ages. — The 
Hand  of  Life  upon  the  Earth.— The  Problem  of  Petrog- 
raphy.— Note  on  the  Scientific  Development  of  Geog- 
raphy.—An  Illustration  of  Oceanography  ..v 225 


BOOK  THREE. 

SCIENCE  OF  OKGANISMS :  LIFE-LORE. 


CHAPTER  VIII. 

THE  DEEPENING  OF  PHYSIOLOGY. 

Historical  Outline. — Physiology  of  the  Living  Organism  as 
a  Whole. — Study  of  the  Functions  of  Organs. — Physiology 
of  Tissues. — The  Life  of  Cells. — As  regards  Protoplasm. 
— The  Unsolved  Secret  of  the  Organism. 283 


The  Morphological  Question  and  its  Progressive  Answers. — 
Foundations  of  Morphology. — The  Appreciation  of  Fossils. 
— Minute  Analysis 329 


CHAPTER  X. 

GEXEOLOGICAL. 

Geneology.— Development  of  the  Individual. — Experimental 
Embryology.— Heredity  and  Inheritance 365 


X  CONTENTS. 

CHAPTER  XL 

THE  THEORY  OF  ORGANIC  EVOLUTION. 

FAQI 

The  General  Idea  of  Organic  Evolution. — History  of  the 
Evolution -Idea.  —  The  Present  Aspect  of  the  Evolution 
Theory 424 


BOOK  FOUR 

PSYCHOLOGY,  ANTHROPOLOGY,  AND 
SOCIOLOGY. 

(MIND,  MAN,  AND  SOCIETY.) 


CHAPTER  XII. 
PROGRESS  OF  PSYCHOLOGY. 

Changes  in  Aims  and  Methods. — Correlation  of  Mind  and 
Body. — Experimental  Psychology. — Comparative  Psycho- 
logy.— Development  and  Evolution  of  Mind. — Conclusion..  442 

CHAPTER  XIII. 

ADVANCE  OF  ANTHROPOLOGY. 

Man's  Place  in  Nature. — Antiquity  of  Man. — The  Human 
Species. — Races  of  Mankind. — Evolution  of  Language. — 
Appreciation  of  Folk-Lore. — Factors  in  the  Evolution  of 
Man 473 

CHAPTER  XIV. 

SUGGESTIONS  OF  SOCIOLOGY. 

Scope  of  Sociology. — Historical  Note. — Lines  of  Sociologi- 
cal Inquiry. — The  Social  Organism.  —  "Lieu,  Travail, 
Famille."— Classification  of  the  General  Factors  of  Social 
Evolution 496 


PROGRESS  OF  SCIENCE  IN  THE 
CENTURY. 


BOOK  ONE. 
INTRODUCTORY. 


CHAPTEK  I. 

THE  SCIENTIFIC  MOOD. 

THE  MEANING  OF  SCIENCE. 

MANY  attempts  have  been  made  to  define  -what  we 
mean  by  "  Science."  "  A  higher  development  of 
common  knowledge"  (Spencer)  ;  "  organised  common 
sense  "  (Huxley)  ;  "  classified  and  criticised  knowl- 
edge " ;  "  the  universal  element  in  knowledge " ; 
"  an  understanding  of  facts  " ;  "  our  correlated  ex- 
perience,"— are  among  the  many  suggestions.  It 
will  be  noted  that  these  definitions,  though  all  some- 
what vague,  suggest  two  ideas:  (a)  that  science  is 
not  something  by  itself,  apart  from  other  knowledge, 
or  confined  to  any  particular  order  of  facts;  and 
(&)  that  it  has  none  the  less  a  distinctive  feature,  as 
expressed  by  some  word  like  "  organised  "  or  "  sys- 
tematised."  The  fact  is  that  whenever  we  gather 


2         PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

facts  and  classify  them,  detect  their  inter-relations 
and  formulate  their  sequences,  there  is  science.  The 
subject  of  enquiry  may  be  man  or  beast,  star  or 
tree,  a  language  or  the  atmosphere,  institutions  or 
fossils,  the  growth  of  ideas  or  the  development  of 
an  egg — all  come  within  the  scope  of  scientific  en- 
quiry whose  far-off  goal  is  an  interpretation  of  the 
known  world.  The  distinctive  feature  is  in  the 
method, — making  sure  of  facts,  observing  their  inter- 
relations, grouping  them  according  to  their  like- 
nesses of  sequence,  and  inventing  descriptive  for- 
mulae which  sum  them  up.  Facts  are  essential, 
but  it  is  evident  that  they  alone  do  not  constitute  a 
science;  they  must  be  correlated,  interpreted,  for- 
mulated. As  Sir  Lyon  Play  fair  once  put  it,* 
"  isolated  facts  may  be  viewed  as  the  dust  of  science," 
— dust  only,  but  dust  is  not  to  be  despised,  for, 
as  he  went  on  to  say,  "  to  it  when  the  rays  of  light 
act  upon  its  floating  particles  we  owe  the  blue  of  the 
heavens  and  the  glories  of  the  sky." 

Though  it  may  sound  for  a  moment  like  a  paradox, 
the  scientific  mood  does  not  necessarily  involve  any 
particular  knowledge  of  this  or  that  science. 
Many  business  men,  for  instance,  who  are  almost 
quite  ignorant  of  chemistry  or  physics,  botany 
or  zoology,  astronomy  or  geology,  but  who  have 
carefully  disciplined  themselves  in  regard  to  some 
restricted  series  of  facts  involved  in  their  daily 
work,  have  acquired  the  scientific  mood  in  a  high 
degree  of  development.  The  same  may  be  said  of 
many  a  one  well  disciplined  in  the  "  Humanities," 
though  his  title  of  "  scholar  "  is  often  used  as  if  it 
stood  in  antithesis  to  "  man  of  science." 

*  Pres.  Address,  Rep.  Brit.  Ass.  for  1885,  p.  18. 


THE  SCIENTIFIC  MOOD.  3 

A  CONTRAST  OF  MOODS. 

We  receive  in  our  inheritance  what  may  be  meta- 
phorically called  a  bundle  of  moods — of  various 
shapes  and  sizes,  like  a  bundle  of  sticks  gathered  in 
the  forest.  Among  these  moods,  or  predispositions 
to  particular  lines  of  activity,  three  stand  out  prom- 
inently— the  scientific,  the  artistic,  and  the  practical 
mood.  Most  of  us  have  at  least  the  rudiments  of 
these,  but  in  most  cases  one  is  dominant.  It  is 
part  of  the  aim  of  education  to  adjust  the  propor- 
tions of  our  moods,  and  to  foster  a  minute  rudiment 
into  realisation.  First  there  is  the  mood  of  the 
dominantly  practical  man,  who,  though  in  part  scien- 
tific and  usually  a  man  of  feeling,  is  characteristi- 
cally concerned  with  the  possibilities  of  action.  The 
whole  trend  of  his  mind  is  towards  doing,  not  towards 
knowing.  He  is  seeking  after  social  amelioration, 
not  after  descriptive  formulae. 

There  is  obviously  much  to  be  said  for  the  dom- 
inance of  the  practical  mood.  It  seems  likely  that 
man's  first  relations  to  nature  were  predominantly 
practical,  and  it  is  certain  that  in  old  practical  lore 
many  of  the  sciences — such  as  astronomy,  botany, 
physiology — had  their  roots,  and  that  fresh  vigour 
has  often  come  to  science  by  a  tightening  of  its  con- 
tact with  the  affairs  of  daily  life.  There  is  no  doubt 
that  the  practical  mood  is  as  natural  and  necessary 
and  dignified  as  any  other.  Without  it  science  tends 
to  become  pedantic  and  art  decadent.  Yet  when  the 
practical  mood  becomes  altogether  dominant,  when 
things  get  into  the  saddle  and  over-ride  ideas  and 
ideals  and  all  good  feeling,  when  the  multiplication 
of  loaves  and  fishes  becomes  the  only  problem  in 
the  world,  we  know  the  results  to  be  vicious.  The 


4         PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

vices  of  the  hypertrophied  practical  mood  are — be- 
littlement,  baseness,  brutality.  We  cannot  but  have 
a  great  respect  for  the  dominant  practical  mood, 
and  yet  if  it  is  left  unchecked  by  scientific  discipline 
and  artistic  culture,  it  tends  to  run  riot.  The  prac- 
tical man  elects  to  do,  not  know,  but  action  without 
knowledge  is  often  our  undoing.  Ignorant  practice 
may  be  more  dangerous  than  any  dogma.  The  prac- 
tical man  will  have  "  nothing  to  do  with  sentiment," 
though  he  prides  himself  in.  keeping  close  to  the 
facts ;  he  cannot  abide  any  theory  and  yet  he  is  im- 
bued with  a  Martin  Tupperism  which  gives  a  false 
simplicity  to  the  problems  of  life ;  he  will  live  in  what 
he  calls  "the  real  world,"  and  yet  he  often  hugs 
close  to  himself  the  most  unreal  of  ideals. 

Secondly,  there  is  a  man  of  dominantly 
artistic  mood,  which  seems  to  find  expression  in 
Schiller's  words : — "  0  wunderschon  ist  Gottes  Erde, 
und  schon  auf  iTir  ein  MenscJi  zu  sein; "  "  How 
beautiful  is  God's  earth,  how  good  it  is  to  live  a 
man's  life  upon  it." 

From  man's  first  emergence  until  to-day,  the  drama 
of  nature  has  doubtless  appealed  to  human  emotions. 
Especially,  perhaps,  as  he  gained  firmer  foothold  in 
the  world,  secured  by  his  wits  against  stronger  rivals 
and  a  careless  environment,  did  the  emotional  tone 
rise  into  dignity  as  a  distinct  mood,  finding  its  ex- 
pression in  painting  and  carving,  song  and  story, 
music  and  the  dance.  The  herbs  and  the  trees,  the 
birds  and  the  beasts,  sent  tendrils  into  the  human 
heart,  claiming  and  finding  kinship. 

Like  the  practical  mood,  so  the  emotional  mood  has 
its  obvious  virtues.  It  is  part  of  the  salt  of  life.  In 
a  noisy  world  it  helps  to  keep  us  aware  of  the  har- 
mony in  the  heart  of  things. 


THE  SCIENTIFIC  MOOD.  5 

Yet  it  has  its  vices;  if  unruled  or  uncorrelated, 
if  uncurbed  by  science,  if  unrelated  to  the  prac- 
tical problems  of  life,  it  tends  to  become  morbid, 
mawkish,  mad.  There  may  be  over-feeling,  just  as 
there  may  be  over-doing.  Most  serious  consequences 
of  feeling  without  knowledge,  of  sympathy  without 
synthesis  (in  the  language  of  the  learned),  are  well 
known  in  the  practical  aff airs  of  to-day. 

On  the  other  hand,  we  must  not  be  slow  to  admit 
that  just  as  the  practical  man  has  some  justification 
when  he  reacts  from  science,  because,  as  he  says,  it 
is  too  theoretical,  so  the  artist,  poet,  or  man  of  feel- 
ing has  some  justification  when  he  recoils  from 
science  because  it  is  disproportionately  analytic. 
It  must  be  granted  that  science,  like  a  child  pulling 
a  flower  to  bits,  is  apt  to  dissect  more  than  it  re- 
constructs, and  to  lose  in  its  analysis  the  vision  of 
unity  and  harmony  which  the  artist  has  ever  before 
his  eyes.  Perhaps,  however,  if  the  artist  had  pa- 
tience, he  would  often  find  that  science  restores  the 
unity  with  more  meaning  in  it  than  before. 

Thirdly,  there  is  the  dominant  scientific  mood. 
To  this  mood  the  world-picture  is  no  phantasma- 
goria, but  a  scene  in  an  ordered  drama;  even  its 
beauty  is  not  kaleidoscopic  but  rather  of  growth.  To 
the  scientific  mood  it  is  plain  that  through  the  mul- 
tiplicity of  items  great  likenesses  are  observable, 
which  admit  of  being  summed  up  in  brief  descrip- 
tive formulae — laws  of  motion,  gravitation,  in- 
destructibility of  matter,  conservation  of  energy, 
development  from  the  apparently  simple  to  the  ob- 
viously complex  evolution. 

Although  science  has  some  of  its  roots  in  practice, 
and  often  receives  stimulus  from  the  actual  needs 
of  the  day,  it  is  not  practical  either  in  main  inten- 


6         PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

tion  or  in  main  result.  Its  main  intention  is  to 
describe  in  the  simplest  possible  formulae,  to  classify 
and  inter-relate  sense-impressions,  to  interpret  the 
known  world ;  its  main  result  is  an  intellectual  system 
and  the  development  of  a  certain  way  of  looking  at 
things. 

Similarly,  though  emotion  has  influenced  the 
growth  of  natural  knowledge  not  a  little  both 
for  good  and  ill,  and  though  scientific  discoveries 
have  in  turn  given  nutriment  to  emotion,  science  is 
certainly  in  itself  non-emotional. 

The  student  of  science  seeks,  not  like  the  practical 
man,  to  realise  the  ideal,  but  rather  to  idealise  [con- 
ceptualise] the  real,  or  those  fractions  of  reality 
which  constitute  his  experience.  He  elects  pri- 
marily to  know,  not  do.  He  would  make  the  world 
translucent,  not  that  emotion  may  catch  the  glimmer 
of  the  indefinable  light  that  shines  through,  but  for 
other  reasons, — because  of  his  inborn  inquisitiveness, 
because  of  his  dislike  of  obscurities,  because  of  his 
craving  for  a  system — an  intellectual  system  in 
which  phenomena  are  provisionally  unified. 

Like  the  other  moods,  the  scientific  mood  has  its 
virtues  of  method  and  ideal.  It  is  painstaking,  pa- 
tient, precise;  it  is  careful,  conscientious,  contriv- 
ing; it  aims  at  making  a  working  thought-model  of 
the  universe. 

But  it  has  also  its  vices,— of  over-knowing,  of 
ranking  science  first  and  life  second  (as  if  science 
were  not  after  all  for  the  evolution  of  life),  of  ignor- 
ing good  feeling  (as  if  knowledge  could  not  be  bought 
at  too  dear  a  price),  of  pedantry  (as  if  science  were 
a  "  preserve  "  for  expert  intellectual  sportsmen,  and 
not  an  education  for  the  citizen),  of  maniacal  muck- 
raking for  items  of  facts  (as  if  facts  alone  consti- 


THE  SCIENTIFIC  MOOD.  7 

tuted  science).  But  it  is  a  natural  and  necessary  ex- 
pression of  the  developing  human  spirit,  and  supplies 
the  foundation  without  which  practice  is  merely  em- 
pirical and  emotion  superstitious. 

CHABACTEEISTICS    OF    THE    SCIENTIFIC    MOOD. 

In  his  stimulating  presidential  address  at  the  meet- 
ing of  the  British  Association  at  Dover  in  1899, 
Sir  Michael  Foster  raised  the  question  of  the  dis- 
tinctive features  of  the  scientific  spirit  "  What 
are  the  qualities,"  he  asked,  "  the  features  of  that 
scientific  mind  which  has  wrought,  and  is  working, 
such  great  changes  in  man's  relation  to  nature  ?  " 
And  his  answer  was  that  the  features  of  the  fruitful 
scientific  mind  are  in  the  main  three.* 

"  In  the  first  place,  above  all  other  things,  his 
nature  must  be  one  which  vibrates  in  unison  with 
that  of  which  he  is  in  search ;  the  seeker  after  truth 
must  himself  be  truthful,  truthful  with  the  truthful- 
ness of  nature;  which  is  far  more  imperious,  far 
more  exacting  than  that  which  man  sometimes  calls 
truthfulness. 

"  In  the  second  place,  he  must  be  alert  of  mind. 
Nature  is  ever  making  signs  to  us,  she  is  ever  whis- 
pering to  us  the  beginnings  of  her  secrets ;  the  scien- 
tific man  must  be  ever  on  the  watch,  ready  at  once  to 
lay  hold  of  Nature's  hint,  however  small,  to  listen  to 
her  whisper,  however  low. 

"  In  the  third  place,  scientific  enquiry,  though  it 
be  pre-eminently  an  intellectual  effort,  has  need  of 
the  moral  quality  of  courage — not  so  much  the  cour- 
age which  helps  a  man  to  face  a  sudden  difficulty  as 
the  courage  of  steadfast  endurance." 

*  Report  British  Association  for  the  Advancement  of 
Science,  1899,  pp.  16-17. 

B 


8         PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

To  the  obvious  objection  that  these  three  qualities 
of  truthfulness,  alertness,  and  courage,  though,  let 
us  hope,  possessed  by  the  scientific  man,  are  not  in 
any  way  peculiar  to  him,  but  "  may  be  recognised  as 
belonging  to  almost  every  one  who  has  commanded  or 
deserved  success,  whatever  may  have  been  his  walk 
in  life,"  Sir  Michael  answered :  "  That  is  exactly 
what  I  would  desire  to  insist,  that  the  men  of  science 
have  no  peculiar  virtues,  no  special  powers.  They 
are  ordinary  men,  their  characters  are  common, 
even  commonplace.  Science,  as  Huxley  said,  is 
organised  common  sense,  and  men  of  science  are  com- 
mon men,  drilled  in  the  ways  of  common  sense." 

Let  us  endeavour  to  make  the  diagnosis  of  the 
scientific  mood  a  little  more  definite.  The  follow- 
ing has  at  least  the  interest  of  having  been  almost 
entirely  written  before  the  delivery  of  Sir  Michael 
Foster's  stimulating  address. 

(a)  As  a  first  characteristic  of  the  scientific 
mood — corresponding  to  what  has  been  above  referred 
to  as  "  truthfulness,"  we  may  note  a  passion  for  facts. 
'And  what  are  more  difficult  to  catch  than  facts ;  they 
are  more  elusive  than  ideas.  How  difficult  it  is 
even  in  regard  to  simple  problems  to  get  a  grip  of 
the  facts  of  the  case !  How  difficult  it  is  for  any  one 
with  even  a  dash  of  the  artistic  mood  to  relate  an 
occurrence  accurately !  Most  of  us  are  Munchausens 
in  a  small  way,  but  with  less  sense  of  humour.  Just 
as  we  may  distinguish  carpenters  who  can  work  to 
this  or  that  fraction  of  an  inch  of  accuracy;  so  we 
must  distinguish  one  another  as  able  to  observe  or 
to  record  to  this  or  that  degree  of  truthfulness. 

"  Man,  unscientific  man,  is  often  content  with 
'  the  nearly '  and  '  the  almost.'  Nature  never  is. 
It  is  not  her  way  to  call  the  same  two  things  which 


THE  SCIENTIFIC  MOOD.  9 

differ,  though  the  difference  may  be  measured  by 
less  than  the  thousandth  of  a  milligramme  or  of  a 
millimetre,  or  by  any  other  like  standard  of  minute- 
ness. And  the  man  who,  carrying  the  ways  of  the 
world  into  the  domain  of  science,  thinks  that  he  may 
treat  Nature's  differences  in  any  other  way  than  she 
treats  them  herself,  will  find  that  she  resents  his 
conduct ;  if  he  in  carelessness  or  in  disdain  overlooks 
the  minute  difference  which  she  holds  out  to  him  as 
a  signal  to  guide  him  in  his  search,  the  projecting 
tip,  as  it  were,  of  some  buried  treasure,  he  is  bound 
to  go  astray,  and,  the  more  strenuously  he  struggles 
on,  the  farther  will  he  find  himself  from  his  true 
goal."* 

Many  people — most  excellent  in  virtues — seem 
constitutionally  incapable  of  accurately  reporting  an 
occurrence ;  many  more  seem  quite  unable  to  see  the 
difference  between  an  observation  and  an  inference. 

The  scientific  worker  is  himself  well  aware 
that,  in  measurements  and  observations,  only  an 
approximate  accuracy  can  be  attained,  and  that 
the  degree  of  approximation  varies  with  the  indi- 
vidual. But  this  relativity  of  accuracy  is  far  from 
being  generally  recognised,  and  scientific  state- 
ments often  get  credit  for  a  precision  which  they 
do  not  claim.  The  personal  equation  has  been  for 
a  long  time  frankly  recognised  and  allowed  for  in 
astronomy;  it  is  also  sometimes  estimated  in  chem- 
istry and  physics,f  but  we  hear  too  little  of  it  in 
the  less  exact  sciences  such  as  biology  and  psy- 
chology. 

Even  apart  from  intellectual  training,  may  it  not 
be  claimed  that  the  discipline  of  the  chemical  balance, 

*  Sir  Michael  Foster,  loc.  cit.  p.  16. 
f  See  Ostwald's  Text-book  of  General  Chemistry. 


10      PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

of  analysis,  of  dissection,  of  faithful  drawing,  is  one 
of  the  most  effective  factors  in  the  evolution  of 
truthfulness?  Many  will  agree  with  Agassiz  that 
some  training  in  natural  science  is  one  of  the  best 
preparations  a  man  can  have  for  work  in  any  depart- 
ment of  life  where  accurate  carefulness  and  ad- 
herence to  the  facts  of  the  case  means  much.  Long 
ago  Bacon  said :  "  We  should  accustom  ourselves  to 
things  themselves,"  and  this — to  distinguish  between 
appearance  and  reality — is  what  the  scientific  mood 
seeks  after. 

It  was  Huxley  who  spoke  of  "  that  enthusiasm  for 
truth,  that  fanaticism  of  veracity,  which  is  a  greater 
possession  than  much  learning;  a  nobler  gift  than 
the  power  of  increasing  knowledge."  It  is  one  of 
the  motive  forces  of  scientific  progress. 

If  every  virtue  has  its  vice  and  every  function  its 
disease,  so  danger  may  lurk  in  this  precious  posses- 
sion,— a  passion  for  facts.  It  may  become  a  mania 
for  information  and  an  intellectual  intemperance. 
Unskilful  teaching  or  careless  learning  may  result 
in  mere  fat  without  muscle,  or  in  the  matter-of-fact 
man — one  of  the  most  unscientific  of  persons — 
who  ignores  one  of  the  biggest  of  all  facts,  the  reality 
of  ideas. 

Any  mood  may  in  extreme  development  become 
vicious,  and  the  passion  for  facts  may  become  so  pre- 
dominant that  it  implies  violence  to  emotional  sanity 
and  disloyalty  to  the  ideal  of  a  full  and  healthy  hu- 
man life.  Take  an  illustration  from  real  life.  The 
great  embryologist  Von  Baer  once  shut  himself  up  in 
his  study  when  snow  was  upon  the  ground,  and  did 
not  come  out  again  until  the  rye  was  in  harvest.  He 
was  filled,  he  tells  us,  with  uncontrollable  pathos 
at  the  sight.  "  The  laws  of  development  may  be 


THE  SCIENTIFIC  MOOD.  H 

discovered  this  year  or  many  years  hence — by  me 
or  by  others — what  matters  it? — it  is  surely  folly 
to  sacrifice  for  this  the  joy  of  life  which  nothing  can 
replace."  Indeed  life  is  not  for  science,  but  science 
for  the  development  of  life. 

These  are  days  of  popularising,  in  magazine  ar- 
ticles and  on  lecture  platforms,  and  much  of  this  is 
justifiable  and  healthy,  for  science  can  no  longer  be 
defined  off  as  a  preserve  for  the  learned.  Yet  there 
is  the  risk  of  giving  a  false  simplicity  to  problems, 
or  of  suggesting  that  there  are  royal  roads  to  learn- 
ing; the  sin  easily  besets  us  of  depreciating  the  dig- 
nity of  a  hard-won  fact.  Therefore  at  the  risk  of  ex- 
ceeding triteness,  we  would  emphasise  that  a  genuine 
passion  for  facts  implies  a  certain  seriousness,  a  rever- 
ence for  what  is  beneath  (in  Goethe's  words),  a  re- 
spect for  facts  when  one  gets  them.  Though  we  need 
not  be  always  in  the  scientific  mood — for  which  we 
are  truly  thankful — we  must  be  scientific  when  we 
propose  so  to  be.  "  Science,"  Bacon  said,  "  is  not  a 
terrace  for  a  wandering  and  variable  mind  to  walk 
up  and  down  with  a  fair  prospect." 

What  we  mean  by  saying  that  we  need  not  be 
always  scientific  is  simply  that  the  scientific  mood 
is  sometimes  unnatural  and  irrelevant.  To  botanise 
upon  our  mother's  grave  is  the  classic  illustration, 
and  for  another  we  may  refer  to  the  medical  man's 
discovery  that  Botticelli's  "  Venus,"  in  the  Uffizi  at 
Florence,  is  suffering  from  consumption,  and  should 
not  be  riding  across  the  sea  in  an  open  shell,  clad  so 
scantily. 

(6)  Following  from  the  passion  of  facts,  is  a 
second  characteristic  of  the  scientific  mood,  namely, 
cautiousness,  or  distrust  of  finality  and  dogmatism 
of  statement.  Scotsmen  have  done  well  for  the  ad- 


12      PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

vancement  of  science ;  they  are  said  to  stand  far  above 
the  average  in  the  nineteenth  century;  perhaps  this 
is  in  part  because  they  are  so  "  canny,"  so  unwilling 
to  commit  themselves  unless  they  are  sure.  It  may 
even  be  that  the  excessive  changeableness  of  Scotch 
weather  has  helped  to  engender  the  characteristic 
mood  of  caution.  Sometimes,  indeed,  the  cautious- 
ness becomes  almost  morbid,  when  three  saving 
clauses  are  inserted  in  a  single  sentence.  One  recalls 
Stevenson's  story  of  the  sailor : — "  Bill,  Bill,"  says  I, 
"  or  words  to  that  effect" 

No  doubt  the  scientific  mood  is  continually  making 
hypotheses  or  guesses  at  truth;  the  scientific  use  of 
the  imagination  is  part  of  our  method.  But  what 
we  have  to  guard  against  is  the  insidious  tendency 
to  mistake  provisional  hypotheses  for  full-grown 
theories,  and,  still  worse,  for  dogmas. 

As  Prof.  W.  K.  Brooks  says  in  his  Foundations 
of  Zoology :  "  The  hardest  of  intellectual  virtues 
is  philosophic  doubt,  and  the  mental  vice  to  which  we 
are  most  prone  is  our  tendency  to  believe  that  lack  of 
evidence  for  an  opinion  is  a  reason  for  believing  some- 
thing else.  .  .  .  Suspended  judgment  is  the  greatest 
triumph  of  intellectual  discipline."  As  Huxley  said 
— and  who  has  had  the  scientific  mood  more  strongly 
developed — "  The  assertion  that  outstrips  the  evi- 
dence is  not  only  a  blunder  but  a  crime."  Just  as 
burnt  bairns  dread  the  fire,  so  the  scientific  mood, 
often  deceived  by  hearsay  evidence,  by  incomplete 
induction,  by  the  will-o'-the-wisp  glamour  of  a  seduc- 
tive idea,  by  inference  mixed  up  with  observation, 
and  even  by  wilful  falsehood,  becomes  more  and  more 
cautious,  distrustful,  "  canny." 

Another  aspect  of  the  quality  of  cautiousness 
which  characterises  the  scientific  mood  is  distrust  of 


THE  SCIENTIFIC  MOOD.  13 

personal  bias  in  forming  judgments.  It  should 
always  be  possible  to  eliminate  opinion  from  all 
scientific  conclusions ;  their  validity,  in  fact,  depends 
upon  this.  "  The  scientific  man  has  above  all  things 
to  strive  at  self -elimination  in  his  judgments,  to  pro- 
vide an  argument  which  is  as  true  for  each  individual 
mind  as  for  his  own.  The  classification  of  facts,  the 
recognition  of  their  sequence  and  relative  signifi- 
cance, is  the  function  of  science,  and  the  habit  of 
forming  a  judgment  upon  these  facts,  unbiassed  by 
personal  feeling,  is  characteristic  of  what  may  be 
termed  the  scientific  frame  of  mind."  * 

"  The  world,"  Faraday  writes,  "  little  knows  how 
many  of  the  thoughts  and  theories  which  have  passed 
through  the  mind  of  a  scientific  investigator  have 
been  crushed  in  silence  and  secrecy  by  his  own  severe 
criticism  and  adverse  examination;  that  in  the  most 
successful  instances  not  a  tenth  of  the  suggestions, 
the  hopes,  the  wishes,  the  preliminary  conclusions 
have  been  realised."  As  a  complementary  statement, 
another  quotation  from  the  same  great  authority  may 
be  permitted : — "  The  philosopher  should  be  a  man 
willing  to  listen  to  every  suggestion,  but  determined 
to  judge  for  himself.  He  should  not  be  biassed  by 
appearances;  have  no  favourable  hypotheses;  be  of 
no  school,  and  in  doctrine  have  no  master.  He  should 
not  be  a  respecter  of  persons,  but  of  things.  Truth 
should  be  his  primary  object.  If  to  these  qualities 
be  added  industry,  he  may  indeed  hope  to  walk  with- 
in the  veil  of  the  Temple  of  Nature." 

(c)  A  third  characteristic  of  the  scientific  mood 
is  dislike  of  obscurities,  of  blurred  vision,  of  foggi- 
ness.  We  instinctively  discount  the  scientific  abili- 

*  Karl  Pearson,  Grammar  of  Science,  rev.  edition,  1900,  • 
p.  6. 


14      PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

ties  of  the  student  who  always  has  his  microscope 
wrongly  focussed  and  is  satisfied  with  the  ill-defined 
image,  or  of  the  other  whose  dissection  is  invariably 
either  a  mince  or  a  tangle,  or  of  the  other  who  is 
never  quite  sure  whether  he  knows  a  thing  or  not. 
Ignorance  in  itself  is  no  particular  reproach;  the 
point  is  to  know  when  we  know  and  when  we  don't, 
and  it  is  one  of  the  characteristics  of  the  scientific 
mood  that  it  will  have  yes  or  no  to  this  question. 

Those  of  the  scientific  mood  are  mainly  trying  to 
construct  a  working-thought-model  of  the  outer 
world,  to  form  a  mental  image  which  will  be  a  living 
picture, — an  intellectual  cinematograph.  In  other 
words  they  would  make  the  world  translucent,  as 
translucent  as  the  human  body  becomes  to  the  skilled 
anatomist. 

Clerk-Maxwell's  boyish  question — "  What  is  the 
go  of  this  ? " — and,  when  put  off  with  some  verbal- 
ism, "  What  is  the  particular  go  of  this  ?  "  is  a  ques- 
tion characteristic  of  the  scientific  mood,  which  may 
be  applied  to  any  order  of  facts. 

The  mole  has  a  sort  of  half-finished  lens,  which 
is  physically  incapable  of  throwing  a  precise  image 
on  the  retina.  If  there  is  any  image,  it  must  be 
a  blurred  tangle  of  lines.  In  our  busy  lives,  we  tend 
to  acquire  mole-like  lenses  in  regard  to  particular 
orders  of  facts ;  we  see  certain  things  clearly,  others 
are  blurs;  but  the  scientific  mood  is  in  continual 
protest  against  obscurities,  insisting  upon  lucidity. 

Thus  we  feel  the  force  of  one  of  Bacon's  most 
historically  true  aphorisms,  which  declares  "  Truth 
to  emerge  sooner  from  error  than  from  confusion." 
It  is  a  great  step  when  a  false  notion  is  formulated. 
The  definitising  of  error  has  been  the  beginning  of 
its  disappearance.  As  soon  as  the  evil  genie  of  the 


THE  SCIENTIFIC  MOOD.  15 

Eastern  tales  took  on  some  definite  bodily  form  there 
was  some  chance  of  tackling  him ;  as  a  mere  wraith 
he  was  invulnerable. 

(d)  A  fourth  characteristic  of  the  scientific  mood 
is  a  sense  of  the  inter-relations  of  things.  The  real- 
isation of  nature  as  a  great  inter-connected  system  is, 
indeed,  one  of  the  ends  of  science;  to  be  on  the  out- 
look for  inter-relations  is  diagnostic  of  the  mood. 
As  long  as  the  collection  and  registration  of  facts 
preoccupies  the  energies  and  attention,  scientific 
enquiry  has  hardly  begun.  As  Mr.  Pearson  says, 
"  The  classification  of  facts,  the  recognition  of  their 
sequence  and  relative  significance  is  the  function  of 
science." 

To  put  it  more  concretely,  the  student  of  biology, 
for  instance,  has  hardly  caught  on  at  all  unless  he 
has  some  realisation  of  the  web  of  life,  the  correla- 
tion of  organisms.  He  must  have  some  apprecia- 
tion of  the  "  system  of  nature,"  of  the  links  between 
old  maids,  cats,  bees,  and  clover  crop ;  between  earth- 
worms and  the  world's  bread-supply;  between  mos- 
quitoes and  malaria ;  between  white  ants  and  African 
agriculture;  between  ivory  ornaments  and  the  slave 
trade. 

To  sum  up:  the  scientific  mood,  whose  diffusion 
through  wide  circles  has  been  one  of  the  achieve- 
ments of  the  latter  half  of  the  nineteenth  century, 
is  characterised  by  a  passion  for  facts,  an  alert  cau- 
tiousness, a  striving  after  clearness  of  vision,  and  a 
sense  of  inter-relations.  To  which,  as  will  be  after- 
wards made  plain,  it  should  perhaps  be  added  that 
the  consistent  scientific  mood  does  not  at  all  concern 
itself  with  metaphysical  problems  or  ultimate  inter- 
pretations. These  may  be  legitimately  complemen- 
tary to  science,  but  if  the  word  is  to  retain  its  present 
meaning,  they  are  beyond  its  scope. 


16       PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 


THE  AIM   OF   SCIENCE. 

Briefly  stated,  the  primary  aim  of  science  in- 
cludes the  observation,  description,  and  interpreta- 
tion of  the  knowable  universe. 

Concerning  the  need  for  careful  observation  and 
accurate  description,  enough  has  been  said  in  our  ex- 
position of  the  characteristics  of  the  scientific  mood ; 
it  is  necessary,  however,  to  give  particular  attention 
to  the  nature  of  a  scientific  interpretation, — in  re- 
gard to  which  misunderstanding  is  rife. 

The  man  of  scientific  mood  becomes  aware  of  cer- 
tain fractions  of  reality  which  interest  him;  he  pro- 
ceeds to  become  more  intimately  aware  of  these ;  i.e., 
to  make  his  sensory  experience  of  them  as  full  as 
possible.  He  seeks  to  arrange  them  in  ordered 
series,  to  detect  their  inter-relations  and  likenesses 
of  sequence;  he  tries  to  reduce  them  to  simpler 
terms  or  to  find  their  common  denominator;  and 
finally,  he  endeavours  to  sum  them  up  in  a  general 
formula,  often  called  a  "  law  of  nature." 

Aristotle  defines  the  aim  when  he  says,  "  Art  [or 
as  we  should  say,  Science]  begins  when,  from  a 
great  number  of  experiences,  one  general  conception 
is  formed  which  will  embrace  all  similar  cases." 
Similarly  the  nature  of  scientific  explanation  is  sug- 
gested by  Kirchhoff's  definition  of  mechanics,  as  the 
science  of  motion,  whose  object  it  is  "  to  describe 
completely  and  in  the  simplest  manner  the  motions 
that  occur  in  nature." 

With  the  advance  of  clear  thinking  our  way  of 
looking  at  facts  has  altered  not  a  little,  and  even 
when  we  use  the  same  words  as  our  forefathers  did 
we  do  not  always  mean  the  same  thing.  Thus  whea 


THE  SCIENTIFIC  MOOD.  17 

the  lecturer  says  that  a  gas  "  obeys  Boyle's  Law,"  he 
is  using  the  language  of  the  past  and  suggesting  a 
conception  of  the  order  of  nature  which  is  no  longer 
current.  "  We  must  confess,"  says  Prof.  J.  J". 
Poynting,*  "  that  physical  laws  have  greatly  fallen 
off  in  dignity.  No  long  time  ago  they  were  quite 
commonly  described  as  the  Fixed  Laws  of  Nature, 
and  were  supposed  sufficient  in  themselves  to  govern 
the  universe.  Now  we  can  only  assign  to  them  the 
humble  rank  of  mere  descriptions,  often  tentative, 
often  erroneous,  of  similarities  which  we  believe  we 
have  observed." 

Prof.  Poynting  goes  on  to  say  that  a  "  law  of  na- 
ture explains  nothing — it  has  no  governing  power, 
it  is  but  a  descriptive  formula  which  the  careless 
have  sometimes  personified.  There  may  be  psycho- 
logical and  social  generalisations  which  really  tell 
us  why  this  or  that  occurs,  but  chemical  and  phys- 
ical generalisations  are  wholly  concerned  with  the 
how." 

In  other  words,  if  we  may  condense  a  little  of 
Poynting's  admirable  discourse,  concurrently  with 
the  change  in  our  conception  of  physical  law  has 
come  a  change  in  our  conception  of  physical  expla- 
nation. The  change  is  in  our  recognition  that  "  we 
explain  an  event  not  when  we  know  '  why '  it  hap- 
pened, but  when  we  know  '  how '  it  is  like  something 
else  happening  elsewhere  or  otherwise — when,  in 
fact,  we  can  conclude  it  as  a  case  described  by  some 
law  already  set  forth.  In  explanation  we  do  not 
account  for  the  event,  but  we  improve  our  account  of 
it  by  likening  it  to  what  we  already  knew."  In 
short,  the  notion  of  antecedent  purpose — which  rises 

*  Address,  Section  A,  Report  of  British  Ass.  for  1889,  pp. 
616-17. 


18       PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

at  once  in  our  minds  when  we  try  to  explain  human 
action — is  irrelevant  in  physical  seienca 

On  the  same  subject,  Dr.  J.  T.  Merz  writes  as 
follows  in  his  impressive  history  of  scientific  thought 
in  the  nineteenth  century :  "  A  complete  and  simple 
description — admitting  of  calculation — is  the  aim  of 
all  exact  science.  .  .  .  We  shall  not  expect  to  find 
the  ultimate  and  final  causes,  and  science  will  not 
teach  us  to  understand  nature  and  life.  .  .  .  Science 
means  *  the  analysis  of  phenomena  as  to  their  ap- 
pearance in  space  and  their  sequence  in  time.'  "  * 

Thus  the  common  assertion  that  science  gives  ex- 
planations of  nature  is  a  misunderstanding,  if  the 
word  explanation  is  taken  to  mean  more  than  a  de- 
scriptive formula.  The  word  ultimate  does  not  oc- 
cur in  the  scientific  dictionary.  The  biologist  draws 
cheques,  but  they  are  all  backed  by  such  words  as 
protoplasm  and  germ-plasm;  and  a  little  enquiry 
suffices  to  show  that  these  words  imply  conceptual 
hypotheses  invented  to  express  the  facts  and  war- 
ranted by  the  success  with  which  they  fit  these.  The 
physicist's  bills,  similarly,  are  accepted  on  the  credit 
of  the  ubiquitous  ether,  the  mighty  atom,  or  the  like, 
but  these  again  are  conceptual  hypotheses  invented 
to  summarise  the  sequence  of  phenomena. 

Let  us  take  a  concrete  case.  "  The  law  of  gravi- 
tation is  a  brief  description  of  how  every  particle  of 
matter  in  the  universe  is  altering  its  motion  with 
reference  to  every  other  particle.  It  does  not  tell 
us  why  particles  thus  move;  it  does  not  tell  us  why 
the  earth  describes  a  certain  curve  round  the  sun.  It 
simply  resumes,  in  a  few  brief  words,  the  relation- 

*  J.  T.  Merz.  A  History  of  European  Thought  in  the  Nine- 
teenth Century.  Vol.  I.,  Introduction — Scientific  Thought, 
Part  I.,  1896,  pp.  382-3. 


THE  SCIENTIFIC  MOOD.  19 

ships  observed  between  a  vast  range  of  phenomena. 
It  economises  thought  by  stating  in  conceptual  short- 
hand that  routine  of  our  perceptions  which  forms  for 
us  the  universe  of  gravitating  matter." 

SCIENTIFIC  METHOD. 

From  what  we  have  already  said  it  should  be 
plain  that  science  has  no  mysterious  methods  of  its 
own.  Its  method  is  the  method  of  common  sense. 
In  his  little  book  on  scientific  thinking, f  Dr.  Adolf 
Wagner  points  out  with  great  vivacity  that  science 
is  characterised  as  an  intellectual  attitude;  it  is  not 
any  particular  body  of  facts;  it  has  no  peculiar 
method  of  inquiry;  it  is  simply  sincere  critical 
thought,  which  admits  conclusions  only  when  these 
are  based  on  evidence.  Let  us,  however,  briefly  indi- 
cate some  of  the  chief  steps  in  the  scientific  treat- 
ment of  a  given  problem. 

(a)  Observation  of  Facts. — The  first  step  is  to 
make  sure  of  the  facts  concerning  which  a  problem 
has  been  raised  in  the  inquisitive  mind.  Here  the 
fundamental  virtues  are  precision,  caution,  clear- 
ness, and  impartiality.  The  rough  and  ready 
record,  the  second-hand  evidence,  the  vague  impres- 
sion, the  picking  of  facts  which  suit  must  be  elimi- 
nated. Hence,  since  the  observer  is  a  fallible  mortal, 
the  importance  of  co-operation,  of  independent  ob- 
servation on  the  same  subject,  of  instrumental  means 
of  extending  the  range  and  delicacy  of  our  senses, 
and  of  automatic  methods  of  registration,  such  as 
photography  supplies. 

•Karl  Pearson,  The  Grammar  of  Science,  rev.  ed.,  1900, 
p.  99. 

t  A.  Wagner,  Studien  und  Sklzzen  aus  Naturwissenschaft 
und  Philosophic.  I.  Ueber  toissenschaftliches  Denken  und 
tiler  populdre  Wissenschaft,  Berlin,  1899,  p.  79. 


20       PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

(&)  Classification  of  Facts. — In  many  cases  after 
the  accumulation  of  data,  much  time  must  be  spent 
in  their  arrangement.  A  careful  worker  at  the  prob- 
lem of  migration  in  birds,  like  Mr.  Eagle  Clarke, 
may  require  for  the  classification  of  his  data  a  longer 
time  than  was  spent  in  their  collection.  If  the  facts 
are  to  form  part  of  the  body  of  science,  they  must 
be  made  readily  available,  and  this  process  of  diges- 
tion is  often  slower  than  that  of  ingestion.  If 
the  aim  be  to  detect  similarities  of  sequence  the  facts 
must  be  grouped  in  ordered  series.  Here,  in  many 
cases,  the  use  of  graphs,  curves,  and  mathematical 
methods  has  proved  itself  invaluable,  notably,  for  in- 
stance, in  Galton's  work  on  inheritance,  or  in  the  re- 
cent statistical  studies  on  variation. 

It  has  been  a  common  experience  in  the  arrange- 
ment of  data  that  some  minute  discrepancy  has  re- 
vealed itself,  and  that  the  following  of  this  at  first 
perhaps  puzzling  occurrence  has  led  to  the  elucida- 
tion of  the  whole  problem.  Thus  it  has  become  a 
maxim  in  science  that  no  apparent  departure  from 
the  rule  or  general  sequence  should  be  treated  as 
trivial,  and  no  minute  discrepancy  disregarded. 
That  nitrogen  obtained  from  chemical  combinations 
should  be  about  one-half  per  cent,  lighter  than  that 
obtained  from  the  atmosphere,  may  seem  a  very 
minute  fact,  but  it  led  Lord  Rayleigh  and  Professor 
W.  Ramsay  to  the  discovery  of  Argon. 

(c)  Analysis. — With  scientific  problems  of  a  cer- 
tain order,  there  is  often  need  for  a  preliminary 
process  of  analysis  before  the  desired  data  can  be 
obtained.  Whenever  we  get  below  the  surface  phe- 
nomena of  life — patent  to  the  observer — we  have  to 
dissect,  to  cut  sections,  to  take  advantage  of  chemical 
analysis  and  so  on.  The  end  desired  is  a  re-state- 


THE  SCIENTIFIC  MOOD.  21 

ment  in  simpler  terms,  or  in  another  sense,  in  more 
generalised  terms;  and  to  effect  this  analysis  is  in 
itself  a  scientific  problem. 

(d}  Hypothesis. — There  is  no  doubt  that  some 
conclusions  have  arisen  in  the  mind  as  if  by  a  flash 
of  insight,  but  even  these  have  perhaps  been  due  to 
processes  of  unconscious  cerebration.  In  the  ma- 
jority of  cases,  the  process  is  a  slower  one,  the  scien- 
tific imagination  devises  a  possible  solution — an  hy- 
pothesis— and  the  investigator  proceeds  to  test  it.  In 
other  words,  he  forges  intellectual  keys  and  then  tries 
if  they  fit  the  lock.  If  the  hypothesis  does  not  fit,  it 
is  rejected  and  another  is  made.  The  scientific 
workshop  is  full  of  discarded  keys.  Nor  can  it  be 
forgotten  that  even  those  conclusions  which  com- 
mend themselves  at  first  sight  have  to  submit  to  the 
process  of  testing  like  those  which  were  tried  with 
less  confident  fingers.  It  matters  little,  except  to 
the  logician,  whether  the  hypothesis  was  reached  as 
an  induction  from  many  particulars  or  as  a  deduc- 
tion from  some  previously  established  conclusion; 
in  either  case  the  result  is  a  provisional  hypothesis, 
which  has  then  to  be  tested. 

Newton  said  in  his  Principia  that  he  did  not  make 
hypotheses  (Hypotheses  non  fingo},  and  yet  he,  like 
all  great  scientific  workers,  certainly  did,  for  in- 
stance in  his  corpuscular  hypothesis  of  light,  which 
has  turned  out  to  be  erroneous.  The  fact  is  that 
there  are  different  kinds  of  hypotheses, — there  are 
guesses  at  truth  which  have  no  experimental  basis, 
which  are  usually  prompted  by  some  big  conclusion 
dominating  the  mind  of  the  guesser,  such  as  Sweden- 
berg's  nebular  hypothesis;  and  there  are  scientific 
hypotheses  which  are  more  or  less  carefully  con- 
structed systems,  harmonised  with  existing  knowl- 


22       PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

edge,  and  projected  upon  nature  to  satisfy  our  desire 
for  continuity.  They  relate  to  what  lies  beyond  the 
range  of  observation,  beyond  the  range  of  our  sense- 
impressions. 

An  interesting  method  of  testing  the  accuracy  of  a 
formula  is  to  use  it  as  a  basis  for  prediction.  Many 
observant  people  are  familiar  with  a  mild  form  of 
scientific  prophecy  in  connection  with  the  weather. 
After  long  observation  they  hazard  a  generalisation, 
in  private,  if  they  are  wise;  and  they  test  this  by  a 
prediction.  As  this  is  usually  wrong,  they  conclude 
that  their  generalisation  had  not  a  sufficiently  wide 
basis.  But  better  examples  may  be  found  in  the 
prediction  of  Neptune  by  Adams  and  Leverrier 
(from  calculations  based  on  the  gravitation-formula) 
and  the  subsequent  discovery  of  that  planet  by 
Galle;  or  in  the  prediction  of  the  element  german- 
ium by  Mendelejeff  and  its  discovery  by  Winkler. 

(e)  Test  Experiments  and  Control  Experiments. 
— The  distinction  between  an  observation  and  an  ex- 
periment seems  quite  artificial,  the  point  of  contrast 
being  that  in  the  former  we  study  the  natural  course 
of  events,  while  in  the  latter  we  arrange  for  the  oc- 
currence of  certain  phenomena.  In  studying  the 
effect  of  electric  discharges  on  living  plants  we  might 
wait  for  the  lightning  to  strike  trees  in  our  vicinity ; 
but  as  this  would  be  worse  than  tedious,  we  prefer 
to  mimic  the  natural  phenomenon  in  the  laboratory. 
This  is  obviously  a  distinction  without  a  difference, 
and  instead  of  calling  the  first  step  (a)  observation, 
as  we  have  done,  we  might  equally  well  have  used 
the  word  experiment. 

On  the  other  hand,  at  a  later  stage  in  the  scientific 
treatment  of  a  problem,  our  opportunities  for  experi- 
ment can  be  profitably  used,  not  for  accumulating 


THE  SCIENTIFIC  MOOD. 


23 


more  data,  but  for  putting  our  hypothesis  to  the 
proof.  We  allude  to  what  are  called  test  or  crucial 
experiments  and  control  experiments.  Much  of  the 
success  of  a  scientific  worker  may  depend  on  his 
ingenuity  in  thinking  out  crucial  experiments  and 
on  his  rigorous  use  of  control  experiments. 

When  bacteriology  was  in  its  infancy,  Pasteur  put 
his  theory  that  putrefaction  was  the  result  of  the  life 
of  micro-organisms  to  a  crucial  test  when  he  steri- 
lised readily  putrescible  substances,  and,  having  her- 
metically sealed  the  vessel,  kept  them  for  years  with- 
out the  occurrence  of  any  putrefaction. 

When  Yon  Siebold  and  his  fellow-workers  had 
gradually  convinced  themselves  that  certain  bladder- 
worms  in  various  animals  used  as  food  were  the 
young  stages  of  certain  tapeworms  occurring  in  man, 
they  made  the  crucial  experiment  of  swallowing  the 
bladderworms  and  proved  the  accuracy  of  their  con- 
clusion by  becoming  shortly  afterwards  infected  with 
tapeworm. 

The  control  experiment  is  closely  akin.  A  cray- 
fish is  known  to  have  a  sense  of  smell.  Various  rea- 
sons lead  the  enquirer  to  conclude  that  this  sense  has 
its  seat  in  the  antennules.  He  may  verify  this  by 
observing  that  a  crayfish  without  these  appendages 
will  not  respond  to  a  strong  odour,  but  he  would  not 
be  satisfied  unless  he  had  shown  that  in  exactly  the 
same  conditions  and  to  exactly  the  same  stimulus  an- 
other crayfish  with  its  antennules  intact  did  actively 
respond.  Having  gone  so  far,  he  would  proceed  to 
localise  the  sense  more  precisely;  microscopic  re- 
search would  direct  his  attention  to  peculiarly  shaped 
bristles  on  the  antennules.  By  shaving  these  off,  and 
observing  that  response  to  strong  odours  ceased,  he 
would  prove  his  point,  but  again,  in  view  of  possible 


24      PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

error,  he  would  confirm  his  conclusion  by  control  ex- 
periments with  normal  animals.  The  above  case 
illustrates  a  combination  of  the  method  of  exclusion 
with  the  use  of  control  experiments. 

(/)  Formulation  and  Incorporation. — The  final 
step  is  to  sum  up  what  has  been  attained  in  terms 
as  clear  and  terse  as  possible,  and  to  add  the  dis- 
covery to  what  has  been  already  established.  The 
digested  data  are  absorbed  into  the  body  of  science. 
If  the  discovery  is  one  of  magnitude  it  will  be  expres- 
sible as  a  formula,  which  should  have  the  criterion 
of  universal  validity  in  the  minds  of  all  who  are  able 
to  estimate  the  evidence.  But  even  here,  in  our 
judgment,  there  should  arise  the  final  question  of 
considering  how  the  new  generalisation  consists  with 
others,  or  in  wider  terms,  how  it  is  related  to  the 
sum  of  human  experience.  Should  it  be  markedly 
inconsistent,  as  the  evolution-formula  seemed  at  first 
to  so  many,  there  may  be  need  for  re-consideration. 
The  body  may  have  to  adapt  itself — possibly  not 
without  pain — to  its  new  food. 

Finally,  to  quote  once  more  from  Prof.  Karl  Pear- 
son :  "  The  scientific  method  is  marked  by  the  fol- 
lowing features: — (a)  careful  and  accurate  classi- 
fication of  facts  and  observation  of  their  correlation 
and  sequence;  (6)  the  discovery  of  scientific  laws 
by  aid  of  the  creative  imagination;  and  (c)  self- 
criticism  and  the  final  touchstone  of  equal  validity 
for  all  normally  constituted  minds." 


CHAPTER  IT. 

THE  UNITY  OF  SCIENCE. 

C:LASSIFICATION  OF  THE  SCIENCES. 

SINCE  science  presumes  to  take  the  whole  uni- 
verse for  its  province,  and  faces  the  immense  prob- 
lem of  the  order  of  nature,  it  is  not  surprising  that 
a  division  of  intellectual  labour  has  been  found  con- 
venient, and  that  separate  sciences  have  been  defined 
off,  each  with  particular  problems  and  special  meth- 
ods. This  is  an  adaptation  to  the  shortness  of  hu- 
man life  and  the  limitations  of  human  faculty,  for 
while  there  is  nothing  but  laziness  and  mis-education 
to  hinder  an  intelligent  citizen  from  having  scientific 
interest  in  all  orders  of  facts,  the  long  discipline 
which  a  science  requires  renders  it  impossible  that 
any  average  man  will  succeed  in  gaining  masterly 
familiarity  with  more  than  one  department  of  knowl- 
edge. 

The  title  of  the  old  Scotch  professorships  of  "  Civil 
and  Natural  History  "  perhaps  expressed  more  than 
one  good  idea, — for  instance,  that  man  must  be 
studied  in  relation  to  his  environment,  or,  again,  that 
the  history  of  non-human  organisms  might  have  some 
light  to  throw  upon  the  history  of  mankind,  but  the 
ideal  suggested  was  too  ambitious  for  ordinary  mor- 
tals. The  fact  is  that  a  compromise  has  to  be  made 
between  two  desirabilities.  On  the  one  hand,  the 


26       PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

aim  of  science-teaching,  which  is  a  culture  of  the 
scientific  mood  and  an  appreciation  of  scientific 
method,  seems  more  likely  to  be  attained  by  a 
thorough  study  of  some  one  order  of  facts  than  by 
an  intellectual  ramble  through  the  universe;  on  the 
other  hand,  the  true  dignity  and  value  of  science  can- 
not be  appreciated  if  the  unity  of  nature  and  of 
knowledge  be  practically  denied.  Superficiality  re- 
sults from  lack  of  specialisation,  and  pedantry  from 
too  much  of  it.  Let  us  briefly  consider  some  of  the 
classifications  which  have  been  found  convenient. 
Francis  Bacon  (1561-1626)  recognised  three  de- 
partments of  human  learning:  (1)  History  (based 
on  memory)  both  "natural"  and  "civil";  (2) 
Poesy  (based  on  imagination)  ;  and  (3)  Philosophy 
or  the  Sciences  (based  on  reason),  including  Divin- 
ity, which  has  to  do  with  revelation,  and  Natural 
Philosophy,  which  deals  with  God,  Nature,  and 
Man!  There  is  little  in  this  classification  which 
can  be  of  service  to  us  to-day  in  mapping  out 
the  territory  of  science,  but  it  is  interesting  (as 
Karl  Pearson  points  out)  to  notice  the  suggestion 
that  "  The  divisions  of  knowledge  are  not  like 
several  lines  that  meet  in  one  angle,  but  are  rather 
like  branches  of  a  tree  that  meet  in  one  stem." 
Auguste  Comte  (1798-1857)  recognised  six  fun- 
damental sciences:  Mathematics,  Astronomy,  Phys- 
ics, Chemistry,  Biology,  Sociology — and  a  supreme 
or  final  science  of  Morals.  He  sought  to  eliminate 
from  his  system  all  that  is  not  based  on  experience, 
and  he  introduced  the  important  conception  of  a 
hierarchy  of  knowledge,  that  is  to  say  the  idea  that 
one  department  of  science  is  dependent  on  another, 
sociology  on  biology,  biology  on  chemistry,  chemis- 
try on  physics,  and  so  on.  Without  pretending  that 


THE  UNITY  OF  SCIENCE.  27 

the  facts  of  life  can  be  re-stated  in  terms  of  chemistry 
and  physics,  or  that  the  biologist  has  given  into  his 
hands  the  key  to  the  problems  of  human  society,  we 
may  profitably  recognise  that  an  understanding  of 
the  organism  is  facilitated  by  the  results  of  chemical 
and  physical  science,  and  that  the  data  of  biology 
are  full  of  suggestion  to  the  sociologist. 

It  may  be  true — many  would  call  it  obvious — that 
life  transcends  the  categories  of  mechanism,  or,  in 
other  words,  that  the  formula  of  physics  do  not  suf- 
fice to  re-express  the  facts  of  life.  Yet  it  must  be 
admitted  that  vital  phenomena  have  become  more  in- 
telligible— more  readily  dealt  with  in  thinking — 
since  Biology  began  to  avail  itself  of  the  aid  of  Chem- 
istry and  Physics.  It  may  be  true  that  man  tran- 
scends the  categories  of  Biology,  and  it  seems  to  many 
that  man  as  compared  with  the  Amoeba  expresses 
an  entirely  new  synthesis,  just  as  the  Amoeba  does 
in  relation  to  a  mineral,  and  that  the  secret  of  both 
new  syntheses  remains  as  yet  hidden.  Yet  it  must 
be  admitted  that  human  life  has  become  more  intel- 
ligible— more  readily  dealt  with  in  thinking — since 
Psychology  and  Sociology  condescended  to  listen  to 
the  suggestions,  confessedly  still  immature,  offered  by 
Biology.  On  the  other  hand,  it  seems  historically 
true  that  such  valuable  ideas  as  division  of  labour  and 
evolution  were  made  clear  in  regard  to  human  affairs 
before  they  were  transferred  to  and  re-illustrated  in 
the  study  of  organisms.  There  is  a  sense  in  which 
the  Amoeba  may  be  said  to  be  of  use  in  the  interpreta- 
tion of  man;  but  it  is  also  true  that  the  study  of 
man  has  reacted  upon  the  biological  interpretation  of 
the  Amoeba.  Similarly  great  advances  were  made 
by  Chemistry  when  attention  was  extended  from  in- 
organic to  organic  substances,  and  there  are  at  least 


28      PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

hints  that  the  application  of  the  Evolution-idea  to 
the  problems  of  the  inorganic  will  make  for  progress. 
It  was  this  idea  of  the  interdependence  of  different 
scientific  disciplines  which  especially  marked  Comte's 
classification.  Herbert  Spencer  (1864)  "combined 
the  '  tree '  system  of  Bacon  with  Comte's  exclusion 
of  theology  and  metaphysics  from  the  field  of  knowl- 
edge," *  and  he  focussed  the  distinction  between  the 
Abstract  sciences  of  Logic  and  Mathematics  (which 
deal  with  our  methods  of  conceptual  description) 
and  the  Concrete  sciences  which  are  conceptual  de- 
scriptions of  phenomena.  In  other  words,  f  the 
abstract  sciences  deal  with  modes  of  perception,  the 
concrete  sciences  with  the  contents  of  perception. 

Eor  the  most  detailed  map  of  science  as  yet  worked 
out,  we  may  refer  to  the  concluding  chapter  of  Karl 
Pearson's  Grammar  of  Science,  noticing  only:  (1) 
that  it  has  been  almost  unanimously  recognised  as 
convenient  that  the  sciences  dealing  with  organisms 
(Biology,  Psychology,  Sociology)  should  be  distin- 
guished from  those  which  deal  with  inorganic  phe- 
nomena (Chemistry  and  Physics) ;  and  (2)  that 
different  departments  are  bound  together,  e.g.,  ap- 
plied mathematics  linking  the  abstract  to  the  concrete, 
chemical  physiology  linking  the  study  of  the  in- 
organic to  that  of  the  organic. 

Thus,  the  broad  lines  of  the  scientific  map  may  be 
represented  in  a  scheme  like  this : — 

*  Karl  Pearson,  Grammar  of  Science,  rev.  ed.f  London, 
1900,  p.  513. 
t  Ibid.,  p.  515. 


THE  UNITY  OF  SCIENCE. 


29 


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THE    COKKELATION    OF    KNOWLEDGE. 

Verworn  speaks  of  Johannes  Miiller  (1801-1858) 
as  "  one  of  those  monumental  figures  that  the  history 
of  every  science  brings  forth  but  once.  They  change 
the  whole  aspect  of  the  field  in  which  they  work,  and 
all  later  growth  is  influenced  by  their  labours."  When 
we  enquire  into  the  secret  of  Miiller's  achievements, 
we  find  that  he  combined  genius  with  unsurpassed 
working-power,  but  it  is  important  to  notice  more 
definitely  what  we  may  call  his  sense  of  the  correla- 
tion of  knowledge.  "  He  did  not  recognise  one 
physiological  method  alone,  but  employed  boldly 
every  mode  of  treatment  that  the  problem  of  the 
moment  demanded.  Physical,  chemical,  anatomical, 
zoological,  microscopic  and  embryological  knowledge 
and  methods  equally  were  at  his  disposal,  and  he 
employed  all  of  these  whenever  it  was  necessary  for 
the  accomplishment  of  his  purpose  at  the  time."  * 

If  we  take  Pasteur  (1822-1895)  as  another  repre- 
sentative figure  in  nineteenth  century  science,  we  may 
*  Max  Verworn,  General  Physiology,  trans.  1899,  p.  20. 


30      PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

read  the  same  lesson.  Far  from  being  pre-occupied 
with  vivisection  and  inoculation,  as  the  commonplace 
summary  too  often  suggests,  he  passed  in  an  ever- 
widening  spiral  of  scientific  investigation  from  his 
rural  centre  upwards,  from  tanpit  to  vat  and  vintage, 
from  manure  heaps,  earth-worms,  and  water-supply 
to  the  problems  of  civic  sanitation.  On  each  radius 
on  which  he  paused  he  left  either  a  method  or  a  clue, 
and  set  some  other  enquirer  at  work.  Biologist  and 
brewer,  chemist  and  physician,  agriculturalist  and 
surgeon, — and  how  many  more — have  all  felt  the 
influence  of  his  achievements,  and  part  of  the  secret 
of  these  lay  in  his  sense  of  the  correlation  of  knowl- 
edge, in  his  grasp  of  the  fact  that  workers  in  different 
departments  of  science  have  much  to  say  to  each 
other.* 

Another,  and  again  a  different  illustration  may  be 
found  in  the  work  of  Darwin.  It  was  natural  that 
one  who  discerned  so  vividly  the  correlation  of  or- 
ganisms should  also  realise  the  correlation  of  knowl- 
edge. We  see  this,  for  instance,  as  we  turn  over 
the  pages  of  The  Origin  of  Species,  The  Descent 
of  Man,  Variation  under  Domestication,  and  his 
other  great  works,  and  infer  from  the  foot-notes 
something  of  the  range  of  the  fields  in  which  he 
gleaned.  We  see  it  in  his  recognition  of  the  far- 
reaching  scope  of  the  doctrine  of  descent,  that  it  be- 
longs not  merely  to  the  biologist,  but  affects  psychol- 
ogy and  sociology,  the  whole  life  of  man  and  society. 
He  once  expressed  satisfaction  that  he  had  not  been 
permitted  to  become  a  "  specialist " ;  it  is  hardly  too 
much  to  say  that  there  is  no  specialism  in  concrete 
organic  science  which  he  has  left  unaffected. 

*  P.  Geddes  and  J.  Arthur  Thomson,  "  Louis  Pasteur," 
Contemporary  Review,  Nov.,  1895,  pp.  632-644. 


THE  UNITY  OF  SCIENCE.  31 

Let  us  take  an  illustration  from  the  history  of 
astronomy.  Apart  from  pioneer  suggestions,  as- 
tronomy was  till  the  middle  of  the  century  a 
science  descriptive  of  the  movements  of  the  heavenly 
bodies.  But  the  establishment  of  spectroscopy  by 
Kirchhoff  and  Bunsen  was  the  beginning  of  a  close 
correlation  between  astronomy  and  other  sciences. 
Formerly  "  it  was  enough  that  she  possessed  the  tele- 
scope and  the  calculus.  Xow  the  materials  for  her 
inductions  are  supplied  by  the  chemist,  the  elec- 
trician, the  enquirer  into  the  most  recondite  myster- 
ies of  light  and  the  molecular  constitution  of  matter. 
She  is  concerned  with  what  the  geologist,  the  meteor- 
ologist, even  the  biologist,  has  to  say ;  she  can  afford 
to  close  her  ears  "to  no  new  truth  of  the  physical  or- 
der. Her  position  of  lofty  isolation  has  been  ex- 
changed for  one  of  community  and  mutual  aid."  * 

XEED  FOB  CRITICISM  OF  SCIENTIFIC  WOBK. 

A  large  part  of  the  scientific  work  done  year  after 
year  is  instinctive  and  spontaneous  rather  than  delib- 
erate and  controlled.  It  is  done  because  the  doers 
have  delight  in  it,  a  "  natural  taste,"  as  they  say,  and 
thus  self-criticism  as  to  the  value  of  it  is  silenced. 
The  result  is  an  enormous  waste  of  mental  energy. 
Big-brained  men  often  fritter  away  their  intelligence 
on  the  study  of  trivialities,  which  may  be  admirable 
as  what  used  to  be  called  an  "  elegant  amusement," 
but  represents  a  great  loss  to  science. 

It  is  perhaps  useful  at  times  to  stand  by  and 
calmly  watch  the  succession  of  gifts  laid  upon  the 
altar  of  science.  There  are  the  well-finished  offer- 
ings of  those  who  have  what  seems  to  some  of  us  so  in- 

*  A.  M.  Clerke,  History  of  Astronomy  in  the  Nineteenth 
Century,  1885,  p.  183. 


32      PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

estimably  precious — the  leisure  to  work  thoroughly 
undisturbed ;  there  are  the  ill-finished  offerings  of  the 
impetuous,  and  enthusiastic,  and  hard-driven;  there 
are  humble  offerings  which  have  involved  years  of 
self-denial;  there  are  brilliant  offerings  which  have 
meant  but  a  few  flashes  of  clear  insight;  there  are 
tarnished  offerings  which  have  been  gained  illegiti- 
mately ;  there  are  heroic  offerings  which  are  received 
in  absentia  from  those  who  have  died  to  know ;  there 
are  epoch-making  offerings,  like  those  of  Newton  or 
of  Darwin,  which  set  the  whole  altar  aflame. 

One  cannot  see  this  vision  of  the  altar  of  science 
without  being  impressed.  There  is  a  majesty  in  the 
advancement  of  knowledge,  and  a  sublime  patience 
in  research.  But  it  is  difficult  to  tell  how  much  of 
the  work  would  be  regarded  as  effective  expenditure 
of  energy  by  a  sufficiently  wise  judge,  wise  for  science 
and  wise  for  humanity.  The  only  sufficiently  wise 
judge  is  Time,  whose  decisions  are  often  very  slow. 
That  contemporary  appreciation  of  an  offering  has 
often  been  far  from  just  is  one  of  the  most  obvious 
facts  in  the  history  of  science. 

But  as  one  lingers  near  this  "  altar  of  science," 
one  must  be  much  absorbed  if  one  does  not  hear  a 
murmur  of  dissentient  voices.  The  practical  man 
growls  over  the  time  spent  in  the  classification  of 
seaweeds  when  "  what  we  want  is  more  wheat,"  over 
embryological  research  instead  of  fish-hatching,  over 
the  theoretical  puzzles  of  geology  instead  of  the 
search  for  more  coal  and  iron.  When  the  practical 
man  supports  the  scientific  worker,  he  has  doubt- 
less some  right  to  control  the  direction  of  his 
activities,  though  it  is  not  very  clear  that  much 
good  has  ever  come  of  this.  Man  does  not  live  by 
bread  alone,  and  some  of  the  most  important  practical 


THE  UNITY  OF  SCIENCE.  33 

results,  such  as  the  use  of  antiseptics,  have  been 
reached  by  very  circuitous  paths.  It  did  not  seem  a 
very  promiseful  beginning  which  Pasteur  found  in 
the  study  of  tartrate  crystals,  and  yet  what  a  begin- 
ning it  was ! 

It  is  long  since  Bacon  replied  to  the  objection  of 
the  practical  mood  which  we  have  just  noted.  We 
may  recall  his  vindication  of  investigations  which 
are  light-giving  (lucifera)  against  those  which  are  of 
direct  practical  utility  (fructifera)  ;  and  the  deliver- 
ance "  Just  as  the  vision  of  light  itself  is  something 
more  excellent  and  beautiful  than  its  manifold  uses, 
BO  without  doubt  the  contemplation  of  things  as  they 
are,  without  superstition  or  imposture,  without  error 
or  confusion,  is  in  itself  a  nobler  thing  than  a  whole 
harvest  of  inventions." 

But  there  are  many  other  dissentient  voices.  The 
humanitarians  mutter  "  cruelty,"  "  inhuman  curios- 
ity," "  barbarous  inquisitiveness,"  "  triviality."  The 
scholars  say  with  a  smile,  "  We  would  rather  know 
the  thoughts  of  Plato  and  Aristotle  than  pore  over  the 
entrails  of  an  antediluvian  frog," — "  a  Kindergar- 
ten study  at  the  best  is  your  Natural  Science."  The 
poets  and  artists  laugh  and  say,  "  Grubbers  among 
dust  and  ashes,  besmirching  the  wings  which  might 
lift  you  as  eagles,"  "  a  botany  which  teaches  that 
there  is  no  such  thing  as  a  flower,"  "  a  biology  which 
has  become  necrology,"  "  a  chemistry  which  has 
flooded  the  world  with  aniline  dyes,"  "  a  physiology 
which  has  made  a  debased — not  kailyard,  but  mid- 
den-heap— literature  possible,"  and  so  on. 

These  and  a  hundred  other  criticisms  reach  the 
ear,  and  though  a  retort  may  readily  be  made  to  each, 
the  feeling  remains  that  there  is  some  justice  in  most 
of  them,  that  scientific  industry  is  not  always  suf- 


34      PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

ficiently  self-critical.  To  rise  above  particular  criti- 
cisms to  a  general  basis  of  criticism  would  be  a  great 
gain,  and  perhaps  this  may  be  found  in  a  recognition 
of  what  may  be  called  The  Three  Unities. 

UNITY  OF  LIFE. 

The  first  of  these  unities  is  the  Unity  of  Life.  We 
have  already  referred  to  the  three  main  moods  or  atti- 
tudes of  mind  observable  in  human  relations  to  na- 
ture— practical,  emotional,  and  scientific.  They  find 
expression  in  doing,  feeling,  and  knowing;  in  prac- 
tice, in  art,  and  in  science;  they  may  be  symbolised 
by  hand,  heart,  and  head. 

We  are  not  of  course  supposing  the  existence  of 
altogether  separable  faculties,  or  nonsense  of  that 
sort;  we  do  not  say  that  there  are  any  purely  prac- 
tical, or  exclusively  emotional,  or  solely  scientific 
men;  we  simply  note  what  appears  to  be  a  fact  of 
life  that  we  can  practically  distinguish  around  us 
the  doers,  the  feelers,  and  the  knowers.  And  as 
one  of  the  moods  often  has  temporary  dominance, 
we  are  all  apt  to  err  in  over-doing,  or  over-feeling,  or 
over-knowing. 

It  is  believed  by  most  comparative  physiologists 
that  the  ears  of  many  of  the  simpler  animals  are 
not  hearing  ears,  but  rather  directive  organs,  impor- 
tant in  balancing,  equilibrating,  and  orientation.  It 
is  such  an  equilibrating  organ  that  we  all  need  to 
help  us  to  adjust  the  balance  of  our  moods. 

Our  thesis  then  is  that  some  measure  of  complete- 
ness of  life — in  ideal  at  least — is  the  condition  of 
sanity  in  human  development.  A  thoroughly  sane 
life  implies  a  recognition  of  the  trinity  of  knowing, 
feeling,  and  doing.  It  spells  health,  wholeness,  holi- 
ness, as  Edward  Carpenter  has  said. 


THE  UNITY  OF  SCIENCE.  35 

Contrariwise,  non-humane  activity,  whether  prac- 
tical, emotional,  or  scientific,  implies  primarily  a 
denial  of  the  trinity  referred  to,  a  violence  to  the 
unity  of  life.  The  one-sided  man  has  let  at  least  two 
of  the  lights  of  life  die  out. 

To  be  wholly  practical  is  to  grub  for  edible  roots 
and  see  no  flowers  upon  the  earth  nor  the  stars  over- 
head; to  be  wholly  emotional  is  to  become  unreal 
and  effervescent ;  to  seek  only  to  know  is  to  deny  our 
birth-right  and  birth-duty  as  social  organisms. 

The  various  sins  of  our  relations  to  nature — sins 
of  ignorance,  indifference,  irreverence,  cruelty,  ob- 
scurantism, and  so  on — all  imply  some  denial  of  the 
trinity. 

Science  for  its  own  sake  requires  to  be  continu- 
ally moralised  and  socialised,  oriented,  that  is  to 
say,  in  relation  to  other  ideals  of  human  life  than 
its  own  immediate  one  of  working  out  an  intellectual 
cosmos.  Our  science  requires  to  be  kept  in  touch  at 
once  with  our  life  and  with  our  dreams;  with  our 
doing  and  with  our  feeling;  with  our  practice  and 
with  our  poetry.  Synergy  and  sympathy  are  needed 
to  complete  a  synthesis. 

If  the  above  be  a  reasonable  position,  it  suggests 
that  the  scientific  way  of  looking  at  the  world  is  not 
the  only  one.  There  are  many  whose  outlook  ex- 
presses quite  a  different  mood.  As  we  have  seen, 
the  student  of  science  does  not  pretend  to  explain 
the  order  of  nature,  he  simply  tries  to  re-describe  it 
in  general  conceptual  formulae,  and  he  believes  that 
his  task  is  justified  by  the  results — intellectual, 
emotional,  and  practical.  He  has  a  right  to  insist 
on  being  heard  as  to  the  aim  of  his  own  industry, 
but  it  does  not  follow  that  his  statements  are  of 
equal  value  when  he  speaks  of  other  than  scientific 


36      PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

expressions  of  the  developing  human  spirit.  Irri- 
tated by  the  way  in  which  others  misunderstand  him, 
he  often  misunderstands  them.  Thus  as  an  expres- 
sion of  the  recoil  of  the  scientific  mood  from  meta- 
physical speculation — a  recoil  which  seems  to  us 
largely  due  to  misunderstanding  of  aims — we  may 
quote  what  Liebig  said  of  Schelling:  "I  myself 
spent  a  portion  of  my  student  days  at  a  university 
where  the  greatest  philosopher  and  metaphysician  of 
the  century  charmed  the  thoughtful  youth  around 
him  into  admiration  and  imitation;  who  could  at 
that  time  resist  the  contagion  ?  I  too  have  lived 
through  this  period — a  period  so  rich  in  words  and 
ideas  and  so  poor  in  true  knowledge  and  genuine 
studies;  it  cost  me  two  precious  years  of  my 
life."  * 

The  above  citation  expresses  the  opinion  of  many 
scientific  workers,  and  yet  is  it  not,  to  say  the  least, 
arrogant,  to  attempt  to  ignore  the  attempts  which 
have  been  made  throughout  all  the  ages  to  re-express 
the  order  of  nature  in  transcendental  or  metaphysical 
terms?  "  The  search  after  ultimate  causes,"  says 
Dr.  Merz,  "  may  perhaps  be  given  up  as  hopeless ; 
that  after  the  meaning  and  significance  of  the  things 
of  life  will  never  be  abandoned :  it  is  the  philosophi- 
cal or  religious  problem." 

We  cannot  readily  understand  a  phenomenon 
which  seems  to  occur — that  of  an  active  and  well- 
disciplined  brain  in  which  there  are,  so  to  speak, 
idea-tight  compartments,  the  contents  of  which  are 
prevented  from  mutual  influence.  The  mental  like 
the  bodily  life  should  be  a  unified  system  of  correla- 

*  Veber  das  Studium  der  Naturwissenschaften.  On  the 
Study  of  the  Natural  Sciences,  1840,  cited  by  E.  von  Meyer, 
History  of  Chemistry,  1891. 


THE  UNITY  OF  SCIENCE.  37 

tions.  It  cannot  be  normal  that  a  man  should  cher- 
ish incompatible  ideas.  But  that  is  not  to  say  that 
he  may  not  be  both  scientific  and  metaphysical,  or 
both  scientific  and  poetical.  These  are  indeed 
different  moods,  but  complementary  rather  than  in- 
compatible, and  disharmony  results  only  when  they 
are  allowed  to  mix  with  one  another  in  verbal  state- 
ments, or  when  the  particular  concrete  expressions 
given  to  the  poetic  or  philosophic  activity  happen 
to  be  at  variance  with  sound  science.  Between  the 
moods  there  is  no  variance.  The  different  moods 
express  different  ways  of  looking  at  things,  and 
use  as  it  were  words  of  different  languages.  The 
evolutionist  postulates  a  beginning  somewhere, — 
an  initial  order  of  nature  instituted  in  some  fashion 
quite  unknown  and  implying  the  potentialities  of 
the  future  in  some  fashion  quite  unknown;  the 
creationist  gives  in  non-scientific  or  transcendental 
terms  some  account  of  the  institution  of  the  order 
of  nature;  the  ideas  are  not  antithetical,  they  are 
incommensurable.  Moreover,  if  we  may  take  an- 
other point  of  view  for  a  moment,  the  teaching  of 
the  history  of  science  leads  us  to  a  strong  feeling  of 
gratitude  to  the  deductive  or  a  priori  thinkers.  They 
were  at  least  thinking — often  with  a  broad  perspec- 
tive— and  that  cannot  always  be  said  of  researchers. 
They  may  have  interpolated  fanciful  ideas  where 
facts  alone  are  decisive,  their  deductions  may  have  led 
induction  off  the  scent,  they  may  have  blinded  vision 
by  preconceptions  and  deranged  reasoning  by  preju- 
dices, they  may  have  caused  confusion  by  mixing  up 
objective  and  subjective  terms,  and  done  many  other 
evil  things ;  but  it  is  a  historical  fact  that  astrology 
led  on  to  astronomy,  alchemy  to  chemistry,  cosmolo- 
gies to  geology,  and  superstitious  medical  lore  to 


38       PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

physiology.     Even  the  frequent  break-downs  of  the 
a  priori  methods  prompted  a  posteriori  enquiry. 

UNITY   OF   SCIENCE. 

The  second  unity — a  recognition  of  which  makes 
for  sanity — is  the  unity  of  science  or  knowledge. 
The  sciences  in  the  broadest  sense  form  one  body  of 
truth.  Blocked  apart  for  practical  convenience, 
treated  of  in  separate  books,  expounded  by  different 
teachers,  investigated  in  different  laboratories,  they 
are  parts  of  one  discipline,  illustrations  of  one 
method,  expressions  of  one  mood,  and  attempts  to 
make  clear — if  never  to  solve — the  one  great  prob- 
lem of  the  Order  of  Nature.  The  sciences  have  their 
ideal  completeness  only  when  inter-related.  This  is 
the  ideal  alike  of  the  philosopher's  stone,  of  the  en- 
cyclopaedic movement,  and  of  the  most  modern  scien- 
tific synthesis. 

This  note  of  the  unity  of  the  sciences  is  sounded — 
though  so  often  quickly  silenced — in  the  word  Uni- 
versity. Its  value  is  demonstrated  by  the  history  of 
the  sciences,  which  shows  how  often  a  fresh  contact 
between  two  departments  has  led  to  great  advances. 
It  becomes  insistent  when  we  consider  a  big  subject 
like  the  physiology  of  marine  organisms,  which  there 
is  no  hope  of  understanding  except  through  the  com- 
bined efforts  of  chemist  and  physicist,  botanist  and 
zoologist,  meteorologist  and  geographer. 

Whether  we  take  a  hint  from  the  term  "  Natural 
History,"  or  from  the  word  "  Organisata,"  which 
Linnaeus  used  to  include  both  animals  and  plants,  or 
from  Comte's  hierarchy  of  the  sciences,  or  from 
Caird's  essay  on  the  unity  of  science,  or  from 
Spencer's  Synthetic  Philosophy — we  have  purposely 
chosen  incongruous  examples —  we  hear  the  same  note 


THE  UNITY  OF  SCIENCE.  39 

of  unity.  It  is  the  end  towards  which  our  teaching 
and  learning  must  move,  even  if  the  curve  be  asymp- 
totic. 

As  we  have  already  noted,  the  study  of  living  crea- 
tures stands  midway  between  the  chemical  and  phys- 
ical sciences,  which  are  in  a  sense  beneath  it,  and  the 
mental  and  social  sciences,  which  are  in  a  sense 
above  it ;  there  are  lights  from  below  and  lights  from 
above;  and  to  attempt  to  shut  out  either  means  un- 
necessary obscurity.  The  living  organism  is  a  syn- 
thesis, whose  secret  has  certainly  not  been  solved, 
but  we  are  surely  saved  from  some  misunderstand- 
ings of  it  by  the  results  of  other  sciences  than  Bi- 
ology. 

Thus,  there  comes  to  the  aid  of  the  biologist  or 
any  other  scientific  worker,  this  criterion:  Am  I, 
as  a  thinker,  teacher,  and  investigator,  recognising, 
respecting,  doing  no  violence  to,  the  unity  of  science? 
'Am  I  recognising  other  disciplines,  other  bodies  of 
thought,  as  I  wish  that  they  should  recognise  mine  I 
Even  more  positively,  the  criterion  might  read: 
Does  this  piece  of  work  in  any  way  tend  to  the  real- 
isation of  the  Unity  of  Science  ? 

UNITY  OF  NATURE. 

A  third  unity  may  perhaps  be  spoken  of  as 
the  unity  of  nature — by  which  we  mean  to  refer 
both  to  the  unity  of  the  particular  subject  of 
scientific  enquiry,  and  to  the  unity  of  the  whole 
system  of  things.  To  the  psychologist,  the  unity 
which  must  not  be  lost  sight  of  is  that  of  the  person- 
ality which  he  is  studying.  To  the  biologist,  the 
unity  which  cannot  be  ignored  without  fallacy  is 
the  unity  of  the  organism.  But  besides  these  there 
is  the  unity  of  the  whole  system  of  nature  in  which 

D 


4:0      PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

part  is  linked  to  part  by  sure,  though  often  subtle 
bonds  in  which  nude  isolation  is  as  rare  as  a  vacuum. 
In  regard  to  all  matters  we  have  many  questions  to 
ask,  each  difficult,  each  interesting,  each  often  re- 
quiring special  methods  of  investigation,  and  in  the 
search  of  answers  we  are  sometimes  apt  to  forget  the 
unity  of  the  subject.  There  can  be  no  doubt,  for  in- 
stance, that  in  the  eager  pursuit  of  comparative 
anatomy,  or  chemical  physiology,  or  any  other  par- 
ticular line  of  biological  enquiry,  the  unity  of  the 
organism  is  often  forgotten.  The  same  is  true, 
though  perhaps  less  markedly,  in  other  sciences, 
where  the  fascination  of  some  one  aspect  or  method 
causes  the  investigator  to  lose  his  sense  of  the  unity 
of  his  subject.  Specialism  of  enquiry  is  necessary 
and  valuable,  but  it  loses  its  virtue  if  the  specialist 
remain  like  a  beetle  in  a  rut,  the  sides  of  which  form 
the  horizon. 

Thus  we  reach  a  third  criterion  of  scientific  work 
and  thought ;  we  must  force  upon  ourselves  the  ques- 
tion— Am  I  studying  this — whatever  it  is — as  I 
would  have  myself  studied,  as  a  whole,  as  a  unity, 
and  moreover  as  a  part  in  the  great  system  of  things 
which  we  call  Nature,  which  is  also  a  Unity  ? 

To  sum  up,  there  are  a  certain  number  of  'isms 
which  we  scornfully  call  fads.  They  express  a  loss 
of  perspective, — intellectual,  emotional,  or  practical, 
the  dominance  of  some  fixed  idea  which  distorts  or 
obscures  vision.  It  is  easy  to  scoff  at  one  or  other  of 
these  fads,  but  the  chances  are  that  we  are  ourselves 
victims.  It  is  more  in  the  line  of  progress  to  study 
their  meaning,  and  then  we  see  that  they  are  often 
reactions  against  some  denial  of  the  unity  of  life,  the 
unity  of  science,  the  unity  of  nature,  or  some  greater 
unity  than  these. 


CHAPTEE  III. 

PBOGRESSIVE^ESS  OF  SCIENCE. 

THE  FIBST  CONDITION  OF  SCIENTIFIC  PKOGBESS. 

~No  one  who  has  watched  a  colony  of  ants  with 
anv  precision  will  find  it  easy  to  agree  with  the 
ancient  proverbialist  that  the  "  little  people "  are 
"  exceeding  wise,"  if  we  mean  by  "  wise  "  to  imply 
anything  like  "  knowing  "  or  "  scientific  "  in  the  hu- 
man connotation  of  these  terms.  Ants  are  marvel- 
lous creatures  of  routine,  but  they  are  foolish  before 
the  new.  Their  little  complex  brains  are  well-stocked 
compendia  of  ready-made  nervous  mechanisms,  but 
they  are  eminently  non-educable.  It  is  very  difficult 
to  prove  that  the  little  people  are  able  to  profit  by 
experience  at  all.  Therefore,  if  one  were  inclined  to 
give  a  lifetime  to  the  education  of  insects,  one  would 
not  begin  with  ants.  Their  brains  are  too  much 
"  set,"  or  stereotyped,  to  be  readily  docile.  It  would 
be  unwise  to  be  dogmatic  regarding  this  difficult  prob- 
lem, but  the  general  verdict  of  present  biological 
and  psychological  research  on  the  behaviour  of  ants 
is,  that  their  marvellous  powers  are  not  acquired  by 
the  individual  in  relation  to  the  particular  needs 
of  its  life,  are  not  readily  modifiable  to  suit  novel 
contingencies  even  of  a  simple  kind,  are  not,  in  the 
strict  sense,  intelligent,  but  are  hereditary  instincts 
which  have  arisen  in  the  course  of  a  long  series  of 
generations  by  the  action  of  natural  selection  on 
germinal  variations. 

If  a  disaster  befell  the  ant-hill  and  reduced  the 


42      PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

community  to  the  minimum  number  necessary  to 
avoid  extinction — say  to  a  fertile  queen  with  two 
or  three  workers  to  look  after  her — there  seems  no 
reason  to  doubt  that  in  a  short  time  the  whole  ant- 
hill would  contain  a  population  as  effective  as  before. 
Their  powers  are  implied  in  their  brain-inheritance ; 
their  capabilities  of  effective  response  to  their  en- 
vironment have  little  or  no  external  registration. 

It  is  possible  that  in  some  animals,  where  a  social 
life  is  sustained  generation  after  generation,  there 
may  be  something  corresponding  to  tradition  which 
gradually  grows  larger  in  its  content,  which  forms 
what  may  be  called  an  external  heritage  as  contrasted 
with  a  natural  or  organic  inheritance. 

It  is  also  to  be  noted  that  some  of  the  higher  ani- 
mals seem  to  have  words — particular  sounds  in- 
dicative of  certain  things  or  expressive  of  definite 
emotional  states — and  it  can  hardly  be  doubted  that 
the  existence  of  these  will  facilitate  mental  processes. 
In  some  cases,  too,  the  permanent  products  which 
animals  make — dwellings,  nests,  roads,  and  the  like 
— may  become  suggestive  symbols,  and  may  be  of 
some  importance  as  stimuli  to  successive  genera- 
tions. 

Yet  after  all  these  admissions  are  made,  it  re- 
mains as  a  great  contrast  between  man  and  animals 
that  our  possession  of  language  and  methods  of  re- 
cording conclusions  makes  the  progress  of  science 
possible.  In  the  case  of  ants  it  seems  as  if  the  brain 
had  evolved  in  the  direction  of  a  more  and  more  per- 
fect automaton ;  in  the  case  of  man,  the  existence  of 
external  means  of  registration  has  made  it  possible 
for  the  brain  to  be  born  more  and  more  plastic,  less 
weighted  by  an  inheritance  of  ready-made  powers,  in 
a  word,  more  educable.  "  To  the  educable  animal — 


PROGRESSIVENESS  OF  SCIENCE.  4.3 

the  less  there  is  of  specialised  mechanism  transmitted 
by  heredity,  the  better.  The  loss  of  instinct  is 
what  permits  and  necessitates  the  education  of  the 
receptive  brain."  * 

In  this  book-ridden  age  when  the  student  so  often 
laboriously  uses  another's  eyes  instead  of  lifting  his 
own,  and  when  many,  as  a  stern  critic  has  said, 
"  seem  unable  to  cerebrate  except  in  the  presence  of 
print,"  the  hasty  wish  has  sometimes  been  expressed 
that  all  books  could  be  burned.  But,  however,  in- 
teresting the  century  succeeding  the  conflagration 
might  be — with  enthusiastic  reconstructing  of  the 
classics  from  reminiscences  and  with  uninhibited  in- 
dependence of  inquiry — it  is  probably  safe  to  say 
that  men  would  return  to  the  conclusion  which  we 
are  now  expounding,  that  the  first  condition  of  the 
progressiveness  of  the  sciences  is  in  permanent 
methods  of  external  registration.  Extraordinary, 
indeed,  would  be  the  calamity  if  the  Temple  of 
Science  should  fall  like  the  Tower  of  Babel,  if  all 
the  living  embodiments  of  science  should  suddenly 
disappear,  if  all  the  instruments  and  inventions  which 
are  suggestive  symbols  of  hard-won  generalisations 
should  be  lost,  if  all  the  phrases  which  condense 
discoveries  into  formulae  should  be  wiped  out  of 
human  language — then  we  should  have  to  begin  at 
the  beginning  again.  The  prime  condition  of  the 
progressiveness  of  science  is  in  external  modes  of 
registration, — in  words  and  formulae,  symbols  and 
instruments. 

THE  FACT  OF  PEOGEESS. 

In    an    eloquent    lecture    on    "  The  Progressive- 
ness    of    the    Sciences,"  the    late    Principal    John 
*E.  Ray  Lankester,  Nature,  LXL,  1900,  p.  625. 


44      PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

Caird  spoke  as  follows :  "  The  history  of  human 
knowledge  is  a  history,  on  the  whole,  of  a  continu- 
ous and  ever-accelerating  progress.  In  some  of 
its  departments  this  characteristic  may  be  more 
marked  and  capable  of  easier  illustration  than  in 
others.  External  accidents,  affecting  the  history  of 
nations,  may  often  have  disturbed  or  arrested  the  on- 
ward movement,  or  even,  for  a  time,  seem  to  have 
altogether  obliterated  the  accumulated  results  of  the 
thought  of  the  past.  But  on  the  whole  the  law  is  a 
constant  one  which  constitutes  each  succeeding  age 
the  inheritor  of  the  intellectual  wealth  of  all  pre- 
ceding ages,  and  makes  it  its  high  vocation  to  hand 
on  the  heritage  it  has  received,  enriched  by  its  own 
contributions,  to  that  which  comes  after.  In  almost 
every  department  of  knowledge  the  modern  student 
begins  where  innumerable  minds  have  been  long  at 
work,  and  with  the  results  of  the  observation,  the 
experience,  the  thought  and  speculation  of  the  past 
to  help  him.  If  the  field  of  knowledge  were  limited, 
this,  indeed,  would,  from  one  point  of  view,  be  a 
discouraging  thought;  for  we  should  in  that  case  be 
only  as  gleaners  coming  in  at  the  close  of  the  day 
to  gather  up  the  few  scanty  ears  that  had  been  left, 
where  other  labourers  had  reaped  the  substantial 
fruits  of  the  soil.  But,  so  far  from  that,  vast  and 
varied  as  that  body  of  knowledge  which  is  the  result 
of  past  research  may  seem  to  be,  the  human  race 
may,  without  exaggeration,  be  said  to  have  only  en- 
tered on  its  labours,  to  have  gathered  in  only  the  first 
fruits  of  a  field  which  stretches  away  interminably 
before  it."  * 

It  is  one  of  the  aims  of  this  volume  to  illustrate 

*  A  lecture  delivered  In  1875.    Reprinted  in  Lectures  and 
Addresses,  1899. 


PROGRESSIVENESS  OF  SCIENCE.  45 

the  progress  of  the  sciences  within  a  century,  and 
there  are  many  ways  in  which  the  impression  of 
progressiveness  may  be  made  vivid.  Many  of  the 
articles  in  the  older  Encyclopaedias  are  splendid 
pieces  of  intellectual  workmanship,  but  to  read  one 
of  them  and  then  its  correspondent  in  a  modern 
encyclopaedia  is  like  a  sudden  transition  from  an 
incipient  spring  to  midsummer.  And  yet  we  know 
that,  to  our  successors,  this  modern  article  will  soon 
seem  quite  vernal. 

There  have  been  scientific  works  like  those  of 
Aristotle,  Pliny,  and  Galen  which  lasted  in  varied 
forms  through  centuries ;  and  there  are  masterpieces, 
like  the  books  of  Euclid,  and  Newton's  Principia, 
which  in  some  form  will  be  text-books  while  learning 
lasts;  but  every  one  knows  that  nowadays  even  the 
best  of  text-books  is  very  short-lived. 

If  we  take  a  survey  of  the  sciences,  from  astron- 
omy to  sociology,  how  striking  are  the  changes,  alike 
as  to  facts  and  ideas,  in  the  last  hundred  years.  He 
must  be  indeed  blase  or  callous  who  does  not  feel  ex- 
hilaration in  the  thought  of  the  advance  in  the  in- 
terval between  Laplace  and  Lockyer ;  between  Count 
Rumford  and  Lord  Kelvin;  between  Hutton  and 
Playfair  and  the  Geikies;  between  Richard  Owen 
and  Louis  Agassiz  on  the  one  hand,  Cope  and  Zittel 
on  the  other;  between  Cuvier  and  Huxley;  between 
Lamarck  and  Ray  Lankester ;  between  Von  Baer  and 
Francis  Balfour;  between  Bichat  and  Sir  Michael 
Foster;  between  Erasmus  Darwin  and  his  grand- 
son ;  between  Reimarus  and  Romanes ;  between  Prich- 
ard  and  Taylor;  between  Adam  Smith  and  Herbert 
Spencer.  To  any  one  who  knows  even  a  little  con- 
cerning the  history  of  science  the  contrasts  of  these 
coupled  names  must  stimulate  afresh  the  impression 


46       PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

that  there  are  few  facts  more  marvellous  and  inspir- 
ing than  the  advancement  of  science. 

ITS   NECESSITY. 

The  primary  reason  for  the  progressiveness  of 
science  is  simply  that  the  scientific  mood  is  a  natural 
and  necessary  expression  of  the  developing  human 
spirit.  It  may  be  thwarted,  discountenanced,  even 
banned,  as  it  was  during  the  early  mediaeval  cen- 
turies, but  stifled  it  cannot  be.  The  innate  inquisi- 
tiveness,  the  passion  for  facts,  the  active  scepticism, 
the  desire  after  lucidity,  and  the  other  qualities  to 
which  we  have  referred  as  characteristics  of  the 
scientific  mood,  may  be  widespread  or  confined  to 
small  circles  of  enquirers,  may  be  exhibited  in  re- 
gard to  all  orders  of  facts  or  restricted  to  a  single 
department,  but  the  scientific  mood  is  essential  to 
man's  nature,  and  science  will  not  cease  to  progress 
until  both  practice  and  poesy  have  likewise  come  to 
an  end. 

There  is  no  doubt  that  many  pieces  of  scientific 
research  are  entered  upon  with  the  set  purpose  of 
solving  practical  problems;  on  the  other  hand  much 
scientific  activity  is  as  spontaneous  and  instinctive  as 
a  great  part  of  artistic  activity  is :  in  other  words,  it 
is  a  natural  expression  of  the  man.  In  evidence  of 
this,  at  a  time  when  the  pursuit  of  science  is  so  often 
a  "  profession  "  and  a  "  Brodwissenschaft"  one  may 
recall  that  up  and  down  through  the  country  one 
finds  many  obscure  enthusiasts  pursuing  in  their  lei- 
sure hours,  or  in  hours  when  others  sleep,  some 
path  of  scientific  enquiry — astronomical,  geological, 
botanical,  zoological,  or  otherwise — in  most  cases 
without  hope  of  or  wish  for  reward,  without  desire 


PROGRESSIVENESS  OF  SCIENCE.  47 

for  publicity  or  publication,  for  they  are  genuine 
amateurs  in  the  literal  sense. 

Another  way  of  illustrating  the  ineradicable  sci- 
entific mood  is  to  consider  a  few  biographies  of 
eminent  workers,  and  to  notice  how  often  the  environ- 
mental conditions  were  the  very  reverse  of  propi- 
tious. The  "  Pursuit  of  Knowledge  under  Difficul- 
ties "  is  a  well-worn  theme, — of  considerable  interest 
to  those  who  have  had  experience  in  the  task  of  try- 
ing to  induce  uninterested  students  to  pursue  knowl- 
edge under  the  most  favourable  conditions. 

It  may  perhaps  be  argued  that  although  the  sci- 
entific mood  is  characteristically  human  and  must 
therefore  persist,  while  man  as  we  know  him  does, 
yet  the  subjects  of  enquiry  are  limited  and  the  range 
of  our  sense-experience  is  not  infinite.  Therefore 
there  must  be  an  end  to  the  progress  of  science,  and 
a  time  must  come  when  the  confession  ignoramus 
will  be  no  longer  heard  in  the  land,  for  all  the  prob- 
lems that  have  not  been  solved  will  be  insoluble,  and 
ignorabimus  will  remain  as  the  only  word  of  intel- 
lectual modesty.  It  can  hardly  be  said  that  this 
question  of  the  completion  of  scientific  enquiry  is 
one  of  practical  politics,  but  it  may  not  be  unprofit- 
able to  consider  it  for  a  little. 

It  was  surely  a  momentary  aberration  which  led 
a  great  zoologist  to  suggest  not  long  ago,  in  the 
enthusiasm  of  a  retrospect,  that  it  was  now  about 
time  for  us  to  be  making  a  list  of  the  things  we  did 
not  know.  A  very  different  suggestion  was  made  in 
a  remarkable  sentence  in  the  presidential  address 
delivered  by  the  late  Dr.  Edward  Orton  at  the  1899 
meeting  of  the  American  Association  for  the  Ad- 
vancement of  Science.  "  The  founders  of  the  As- 
sociation, fifty  years  ago,  clearly  saw  that  they  were 


48      PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

in  the  early  morning  of  a  growing  day.  The  most 
unexpected  and  marvellous  progress  has  been  made 
since  that  date,  but  as  yet  there  is  no  occasion  for, 
and  no  prospect  of  modifying  the  title  (Association 
for  the  Advancement  of  Science).  We  are  still  la- 
bouring for  the  advancement  of  science,  for  the  dis- 
covery of  new  truth.  The  field,  which  is  the  world, 
was  never  so  white  unto  the  harvest  as  now,  but  it 
is  still  early  morning  on  the  dial  of  science."  It  is 
this  last  sentence  which  should  be  pondered  over  by 
any  one  who  is  inclined  to  speak  or  think  or  act  as 
if  it  were  already  late  afternoon ! 

The  fact  is,  that  to  whatever  department  of  scien- 
tific enquiry  we  turn,  we  find  an  embarrassment  of 
unsolved  problems.  Everywhere  there  is  a  widening 
outlook,  a  more  and  more  intensive  analysis,  but  never 
a  hint  of  finality.  Everywhere  we  hear  the  words, 
"  for  leagues  and  leagues  beyond,  and  still  more  sea." 
It  might  seem  to  some  that  an  old-established  and 
persistently  prosecuted  department  of  science  like 
human  anatomy  must  be  now  almost  exhausted,  but 
among  the  experts  the  suggestion  would  be  received 
with  derision.  It  might  seem  to  some  that  a  little 
animal  like  the  lancelet,  every  millimetre  of  whose 
body  has  been  subjected  to  the  scrutiny  of  the  keen- 
est zoological  observers,  must  be  now  almost  com- 
pletely known,  but  the  suggestion  is  one  that  only 
an  outsider  could  make.  We  have  not  nearly  fin- 
ished with  this  one  animal,  and  is  it  not  a  little 
one?  The  animal  cell  has  been  studied  with  the 
most  assiduous  carefulness,  with  gradually  perfected 
microscopes,  with  ingenious  devices  of  fixing  and 
staining  and  cutting,  for  more  than  three-quarters 
of  a  century,  and  yet  it  remains  very  imperfectly 
known.  We  may  recall,  for  instance,  that  the  dia- 


PROGRESSIVENESS  OF  SCIENCE.  49 

covery  of  the  central  corpuscles  or  centrosomes — 
somewhat  enigmatical,  apparently  very  important, 
and  practically  constant  components  of  the  animal 
cell — members  of  the  "  cell-firm  " — dates  from  only 
a  few  years  ago. 

N"or  should  it  be  forgotten  that  we  live  in  a  world 
of  change,  in  which  a  process  of  evolution  is  going 
on,  and  that,  therefore,  the  subject-matter  of  a  sci- 
ence is  developing  just  as  the  science  is.  We  hear  of 
stars  that  die  and  of  others  that  are  a-making  (we 
may  use  the  present  tense  though  the  events  are,  of 
course,  vastly  older  than  our  observation  of  them)  ; 
even  in  a  human  lifetime — the  minutest  moment 
compared  with  the  earth's  age — the  features  of  a 
countryside  may  change  perceptibly,  indeed  a  shors 
may  get  a  new  face  in  a  single  storm;  the  distribu- 
tion of  plants  and  animals  is  in  process  of  rapid 
flux;  the  characters  of  organisms,  including  our- 
selves, are  slowly  but  surely  changing.  Thus  with 
an  evolving  subject-matter  before  our  eyes,  we  need 
say  little  about  the  prospect  of — completed  science. 

SCIENTIFIC   CONCLUSIONS   OF  THE  FIRST  MAGNITUDE. 

We  hear  so  much  nowadays  in  regard  to  the 
rapid  progress  of  science  that  there  seems  some  dan- 
ger lest  our  impression  become  exaggeratedly  san- 
guine. In  more  critical  moods,  however,  the  suspi- 
cion arises  that  in  spite  of  the  rapid  accumulation  of 
natural  knowledge,  information  often  proves  itself 
the  death  of  wit ;  and  that  in  spite  of  the  remarkable 
diffusion  of  the  scientific  mood  throughout  wide  cir- 
cles in  our  community,  the  growth  of  scientific  in- 
sight is  really  very  slow. 

That  this  suspicion  is  not  unfounded  becomes  clear 


50      PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

when  we  consider  the  small  number  of  scientific  gen- 
eralisations which  we  can  venture  to  describe  as  of 
the  first  magnitude.  We  begin  to  count  these:  The 
doctrine  of  the  indestructibility  of  matter,  foreseen 
by  Democritus,  but  for  practical,  scientific  purposes 
only  about  a  century  old — dating  from  Lavoisier; 
the  doctrine  of  the  conservation  of  energy,  with  its 
corollaries  of  transformability  and  dissipation;  the 
theory  of  gravitation,  with  its  far-reaching  applica- 
tions; and  the  theory  of  organic  evolution  which 
will  be  linked  for  ever  with  the  name  of  Charles 
Darwin. 

But  after  we  have  enumerated  these,  we  begin  to 
hesitate.  Are  there  any  others  on  the  same  plane, 
which  thoughtful  men  accept  without  hesitation  and 
without  saving  clauses,  to  lose  any  of  which  would 
spell  intellectual  disaster?  Should  we  include,  for 
instance,  what  is  grandiloquently  called  the  Law  of 
Biogenesis — which  states  that,  so  far  as  we  know, 
every  living  creature  has  its  parentage  in  another 
living  creature  or  in  two  other  living  creatures  ?  This 
is  a  big  fact,  no  doubt,  but  it  is  hardly  more  than 
an  empirical  fact,  and  there  are  many  who  suppose 
from  foreshadowings  which  they  see  that  the  coming 
events  of  the  next  quarter  of  a  century  will  con- 
vince us  that  this  at  present  unimpeachable  conclu- 
sion will  be  shown  to  be  fallacious,  not  in  itself  per- 
haps, but  in  its  suggestion  of  an  impassable  gulf 
between  the  not-living  and  the  living.  Or  should  we 
include  the  "  biogenetisches  Orunagesetz " — the  Re- 
capitulation Doctrine — that  the  individual  develop- 
ment recapitulates  the  racial  evolution,  or  that  the 
organism  in  its  becoming  climbs  up  its  own  genea- 
logical tree  ?  but  there  are  many  who  will  agree  with 
Mr.  Sedgwick — the  eminent  zoologist  of  Cam- 


PROGRESSIVENESS  OF  SCIENCE.  51 

bridge — that  before  this  recapitulation  doctrine  can 
be  accepted  it  must  be  subjected  to  emendations  so 
serious  that  it  comes  to  resemble  a  shoe  cobbled  so 
often  that  almost  nothing  of  the  original  structure 
remains.  We  read  of  the  stuffed  horse  of  Wallen- 
stein  at  Prag  which  has  "  only  the  head,  legs,  and 
part  of  the  body  renewed,"  and  the  "  biogenetisches 
Grundgesetz "  seems  much  in  the  same  state  at 
present.  In  revised  form  it  must  prove  its  power  of 
survival  a  little  longer,  before  we  can  admit  it  to  a 
place  of  honour  among  the  scientific  generalisations 
of  the  first  magnitude. 

A  recent  paper  on  the  cardinal  principles  of  science 
reminds  us  that  we  have  overlooked  "  The  Uniform- 
ity of  Nature,"  which  states  that  in  similar  condi- 
tions similar  things  are  likely  to  happen,  and  also 
the  platitudinarian  doctrine  of  "  The  Responsivity  of 
Mind,"  which  asserts  that  minds  react  in  similar 
ways  to  similar  stimuli.  "With  every  wish  to  be 
generous,  we  cannot  throw  these  in,  for  the  first  seems 
a  platitude — a  fallacious  platitude — and  the  second, 
well,  it  is  a  corollary  of  the  first. 

Huxley  gets  credit  for  the  phrase  "  The  Uni- 
formity of  Nature,"  which  has  been  called  a  cardinal 
principle,  indeed  the  cardinal  principle  of  science. 
But  if  Huxley  made  the  phrase,  which  we  doubt, 
it  does  not  seem  so  happy  as  some  others  that  he 
minted.  It  is  difficult  to  state  clearly  what  the  so- 
called  principle  means.  That  there  are  uniformities 
of  sequence  in  the  world  around  us  all  will  admit, 
—else  there  were  no  science  possible — but  what  the 
uniformity  is  remains  obscure.  We  believe  that  the 
gravitation  formula  fits  wherever  it  can  be  applied, 
that  is  one  uniformity;  we  find  no  evidence  to 
warrant  our  doubting  that  what  we  call  matter  and 


52      PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

energy  always  persist  however  their  forms  of  expres- 
sion may  change,  here  are  two  other  uniformities — 
or,  perhaps,  the  two  are  one ;  but  there  are  not  many 
other  conclusions  which  admit  of  the  same  univer- 
sality of  application  and  verifiability  of  accuracy. 
We  know  the  "  law  of  biogenesis,"  omne  vivum  e 
vivo,  to  mean  that,  so  far  as  our  experience  goes,  every 
living  creature  springs  from  some  other  living  crea- 
ture; we  do  not  know  of  any  exception  to  the  state- 
ment, but  we  see  no  warrant  in  this  for  asserting  that 
the  so-called  law  was,  or  will  be,  or  even  is  always 
true.  And  the  same  doubt,  which  becomes  more  as- 
sertive when  we  consider  this  last  instance,  is  not 
silent  even  in  regard  to  the  alleged  indestructibility 
of  matter  or  the  alleged  indestructibility  of  power. 
It  does  not  seem  particularly  forcible  to  retort  that 
"  one  cannot  conceive  of  the  reverse  happening,"  for 
it  is  not  so  long  since  a  belief  in  spontaneous  genera- 
tion was  widespread,  or  since  the  idea  that  the  earth 
was  not  the  hub  of  the  universe  was  deemed  by  many 
— and  these  not  small-brained  men — "  quite  incon- 
ceivable." And  these  were  the  very  words  of  Mother 
Grundy  when  she  first  heard  of  the  Doctrine  of  De- 
scent. 

In  short,  is  there  not  a  radical  fallacy  in  the  phrase 
"  The  Uniformity  of  Nature,"  since  our  so-called 
natural  laws  are  only  descriptive  formulae  of  what 
is  seen  and  known  in  given  conditions  of  space  and 
time,  neither  "  governing  nature,"  nor  "  explaining 
nature  "  ?  As  descriptive  formulae  of  observed  phe- 
nomena, presumably  descriptive  of  similar  unobserved 
phenomena,  they  make  it  easier  for  us  to  look  out 
upon  the  world  without  intellectual  biliousness — in- 
deed with  the  greatest  of  joy,  to  follow  the  course  of 
events  with  some  appreciation  of  their  orderliness, 


PROGRESSIVENESS  OF  SCIENCE.  53 

to  utilise  them  for  our  practical  purpose ;  but,  surely, 
it  is  time  that  we  ceased  supposing  that  they  enable 
us  to  explain,  to  see  the  ultimate  causes,  the  "  real 
inwardness,"  of  what  we  observe. 

But  even  if  the  reiterated  distinction  between 
descriptive  formulae  and  explanations  be  not  admitted 
— its  vindication  will  be  found  in  Karl  Pearson's 
Grammar  of  Science, — it  may  perhaps  be  granted 
that  the  less  we  say  about  the  Uniformity  of  Nature 
the  better  for  the  consistency  of  our  scientific  mood. 

Is  not  the  whole  point  expressed  in  Bacon's 
aphorism  ? — "  Man,  as  the  minister  and  interpreter 
of  nature,  does  and  understands  as  much  as  his  ob- 
servations on  the  order  of  nature,  either  with  regard 
to  things  or  the  mind,  permit  him,  and  neither  knows 
nor  is  capable  of  more."  It  is  difficult,  perhaps, 
to  say  what  the  word  "  understand  "  means  in  this 
aphorism,  but  if  it  mean  "  redescribe  in  simpler 
terms,"  it  expresses  our  present  position. 

There  is  another  consideration  which  should  per- 
haps give  us  pause  in  our  talk  about  the  Uniformity 
of  Nature.  It  may  be  illustrated  by  the  following 
quotation  from  a  paper  by  Winkler.* 

"  Four  hundred  years  ago  Nicholas  Copernicus 
left,  as  a  young  master  of  philosophy  and  of  medicine, 
the  old  university  of  Ulica  St.  Anny,  at  Cracow,  to 
go  to  Bologna  and  to  Rome  for  the  purpose  of  con- 
secrating his  talents  as  a  mathematician  to  the  study 
of  astronomical  sciences.  There,  attacking  the 
enigma  of  the  firmament,  he  finally  attained  the 
certainty  that  the  earth  was  not,  as  had  been  hitherto 
believed,  a  central  fixed  world,  but  a  sphere  suspended 
freely  in  space,  a  planet  similar  to  the  other  planets, 

*  Transl.  in  Rep.  Smithsonian  Inst.  for  1897,  pp.  237-246. 


54      PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

turning  around  the  sun  and  having  a  movement  of 
rotation  around  its  own  axis  under  the  action  of 
gravitation.  It  was,  indeed,  a  true  revolution  in 
the  theories  that  had  been  hitherto  held,  this  theory 
that  fixed  the  sun  in  the  firmament  in  spite  of  its 
daily  ascent  and  disappearance;  an  idea  that,  at  the 
present  day,  has  become  familiar  to  us.  And  fur- 
ther, we  now  know  that  neither  is  the  sun  itself 
fixed,  but  that  it  is  drawn  with  all  its  cortege  of 
planets  along  a  course  without  end,  across  space  with- 
out limit.  Whence  comes  it  and  whither  goes  it? 
Properly  speaking,  we  know  nothing  about  it,  and 
doubtless  we  will  never  know  either  its  origin 
or  its  end;  but  as  the  earth  turns  around  this 
movable  sun,  it  hence  results  that  our  planet  does 
not  describe  a  closed  path,  but  a  sort  of  spiral,  and 
that  it  never  returns  to  a  spot  that  it  has  once  quitted. 
Each  second  takes  our  planet  to  a  new  point  in  the 
universe,  and  from  this  incessant  displacement  it 
ought  to  follow  that  no  phenomenon  or  event  can 
ever  reproduce  exactly  any  anterior  phenomenon. 
Clouds  may  resemble  each  other,  as  one  sunrise  re- 
sembles another,  but  there  is  never  an  absolute  coin- 
cidence, and  it  would  seem  that  these  variations  ought 
to  be  perpetuated  throughout  the  course  of  time  that 
is  embraced  by  the  history  of  humanity. 

"  It  would  be  useless  to  push  further  these  con- 
siderations, they  are  merely  speculations;  but  they 
lead  to  this  thought,  which,  although  unsupported, 
continually  recurs  to  our  mind — the  possibility  of  a 
progressive  transformation  of  matter  in  a  given  direc- 
tion, in  that  they  show  that  everything  that  is  with 
us  is  drawn  along  in  a  dizzy  course  across  an  un- 
known immensity." 

Let  us  return,  however,  to  our  particular  point 


PROGRESSIVENESS  OF  SCIENCE.  55 

in   this   section,   which   was   the   small   number   of 
scientific  generalisations  of  the  first  magnitude. 

What,  some  one  may  indignantly  ask,  what  of  the 
atomic  theory,  the  periodic  law,  the  kinetic  theory 
of  gases,  the  mechanical  theory  of  heat,  the  un- 
dulatory  theory  of  light,  the  cell-theory,  Weber's  law, 
and  so  on  ?  To  which  we  would  answer  that  while 
these  are  doubtless  of  importance,  they  lack  the 
generality  and  the  intellectual  influence  of  the  four 
great  generalisations  already  mentioned — the  in- 
destructibility of  matter,  the  conservation  of  energy, 
the  formula  of  gravitation,  and  the  theory  of  organic 
evolution.  What  impresses  one  then  is,  that  scientific 
generalisations  of  the  first  magnitude  are  few,  and 
therefore  that  the  scope  for  progressive  science  kas 
at  present  no  visible  boundaries. 


FACTOES  IN  FURTHER  PROGRESS. 

(a)  Growing  Intensity  of  the  Scientific  Mood. — 
It  cannot  be  doubted  that  serious  scientific  study  is 
now  common  in  circles  where  half  a  century  ago  it 
was  rare;  this  means  an  increasing  body  of  observ- 
ers, critics,  and  formulators.  It  is  also  certain  that 
scientific  methods  are  now  being  applied  to  orders  of 
phenomena  which  half  a  century  ago  were  observed 
and  discussed  in  a  very  easy-going  and  light-hearted 
fashion.  Some  one  has  said  rather  bitterly  that 
every  science  must  pass  through  three  periods:  of 
presentiment  or  of  faith,  of  sophistry,  and  of  sober 
research ;  but  it  may  be  confidently  asserted  that  most 
departments  of  science  have  now  entered  upon  the 
third  period. 

It  is  not  long  since  comparative  psychology  was, 


56       PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

apart  from  a  few  classical  works,  for  the  most  part 
anecdotal.  Precision  of  observation  and  record  was 
blurred  by  fancies;  facts  and  inferences  from  facts 
were  subtly  intermingled ;  experiment  was  almost  un- 
known, indeed  scarcely  thought  of;  and  transcen- 
dental preconceptions  prejudiced  the  whole  outlook. 
But  these  blemishes  are  rapidly  disappearing,  and 
we  see  the  rise  of  a  young  science, — careful,  pains- 
taking, precise,  given  to  measuring  and  experiment- 
ing. 

To  take  another  illustration.  It  is  well  known 
that  one  of  the  master-keys  to  evolutionist  problems 
is  labelled  "  variation"  by  which  is  usually  meant 
the  process  or  the  result  of  innate  or  constitutional 
change  which  renders  a  living  creature  from  birth 
onwards  more  or  less  different  from  its  parents. 
Since  the  process  of  variation  furnishes  a  great 
part,  if  not  the  whole,  of  what  may  be  called  the  raw 
material  of  progress,  its  importance  is  obviously 
fundamental.  And  yet  the  post-Darwinian  history 
of  biological  activity  in  reference  to  variation  has 
only  recently  begun  to  be  creditable  to  science. 

Let  us  quote  a  few  sentences  from  Mr.  Bateson's 
Materials  for  the  Study  of  Variation  (1894) — a 
work  which  has  done  much  to  lift  our  feet  out  of  the 
mire.  "  We  are  continually  stopped  by  such  phrases 
as,  '  if  such  and  such  a  variation  then  took  place  and 
was  favourable/  or,  (  we  may  easily  suppose  circum- 
stances in  which  such  and  such  a  variation  if  it  oc- 
curred might  be  beneficial,'  and  the  like.  The  whole 
argument  is  based  on  such  assumptions  as  these — 
assumptions  which,  were  they  found  in  the  arguments 
of  Paley  or  of  Butler,  we  could  not  too  scornfully 
ridicule.  '  If,'  say  we  with  much  circumlocution, 
'  the  course  of  Nature  followed  the  lines  we  have 


PROGRESSIVENESS  OF  SCIENCE.  57 

suggested,  then,  in  short,  it  did.'  That  is  the  sum 
of  our  argument.  .  .  .  Surely,  then,  to  collect  and 
codif y  the  facts  of  Variation  is  the  first  duty  of  the 
naturalist.  This  work  should  be  undertaken  if  only 
to  rid  our  science  of  that  excessive  burden  of  contra- 
dictory assumptions  by  which  it  is  now  oppressed. 
...  If  we  had  before  us  the  facts  of  Variation 
there  would  be  a  body  of  evidence  to  which  in  these 
matters  of  doubt  we  could  appeal.  We  should  no 
longer  say  '  if  Variation  take  place  in  such  a  way/  or 
'  if  such  a  variation  were  possible '  ;  we  should  on  the 
contrary  be  able  to  say,  '  since  Variation  does,  or  at 
least  may  take  place  in  such  a  way,'  (  since  such  and 
such  a  Variation  is  possible,'  and  we  should  be  ex- 
pected to  quote  a  case  or  cases  of  such  occurrence  as 
an  observed  fact." 

It  was  in  this  mood  that  Bateson  compiled  his 
invaluable  work,  which,  though  still  represented  by 
only  Part  I.,  has  been  a  big  stride  towards  a  more 
scientific  basis  for  the  study  of  organic  evolution.  It 
has  been  followed  by  numerous  statistical  studies  of 
actually  occurring  variations,  by  experimental  at- 
tempts to  distinguish  between  germinal  variations 
and  bodily  acquired  modifications  (due  to  the  in- 
fluence of  functions  and  environment),  and  so  on. 
The  point  is,  that  here,  as  in  many  other  cases,  an 
over-impetuous,  undoubtedly  too  easy-going  science, 
has  had  to  retrace  its  steps,  and  to  begin  again  where 
science  always  begins,  in  precise  and  unprejudiced 
observation  and  recording  of  facts,  in  measurement, 
and  in  experiment. 

(6)  A  Fuller  Recognition  of  fhe  Unities. — When 
we  recall  the  fact  that  qualitative  advance  is  very 
slow,  while  quantitative  advance  is  exceedingly  rapid, 
we  are  led  to  enquire  whether  there  may  not  be  some 


58       PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

deep  reason  for  this.  Perhaps  the  chief  reason  is 
the  limitation  of  human  faculty  which  so  readily 
leads  to  a  disregard  of  what  we  have  called  the  Three 
Unities.  The  limitation  is  partly  the  result  of  mis- 
education,  the  persistent  tendency  to  fill  the  mind 
instead  of  evolving  it,  to  set  it  in  grooves  instead  of 
allowing  it  free  scope.  It  is  also  due  to  the  pressure 
of  social  conventions,  which  nip  the  buds  of  individu- 
ality, frown  down  idiosyncrasies,  and  allow  no  elbow 
room  (Abanderungsspielraum}  to  novel  variations, 
which  are,  after  all,  the  potentialities  of  progress.  It 
is  also  due  to  the  pressure  of  the  struggle  for  exist- 
ence, which  forces  the  young  enquirer  to  premature 
specialism,  that  he  may  thereby  make  a  name  and  a 
position  for  himself.  "  Er  will  sich  nahren,  Kinder 
zeugen"  and  so  on.  If  we  may  define  a  genius  as 
one  who  has  by  inheritance  and  appropriate  culture 
an  unusual  complement  of  powers  all  in  strong  devel- 
opment,— poetic  as  well  as  scientific,  or  practical  as 
well  as  philosophical,  or  otherwise, — there  are  many 
facts  within  our  experience  which  suggest  the  sad 
conclusion  that  for  one  genius  who  makes  himself 
felt,  there  are  perhaps  nine  whose  light  is  hidden 
under  a  bushel.  It  is  for  this  reason  that  many  who 
are  under  no  delusion  as  to  the  equality  of  men  or  the 
triumph  of  democracy  would  favour  every  measure 
which  opens  the  portals  of  learning — let  us  say,  the 
gates  of  our  Universities — more  widely  to  all  sorts 
and  conditions  of  men.* 

There  remains,  however,  another  reason,  that  when 
the  scientific  student,  who  has  retained  an  open  and 
sympathetic  mind,  finds  himself  in  his  maturity  more 
than  ever  aware  of  the  need  for  correlation  in  knowl- 

*  This  is  now  pecuniarily  possible  in  Sootland,  thanks  to 
Mr.  Carnegie's  magnificent  gift. 


PROGRESSIVENESS  OF  SCIENCE.  59 

edge-making  or  for  co-operation  in  science,  he  is  also 
likely  to  find  himself  pre-occupied  with  his  own 
problems,  mastered  by  his  strongest  personal  interests, 
burdened  by  immediate  duties,  with  neither  time 
nor  energy  left  for  that  effort  which  an  active  reali- 
sation of  the  unities  implies.  For  lack  of  sympathy 
in  some  cases,  for  lack  of  synergy  in  other  cases,  the 
progress  of  synthesis  is  sluggish. 

For  this  reason  we  emphasise  our  thesis  that  the 
progressiveness  of  science  depends  first  on  a  realisa- 
tion of  the  Unity  of  Life. 

The  scientist,  by  which  we  mean  the  student  of  the 
order  of  nature,  is  incomplete  in  his  arm-chair;  he 
is  even  incomplete  in  his  laboratory.  He  must  be, 
in  some  measure,  also  a  citizen,  a  man  of  feeling,  and 
a  philosopher!  That  even  his  science  will  suffer 
from  his  practical  denial  of  the  trinity  of  doing,  feel- 
ing and  knowing,  is  our  argument,  and  this  the  slow 
progress  of  science  seems  to  us  to  bear  out.  One 
might  appeal  to  biologists  who  have  because  of  their 
expert  knowledge  been  appointed  to  serve  on  gov- 
ernmental commissions,  dealing  with  practical  prob- 
lems of  life,  and  ask  whether,  after  allowing  for 
the  delay  of  their  personal  investigations,  they  did 
not  return  to  these  with  new  zest,  widened  outlook, 
and  fresh  insight.  The  German  government  digni- 
fies prominent  scientists  with  the  title  of  GeJieimrath 
or  Privy  Councillor,  and  in  many  cases  there  is  an 
honour  conferred,  and  that  is  all.  But  behind  the 
honorary  title,  there  is  the  suggestion — sometimes 
realised — that  the  expert  advice  thus  dignified  is  at 
the  service  of  the  government  in  critical  situations, — 
a  plague,  a  famine,  an  exploitation  of  new  territory 
and  so  forth.  That  the  same  sort  of  expert  advice 
should  be  at  the  command  of  all  nations  who  nurture 


60       PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

scientific  academies  and  scientific  professors,  seems 
sound  common  sense,  and  that  it  would  be  the  better 
for  science,  as  well  as  for  the  community,  if  this  were 
oftener  called  into  exercise  seems  equally  obvious. 

We  have  illustrated  our  point  by  reference  to  the 
need  for  contact  with  the  practical  problems  of  life ; 
but  a  strong  case  could  also  be  made  for  the  advantage 
which  science  would  gain  by  endeavouring  at  least  to 
understand  the  point  of  view  of  the  artist  and  the 
philosopher. 

Secondly,  the  progressiveness  of  science  depends 
upon  a  fuller  realisation  of  what  we  have  called  the 
unity  of  science.  Mineralogy  and  petrography  have 
acquired  new  vitality  and  greatly  enhanced  impor- 
tance since  they  became  definitely  chemical;  the 
method  of  spectrum  analysis  has  brought  astronomy 
from  a  position  of  isolation  into  intimate  contact 
with  chemistry  and  physics;  the  recent  development 
of  physical  chemistry  is  another  instance  of  happy 
and  fruitful  union;  since  physiologists  called 
chemists  to  their  aid  physiological  chemistry  has  be- 
come so  important  that  what  used  to  be  relegated  to 
an  appendix  in  a  physiological  treatise  now  pervades 
the  whole  book ;  psychology  has  listened  to  biological 
results;  and  the  indebtedness  of  social  science  to 
biology  and  the  physical  sciences  is  admitted  by  most 
to  be  of  value,  though  the  contact  is  still  only  in- 
cipient. 

But  while  this  and  more  may  be  said  of  actual  co- 
operation, it  remains  necessary  to  point  out  that 
many  workers,  and  many  departments  of  this  or 
the  other  science,  continue  to  flounder  along,  where- 
as they  might  swim  swiftly  if  they  condescended  to 
take  assistance  and  instruction  from  their  fellow- 
travellers.  After  all,  the  current  is  not  so  swift, 


PROGRESSIVENESS  OF  SCIENCE.  61 

that  there  is  no  time  for  mutual  consultation  by  the 
way. 

Thirdly,  the  progress  of  science  depends  upon  a 
recognition  of  the  unity  of  the  subject,  which  extends 
itself  to  a  recognition  of  the  unity  of  nature.  A 
great  part  of  scientific  work  is  analytic;  we  take 
things  to  pieces — social  institutions,  man,  the  animal, 
the  plant,  the  earth,  the  piece  of  matter — just  as  the 
boy  dissects  the  watch.  And  this  analysis  is  neces- 
sary, as  well  as  fascinating.  The  danger  is  lest  we 
forget  that  it  is  only  a  means  to  an  end — namely,  that 
we  may  put  the  things  together  again  with  a  better 
understanding  of  the  unity  which  we  have  dissolved. 
It  is  plain  that  in  anatomy,  for  instance,  we  make 
an  abstraction  necessary  for  the  purpose  on  hand, 
but  still  an  abstraction — for  we  leave  the  life  out 
of  consideration.  Our  point  is,  that  the  analytical 
work  of  the  anatomist  only  fulfils  its  function  when 
the  results  are  brought  as  a  contribution  towards  a 
fuller  understanding  of  the  unity  of  the  organism. 

In  the  same  way,  to  take  another  illustration,  the 
comparative  physiologist  concerns  himself  mainly 
with  an  analysis  of  the  activities  or  functions  of  or- 
gans, tissues,  and  cells  in  different  kinds  of  creatures ; 
and  his  work,  still  very  young,  has  been  rich  in  im- 
portant results,  and  is  full  of  promise.  But,  again, 
for  purposes  of  research,  abstractions  are  necessary, 
the  living  creature  is  abstracted  not  from  its  life — for 
the  physiologist  is  always  concerned  with  activity — 
but  from  its  full  life  as  it  is  lived  in  nature.  Our 
point  is,  that  physiology  does  not  fulfil  itself  until  its 
results  are  brought  as  a  contribution  to  a  fuller 
understanding  of  the  life  as  a  whole — of  what  is  in 
some  sense  a  personality  with  character  and  habits, 
with  a  complex  life  in  a  complex  environment,  a 


62       PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

member  of  a  family,  a  unit  in  a  fauna,  a  thread  in 
the  web  of  life. 

And  although  we  have  taken  our  illustrations  from 
biology,  the  same  condition  of  progress  applies  to  the 
other  sciences.  That  man  cannot  be  studied  to  much 
purpose,  if  he  is  persistently  held  in  artificial  isola- 
tion, is  as  certain  as  is  the  impossibility  of  under- 
standing the  earth  apart  from  the  solar  system. 

To  sum  up,  three  important  factors  in  the  progress 
of  science  are:  a  fuller  recognition  that  science  is 
for  life  and  not  life  for  science,  a  more  practical  ap- 
preciation of  the  benefits  of  co-operation  between 
different  disciplines,  and  a  frank  acknowledgment 
that  analysis  is  a  means  not  at  end. 

But  there  is  another  important  factor ;  namely,  the 
improvement  of  methods, — of  devices  by  which  we 
not  only  extend  the  range  of  our  sense-experience  but 
intensify  our  powers  of  precision.  To  give  an  ac- 
count of  the  development  of  methods  would  be  to 
write  half  of  the  history  of  science,  and  we  must  refer 
for  illustration  to  the  separate  chapters  of  this  book. 
But  how  much  progress  is  suggested  when  we  recall 
the  methods  of  quantitative  analysis  in  chemistry,  of 
measuring  the  different  forms  of  energy  in  physics, 
of  spectrum  analysis  in  astronomy,  of  microscopic 
technique  in  biology,  of  experiment  in  psychology. 
Apart  altogether  from  instrumental  devices,  the  in- 
creasing use  of  mathematical  and  statistical  methods 
in  dealing  with  the  problems  of  biology  furnishes  a 
good  illustration  of  the  fact  that  the  rate  of  progress 
is  partly  dependent  on  the  methods  employed. 

JUSTIFICATION  OF  SCIENCE. 

If  science  be  a  natural  and  necessary  expression  of 


PROGRESSIVENESS  OF  SCIENCE.  63 

the  developing  human  spirit,  this  is  justification 
enough.  Yet  a  more  detailed  justification  may  be  de- 
manded, not  only  by  critics  who  object  to  the  vast  ex- 
penditure of  time  and  money,  labour  and  life,  which 
the  pursuit  of  knowledge  involves,  but  also  by  those 
who  at  times  lose  confidence  and  enthusiasm,  and  are 
inclined  to  cry  "  Vanity  "  with  the  Preacher.  Great 
conclusions  are  few  and  far  between,  practical  dis- 
coveries bring  curses  as  well  as  blessings,  increase  of 
knowledge  often  means  increase  of  sorrow ;  and  there 
is  the  endlessness  of  it,  like  that  of  an  asymptotic  line 
always  approaching  nearer  a  given  curve  but  never 
reaching  it.  "  Advance  brings  us  no  nearer  the  end 
of  our  labour,  for  the  more  we  know  the  more  we  see 
of  what  remains  to  be  known.  Every  problem  laid 
at  rest  gives  birth  to  two  new  problems  which  did  not 
present  themselves  to  the  mind  before."  * 

If  we  can  suppose  a  science — Biology,  for  in- 
stance— arraigned  before  the  bar  of  Humanity,  as  it 
should  for  its  own  sake  feel  itself  arraigned,  the 
lines  of  defence  might  be  briefly  summed  up  as  fol- 
lows :  f 

First,  Biology  is,  like  the  other  sciences,  like  art 
and  poesy,  a  natural  expression  of  human  activity, 
at  once  a  development  and  discipline  of  man.  To 
cease  to  be  scientific  is  to  abdicate  manhood.  Along 
certain  lines  even  the  so-called  savage  is  scientific. 

Second :  and  "  without  prejudice,"  Biology  is  jus- 
tified by  practical  results.  In  spite  of  many  mistakes, 
it  has  made  valuable  contributions  in  relation  to  hu- 
man health,  the  supply  of  food  and  other  necessaries, 

•Alex.  Hill,  An  Introduction  to  Science,  London,  1900, 
p.  41. 

t  See  my  lecture.  "  The  Humane  Study  of  Natural  His- 
tory," in  Humane  Science  Lectures,  London,  1897. 


64      PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

the  use  of  animals,  and  so  forth.  We  say  "  without 
prejudice,"  since  we  cannot,  for  a  moment,  allow 
that  a  science,  as  a  science,  should  ever  submit  to 
the  practical  man's  canon  which  makes  immediate 
utility  a  stringent  criterion  of  worthiness. 

Third,  while  the  partial  pursuit  of  certain  paths 
may  sometimes  have  dulled  or  even  played  false  to 
healthy  emotion,  the  general  result  of  Biology  is  to 
deepen  our  wonder  in  the  world,  our  love  of  beauty, 
our  joy  in  living.  The  modern  botanist  is,  or  at 
least  ought  to  be,  more  aware  of  the  Dryad  in  the 
tree  than  the  Greek  poet  could  be. 

Fourth,  Biology  has  partially  worked  out  certain 
general  conceptions  of  life  and  health,  of  growth  and 
development,  of  order  and  progress, — centred  in  the 
idea  of  evolution, — which  are  not  only  attempts  to 
see  more  clearly  what  is  true,  but  which  make  for 
finer  feeling  and  for  the  betterment  of  life.  No 
doubt  there  have  been  impetuous  attempts  to  apply 
immature  biological  results  to  the  problems  of  hu- 
man conduct;  no  doubt  the  sociologist  has  some- 
times tried  unwisely  to  force  the  biologist's  hand; 
but  one  may  still  maintain  with  confidence  that 
biology  has  justified  itself  in  contributing  to  the 
ascent  of  man. 

In  the  introduction  to  his  Grammar  of  Science* 
Prof.  Karl  Pearson  has  admirably  expounded  tho 
claims  of  science  in  general,  and  his  summary  may 
be  quoted :  "  The  claims  of  science  to  our  support 
depend  on:  (a)  The  efficient  mental  training  it 
provides  for  the  citizen;  (6)  the  light  it  brings  to 
bear  on  many  important  social  problems;  (c)  the 

*  The  author's  statement  was  written  some  years  before 
reading  the  work  cited. 


PROGRESSIVENESS  OF  SCIENCE.  65 

increased  comfort  it  adds  to  practical  life;  (d)  the 
judgment." 

Just  as  Huxley  expressed  himself  at  one  with 
Descartes  in  declaring  as  his  fundamental  motive 
in  scientific  study  "  to  learn  how  to  distinguish 
truth  from  falsehood,  in  order  to  be  clear  about  my 
actions,  and  to  walk  sure-footedly  in  this  life,"  so, 
it  should  be  noted,  Pearson  lays  most  stress  upon 
the  permanent  gratification  it  yields  to  the  aesthetic, 
the  educational  side  of  science :  "  Modern  science, 
as  training  the  mind  to  an  exact  and  impartial 
analysis  of  facts,  is  an  education  specially  fitted  to 
promote  sound  citizenship.  .  .  .  This  first  claim  of 
scientific  training,  its  education  in  method,  is  to 
my  mind  the  most  powerful  claim  it  has  to  state  sup- 
port. I  believe  more  will  be  achieved  by  placing 
instruction  in  pure  science  within  the  reach  of  all 
our  citizens,  than  by  any  number  of  polytechnics  de- 
voting themselves  to  technical  education,  which  does 
not  rise  above  the  level  of  mutual  instruction." 

SCIENCE  AXD  PRACTICAL  UTILITY. 

Science  and  practice  act  and  react  upon  one  an- 
other. On  the  one  hand,  historical  enquiry  shows  that 
a  science  may  arise  out  of  practical  lore  and  that  it 
may  receive  fresh  stimulus  in  every  fresh  application 
to  practical  problems.  In  gathering  herbs  man  gath- 
ered knowledge,  and  in  cultivating  his  garden  he  laid 
the  foundations  of  the  science  of  botany;  to  their 
gathering  and  gardening  most  teachers  of  botany  still 
return  with  pleasure  and  profit.  The  lore  of  the 
hunter  and  the  fisher  is  older  than  all  zoology, 
and  many  will  agree  that  the  vitality  of  the  science 
depends  upon  a  periodic  return  to  the  study  of  the 


66       PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

actual  life  of  animals  as  it  is  lived  in  nature.  It 
may  be  going  too  far  to  say  with  Espinas, — "La, 
pratique  a  partout  devance  la  theorie/'  but  there  is 
no  doubt  as  to  the  progressive  impulse  which  comes 
to  a  science  from  its  corresponding  art. 

On  the  other  hand,  an  exaggeration  of  the  impor- 
tance of  contact  with  practical  problems  and  of  im- 
mediate practical  results,  is,  we  believe,  disastrous  to 
the  welfare  of  science,  and  it  may  not  be  out  of  place 
to  enter  a  brief  protest. 

"  The  fundamental  importance  of  abstruse  re- 
search receives  too  little  consideration  in  our  time. 
The  practical  side  of  life  is  all  absorbent ;  the  results 
of  research  are  utilised  promptly,  and  full  recogni- 
tion is  awarded  to  the  one  who  utilises,  while  the  in- 
vestigator is  ignored.  The  student  himself  is  liable 
to  be  regarded  as  a  relic  of  mediaeval  times.  .  .  . 
The  foundation  of  industrial  advance  was  laid  by 
workers  in  pure  science,  for  the  most  part  ignorant  of 
utility  and  caring  little  about  it.  ...  The  investi- 
gator takes  the  first  step,  and  makes  the  inventor 
possible.  Thereafter  the  inventor's  work  aids  the 
investigator  in  making  new  discoveries,  to  be  utilised 
in  their  turn."*  In  his  admirable  Introduction 
to  Science  (1900)  Dr.  Alex.  Hill  says:  "Great  ad- 
vances have  been  made  by  investigators  whose  object 
was  wholly  technical.  Yet,  if  the  history  of  science 
were  written,  it  would  be  found  that  the  first  step  in 
advance,  the  germ  of  the  discovery  which  became 
fruitful  in  the  hands  of  the  practical  chemist,  the 
mechanician,  the  pathologist,  was  discovered  by  the 
investigator,  for  whom  science  lost  its  interest  as  soon 

"John  J.  Stevenson,  "The  Debt  of  the  World  to  Pure 
Science,"  Pres.  Address,  New  York  Acad.,  February,  1898, 
Science,  March  11,  1898;  Rep.  Smithsonian  Institute  for 
1897,  pp.  325-336. 


PROGRESSIVENESS  OF  SCIENCE.  67 

as  it  could  be  put  to  practical  use."  He  instances 
the  discoveries  preceding  the  use  of  antiseptics  and  of 
Rontgen  rays. 

Undue  insistence  on  practical  results  is  apt  to  be 
unjust,  partly  because  no  one  is  wise  enough  to  pre- 
dict the  outcome  of  a  research,  and  partly  because 
secure  progress  in  science  is  often  extremely  slow. 
The  twitching  legs  of  Galvani's  frog  were  studied  as 
a  theoretical  curiosity ;  who  could  have  told  that  they 
pointed  to  the  flicking  needle  of  the  telegraph?  It 
was  not  for  practical  ends  that  William  Smith 
plodded  afoot  over  England,  neither  resting  nor  hur- 
rying in  his  exploration  of  the  strata,  but  how  much 
of  the  exploitation  of  Britain's  mineral  resources 
had  its  origin  in  his  maps  ?  Or  who  can  say  that  the 
series  of  discoveries  which  found  the  open  sesame 
of  coal-tar  and  brought  forth  its  treasures  had  at  first 
any  practical  outlook  ? 

One  use  which  a  volume  like  this  may  have  is  to 
curb  the  impatience  of  the  practical  man  in  regard  to 
experiments  whose  outcome  he  regards  as  useless,  and 
to  prompt  him  to  a  more  generous  support  of 
scientific  research.  A  little  knowledge  of  the  history 
of  science  may  not  be  altogether  a  dangerous  thing, 
if  it  suggests  that  from  apparently  inauspicious  be- 
ginnings and  from  apparently  unpromising  items  of 
honest  work,  great  results  may  follow.  Spectrum 
analysis— a  method  of  very  great  importance  to 
astronomer  and  physicist,  chemist  and  physiologist — 
had  its  beginning  in  some  apparently  insignificant 
observations  by  Marcgraf,  Herschel,  and  others. 
Pasteur's  at  first  sight  extremely  theoretical  re- 
searches on  the  hemihedral  facets  of  tartrate  crystals 
were  logically  as  well  as  actually  connected  with  his 
practical  researches  on  fermentation. 


68      PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

Over  and  over  again  in  the  course  of  the  history  of 
science  we  find  illustrations  of  the  long  gestation  of 
scientific  truth.  Minerva-like  birth  is  rare.  "  Dis- 
coveries which  proved  all  important  in  secondary  re- 
sults do  not  burst  forth  full  grown;  they  are,  so  to 
say,  the  crown  of  a  structure  raised  painfully  and 
noiselessly  by  men  indifferent  to  this  world's  affairs, 
caring  little  for  fame  and  even  less  for  wealth. 
Facts  are  gathered,  principles  are  discovered,  each 
falling  into  its  own  place,  until  at  last  the  brilliant 
crown  shines  out,  and  the  world  thinks  it  sees  a 
miracle."  *  But  it  was  after  waiting  and  working 
for  almost  a  score  of  years  that  Darwin  published  his 
theory  of  natural  selection. 

Another  good  illustration  of  the  gradual  emergence 
of  an  important  conclusion  is  to  be  found  in  the 
history  of  the  kinetic  theory  of  gases.  We  usually, 
and  rightly,  associate  this  conception  with  the  names 
of  Joule  and  Clausius,  and  fix  the  date  about  1857, 
but  "  the  researches  of  Paul  du  Bois-Reymond  and 
others  have  unearthed  a  whole  list  of  authors  who,  in 
more  or  less  definite  ways,  had  resorted  to  the  hypo- 
thesis of  a  rectilinear  translatory  motion  of  the 
molecules  in  order  to  explain  the  phenomena  of  pres- 
sure and  other  properties  of  gases.  Among  these 
Daniel  Bernouilli  (in  his  Hydrodynamica,  1738), 
seems  to  have  expressed  the  clearest  views,  and  he  is 
usually  now  named  as  the  "  father  of  the  hypoth- 
esis." f 

While  then  we  hold  firmly  that  science  is  for  life 
and  not  life  for  science,  we  protest  against  a  narrow 
rendering  of  the  words  "  for  life."  The  practical 
man's  impatient  "What's  the  use  of  it  ?  "  often  reveals 

*  J.  J.  Stevenson,  Rep.  Smithsonian  Inst.,  for  1897,  p.  325. 
t  J.  T.   Merz,  History,  1896,  p.  433. 


PROGRESSIVENESS  OF  SCIENCE.  69 

a  vulgar  materialism.  "  Truer  relations  of  science 
to  industry  are  implied  in  Greek  mythology.  Vul- 
can, the  god  of  industry,  wooed  science,  in  the  form 
of  Minerva,  with  a  passionate  love,  but  the  chaste 
goddess  never  married,  although  she  conferred  upon 
mankind  nearly  as  many  arts  as  Prometheus,  who, 
like  other  inventors,  saw  civilisation  progressing  by 
their  use  while  he  lay  groaning  in  want  on  Mount 
Caucasus."  * 

*  Sir  Lyon  Playfair,  Pres.  Address,  Rep.  Brit.  Ass.,  1885, 
p.  17. 


BOOK  TWO. 
MATTER  AND  ENERGY. 


CHAPTER  IV. 

A  CENTUEY  OF  CHEMISTRY. 

SEARCH  FOR  THE  ELEMENTS. 

Different  Kinds  of  Things. — An  inquisitive  out- 
look on  the  world  at  once  gives  us  the  impression  of 
an  enormous  number  of  different  kinds  of  things — 
different  in  substance  or  composition  as  well  as  in 
form  and  activity — and  we  feel  the  need  of  arranging 
these  in  some  order. 

If  we  continue  our  inquisitive  outlook  we  soon  per- 
ceive that  no  small  part  of  the  apparent  variety  of 
the  things  we  see  around  us  is  due  to  the  fact  that 
different  stuffs  or  kinds  of  matter  occur  mixed  up 
together.  If  we  take  a  handful  of  coarse  sand  from 
the  shore,  we  can,  by  working  for  a  few  hours,  put 
it  into  some  order,  placing  fragments  of  lime  shells 
in  one  corner  and  pieces  of  quartz  in  another,  and  so 
on.  But  this  sorting  out  is  easy  work,  and  can  be 
done  by  a  machine ;  it  is  not  the  chemist's  problem, — 
he  deals  with,  the  changes  in  the  nature  of  substances 
which  are  not  mixtures.  Among  these  not-mixtures 
it  is  necessary  to  distinguish  (1)  a  certain  number  of 
definite  kinds  of  matter  which  cannot  be  separated  by 
any  known  means  into  unlike  parts,  such  as  iron  and 


A  CENTURY  OF  CHEMISTRY.  71 

carbon;  and  (2)  others  which,  by  heating  or  other- 
wise, can  be  broken  up  (not  sorted  out)  into  unlike 
parts,  such  as  sugar  and  salt.  In  other  words,  after 
sorting  out  the  heterogeneous  mixtures  the  chemist 
has  to  do  with  the  two  sets  of  homogeneous  stuffs  to 
which  we  have  just  referred — which  are  familiarly 
known  as  Elements  and  Compounds. 

Though  many  of  the  elementary  substances,  such 
as  copper,  gold,  iron,  lead,  silver,  tin,  zinc,  sulphur, 
have  been  known  from  remote  antiquity,  the  recogni- 
tion of  elements  as  such — i.e.,  as  substances  which 
cannot,  so  far  as  we  know  at  the  time,  be  resolved 
into  other  kinds  of  matter — practically  dates  from 
Robert  Boyle,  the  author  of  The  Sceptical  Chymist 
(1680). 

A  hundred  years  later,  Lavoisier,  who  first  made 
the  conception  of  elements  practically  useful  in 
scientific  research,  enumerated  thirty-three  (includ- 
ing light  and  heat),  but  the  list  increased  by  leaps 
and  bounds  during  the  nineteenth  century.  Thus  Sir 
Humphry  Davy  discovered  six  new  metals  between 
1808  and  1810,  and  the  Swedish  chemist  Berzelius 
added  an  equal  number  in  about  the  same  time.  As 
was  to  be  expected,  the  practical  interests  of  miner- 
alogy and  metallurgy,  especially  in  Sweden  and 
Germany,  gave  zest  to  the  search  after  elements, 
and  led  Scheele  and  others  to  many  discoveries. 
By  1830,  Lavoisier's  list  was  nearly  doubled,  and  it 
is  still  being  added  to. 

Interactions  of  Elements. — Another  impression 
that  we  get  from  our  outlook  is  that  things  are 
changeful.  We  see  stones  weathering  and  crum- 
bling, shells  being  dissolved  away,  iron  rusting,  coal 
burning,  and  thousands  of  other  changes,  which  ex- 
cite curiosity  and  offer  problems  to  be  solved. 


72       PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

A  moment's  reflection  will  show  that  two  some- 
what different  sets  of  changes  go  on  around  us.  In 
the  frosty  night  water  changes  into  ice;  the  sun 
rises,  and  the  ice  changes  into  water;  in  the  bright 
sunshine  the  water  may  even  pass  into  the  air  as 
vapour.  Here  we  have  one  of  the  most  familiar 
instances  of  a  change  of  state,  but  the  water  remains 
in  a  real  sense  water  all  the  time.  There  is  no 
change  in  the  nature  of  the  stuff,  and  it  is  with 
changes  in  the  nature  of  the  stuff  that  chemistry 
has  primarily  to  do,  with  the  change,  for  instance, 
which  occurs  when,  by  an  electric  current,  water  is 
decomposed  into  its  two  constituents,  hydrogen  and 
oxygen.  The  chemist  has  as  his  fundamental  prob- 
lem, not  merely  the  recognition  and  isolation  of 
elements,  but  their  affinity  in  relation  to  one  an- 
other, their  capacity  of  exerting  chemical  action  or 
inducing  chemical  change. 

Detection  of  an  Element. — The  question  natur- 
ally rises  in  the  mind,  how  does  the  chemist  know 
when  a  given  substance  is  an  element  or  not ;  and  the 
only  scientific  answer  is  that  all  substances  should 
be  assumed  to  be  compounds  until  all  known  methods 
of  decomposing  them  have  been  tried  without  suc- 
cess. "  If  the  products  we  obtain  always  weigh  more 
than  the  substance  itself  and  never  less,  no  matter  to 
what  changes  it  has  been  subjected,  then,  provided 
each  change  is  complete  and  accompanied  by  no  loss 
of  substance  through  our  imperfect  methods,  we  are 
constrained  to  regard  that  substance  as  an  ele- 
ment," * 

Thus  the  chemical  conception  of  an  element  is 
simply  that  of  an  undecomposed — not  necessarily 

*  Ostwald,  Outlines  of  General  Chemistry,  trans.  J. 
Walker.  1890,  Chap.  II.,  "  The  Elements,"  p.  9. 


A  CENTURY  OF  CHEMISTRY.  73 

undecomposable  substance — since  we  must  always 
bear  in  mind  that  an  increased  perfection  of  method 
may  result  in  the  decomposition  of  what  was  pre- 
viously regarded  as  elementary. 

Recent  Discoveries  of  New  Elements. — During 
the  last  quarter  of  a  century  the  number  of  known 
elements  has  been  very  rapidly  increased.  In  a  gen- 
eral way,  it  may  be  said  that  analysis  has  become 
more  penetrating,  but  there  are  several  particular 
reasons  for  the  increase.  (1)  It  was  by  the  electro- 
lytic decomposition  of  alkaline  earths  that  Davy  dis- 
covered potassium  and  sodium;  this  was  about  the 
beginning  of  the  century,  and  the  discoverer  had  at 
his  command  only  a  feeble  Voltaic  pile;  now  in- 
tensely powerful  currents  are  utilised,  and  it  was  by 
these  that  Moissan,  for  instance,  was  able  to  isolate 
fluorine  from  its  combinations.  (2)  Spectrum 
analysis  has  shown  the  existence  of  a  series  of  ele- 
ments with  characteristic  spectra,  and  it  is  a  remark- 
able fact  that  one  of  these,  helium,  was  known  from 
the  sun  before  it  was  discovered  in  the  earth.  (3) 
Certain  theoretical  conceptions,  such  as  Mendelejeffs 
periodic  law,  have  led  chemists  to  look  out  for  and  to 
find  elements  whose  existence  was  predicted  on  a 
priori  grounds.  Thus  Xilson  in  1879  discovered 
scandium  which  Mendelejeff  had  foretold.  Gallium, 
discovered  by  Lecoq  de  Boisbaudran  in  1875,  and 
germanium,  discovered  by  Winkler  in  1886,  are  other 
famous  examples. 

Argon. — Two  of  the  latest  additions  to  the  list  of 
elements  deserve  special  notice.  In  1892,  Lord 
Eayleigh  directed  attention  to  the  fact  that  nitrogen 
obtained  chemically  was  about  one-half  per  cent, 
lighter  than  that  got  from  the  air,  and  it  was  this 
minute  discrepancy  which  led  him  to  look  for  and 


74      PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

discover  a  heavier  gas  in  the  atmosphere.  In  tho 
meantime,  and  independently,  Prof.  W.  Ramsay  dis- 
covered the  same  gas  by  removing  the  nitrogen  by 
means  of  red-hot  magnesium.  Combining  their  re- 
sults, the  two  investigators  published  their  memoir 
on  Argon,  "  which  will  go  down  to  posterity  among 
the  greatest  achievements  of  an  age  renowned  for  its 
scientific  activity  "  (Meldola). 

Argon  is  an  extraordinarily  inactive  or  chemically 
indifferent  gas  of  great  density;  occurring  along  with 
atmospheric  nitrogen,  forming  about  8  or  9  per  cent, 
of  the  volume.  It  can  be  separated  by  incandescent 
magnesium  or  by  the  continued  action  of  the  electric 
spark,  and  in  the  latter  way  Cavendish  seems  actually 
to  have  produced  it  a  hundred  years  ago !  Alone  or 
along  with  helium  it  has  been  found  in  natural 
waters,  in  minerals,  and  in  a  meteorite.  It  is  not 
known  to  form  combinations,  and  it  does  not  fit  in 
well  with  the  periodic  system,  so  that  its  real  nature 
remains  the  subject  of  enquiry.  That  it  is  truly 
an  element  is  suggested  by  the  distinctness  of  its 
electric  spark  spectrum  and  by  the  discovery  that 
the  molecule  is  monatomic,  but  the  possibility  re- 
mains that  it  is  a  mixture  of  monatomic  gases. 

Helium. — The  facts  in  regard  to  the  discovery  of 
helium  are  not  less  interesting.  In  1868  Frankland 
and  Lockyer  had  observed  a  particular  line  D  in  the 
solar  spectrum  which  they  attributed  to  the  presence 
of  an  element — helium — then  unknown  upon  the 
earth.  It  was  also  recognised  in  the  spectrum  of 
Orion  and  other  fixed  stars.  Subsequently  the  line  of 
helium  was  seen  by  Palmieri  (1882)  in  the  lava  of 
Vesuvius,  and  Hildebrand  observed  in  1891  what 
were  probably  its  lines  in  a  spectrum  of  the  nitrogen 
gas  which  he  got  by  heating  or  otherwise  treating 


A  CENTURY  OF  CHEMISTRY.  75 

uranium  ore.  While  demonstrating  argon  in  the 
nitrogen  gas  obtained  from  Cleveite,  Prof.  Kamsay 
observed  in  1895  another  bright  yellow  line,  and  this 
Sir  William  Crookes  recognised  as  the  D  line  of 
helium. 

Helium  has  now  been  found  in  many  ores,  in 
mineral  waters,  and  in  very  minute  quantities  in  the 
air.  It  is  the  lightest  of  all  the  gases  except 
hydrogen,  and  Dr.  Johnstone  Stoney  has  suggested 
that  this  may  explain  the  paucity  of  these  two  ele- 
ments in  a  free  state  upon  the  earth  while  they  are 
abundant  in  the  universe.  As  Winkler  puts  it,  "  the 
comparatively  small  force  of  the  earth's  gravitation 
does  not  form  a  sufficient  counterpoise  to  the  velocity 
of  their  molecules,  which  therefore  escape  from  the 
terrestrial  atmosphere  unless  restrained  by  chemical 
combination.  They  then  proceed  to  reunite  around 
great  centres  of  attraction,  such  as  fixed  stars,  in 
whose  atmospheres  these  elements  exist  in  large 
quantities."  * 

Helium,  like  argon,  is  believed  to  be  monatomic, 
and  it  is  not  known  to  enter  into  chemical  combina- 
tion. There  remains  much  uncertainty  in  regard 
to  its  position,  some  maintaining,  for  instance,  that 
it  is  composed  of  two  gases. 

SUMMARY. — It  is  the  business  of  chemistry  to 
distinguish  the  different  kinds  of  matter,  and  to 
study  their  transformations.  Heterogeneous  mix- 
tures have  to  be  distinguished  from  homogeneous  com- 
pounds and  elements.  A  homogeneous  substance 
which  cannot  be  decomposed  by  known  means  is 
called  an  element.  Careful  searching  and  more  ac- 


*  Trans,  of  a  paper  in  Rep.  Smithsonian  Inst.  for  1897, 
p.   244. 


76      PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

curate  methods  have  resulted  in  an  enormous  increase 
in  the  list  of  elements  in  the  course  of  the  nineteenth 
century.  Special  interest  is  attached  to  the  recent 
discovery  of  argon  and  helium. 

THEOBY  OF  COMBUSTION  AND  THE  CONSERVATION  OF 
MATTER. 

Theory  of  Combustion. — Since  the  science  of 
chemistry  has  to  do  with  the  changes  in  the  nature  of 
substances  when  they  combine  or  separate,  and  since 
burning  is  one  of  the  most  obvious  of  these  changes, 
it  is  natural  that  we  should  give  prominence  to  the 
theory  of  combustion.  But  there  is  another  reason 
why  we  should  do  so  here,  namely,  that  some  under- 
standing of  combustion  marks  the  beginning  of  the 
century-period  with  which  our  brief  historical  sketch 
deals.  It  is  hardly  too  much  to  say  that  modern 
chemistry  dates  from  the  time  when  the  burning  fire 
began  to  be  in  some  measure  intelligible,  or,  what 
conies  almost  to  the  same  thing,  from  the  time  when, 
oxygen  and  carbonic  acid  gas  having  been  discovered, 
it  became  possible  to  measure  the  changes  which  take 
place  in  a  combustion. 

It  is  interesting,  as  we  sit  by  the  fireside,  to  think 
of  the  different  ways  in  which  the  familiar  sight 
has  been  regarded  by  successive  generations  of  men, 
from  the  time  when  the  four  elements  were  first 
vaguely  imagined  to  the  days  of  "  phlogiston  "  and 
"  principles  of  combustion,"  and  thence  to  tho 
present  day, — a  long  story  of  changing  ideas.  But 
it  is  sufficient  for  our  purpose  here  to  recall,  that  it 
was  not  until  about  a  century  ago  that  there  was 
anything  approaching  to  a  scientific  vision  of  the 
burning  fire. 


A  CENTURY  OF  CHEMISTRY.  77 

The  Greeks  and  Romans  who  accepted  the  four 
elements  of  Empedocles — fire,  water,  earth,  and  air 
— regarded  fire  as  a  material  substance,  and  combus- 
tion as  the  separation  or  liberation  of  the  fire-stuff 
from  other  material.  In  the  seventeenth  century, 
Becher  and  Stahl  regarded  combustion  as  the  separa- 
tion of  "  inflammable  earth,"  or  the  escape  of 
"phlogiston,"  a  compound  substance;  for  "only 
compound  substances  can  burn."  For  a  long  time 
this  Phlogiston  theory  was  generally  accepted,  and 
proved  a  useful  stimulus  to  research.  But  the  re- 
peated demonstration  of  increase  of  weight  on  com- 
bustion, the  evidence  that  part  of  the  air  is  absorbed 
during  the  burning,  Newton's  suggestion  that  fire 
was  not  a  special  substance  at  all,  and,  especially, 
the  discovery  of  oxygen,  hydrogen,  carbon-dioxide, 
and  other  gases,  seriously  affected  the  vitality  of  the 
theory,  and  finally  shattered  its  constitution.  It  be- 
came the  subject  of  most  ingenious  doctoring,  and 
died  a  lingering  death  in  the  end  of  the  eighteenth 
century. 

What  John  Mayow,  with  penetrating  insight,  had 
almost  discerned  more  than  a  century  before,  that 
burning  means  a  union  of  something  in  the  air  with 
inflammable  particles  in  the  stuff  that  burns,  became 
clearer  when  Priestley  discovered  oxygen  in  1771, 
when  Lavoisier  interpreted  combustion  as  oxidation 
in  1775,  and  when  Cavendish  showed  that  water  was 
a  combination  of  hydrogen  and  oxygen  in  1784. 

It  is  interesting  to  notice  that  although  Priestley 
had  discovered  oxygen  and  supposed  that  air  sup- 
ports combustion  in  virtue  of  the  oxygen  which  it 
contains,  he  died  a  believer  in  phlogiston;  and  that 
although  Scheele — "  the  ideal  of  a  pure  experimental 
chemist,  the  discoverer  of  numberless  substances,  who 


78       PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

possessed  in  the  highest  degree  the  faculty  of  obser- 
vation " — had  also  discovered  oxygen,  he  was  unable 
to  free  himself  from  the  bondage  of  phlogistic 
theory.  The  same  was  true  of  many  others,  and  it 
is  to  Lavoisier  (1743-1794)  that  we  must  give  the 
credit  of  destroying  the  old  theory  by  replacing  it 
with  a  better.  Here  we  have  one  of  the  many 
instances  which  lead  us  to  say  with  confidence  that 
to  destroy  effectively  one  must  replace.  It  is  true 
that  Lavoisier  stood  on  the  shoulders  of  other 
workers,  but  his  own  experiments  were  not  less  in- 
genious, and,  more  than  any  of  his  predecessors  or 
contemporaries,  he  reached  the  importance  of  precise 
quantitative  measurement.  Thus  he  was  led  to  state 
about  1777  the  fundamental  conclusion  that  in  the 
process  of  combustion,  the  burning  substance  unites 
with  oxygen,  whereby  an  acid  is  usually  produced; 
and  that  the  increase  in  weight  of  the  substance 
burned  is  equal  to  the  loss  in  weight  of  the  air.  His 
researches  also  led  him  to  the  general  proposition 
that  in  all  chemical  reactions  it  is  only  the  kind  of 
matter  that  is  changed,  the  quantity  remaining 
constant ;  and  to  the  brilliant  idea  that  "  heat  is  the 
energy  which  results  from  the  imperceptible  move- 
ments of  the  molecules  of  a  substance." 

The  Conservation  of  Matter. — One  of  the  foun- 
dation-stones of  chemistry — which  every  worker 
builds  upon  with  unquestioning  confidence — is  the 
conservation  of  matter.  We  can  neither  create  nor 
destroy  the  smallest  particle;  the  elements  which 
enter  into  the  composition  of  the  soap-bubble  film  are 
as  lasting  as  those  which  form  the  granite  rocks. 
The  state  of  the  matter  may  wholly  change — from 
solid  to  gaseous,  or  in  other  ways,  the  particular  com- 
binations of  the  elements  may  wholly  change  as  they 


A  CENTURY  OF  CHEMISTRY.  79 

do  when  the  barrel  of  gunpowder  explodes,  but  the 
total  amount  of  matter  is  the  same  in  the  end  as  it 
was  in  the  beginning. 

The  doctrine  of  the  Conservation  of  Matter  states, 
as  Ostwald  puts  it,  that  "the  total  mass  of  the  sub- 
stances taking  part  in  any  chemical  process  remains 
constant."  And  since  masses  of  bodies  are  at  any  one 
place  proportional  to  their  weights,  the  doctrine 
may  read  that  in  any  chemical  process  the  weight 
remains  constant.  If  we  change  the  contents  of  a 
sealed  vessel  by  heating,  or  by  mixtures  brought  about 
through  shaking,  or  otherwise,  we  find  that  the 
weight  at  the  end  equals  the  weight  at  the  begin- 
ning.* 

Although  the  recognition  of  the  conservation  of 
matter  was  brought  about  by  the  work  of  many, 
it  may  be  particularly  associated  with  Lavoisier. 
For  one  of  his  earliest  investigations,  on  the  sup- 
posed conversion  of  water  into  earth,  he  constructed 
what  was  at  the  time  the  most  accurate  balance  in 
existence,  and  he  reaped  the  usual  reward  of  the 
accurate  measurer.  When  he  passed  water  vapour 
over  red-hot  iron  turnings  and  collected  the  resulting 
hydrogen,  he  weighed  everything — the  water,  the  iron 
before  and  after,  and  the  hydrogen.  It  was  by 
such  typical  experiments  that  "  with  the  balance  in 
his  hand,  he  vindicated  the  universality  of  the  prin- 
ciple of  the  conservation  of  matter."  f 

The  establishment  of  the  general  fact  of  the  con- 
servation of  matter  was  of  much  more  than  theoreti- 
cal interest;  it  was  not  only  a  foundation-stone,  but  a 

*  W.  Ostwald,  Outlines  of  General  Chemistry,  trans,  by 
James  Walker,  1890,  Chap.  I. 

t  A.  Ladenburg,  History  of  Chemistry,  trans,  by  L.  Dob- 
bin, 1900.  p.  21. 


80      PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

touch-stone  for  chemistry;  it  supplied  a  quantitative 
test  by  which  the  accuracy  of  research  could  be  con- 
tinually judged. 

THE  ATOMIC  THEORY. 

Before  Dalton. — The  great  chemist  Berzelius, 
following  his  predecessor  Richter,  quotes  on  the  first 
page  of  his  classic  treatise  on  Chemical  Proportions 
the  verse  from  the  Book  of  Wisdom  which  says : — 

Omnia  in  mensurd  et  numero  et  pondere  disposuisti. 
Thou  hasfc   ordered  all  things    in    measure  and    number    and 
weight.  — Sap.  XI.  21. 

This  may  be  regarded  by  some  as  expressing  a  re- 
markable prevision  of  one  of  the  great  results  of 
chemical  science, — that  exact  quantitative  relations 
are  always  implied  in  qualitative  changes  of  sub- 
stance. But  whether  it  was  a  prevision  or  not,  the 
verse  quoted  found  no  scientific  commentary  till 
towards  the  end  of  the  eighteenth  century,  and  the 
commentary  then  begun  is  still  in  progress. 

The  invention  of  accurate  balances — like  Lavoi- 
sier's— made  it  possible  to  pass  beyond  the  detection 
of  chemical  elements  to  some  understanding  of  ma- 
terial architecture.  And  there  seem  to  have  been 
many  who  were  simultaneously  pondering  over  the 
problem.  Thus  Jeremias  Benjamin  Richter,  a  math- 
ematical chemist  born  before  his  time,  published  in 
1792-1794  a  treatise  on  Stoicheiometry,  or  "  the  art 
of  measuring  chemical  elements,"  in  which  he  showed 
that  acids  and  bases  combine  in  definite  quantita- 
tive proportions  to  form  neutral  salts.  About  the 
same  date  Proust  drew  the  familiar  distinction  be- 
tween chemical  mixtures  and  chemical  compounds, 
pointing  out  that  the  latter  are  characterised  by  quite 
definite  proportions,  whether  formed  artificially  in 


A  CENTURY  OF  CHEMISTRY.  81 

the  laboratory  or  found  in  nature.  In  1802  Fischer 
made  the  first  table  of  "  chemical  equivalents,"  show- 
ing what  quantities  of  the  different  alkaline  bases  are 
neutralised  by  the  same  quantity  of  an  acid,  and  con- 
versely for  the  acids. 

But  while  it  is  important  even  in  a  short  historical 
sketch  to  observe  that  scientific  discoverers  have  very 
rarely  a  Minerva  birth,  we  must  not  obscure  the  fact 
that  though  Richter,  Proust,  and  others  were  work- 
ing towards  a  big  conclusion,  it  is  to  John  Dalton 
that  we  are  indebted  for  the  clear  statement  of 
the  fundamental  fact  regarding  chemical  combina- 
tion:— that  substances,  both  simple  and  compound, 
always  combine  in  definite  proportions  of  their 
weights.  In  whatever  way  one  substance  is  trans- 
formed into  another,  the  masses  of  the  two  substances 
always  bear  a  fixed  ratio.  Even  if  several  substances 
react  together,  their  masses  and  those  of  the  new 
bodies  are  always  in  fixed  proportions.  These  facts 
almost  necessarily  lead  to  the  atomic  conception. 

Dalton. — The  doctrine  of  the  Quaker  chemist  de- 
pended partly  on  the  following  results  of  experi- 
ence : — 

"  Ko  new  creation  or  destruction  of  matter  is  with- 
in the  reach  of  chemical  agency.  We  might  as  well 
attempt  to  introduce  a  new  planet  into  the  solar  sys- 
tem, or  to  annihilate  one  already  in  existence,  as  to 
create  or  destroy  a  particle  of  hydrogen  "  (Dalton, 
after  Lavoisier). 

In  a  chemical  compound  the  different  constituents 
are  always  present  in  invariable  proportions  (Dal- 
ton, after  Proust). 

In  the  interactions  of  acids  and  bases,  etc.,  the 
quantity  by  weight  of  an  element,  or  of  a  compound 
which  takes  active  part  in  the  chemical  change  is  al- 


82      PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

ways  expressible  by  a  fixed  number  or  by  a  whole 
multiple  of  that  number.  When  elements  unite  with 
one  another  in  several  different  proportions — e.g., 
oxygen  and  nitrogen — these  proportions  are  related 
to  one  another  in  a  simple  way.  In  other  words,  "  If 
two  substances,  A  and  B,  form  several  compounds,  of 
which  the  compositions  are  all  calculated  with  re- 
spect to  the  same  quantity  of  A,  then  the  quantities 
of  B  combined  with  this  stand  to  each  other  in  a 
simple  ratio "  *  (Law  of  constant  equivalents  and 
multiple  proportions). 

"  Thou  knowest  no  man  can  split  an  atom  "  was 
one  of  Dalton's  sayings,  but  it  should  be  noted  that 
he  meant  by  an  atom  the  smallest  conceivable  particle 
which  exhibits  the  essential  properties  of  the  sub- 
stance in  question.  Thus  he  spoke  of  an  atom  of 
water  (a  compound,  H2  O),  just  as  he  spoke  of  an 
atom  of  carbon. 

With  a  vision  of  the  grained  structure  of  matter 
clearly  before  him,  he  supposed  in  his  theory  that 
while  every  atom  of  a  given  simple  substance  is  like 
every  other  atom  of  that  substance,  the  atoms  of  dif- 
ferent substances  have  different  weights;  that  in 
chemical  union  of  elements  there  is  a  grouping  of 
definite  numbers  of  elemental  atoms  into  more  com- 
plex atoms  of  compounds,  and  contrariwise  in  chemi- 
cal decompositions ;  and  that  the  elements  combine  in 
the  proportions  indicated  by  the  relative  weights  of 
their  atoms  or  in  multiples  of  these.  This  is  the 
atomic  theory  "  which  at  once  changed  chemistry 
from  a  qualitative  to  a  quantitative  science  "  (Ros- 
coe). 

An  examination  of  some  of  Dalton's  manuscripts 
has  led  Koscoe  and  Harden  to  the  conclusion  that 
*  Ladenburg,  p.  55. 


A  CENTURY  OF  CHEMISTRY.  83 

he  was  led  to  adopt  the  atomic  theory  in  chemis- 
try in  the  first  instance  by  purely  physical  considera- 
tions, in  opposition  to  the  view  generally  held  that 
the  discovery  of  combination  in  multiple  proportions 
led  him  to  invent  the  atomic  theory  as  an  interpreta- 
tive formula.  It  seems  that  Dalton,  who  was  not 
well  aware  of  contemporary  continental  work,  was 
led  to  his  great  doctrine,  not  by  making  an  induction 
from  his  laborious  experiments  and  measurements, 
but  by  a  deduction  from  a  theory  of  the  constitution 
of  matter  which  he  devised  to  account  for  some  of  the 
physical  properties  of  gases.  As  in  many  other  in- 
stances in  the  development  of  natural  knowledge  an 
important  conclusion  was  reached  deductively  and 
then  verified  inductively. 

The  way  in  which  Dalton  reached  his  conclusion 
explains  why  he  gave  it  the  extremely  generalised 
form  to  which  we  refer  when  we  speak  of  the  atomic 
theory.  While  he  was  thinking  about  the  definite 
and  fixed  quantitative  proportions  observed  in  chem- 
ical combinations,  he  was  also  experimenting  with 
gases  (about  1790),  and  he  had  visualised  these  as 
consisting  of  distinct  particles : — "  A  vessel  full  of 
any  pure  elastic  fluid  [that  is,  gas]  presents  to  the 
imagination  a  picture  like  one  full  of  small  shot." 

The  idea  that  bodies  are  formed  of  distinct  parti- 
cles was  not  of  course  Dalton's,  but  the  chemical  ap- 
plication was.  The  idea  had  been  suggested  in  New- 
ton's Queries,  and  had  been  used  by  Boyle,  Boer- 
have,  Higgins,  and  others;  it  was  indeed  one  of  the 
legacies  with  which  ancient  philosophy  endowed 
modern  science. 

Atomic  Weights. — But  Dalton  was  not  content  to 
leave  the  atomic  conception  in  this  vague  form,  he 
proceeded,  in  a  manner  epoch-making  though  imper- 


84:      PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

feet,  to  determine  the  relative  weights  of  his  hypo- 
thetical ultimate  particles,  and  drew  up  what  would 
now  be  called  a  table  of  atomic  weights. 

To  do  this  he  required  a  unit  of  comparison, 
and  he  chose  hydrogen,  the  lightest  kind  of  matter 
known.  The  weight  of  an  atom  of  hydrogen  was 
called  one.  Then,  as  8  parts  by  weight  of  oxygen 
combine  with  1  part  by  weight  of  hydrogen  to  form 
water  (combining  weights),  Dalton  argued  that  the 
atom  of  oxygen  weighed  8  times  more  than  that  of 
hydrogen.  And  so  on  for  other  elements. 

It  must  be  borne  in  mind  that  the  atomic  weights 
were  determined  with  reference  to  an  arbitrary 
standard,  and  that  they  had  at  first  only  approximate 
accuracy. 

Summary. — Through  the  aid  of  many,  but  notably 
through  the  pioneering  genius  of  Dalton,  the  atomic 
theory  has  won  a  place  among  the  conceptual  for- 
mulae of  chemistry.  It  cannot  be  said  to  be  proved ; 
indeed,  neither  "proved"  nor  "disproved"  is  an  ap- 
propriate word  to  use  in  regard  to  these  hypotheses. 
The  tests  are  convenience,  comprehensiveness,  and 
consistency  (at  once  with  facts  and  with  other  con- 
ceptions), and  the  atomic  theory  has  stood  these 
tests.  Forestalling  the  history  a  little,  we  may  sum 
up  the  general  idea  in  Ostwald's  words : 

"  All  substances  consist  of  discrete  particles  of 
finite  but  very  small  size — of  atoms.  Undecom- 
posable  substances  or  elements  contain  atoms  of  the 
same  nature,  form,  and  mass.  If  chemical  combina- 
tion takes  place  between  several  elements,  the  atoms 
of  these  so  arrange  themselves  that  a  definite  and 
usually  small  number  of  atoms  of  the  combining 
elements  form  a  compound  atom  which  we  call  a 
molecule.  Every  molecule  of  a  definite  chemical 


A  CENTURY  OF  CHEMISTRY.  85 

compound  (chemical  species)  contains  the  same  num- 
ber of  elementary  atoms  arranged  in  the  same  way. 
If  the  same  elements  can  unite  to  form  different 
compounds,  the  elementary  atoms  composing  the 
molecules  of  the  latter  are  either  present  in  differ- 
ent numbers,  or  if  their  number  be  the  same,  they  are 
differently  arranged"  * 

DEVELOPMENT  OF  THE  ATOMIC  THEOEY. 

Dalton's  atomic  theory,  though  not  final,  was 
fructifying.  It  prompted  a  long  series  of  researches 
which  led,  after  some  vicissitudes,  to  the  establish- 
ment of  the  atomic  view  of  nature  on  a  firmer  and 
broader  basis.  Among  the  steps  of  importance,  we 
may  especially  notice  (1)  the  more  accurate  deter- 
mination of  atomic  weights,  (2)  the  conception  of 
molecules,  (3)  the  kinetic  theory  of  gases,  and  other 
physical  theories  as  to  the  different  states  of  matter, 
and  (4)  the  development  of  organic  chemistry.  The 
general  problem  was  to  form  conceptions  of  material 
architecture  which  would  harmonise  with  the  facts 
of  chemical  change. 

Determination  of  Atomic  Weights. — It  is  well 
known  that  each  element  is  conventionally  de- 
noted by  the  first  letter  or  letters  of  its  Latin  name, 
and  that  with  each  element  a  certain  number  is 
associated;  e.g.,  16  with  oxygen,  14  with  nitrogen, 
12  with  carbon.  This  number,  or  some  multiple  of  it 
by  a  whole  number,  expresses  the  relative  quantity 
of  the  given  element  which  enters  into  compounds. 
It  is  the  combining  mass  (or  weight,  though  weight 
must  vary  with  place),  or  on  Dalton's  theory,  the 
atomic  mass  or  weight, 

*W.  Ostwald,  General  Chemistry,  trans.  1890. 


86       PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

It  has  also  been  noticed  that  in  estimating  these 
numbers,  hydrogen  is  taken  as  a  unit,  because  it 
enters  into  compounds  in  relatively  the  smallest 
weight.  The  other  elements  and  compounds  are 
tabulated  according  to  the  relative  amounts  of  their 
weights  in  forming  compounds  with  hydrogen,  or 
with  some  other  element  whose  equivalent  with  hy- 
drogen has  been  already  estimated.  When  one  and 
the  same  substance  combines  in  several  proportions 
with  another,  as  nitrogen,  for  instance,  does  with 
oxygen,  the  smallest  number  according  to  which  the 
substance  forms  combinations  is  taken,  the  other 
numbers  relating  to  the  same  substance  being  found 
to  be  exact  multiples  of  the  smaller.  So  far  the  Dal- 
tonian  rules. 

What  Dalton  began  was  continued  by  Berzelius, 
Turner,  and  others;  but  we  cannot  enter  into  the 
record  of  toil.  Only  two  or  three  points  of  interest 
can  be  indicated.  The  process  of  determining  the 
atomic  weight  of  an  element  involves:  (1)  finding 
the  combining  proportion  or  equivalent,  and  (2) 
multiplying  this  by  a  factor  (1 — 4)  decided  by  the 
measurement  of  the  vapour  density  (Avogadro's 
Law),  or  by  finding  the  specific  heat  whose  product 
by  the  atomic  weight  is  practically  constant  (Law  of 
Dulong  and  Petit),  or  by  some  other  consideration. 

Berzelius  in  his  determinations  utilised  Gay-Lus- 
sac's  law  of  volumes  (1808)  (that  two  gases  always 
combine  in  simple  proportions  by  volume),  the  law 
of  Dulong  and  Petit  (1819),  and  furthermore  the 
aid  furnished  by  Mitscherlich's  discovery  of  isomor- 
phism (1820).  "  Mitscherlich  established  the  fact 
that  the  corresponding  phosphates  and  arseniates, 
with  the  same  number  of  atoms  of  water,  possess  the 
same  crystalline  form,  so  that  even  the  secondary 


A  CENTURY  OF  CHEMISTRY.  87 

forms  coincide.  Even  at  that  time,  the  same  number 
of  atoms  was  assumed  to  be  present  in  both  acids, 
and  thus  Mitscherlich  arrived  at  the  idea  that  it  was 
similarity  of  atomic  constitution  which  gave  rise  to 
identity  of  form."  * 

This  discovery  was  utilised  by  Berzelius  in  the 
following  rule : — "  When  one  substance  is  isomor- 
phous  with  another  in  which  the  number  of  atoms 
is  known,  then  the  number  of  atoms  in  both  is  known, 
because  isomorphism  is  a  mechanical  consequence  of 
similarity  of  atomic  construction." 

"  The  chemical  edifice  which  Berzelius  erected 
was  a  wonderful  one,  as  it  stood  completed  (for  in- 
organic substances)  at  the  end  of  the  third  decade  of 
the  century.  Even  if  it  cannot  be  said  that  the  fun- 
damental ideas  of  the  system  proceed  exclusively 
from  himself,  and  if  he  is  indebted  to  Lavoisier, 
Dalton,  Davy,  and  Gay-Lussac  for  a  great  deal,  still 
it  was  he  who  moulded  these  ideas  and  theories  into 
a  connected  whole,  adding  also  much  that  was  origi- 
nal. His  electro-chemical  hypothesis  no  doubt  had 
points  of  similarity  with  that  of  Davy,  but,  in  spite 
of  that,  it  was  essentially  different  from  it.  Besides, 
the  first  method  of  atomic  weight  determination,  of 
moderately  general  applicability,  proceeded  from 
Berzelius;  and  this  method  was  so  extraordinarily 
serviceable  that  it  rendered  possible  the  fixing  of  these 
most  important  numbers,  so  that  alteration  was  nec- 
essary in  only  a  few  cases.  "  f 

It  is  important  to  notice,  however,  that  about  1840 
an  error  of  about  2  per  cent,  was  discovered  in  the 
estimate  which  Berzelius  had  made  of  the  atomic 
weight  of  carbon.  This  raised  suspicions  and  further 

*  L,adenburg,  1900,  p.  96. 
fLadenburg,  1900,  pp.  101-102. 

Q 


88       PROGRESS  OF  SCIENCE  IN  THE  CENTURY, 

inaccuracies  were  discovered.  A  revision  became 
imperative,  in  which  Liebig,  Dumas,  Stas,  and  others 
took  part.  Different  methods  of  determination  were 
discovered,  one  method  was  used  to  check  another, 
stimulus  in  the  arduous  task  came  at  different  periods 
from  the  vision  of  supposed  or  real  regularities  con- 
necting the  different  numbers  (Prout  and  Meinecke 
to  Mendelejeff  and  Meyer),  and  gradually  a  well- 
established,  well-criticised  system  of  atomic  weights 
was  worked  out.  To  Cannizzaro  (1858)  in  particu- 
lar credit  is  due  for  utilising  the  specific  heat  method 
as  a  check  on  the  others,  and  Mendelejeff's  periodic 
law  furnished,  as  will  be  seen,  another  valuable  cor- 
rective. 

It  is  a  remarkable  historical  fact,  however,  that 
owing  to  the  relative  unreliability  of  the  methods 
for  determining  the  atomic  weights,  the  conception 
of  the  chemical  atom  fell  for  a  time  into  general 
disrepute.  "  At  the  end  of  the  fourth  decade  of  the 
century,  we  find  the  atomic  theory — the  most  bril- 
liant theoretical  achievement  of  chemistry — aban- 
doned and  discredited  by  the  majority  of  chemists 
as  a  generalisation  of  too  hypothetical  a  character." 
It  was  reserved  for  organic  chemistry  to  re-vindicate 
it,  and  for  physical  researches,  especially  on  gases, 
to  place  it  on  a  yet  firmer  basis. 

Physical  Enquiries  and  the  Concept  of  the  Mole- 
cule.— It  is  now  necessary  to  allude  to  a  path  of 
physical  investigation  which  had  a  most  important 
influence  on  the  atomic  theory,  especially  through 
Avogadro's  Law  and  the  kinetic  theory  of  gases. 

In  1662,  Boyle  had  stated,  as  Mariotte  did  some 
years  afterwards  (1679),  that  the  volume  of  a  gas, 
at  the  same  temperature,  is  inversely  as  the  pressure. 
When  the  pressure  increases,  the  volume  diminishes 


A  CENTURY  OF  CHEMISTRY.  89 

in  inverse  ratio.  In  1802,  Gay-Lussac,  whose  work 
touched  almost  every  department  of  chemistry  with 
important  results,  stated  what  had  been  foreseen 
(as  he  says)  by  Charles  fifteen  years  earlier,  that 
equal  volumes  of  different  gases  change  their  volumes 
equally  with  equal  rise  of  temperature.  Dalton  also 
had  perceived  this  conclusion  (the  law  of  Charles) 
that  all  gases  expand  in  the  same  proportion  for  the 
same  increase  of  temperature.  It  should  be  noted 
that  both  these  laws  (Boyle's  and  Charles')  are  ideal 
formulae  which  only  approximately  fit  the  facts. 

In  1805,  along  with  Alexander  von  Humboldt, 
Gay-Lussac  observed  that  exactly  two  volumes  of 
hydrogen  unite  with  one  volume  of  oxygen  to  form 
water.  From  this  starting-point  he  went  on  to  show 
(1808)  that  similarly  simple  volumetric  relations 
hold  true  in  regard  to  all  gases  which  combine 
chemically  with  one  another,  and  that  the  volumes 
of  the  gaseous  products  formed  always  have  a  simple 
relation  to  the  volumes  of  their  components  (all  be- 
ing measured,  of  course,  at  the  same  pressure  and 
temperature).  "Having  concluded  from  their  simi- 
lar behaviour  with  regard  to  changes  of  pressure 
and  temperature  that  all  gases  possess  a  like  molec- 
ular constitution,  Gay-Lussac  deduced  from  his  re- 
searches (above  referred  to)  the  following  impor- 
tant law: — The  weights  of  equal  volumes  of  both 
simple  and  compound  gases,  and  therefore  their  den- 
sities, are  proportional  to  their  empirically  found 
combining  weight,  or  to  rational  multiples  of  the  lat- 
ter." In  other  words,  if  gases,  like  other  bodies, 
combine  according  to  definite  proportions  of  their 
weights  (Dalton's  law)  ;  and  if  gases  (under  the 
same  pressure  and  at  equal  temperatures)  combine 

*  E.  YOU  Meyer,  History  of  Chemistry,  trans.  1891,  p.  202. 


90       PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

in  definite  proportions  of  their  volumes  (Gay-Lus- 
sac's  law) ;  then,  since  density  of  a  gas  means  the 
amount  of  matter  measured  by  weight  in  the  same 
volume,  it  follows  that  the  combining  weights  of  gases 
bear  a  simple  numerical  proportion  to  their  densities. 

Avogadro's  Law. — Another  important  and  closely 
related  result  was  expressed  in  1811  by  the  Italian 
chemist,  Amadeo  Avogadro  (1776-1856).  He  was 
impressed  by  the  fact  that,  when  there  is  chemical 
interaction  between  gases,  there  is  observable  a  very 
simple  relation  between  the  volumes  concerned.  A 
pint  of  oxygen  combines  with  two  pints  of  hydrogen 
to  form  two  pints  of  steam.  Such  a  simple  fact,  com- 
bined with  others  relating  to  the  physical  properties 
of  gases,  led  him  to  suggest  that  a  given  volume  of 
any  gas  (elementary  or  compound)  contains  the  same 
number  of  molecules  as  the  same  volume  of  any 
other  gas  measured  at  the  same  temperature -and  pres- 
sure. Equal  volumes  of  gases,  equal  numbers  of 
molecules  is  Avogadro's  law, — another  foundation- 
stone  of  modern  chemistry.  It  should  be  noted  that 
similar  views  were  stated  by  Ampere  in  1814,  but 
neither  he  nor  Avogadro  found  contemporary  recogni- 
tion or  even  attention. 

Avogadro  distinguished  between  molecules  inte- 
grantes  and  molecules  elementaires,  or,  as  would  now 
be  said,  between  molecule  and  atom.  "  The  physi- 
cal properties  of  the  gases  (especially  the  similarity 
in  their  behaviour  towards  changes  of  pressure  and 
of  temperature)  led  Avogadro  to  assume  in  equal 
volumes  of  all  gases  the  same  number  of  molecules; 
and  the  distances  of  the  latter  from  one  another  he 
considers  to  be  so  great  in  proportion  to  their 
masses,  that  they  no  longer  exercise  any  attraction 
upon  one  another.  These  molecules  are  not  sup- 


A  CENTURY  OF  CHEMISTRY.  91 

posed,  however,  to  constitute  the  ultimate  particles 
of  matter,  but  are  assumed  to  be  capable  of  further 
subdivision  under  the  influence  of  chemical  forces. 
According  to  Avogadro,  therefore,  substances  (ele- 
ments and  compounds  alike)  are  not  converted,  in 
passing  into  the  gaseous  state,  into  indivisible  par- 
ticles, but  only  into  molecules  integrantes,  -which  in 
turn  are  composed  of  molecules  elementaires"  * 
The  conception  of  a  molecule  is  that  of  the  smallest 
portion  of  a  substance  which  possesses  all  the  prop- 
erties of  that  substance;  it  represents  a  higher  cate- 
gory than  atom ;  thus  the  molecule  of  water  is  repre- 
sented by  the  symbol  H2O,  which  means,  in  part, 
that  the  smallest  particle  of  water  consists  of  two 
atoms  of  hydrogen  united  with  one  atom  of  oxygen. 

Avogadro's  generalisation  has  furnished  one  of  the 
main  grounds  for  determining  the  atomic  weights 
of  the  elements;  and  it  went  far  to  reconcile  Gay- 
Lussac's  discoveries  as  to  gases  with  Dalton's  atomic 
theory.  "We  have  only  space  to  mention  that  another 
ground  for  the  determination  of  atomic  weights  was 
furnished  by  the  researches  of  Dulong  and  Petit 
(1818),  who  showed  the  close  relation  between  the 
specific  heats  of  the  elements  and  their  atomic 
weights,  and  concluded  that  the  atomic  heats  of  all 
elements  (specific  heats  multiplied  by  atomic 
weights)  are  practically  identical ;  i.e.,  that  all  atoms 
have  the  same  capacity  for  heat. 

Avogadro's  recognition  of  the  proportion  between 
the  specific  gravity  of  a  gas  and  its  molecular  weight 
was  slowly  appreciated,!  but  it  has  borne  much  fruit. 
*  Ladenburg,  1900,  pp.  61-62. 

t  Dr.  J.  T.  Merz  notes  in  regard  to  this  belated  recogni- 
tion that  Avogadro's  hypothesis  (1811)  is  not  mentioned  in 
\Vhewell's  History,  nor  in  Kopp's  (1843-1847),  nor  in  Pog- 
gendorfs  Dictionary  (1863). 


92      PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

By  improved  methods  of  determining  the  specific 
gravity  of  gases  and  vapours,  "  the  all-important 
knowledge  of  the  relative  weights  of  the  atoms  and 
molecules  of  elements  and  compounds  has  been  im- 
mensely advanced"  (E.  von  Meyer,  p.  441).  From 
the  study  of  anomalous  vapour-densities,  H.  de  St. 
Claire  Deville  discovered  in  1857  the  fact  of  "  dis- 
association  "  or  the  gradual  decomposition  of  a  com- 
pound with  rise  of  temperature, — the  starting-point 
for  another  series  of  important  investigations. 

Though  confirmed  by  similar  conclusions  (Davy, 
1812,  Ampere,  1814),  Avogadro's  hypothesis: 
"  Equal  volumes,  equal  number  of  particles  "  was 
not  appreciated  until  the  establishment  of  the  kinetic 
theory  of  gases  (q.v.),  and  "  no  substantial  chemical 
reasons  for  its  adoption  were  adduced  until  the  year 
1846,  when  Laurent  published  his  work  on  the  law 
of  even  numbers  of  atoms  and  the  nature  of  the  ele- 
ments in  the  free  state."  * 

Further  Influence  of  Physical  Researches. — 
When  the  century  was  about  half  over,  the  doctrine 
of  fixed  and  multiple  proportions  was  generally  ac- 
cepted (with  some  saving  clauses  for  not-solid  com- 
pounds), but  the  conception  of  atoms  which  lay  be- 
hind this  doctrine  was  looked  at  more  cautiously. 
The  careless  may  have  believed  in  the  physical  exist- 
ence of  these  smallest  indivisible  particles,  but  this 
was  certainly  not  the  general  belief.  And  even  as  a 
symbolism,  as  an  alphabet,  as  a  means  of  notation, 
there  were  many  chemists  who  doubted  if  the  atom- 
concept  was  indispensable  or  even  legitimate.  Cor- 
roboration  had  to  come  from  an  independent  source, 
and  it  came  from  the  physicists,  more  especially 

*  Prof..  R.  Meldola,  Address,  Section  B,  Rep.  Brit.  Ass.  for 
1895,  p.  639. 


A  CENTURY  OF  CHEMISTRY.  93 

from  the  kinetic  theory  of  gases,  taken  in  connection 
with  Avogadro's  law. 

Kinetic  Theory  of  Gases. — As  facts  began  to  ac- 
cumulate showing  a  remarkable  uniformity  in  the 
behaviour  of  different  gases  to  the  same  changes  of 
temperature  and  pressure,  the  need  for  some  concep- 
tion of  the  nature  of  a  gas  made  itself  felt  in  many 
minds.  The  early  suggestions  of  Daniel  Bernouilli 
(1738)  and  of  Waterston,  Graham's  discovery  of  the 
law  of  diffusion,  the  work  of  Herapath,  Joule  and 
Kronig,  the  achievements  of  Clausius  (1857-1862) 
and  Clerk  Maxwell  (1860-1867),  are  some  of  the 
steps  in  a  long  history — the  history  of  the  kinetic 
theory  of  gases,  one  of  the  revolutionising  concepts  of 
modern  science.  According  to  this  theory,  a  gas 
consists  of  innumerable  particles  moving  with  high 
velocity,  overflowing  into  any  free  space  which  is 
available,  thus  securing  that  there  is  the  same  aver- 
age number  in  every  unit  of  volume,  impinging  on 
the  contained  walls,  if  there  are  any,  and  thus  caus- 
ing pressure  which  must  obviously  increase  with  the 
number  of  the  molecules  and  the  mass  and  velocity 
of  each.  Such  is  at  least  a  suggestion  of  the  view 
which  gave  new  life  to  the  atomic  theory,  and  that  at 
a  time  when  it  was  much  in  want  of  support.  When 
it  was  shown  that  precise  and  workable  conceptions 
could  be  formed  of  the  rectilinear  movements  of 
molecules  in  a  gas,  when  the  internal  motion  of  the 
atoms  composing  the  molecules  was  shown  to  be  a 
needful  assumption,  when  the  rate  of  velocity  of  a 
particle  of  hydrogen  gas  was  actually  calculated, 
when  the  laws  of  Boyle,  Gay-Lussac,  and  Avogadro 
were  brought  into  harmony,  and  so  on, — chemistry 
became,  in  a  more  real  sense  than  before,  a  study  of 
the  changes  of  equilibrium  in  atoms. 


94      PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

Extension  of  the  Atomic  Conception. — Here  it 
must  be  recalled  that  while  physical  enquiries  into 
the  constitution  of  matter  [or  attempts  to  form  a 
conception  of  molecular  motion]  were  mainly  con- 
cerned with  gases,  the  solid  and  liquid  states  were 
also  studied.  The  solid  state,  where  the  mass  has  a 
proper  volume  and  a  proper  form,  more  or  less  dif- 
ficult to  change,  began  gradually  to  be  conceived  of 
as  one  in  which  the  relations  of  the  molecules  are 
such  that  mutual  displacement  is  not  easy.  En- 
quiries into  crystallisation  begun  by  Steno  (1669), 
re-stimulated  by  the  genius  of  Hauy  (1781),  con- 
tinued by  many  workers  (Weiss,  Von  Lang,  etc.), 
also  proved  suggestive,  notably,  for  instance,  when 
Mitscherlich  (1820)  elaborated  what  Klaproth 
(1Y98)  had  observed  that  the  same  substance  might 
have  different  crystalline  forms  (e.g.,  calc  spar  and 
arragonite). 

Gradually,  too,  the  atomic  conception  was  extended 
to  liquids  which  differ  from  gases  in  occupying  a 
definite  volume  and  from  solids  in  having  no  proper 
form  and  much  less  internal  friction.  Especially 
through  enquiries  into  the  phenomena  of  osmosis  and 
of  solution,  the  theoretical  conception  of  gases  was 
applied  to  liquids.  But  this  was  hardly  realised 
till  towards  the  end  of  the  century;  indeed  it  may 
be  associated  with  the  work  of  Van't  Hoff  (1887). 

Instead  of  trying  to  follow  the  multitudinous  lines 
of  research,  we  propose  to  take  a  single  illustration 
— the  liquefaction  of  gases — which  may  serve  to  sug- 
gest the  unity  of  the  different  states  of  matter. 

Liquefaction  of  Gases. — Erom  the  time  of  Fara- 
day's researches  in  1823  to  the  recent  work  of  Dewar, 
popular  imagination  has  been  impressed  by  the  re- 
peated announcement,  that  such  and  such  a  gas  had 


A  CENTURY  OF  CHEMISTRY.  95 

yielded  to  the  combined  effects  of  high  pressure  and 
low  temperature,  and  had  been  obtained  in  liquid  or 
solid  form.  Andrews,  Mendelejeff,  Pictet,  Caille- 
tet,  Wroblewski,  Olszewski,  and  many  others  have 
contributed  to  the  striking  series  of  experiments. 

By  a  long  series  of  researches,  extending  through 
the  century,  it  has  been  made  clear  that  all  ponder- 
able matter  may  be  thought  of  as  essentially  of  the 
same  nature,  irrespective  of  what  its  state — solid, 
liquid,  vaporous,  or  gaseous — may  be.  The  differ- 
ences of  state  are  conceived  of  as  due  to  the  way  in 
which  the  relations  of  the  component  particles  are 
affected  by  the  greater  or  less  relative  activity  of  the 
attractive  molecular  forces  and  the  dispersive  ther- 
mal motions.  As  every  one  knows,  water  may  occur 
as  a  solid,  a  liquid,  a  vapour,  or  a  gas  (saturated 
steam  above  720.6°  C.).  "  Above  30.92°  0.  carbonic 
acid  is  a  true  gas;  no  pressure  will  then  liquefy  it; 
but  at  30.92°  C.  a  pressure  of  77  atmospheres,  and 
below  30.92°  C.  progressively  smaller  pressure  will 
condense  it;  at  and  below  that  temperature  (An- 
drews' Critical  Temperature)  gaseous  carbonic  acid 
is  a  '  vapour,'  condensable  by  pressure  alone."  It 
may  also  be  procured  as  a  solid.  Endless  examples 
might  be  given,  for  the  idea  of  necessary  permanence 
of  state  has  now  disappeared, — and  .theoretically  no 
case  is  more  striking  than  another,  though  technical 
difficulties  have  enhanced  the  interest  of  some  par- 
ticular instances. 

It  was  about  the  beginning  of  the  century  that 
!N"orthmore  and  others  liquefied  sulphurous  acid  gas 
by  pressure,  but  progressive  research  on  the  subject 
began  with  the  work  of  Faraday  and  Davy  in  1823. 
They  used  the  method  of  "  enclosing  materials  from 
*  Article  "  Gas,"  by  Daniell,  Chambers's  Encyclopaedia. 


96      PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

which  the  gas  can  be  generated  within  a  tube  strong 
enough  to  resist  the  pressure  of  the  gas  as  it  accumu- 
lated," and  thus  chlorine,  muriatic  acid,  carbonic 
acid,  ammonia  and  many  others  were  liquefied,  es- 
pecially through  the  energetic  work  of  Faraday.* 

In  1835,  Thilorier  published  an  account  of  an 
experiment,  now  familiar  to  students  of  chemistry, 
in  which  he  allowed  a  jet  of  liquid  carbonic  acid  to 
escape  into  a  receiver  where  the  evaporation  of  part 
of  the  liquid  produced  a  temperature  so  low  that  the 
rest  was  frozen  into  fine  snow.  In  1845  Faraday 
combined  the  method  of  low  temperatures  with  that 
of  high  pressures  in  the  hope  of  conquering  the  so- 
called  permanent  gases,  such  as  oxygen,  hydrogen, 
nitrogen.  But  these,  along  with  nitric  oxide,  carbon 
monoxide,  and  methane,  resisted  his  efforts. 

In  1869,  Andrews  expounded  his  definition  of  the 
"critical  point," — the  temperature  (30.92°  C.  for 
carbonic  acid)  above  which  no  amount  of  pressure 
produces  visible  liquefaction,  but  below  which  lique- 
faction occurs  when  the  pressure  is  sufficient.  "  A 
vapour  is  a  gas  at  any  temperature  below  its  critical 
point."  This  step  towards  clearness  led  experi- 
menters to  recognise  that  the  reason  why  oxygen, 
nitrogen,  etc.,  proved  intractable  was  that  sufficient 
low  temperatures  (below  their  critical  points)  were 
not  available. 

In  1875-Y,  by  devices  securing  lower  tempera- 
tures, Raoul  Pictet  and  Louis  Cailletet  succeeded 
in  liquefying  oxygen.  Carbonic  oxide,  marsh  gas, 
nitric  oxide,  and  others  also  yielded  to  the  "  Caille- 
tet pump,"  and  only  nitrogen  and  hydrogen  remained 
unsubdued.  In  1883,  nitrogen  was  liquefied  by  two 
Polish  workers,  Wroblewski  and  Olszewski.  Finally 
*  Tilden,  Short  History  of  Chemistry,  p.  240. 


A  CENTURY  OF  CHEMISTRY.  97 

in  1898,  after  years  of  preparation,  Professor  Dewar 
produced  liquid  hydrogen, — a  clear,  colourless  liquid, 
about  one-sixth  the  density  of  liquid  marsh  gas,  or 
about  one-fourteenth  the  density  of  liquid  water  at 
0°.  As  Prof.  Tilden  remarks :  "  It  was  both  inter- 
esting and  gratifying  that  the  final  victory  which 
crowned  the  long  series  of  successful  attacks  upon 
the  apparently  impregnable  position  of  the  perma- 
nent gases  should  have  been  recorded  in  the  labora- 
tory of  the  Royal  Institution,  where  the  first  suc- 
cesses in  this  field  were  won  by  Faraday." 

DEVELOPMENT  OF  ORGANIC  CHEMISTRY 

Organic  and  Inorganic  Chemistry. — The  distinc- 
tion between  the  substances  found  in  plants  and 
animals  and  those  in  the  not-living  world  is  an  old- 
standing  one.  Rooted  in  the  belief  that  the  sub- 
stances composing  or  formed  by  living  creatures  were 
under  the  domination  of  a  specific  vital  force,  the 
distinction  was  for  a  time  accented  by  the  complex- 
ity of  most  of  the  substances  in  question,  by  the  fact 
that  they  were  often  difficult  to  isolate  and  very 
ready  to  change,  and  by  the  absence  of  a  secure 
method  of  analysing  their  composition.  Later  on, 
the  generalisations  reached  by  the  students  of  inor- 
ganic substances  did  not  seem  to  fit  in  well  with  what 
was  known  in  regard  to  the  organic,  and  the  breach 
was  widened.  It  was  thus  to  a  large  extent  inde- 
pendently that  organic  chemistry  developed,  until  it 
became  strong  enough  to  react  upon  the  study  of  the 
inorganic  with  a  potent  and  progressive  influence. 

"  At  the  beginning  of  the  century,   when  qual- 

*  For  a  brief  account  of  the  subject  the  reader  is  referred 
to  Chapter  IX.  of  Tilden's  Short  History  of  the  Progress 
of  Scientific  Chemistry,  London,  1899. 


98   PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

itative  analysis  had  already  attained  a  high  degree  of 
accuracy,  and  even  the  quantitative  method  had 
found  excellent  exponents  in  Proust,  Klaproth,  and 
iVauquelin,  Lavoisier's  experiments  with  alcohol,  oil, 
and  wax  were  the  only  ones  in  existence,  designed  to 
ascertain  the  composition  of  organic  compounds ;  and 
these,  it  may  easily  be  understood,  were  not  very  ac- 
curate." * 

Some  Factors  in  the  Development  of  Organic 
Chemistry. — The  development  of  organic  chemistry 
which  has  been  characteristic  of  the  latter  half  of  the 
century  has  been  influenced  in  many  ways: — by  the 
elaboration  of  more  perfect  methods  of  determining 
the  composition  of  organic  substances  (Gay-Lussac, 
Liebig,  Wohler,  Bunsen,  Dumas,  and  many  others)  ; 
by  the  clear  recognition,  which  may  be  associated 
with  the  name  of  Berzelius,  that  organic  compounds 
could  not  be  separated  by  any  hard  and  fast  line 
from  inorganic  compounds,  but  illustrated  similar 
laws,  and  might  in  many  cases  be  profitably  regarded 
as  derivations  of  inorganic  compounds;  by  the  fasci- 
nation of  the  methods  of  synthesis  which  gave  the 
chemist  an  almost  creative  power;  and  by  the  enor- 
mous practical  interests  involved,  in  connection,  for 
instance,  with  coal-tar  products,  one  of  the  most  fa- 
miliar of  the  many  possible  illustrations. 

We  may  pause  here  for  a  moment  to  note  the  fine 
instance  of  gradual  discovery  which  the  utilisation 
of  coal-tar  affords.  "  Sixty  years  ago  an  obscure 
German  chemist  obtained  an  oily  liquid  from  coal- 
tar  oil,  which  gave  a  beautiful  tint  with  calcium 
chloride ;  five  years  later  another  separated  a  similar 
liquid  from  a  derivation  of  coal-tar  oil.  Still  later, 
Hofmann,  then  a  student  in  Liebig's  laboratory,  in- 
*  Ladenburg,  1900,  p.  112. 


A  CENTTTR  r  OF  CHEMISTRY.  99 

vestigated  these  substances  and  proved  their  identity 
with  an  oil  obtained  long  before  by  Zinin  from 
indigo,  and  applied  to  them  all  Zinin's  term,  Anilin. 
The  substance  was  curiously  interesting,  and  Hof- 
mann  worked  out  its  reactions,  discovering  that  with 
many  materials  it  gives  brilliant  colours.  The  prac- 
tical application  of  these  discoveries  was  not  long  de- 
layed, for  Perkin  made  it  in  1856.  The  usefulness 
of  the  dyes  led  to  deeper  studies  of  coal-tar  products 
to  which  is  due  the  discovery  of  such  substances  as 
antipyrin,  phenacetin,  ichthyol,  and  saccharin,  which 
have  proved  so  important  in  medicine." 

Wohler's  Synthesis  of  Urea. — As  analyses  of  or- 
ganic substances  accumulated,  it  became  perfectly 
clear  that  the  stuffs  composing  and  formed  by  living 
creatures  did  not  contain  any  peculiar  elements.  It 
was  seen  that  they  consisted  of  compounds  of  carbon 
with  hydrogen,  oxygen,  nitrogen,  and  other  elements 
familiar  in  the  organic  world. 

Those  who  thought  it  important  to  emphasise  the 
distinctions  between  the  living  and  the  not-living 
then  fell  back  upon  the  assertion  that  it  was  in  the 
arrangement  of  the  elements  that  the  uniqueness  of 
organic  substance  lay.  It  was  an  architectural  not  a 
material  distinction,  and  the  architect  was  Vital 
Force. 

It  was  in  the  midst  of  these  opinions  that  Wohler 
in  1828  effected  the  synthesis  of  urea — the  character- 
istic waste  product  of  higher  animals.  Starting 
with  cyanic  acid,  which  he  had  discovered  in  1822, 
he  found  that  urea  was  formed  upon  the  evaporation 
of  a  solution  of  its  ammonium  salt.  Without  the 
aid  of  vital  force  he  had  formed  from  a  simpler  sub- 
stance a  characteristic  organic  product.  It  should 

*  J.  J.  Stevenson,  Rep.  Smithsonian  Inst.  for  1897,  p.  330. 


100    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

indeed  be  noted  that  he  did  not  build  up  urea  from 
its  elements,  but  started  with  cyanic  acid,  which 
would  now  be  classed  as  an  organic  compound. 

Professor  Meldola  has  called  attention  *  to  the  his- 
torical fact  that  Henry  Hennell  deserves  a  place 
among  the  pioneers  of  chemical  synthesis,  for  in 
1826-1828  he  effected  the  synthesis  of  alcohol  from 
ethylene. 

Though  neither  synthesis  was  complete,  the  steps 
were  very  important.  They  indicated  the  beginning 
of  the  end  of  vital  force  as  a  chemical  factor,  the 
beginning,  too,  of  a  remarkable  series  of  synthetic 
achievements, — trichloracetic  acid  (Kolbe),  formic 
acid  and  alcohol  (Berthelot),  indigo,  grape-sugar, 
and  many  more — about  180  in  all — all  of  which  have 
been  artificially  produced. 

Isomerism. — Wohler's  synthesis  of  urea  did  not 
quickly  find  the  recognition  it  deserved,  but  it  doubt- 
less helped  to  break  down  the  arbitrary  distinction 
between  inorganic  and  organic  chemistry,  and  to 
further  the  progress  of  the  latter,  which  began  to  be 
spoken  of  as  the  chemistry  of  the  carbon  compounds. 
But  Wb'hler  was  also  concerned  in  other  steps  hardly 
less  significant. 

The  first  of  these  steps  is  indicated  by  the  word 
isomerism.  Even  Dalton  had  called  attention  to  the 
existence  of  substances  of  identical  chemical  com- 
position, but  with  different  properties,  and  had  sug- 
gested that  this  might  be  explained  by  different  or 
multiple  arrangement  of  the  constituent  atoms.  But 
little  notice  was  taken  of  this.  In  1823  Wb'hler  dis- 
covered the  composition  of  cyanic  acid ;  in  the  follow- 
ing year  Liebig  reported  the  same  composition  for 
fulminic  acid.  These  two  bodies  have  the  same 
*Rep.  Brit.  Ass.  for  1895,  p.  649. 


A  CENTURY  OF  CHEMISTRY.  101 

composition,  but  are  very  different  in  character. 
In  1825  Faraday  showed  that  butylene  has  the  same 
composition  as  ethylene  (olefiant  gas),  though  the 
former  has  twice  the  specific  gravity  of  the  latter. 
In  1830  Kestner  showed  that  racemic  acid  has  the 
same  composition  as  tartaric  acid,  and  hundreds  of 
such  cases  are  now  known.  These  facts  at  first  served 
to  complicate  matters;  they  showed  that  compounds 
with  widely  different  properties  may  contain  the  same 
constituents  and  in  the  same  proportions.  Berzelius, 
in  labelling  the  puzzle  with  the  term  isomerism, 
suggested,  as  Dumas  also  did,  that  the  component 
atoms  must  "  be  placed  together  in  different  ways  " 
in  the  various  isomers,  which  were  the  same  in  com- 
position and  yet  different  in  properties.  The  sug- 
gestion seems  an  easy  one,  especially  when  we  note 
that  "  one  chemical  compound,  a  hydrocarbon  con- 
taining thirteen  atoms  of  carbon  combined  with 
twenty-eight  atoms  of  hydrogen,  can  be  shown  to  be 
capable  of  existing  in  no  less  than  802  distinct 
forms"  (Roscoe).  Indeed,  possible  substances  have 
been  repeatedly  predicted,  and  afterwards  discov- 
ered or  made.  But  for  forty  years  from  Berzelius 
and  Dumas  there  has  been  a  succession  of  attempts 
to  show  how  we  may  reasonably  conceive  of  compo- 
sition being  the  same  while  the  constitution  and  re- 
sulting properties  are  different.  It  seems  likely  that 
the  solution  is  to  be  found  in  the  modern  develop- 
ment which  is  called  "  Chemistry  in  Space." 

Radicals. — But  another  step  with  which  Wb'hler 
•was  associated,  along  with  Liebig,  Bunsen,  Dumas, 
and  others,  was  the  formulation  of  the  radical 
theory.  It  was  well  known  that  salts  are  formed 
from  an  acid  and  a  base  and  can  be  decomposed  into 
these  two  constituents.  For  an  understanding  of  the 


102    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

salt  it  is  more  important  to  recognise  its  two  constitu- 
ents than  to  know  the  quantitative  proportions  of  its 
component  elements.  This  may  suggest  the  idea, 
which  has  been  of  enormous  importance  in  organic 
chemistry,  that  in  the  usually  complex  substances  in- 
volved there  exist  groups  of  elements  which  because 
of  their  stability  of  union,  may  be  said  to  play  the 
part  of  an  element.  Such  a  group  is  called  a  com- 
pound radical.  To  take  a  concrete  case,  in  their  re- 
searches on  bitter  almond  oil  and  the  allied  com- 
pounds, Wohler  and  Liebig  "  showed  that  we  may  as- 
sume the  existence,  in  these  substances,  of  an  oxygen- 
ated group  which  remains  unchanged  in  the  majority 
of  the  reactions,  and  therefore  behaves  like  an  ele- 
mentary substance.  On  this  account,  they  called  it 
the  radical  of  bitter  almond  oil."  * 

In  1837,  Liebig  wrote :  "  We  call  cyanogen  a 
radical  (1)  because  it  is  a  non-varying  constituent 
in  a  series  of  compounds,  (2)  because  in  these  latter 
it  can  be  replaced  by  other  simple  substances,  and 
(3)  because  in  its  compounds  with  a  simple  sub- 
stance, the  latter  can  be  turned  out  and  replaced  by 
equivalents  of  other  simple  substances."  The  idea 
may  seem  to  the  outsider  far  off  and  theoretical,  but 
there  can  be  no  doubt  that  the  formulation  of  the 
radical  theory  not  only  introduced  new  clearness  into 
chemistry,  but  was  most  provocative  of  research,  some 
of  the  results  of  which  have  had  no  small  influence 
on  practical  human  affairs. 

SUMMARY. — Just  as  it  had  been  shown  (Ampere, 
1816)  that  the  salts  of  ammonia  can  be  conveniently 
discussed  and  studied  by  regarding  them  as  salts  of 
a  compound  clement  (NH*)  so  Berzelius,  Dumas, 
Wohler,  Bunsen,  Liebig  and  others  sought  to  work 
*  Ladenburg,  1900,  p.  109. 


A  CENTURY  OF  CHEMISTRY.  103 

out  the  idea  that  organic  compounds  might  be 
brought  into  line  with  inorganic  compounds  by  sup- 
posing that  they  contained  compound  radicals,  like 
cyanogen,  which  'behaved  like  elements.  In  mineral 
substances  the  radicals  are  simple;  in  organic  sub- 
stances they  are  compound. 

Substitution. — About  1840,  Dumas'  idea  of  "  sub- 
stitution "  was  added  to  the  conceptual  formulae  of 
the  organic  chemist.  "  It  was  found  that  one  or  more 
atoms  in  an  organic  compound,  notably  of  hydrogen, 
might  be  replaced  by  an  equal  number  of  atoms 
of  other  elements,  and  that  such  products  of  substi- 
tution retained  similar  qualities,  and  could  be  mutu- 
ally converted  into  each  other,  the  type  of  the  com- 
pound remaining  the  same."  * 

Dumas  showed  that  chlorine  may  replace  hydrogen, 
atom  for  atom,  in  many  organic  compounds,  and  "  it 
may  be  easily  imagined  how  distasteful  such  a  dis- 
covery would  be  to  Berzelius  and  the  school  of  electro- 
chemists,  involving  as  it  does  the  idea  that  a  negative 
element  may  be  exchanged  for  a  positive  element, 
without  a  fundamental  alteration  in  the  chemical 
character  of  the  resulting  compound."  f 

According  to  Roscoe,  the  idea  of  substitution  was 
the  germ  of  Williamson's  researches  on  etherification 
and  those  of  Wurtz  and  Hofmann  on  the  compound 
ammonias — investigations  which  lie  at  the  base  of  the 
structure  of  modern  chemistry — and  had  also  a  pro- 
found influence  on  the  development  of  organic 
synthesis. 

Nuclei  and  Types. — The  older  radical  theory,  in- 
fluenced by  the  facts  of  substitution,  gave  place  to 
the  "  type  theory  "  of  Laurent  and  Gerhardt  and  the 

*  Merz,  History,  Vol.  I.,  p.  410. 
t  Tilden,  Short  History,  p.  15. 

H 


104    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

conception  of  "  nuclei."  "  The  radical,  as  the  per- 
manent constituent  in  organic  compounds, — cor- 
responding to  the  elements  in  inorganic  chemistry, — 
gave  way  to  the  changeable  nucleus,  which  only  pre- 
served its  form ;  the  unchangeable  principle  was 
found  in  the  form,  the  structure  or  type,  instead  of 
in  the  substance  of  the  simple  or  composite  consti- 
tuents." 

Valency. — Time  and  ability  alike  fail  us  to  dis- 
cuss how  the  endeavour  after  systematisation  and 
simplicity  was  continued  by  Kekule  (1829—1896), 
Kolbe  (1818-1884),  A.  W.  von  Hofmann  (1818- 
1892),"Wurtz  (1817-1884),  and  many  others.  The 
radical  theory  was  characteristically  German,  the 
type  theory,  French ;  and  now  we  have  to  notice  a 
more  distinctively  British  contribution, — the  idea  of 
the  "  atomicity  "  or  "  valency  "  of  chemical  substan- 
ces, whether  elements  or  compounds.  With  this  idea 
the  name  of  Frankland  (1852)  ought  perhaps  to  be 
particularly  associated. 

The  conception  of  "  valency,"  or  the  capacity  of 
saturation  of  the  atoms,  was  used  with  great  effect 
by  Kekule.  Almost  simultaneously,  in  1858,  he  and 
Couper  suggested  that  the  carbon  atom  should  be  con- 
sidered as  quadrivalent;  i.e.,  able  to  unite  with  four 
univalent  atoms  or  radicals  (such  as  can  replace  one 
atom  of  hydrogen),  but  not  with  more.  Kekule 
found  in  this  a  key  to  the  constitution  of  many  car- 
bon compounds. 

"  We  have  chiefly,"  Ostwald  says,  "  to  thank 
Kekule  for  carrying  through  this  idea.  In  the 
theory  of  valency,  which  is  at  the  present  time  the 
prevalent  one,  it  is  assumed  that  each  atom  pos- 
sesses a  definite  limited  capacity  for  combining  with 
other  atoms.  This  capacity  is  called  the  valency, 


A  CENTURY  OF  CHEMISTRY.  105 

and  the  atoms  that  can  combine  with  one,  two,  three 
or  four  atoms  (or  equivalent  atoms  or  radicals)  are 
said  to  be  univalent,  bivalent,  trivalent,  or  quadri- 
valent respectively.  Thus  marsh  gas  CH4  illustrates 
the  quadrivalent  character  of  carbon,  and  water  OH2 
the  bivalent  character  of  oxygen. 

Another  development,  foretold  by  Wollaston,  but 
practically  beginning  about  1858,  when  Pasteur 
founded  "  stereochemistry "  and  Kekule  stated  his 
theory  of  chemical  structure,  attained  epoch-making 
expression  in  1875,  when  Van't  Hoff  published  his 
work  entitled  La  Chimie  dans  I' E space  * — an  at- 
tempt to  formulate  a  geometrical  conception  of  the 
manner  in  which  the  hypothetical  atoms  may  be  sup- 
posed to  be  placed  in  space.  Along  with  Le  Bel,  he 
formulated  what  is  called  the  theory  of  "  the  asym- 
metric carbon-atom  "  f  and  initiated  what  may  be  de- 
scribed as  a  mechanical  theory  of  valency,  which  has 
been  further  strengthened  by  the  work  of  Wislicenus 
(1887),  and  other  masters  of  the  chemist's  craft. 

SUMMARY. — The  development  of  organic  chem- 
istry on  its  theoretical  side  affords  a  fine  instance  of 
the  gradual  specialisation  of  an  hypothesis  as  the 
facts  require  it.  The  steps  indicated  by  theories  of 
radicals,  types,  nuclei,  and  valencies  are  steps  to- 
wards a  conception  of  material  architecture  which 
will  consist  with  the  facts  of  chemical  change. 

The  concept  of  the  atom  was  in  its  first  form  too 
simple;  the  study  of  gases  showed  the  necessity  of 
recognising  the  molecule;  the  development  of  or- 
ganic chemistry  enlarged  the  concept  by  the  sug- 
gestion of  radicals  and  nuclei,  equivalents  and  val- 

*  J.  H.  Van't  Hoff.  Chemistry  in  Space,  trans,  and  ed  by 
J.  E.  Marsh,  Oxford,  1891. 

t  One  whose  four  valencies  are  satisfied  by  four  atoms 
or  radicals  of  different  kinds. 


106    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

encies;  the  phenomena  of  right  and  left  handedness 
led  on  to  ideas  of  definite  geometrical  arrangement 
within  the  molecule;  in  these  and  other  ways  the 
atomic  theory  in  its  chemical  applications  has  be- 
come more  and  more  specialised.  "  The  present 
position  of  structural  chemistry  may  be  summed  up 
in  the  statement  that  we  have  gained  an  enormous 
insight  into  the  anatomy  of  molecules,  while  our 
knowledge  of  their  physiology  is  as  yet  in  a  rudi- 
mentary condition"  (Meldola,  1895). 

THE  PERIODIC  LAW. 

A  General  Statement  by  Mendelejeff. — "  Many 
natural  phenomena,"  Mendelejeff  says,  "  exhibit  a 
dependence  of  a  periodic  character.  Thus  the  phe- 
nomena of  day  and  night  and  of  the  seasons  of  the 
year,  and  vibrations  of  all  kinds,  exhibit  variations  of 
a  periodic  character  in  dependence  on  time  and  space. 
But  in  ordinary  periodic  functions  one  variable  varies 
continuously,  while  the  other  increases  to  a  limit,  then 
a  period  of  decrease  begins,  and  having  in  turn 
reached  its  limit,  a  period  of  increase  again  begins. 
It  is  otherwise  in  the  periodic  function  of  the  ele- 
ments. Here  the  mass  of  the  elements  does  not  in- 
crease continuously,  but  abruptly,  by  steps,  as  from 
magnesium  to  aluminium.  So  also  the  valency  or 
atomicity  leaps  directly  from  1  to  2  to  3,  etc.,  without 
intermediate  quantities,  and  in  my  opinion  it  is  these 
properties  which  are  the  most  important,  and  it  is 
their  periodicity  which  forms  the  substance  of  the 
periodic  law.  It  expresses  the  properties  of  the  real 
elements,  and  not  of  what  may  be  termed  their  mani- 
festations usually  known  to  us.  The  external  proper- 
ties of  elements  and  compounds  are  in  periodic  de- 
pendence on  the  atomic  weights  of  the  elements  only 


A  CENTURY  OF  CHEMISTRY.  107 

because  these  external  properties  are  themselves  the 
result  of  the  properties  of  the  real  elements  forming 
the  isolated  elements  or  the  compound.  To  explain 
and  express  the  periodic  law  is  to  explain  and  express 
the  cause  of  the  law  of  multiple  proportions,  of  the 
difference  of  the  elements,  and  the  variation  of  their 
atomicity,  and  at  the  same  time  to  understand  what 
mass  and  gravitation  are.  In  my  opinion  this  is  now 
premature.  But  just  as,  without  knowing  the  cause 
of  gravitation,  it  is  possible  to  make  use  of  the  law  of 
gravity,  so  for  the  aims  of  chemistry  it  is  possible  to 
take  advantage  of  the  laws  discovered  by  chemistry 
without  being  able  to  explain  their  causes.  The 
above-mentioned  peculiarity  of  the  laws  of  chemistry 
respecting  definite  compounds  and  the  atomic 
weights  leads  one  to  think  that  the  time  has  not  yet 
come  for  their  full  explanation,  and  I  do  not  think 
that  it  will  come  before  the  explanation  of  such  pri- 
mary laws  of  nature  as  the  law  of  gravity."  * 

The  general  idea  of  Mendelejeff's  periodic  law  is 
that  the  properties  of  the  elements  are  periodic  func- 
tions of  their  atomic  iveights,  but  while  this  is  a 
simplifying  concept  it  is  not  in  any  way  an  expla- 
nation. 

The  Problem  of  Chemical  Classification. — The 
desire  for  orderly  grouping  is  one  of  the  mainsprings 
of  scientific  work.  Even  artificial  classifications — 
like  the  grouping  of  flowers  according  to  the  number 
of  their  stamens — have  often  justified  themselves, 
though  they  are  apt  to  outlive  their  usefulness.  It  is 
plain  that  natural  classifications — based  on  deep- 
seated  resemblances — must  economise  thought  and 
make  our  outlook  on  the  world  clearer.  Therefore 

*  D.    Mendelejeff .     The    FYinc-iples  of    Chemistry,    trans. 
1897,  Vol.  II.,  pp.  20-21,  foot-note. 


108    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

it  has  often  been  felt  that  the  boon  would  be  great 
if  we  could  arrange  the  different  kinds  of  matter  in 
groups  or  series  corresponding  in  some  measure  to 
the  classes,  orders,  families,  etc.,  in  which  we  ar- 
range plants  and  animals. 

It  is  therefore  hardly  necessary  to  say  that  Men- 
dele  jeff  was  not  the  first  to  be  attracted  by  the  possi- 
bility of  detecting  serial  relations  among  the  chem- 
ical elements.  Apart  from  the  speculations  of  the 
ancients  and  of  the  alchemists,  glimpses  of  a  sup- 
posed orderly  relationship  of  the  various  elements 
seem  to  have  been  frequent  in  the  history  of  chem- 
istry. Particularly  noteworthy  was  the  idea  of  a  fun- 
damental substance,  "  protyle  "  or  "  prothyle,"  often 
identified  with  hydrogen,  of  which  the  other  elements 
were  supposed  to  be  derivatives.  Prof.  Tilden  sums 
up  the  idea  in  the  quotation : — 

' '  All  things  the  world  which  fill 
Of  but  one  stuff  are  spun." 

More  concretely,  the  hypothesis  was  hazarded  anony- 
mously by  Prout  (1815)  that  the  atomic  weights 
of  the  gaseous  elements  are  all  whole  multiples  of 
hydrogen.  And  with  this  view,  supported  by  Mei- 
necke  (181Y),  was  involved  the  suggestion  that  the 
various  elements  might  turn  out  to  be  derivatives 
of  one  primary  form  of  matter,  such  as  hydrogen, 
or  something  of  which  hydrogen  was  an  atomic 
multiple.  It  was  an  evolutionist  speculation,  but 
born  before  its  time.  It  has  been  buried  and  res- 
urrected several  times  throughout  the  century.  De- 
fended in  Britain  by  Thomson,  scouted  by  Berzelius, 
revived  by  Dumas,  it  was  once  more  sent  to  rest 
about  1860  by  Stas,  a  Belgian  chemist,  who  did 
splendidly  accurate  work,  from  1860  onwards,  in 


A  CENTURY  OF  CHEMISTRY.  109 

confirming  the  doctrine  of  the  regularity  of  chemical 
proportions  in  all  combinations. 

Others  again,  without  accepting  any  protyle-hy- 
pothesis,  pointed  out  the  existence  of  serial  regular- 
ities in  the  atomic  weights  of  the  elements,  (Lens- 
sen  1857,  Pettenkofer  1850,  Dobereiner  1817,  and 
even  before  the  atomic  theory,  J.  B.  Kichter  1798). 
Dobereiner  pointed  out  that  a  number  of  elements 
could  be  arranged  in  groups  of  three,  or  triads ;  e.g., 
calcium,  strontium,  and  barium,  the  members  of  each 
triad  having  analogous  properties  and  displaying  a 
certain  regularity  in  the  relations  of  their  atomic 
weights.  This  idea  of  family  characteristics  was 
afterwards  extended  by  Dumas. 

Most  noteworthy,  however,  was  the  work  of  New- 
lands  (1863-4),  who  showed  that  when  the  elements 
were  arranged  according  to  the  magnitude  of  their 
atomic  weights,  "  similar  elements  were  found  at 
approximately  equal  distances  in  the  series;  count- 
ing from  any  one  element,  every  eighth  was  in  gen- 
eral more  similar  to  the  first  than  the  other  ele- 
ments." * 

As  the  eighth  element,  starting  from  a  given  one 
is  a  kind  of  repetition  of  the  first,  like  the  eighth  note 
of  an  octave  in  music,  he  called  the  regularity  "  The 
Law  of  Octaves."  He  did  not  succeed,  however,  in 
fully  carrying  out  his  idea.  In  the  same  year 
(1864),  Dr.  Odling  also  published  a  suggestive  pa- 
per on  "  The  Proportional  lumbers  of  the  Elements 
and  their  Serial  Relations." 

Independent  Discovery  by  Meyer  and  Mendelejeff. 
— We  accept  the  conclusion  of  expert  authorities 
that  in  1869  Lothar  Meyer  and  D.  Mendelejeff  inde- 

*  Ostwald,  General  Chemistry,  trans,  by  Walker,  1890, 
y.  35. 


110    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

pendently  reached  the  same  conclusion: — That  the 
properties  of  the  elements  are  periodic  functions  of 
their  atomic  weights.  "  If  all  the  elements  be  ar- 
ranged in  the  order  of  their  atomic  weights  a  peri- 
odic repetition  of  properties  is  obtained.  This  is  ex- 
pressed by  the  law  of  periodicity;  the  properties  of 
the  elements,  as  well  as  the  forms  and  properties  of 
their  compounds,  are  in  periodic  dependence,  or,  ex- 
pressing ourselves  algebraically,  form  a  periodic 
function  of  the  atomic  weights  of  the  elements." 
"  If  all  the  elements  are  arranged  in  the  order  of 
their  atomic  weights  in  a  series,  their  properties  will 
so  vary  from  member  to  member  that  after  a  definite 
number  of  elements  has  been  passed  either  the  first 
or  very  similar  properties  will  recur."  f  This 
was  the  conclusion  which  Mendelejeff  and  Meyer  ex- 
pounded. 

Let  us  state  the  general  idea  once  more.  When 
the  elements  are  arranged  according  to  the  magnitude 
of  their  atomic  weights,  "  the  elements  following  one 
another  show  apparently  no  regularity  in  properties, 
but  after  the  lapse  of  a  certain  period  the  chemical 
and  physical  behaviour  of  the  elements  now  suc- 
ceeding each  other  strongly  recall  that  of  the  previ- 
ous group,  in  fact,  repeat  it.  The  elements  which 
resembled  one  another  were  therefore  united  into 
groups  or  natural  families,  and  these  in  their  turn 
were  distinguished  from  the  periods,  which  com- 
prised the  elements  whose  atomic  weights  lay  be- 
tween those  of  two  successive  members  of  a  natural 
family."  J 

Scientific  Justification  of  the  Periodic  Law. — It 

*  Mendelejeff,  Principles  of  Chemistry,  Vol.  II.,  trans,  by 
Kamensky  and  Greenaway,  1891,  p.  16. 
f  Ostwald,  General  Chemistry,  trans,  p.  35. 
j  E.  von  Meyer,  History  of  Chemistry,  trans.  1891,  p.  347. 


A  CENTURY  OF  CHEMISTRY.  HI 

may  be  said  in  a  sentence  that  the  general  result  of 
chemical  work,  since  Mendelejeff  and  Meyer  stated 
the  Periodic  Law  in  1869,  has  been  to  show  that  "  al- 
most every  well-defined  and  comparable  property  of 
the  elements  appears  as  a  periodic  function  of  the 
atomic  weights"  (Ostwald).  The  atomic  volume 
shows  the  periodic  variation  most  clearly  (Meyer), 
the  melting  point  of  the  elements  varies  periodically 
(Carnelley),  the  same  holds  true  of  the  specific  gra- 
vities, the  magnetic  properties  of  elements  depend  on 
the  position  occupied  in  the  periodic  system  (Carnel- 
ley), there  is  also  a  periodicity  in  the  amount  of  heat 
developed  in  the  formation  of  the  chlorides,  bromides, 
and  iodides  (Laurie)  ;  these  must  serve  as  illustra- 
tions of  the  manifold  justification  which  the  theory 
has  received. 

The  Test  of  Prophecy. — In  regard  to  vital  phenom- 
ena where  the  operative  factors  are  usually  complex 
and  numerous,  there  are  few  who  would  be  willing  to 
submit  their  favourite  generalisations  to  the  severe 
test  of  using  them  as  a  basis  for  prophecy,  as  the  as- 
tronomer, for  instance,  can  do  with  some  security. 
But  this  severe  test  Mendelejeff  did  apply  to  his 
periodic  law. 

In  his  arrangement  of  elements  into  groups  and 
series,  Mendelejeff  was  compelled  to  leave  certain 
blanks.  He  asserted  that  these  would  be  filled  up 
by  the  discovery  of  new  elements. 

"  He  was  able  to  foretell  the  atomic  weights  and 
other  properties  of  these  elements  from  their  posi- 
tion in  the  system,  with  the  aid  of  the  properties  ob- 
served in  the  groups  and  series,  which,  like  a  system 
of  co-ordinates,  could  be  called  in  to  assist.  Three 
such  blanks  occurred  in  the  first  five  series,  and  these 
he  indicated  as  representing  the  positions  of  eka- 


112    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

boron  (at.  wt.  44),  eka-aluminium  (at.  wt,  68),  and 
eka-silicon  (at.  wt.  72).  Since  that  time,  these  three 
elements  have  been  discovered,  and  they  have  been 
found  to  possess,  approximately,  the  properties  pre- 
dicted by  Mendelejeff.  They  are:  scandium,  discov- 
ered by  Mlson,  with  atomic  weight  44.1;  gallium, 
discovered  by  Lecoq  de  Boisbaudran,  with  atomic 
weight  70;  and  germanium,  discovered  by  Winkler, 
with  atomic  weight  72."  * 

To  sum  up: 

"  The  periodic  law  has  not  only  embraced  the  mu- 
tual relations  of  the  elements  and  expressed  their 
analogy,  but  has  also  to  a  certain  extent  subjected 
to  law  the  doctrine  of  the  types  of  the  compounds 
formed  by  the  elements;  has  enabled  us  to  see  a  regu- 
larity in  the  variation  of  all  chemical  and  physical 
properties  of  elements  and  compounds,  and  has  ren- 
dered it  possible  to  foretell  the  properties  of  ele- 
ments and  compounds  yet  uninvestigated  by  exper- 
imental means;  it  therefore  prepares  the  ground  for 
the  building  up  of  atomic  and  molecular  me- 
chanics." f 

Inorganic  Evolution. — An  alluring,  but  perhaps  il- 
lusory, idea  has  occurred  to  many  chemists  who  have 
pondered  over  the  relations  of  the  elements  to  one 
another, — the  idea  that  chemically  analogous  ele- 
ments may  be  related  in  a  real,  i.e.,  genetic,  sense, 
or  that  they  may  be  derivatives  of  a  common  stock. 
The  historians  of  chemistry  have  shown  that  this  is 
an  ancient  and  frequently  recurrent  idea.  Some  of 
the  early  Greeks  imagined  one  primeval  substance 
developing  into  all  the  different  kinds  of  matter; 

*  Laclenburg,  1900,  p.  313. 

t  Mendelejeff,  Principles  of  Chemistry,  Vol.  II.,  trans., 
p.  34. 


A  CENTURY  OF  CHEMISTRY.  113 

Boyle  spoke  of  "  one  universal  matter  common  to  all 
bodies;"  Dalton  said,  "We  do  know  that  any  of 
the  bodies  denominated  elementary  are  absolutely 
indecomposable ;  "  Graham  suggested  as  conceivable, 
"  that  the  various  kinds  of  matter  now  recognised  as 
different  elementary  substances  may  possess  one  and 
the  same  ultimate  or  atomic  molecules  existing  in 
different  conditions  of  movement."  *  Many  other 
examples  might  be  given,  and  we  have  already  re- 
ferred to  the  views  of  Prout,  Meinecke,  and  Thomas 
Thomson  that  there  is  an  ultimate  relation  between 
hydrogen  and  the  other  elements. 

"  In  1888-9  Sir  William  Crookes  again  raised  the 
question  whether  what  are  called  elements  may  not 
be  compounds,  and  whether  all  may  not  have  arisen, 
by  gradual  condensation,  from  hypothetical  primitive 
material  which  he  called  protyle. 

Accepting  the  suggestion  that  substances  now 
thought  to  be  elements  may  turn  out  to  be  com- 
pounds, Lockyer  has  pictured  the  possible  dissocia- 
tion of  the  elements  in  the  fervent  heat  within  the 
sun's  atmosphere.  It  may  be  so,  but  there  are  no 
certain  facts  as  yet  which  alleviate  the  hypothetical 
character  of  these  imaginings ;  and  it  seems  well  to 
emphasise  that  Mendelejeff  has  expressly  dissociated 
his  periodic  law  from  speculations  as  to  the  deriva- 
tion of  the  elements  from  one  prime  matter. 

CO-OPEBATIOX  OF  CHEMISTRY  A3TD  PHYSICS. 

~No  two  sciences  have  entered  into  a  co-operation  so 
close  as  that  which  now  exists  between  chemistry  and 
physics.  In  a  way  the  alliance  is  almost  ancient,  for 
chemistry  first  became  an  exact  science  by  adopting 

*  See  Sir  Henry  Roscoe's  Pres.  Address,  Rep.  Brit.  Ass. 
for  1887,  p.  8. 


PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

physical  methods  of  weighing  and  measuring;  the 
balance,  which  is  as  familiar  an  emblem  of  chemistry 
as  the  crucible,  is  rather  a  physical  than  a  chemical 
instrument.  But  the  recognition  that  chemical  and 
physical  properties  are  inter-dependent  and  must  be 
studied  together,  practically  dates  from  Lavoisier, 
and  it  has  led  to  a  remarkable  series  of  physico- 
chemical  researches  which  may  be  said  to  form  a 
special  department  of  science.  Kopp  was  one  of  the 
early  workers ;  Ostwald  is  now  one  of  the  leaders. 

Thermochemistry. — A  new  chapter  in  the  history 
of  chemistry  began  with  Lavoisier's  study  of  com- 
bustion and  with  the  resulting  recognition  of  the 
indestructibility  of  matter.  But  Lavoisier  left  the 
dynamics  of  combustion  untouched,  and  another  new 
chapter  dates  from  1843,  from  Joule's  measurement 
of  the  mechanical  equivalent  of  heat,  and  the  result- 
ing recognition  of  the  conservation  of  energy.*  The 
phenomena  of  chemical  activity  assumed  a  new 
aspect  when  it  was  clearly  realised  that  chemical 
changes  involve  only  re-distribution,  but  in  no  case 
any  destruction  of  energy  or  power.  This  also  im- 
plied that  chemical  energy  might  be  measured  in 
terms  of  the  heat  evolved  or  absorbed. 

Let  us  by  means  of  a  quotation  from  Ostwald  gain 
a  clear  impression  of  what  the  main  business  of 
thermochemistry  is.  "  Chemical  energy  is  to  us  the 
least  known  of  all  the  various  forms  of  energy,  as 
we  can  measure  neither  it  nor  any  of  its  factors  di- 
rectly. The  only  means  of  obtaining  information  re- 
garding it  is  to  transform  it  into  another  species  of 
energy.  It  passes  most  easily  and  completely  into 
heat,  and  the  branch  of  science  which  treats  of  the 
measurement  of  chemical  energy  in  thermal  units  is 
*  See  the  Chapter  on  the  Progress  of  Physics. 


A  CENTURY  OF  CHEMISTRY.  115 

called  thermochemistry.  Thermochemistry  is  thus 
the  science  of  the  thermal  processes  conditioned  by 
chemical  processes.  The  quantities  of  heat  evolved  or 
absorbed  measure  the  decrease  or  increase  of  chemi- 
cal energy,  in  so  far  as  other  energy  is  not  involved 
in  the  processes."  * 

Among  the  important  steps  in  thermochemistry 
the  following  may  be  noted : 

The  extension  of  the  law  of  Dulong  and  Petit  by 
Neumann  and  later  by  Regnault  (1839) ;  the  ex- 
periments of  Thomas  Andrews  (1841)  on  the  heat 
produced  during  the  combination  of  acid  and  bases 
in  aqueous  solution;  Herman  Hess's  experimental 
verification  (1840)  of  the  conclusion  that  "the  sev- 
eral amounts  of  heat  evolved  during  the  successive 
stages  of  a  process  are  the  same  in  whatever  orderthey 
follow  one  another  " — a  conclusion  subsequently  re- 
inforced by  Berthelot;  Julius  Thomsen's  vast  accu- 
mulation of  data  (from  1853  onwards)  as  to  heats 
of  formation  and  all  kinds  of  chemical  change;  and 
Berthelot's  equally  voluminous  researches. 

We  need  not,  for  our  purpose,  pursue  the  history 
further.  It  is  enough  to  indicate  that  the  aim  of 
discovering  the  dynamical  laws  relating  to  chemical 
processes  is  one  which  has  not  been  lost  sight  of.  At 
the  same  time,  we  have  to  note  the  conclusion  of  an 
expert  like  Tilden,  that  "notwithstanding  the  labours 
of  half  a  century,  thermochemistry  remains  for  the 
most  part  a  mass  of  experimental  results,  which  still 
await  interpretation." 

The  doctrine  of  the  conservation  of  energy  is  the 
foundation  of  chemical  dynamics.  Every  change  in 
the  arrangement  of  particles  is  accompanied  by  a 

*  Ostwald,  Outlines  of  General  Chemistry,  trans.  1890,  pp. 
208-209. 


116    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

definite  evolution  or  absorption  of  heat.  The  object 
of  thermal  chemistry  is  to  measure  the  energy  of 
chemical  changes  by  thermal  methods,  and  thus  to  get 
nearer  the  fundamental  problem  of  the  dynamics  of 
chemical  affinity. 

Photochemistry. — There  are  few  problems  more 
fascinating  and  more  important  than  those  which  are 
raised  when  we  try  to  follow  the  transformations  of 
sunlight.  Chemical  processes  in  the  sun  give  rise  to 
radiant  energy,  which  is  propagated  with  great  ve- 
locity (3  -f-  1010  cm.  per  second)  through  space, 
with  the  ether  for  its  hypothetical  vehicle.  When  it 
reaches  the  earth,  part  of  it  passes  into  the  form  of 
heat  and  thence  into  many  other  forms,  while  part 
of  it  acting  on  green  plants  resumes  the  form  of 
chemical  energy.  The  radiant  energy  of  sunlight  is 
utilised  by  the  green  leaves  to  split  up  the  carbonic 
acid  of  the  atmosphere  and  to  build  up  the  complex 
substances  which  furnish  food  and  fuel,  not  to  speak 
of  the  most  valuable  super-necessaries  of  life. 

Nor  does  the  radiant  energy  affect  plants  only,  it 
has  a  subtle  influence  on  many  animals,  modifying 
for  instance  the  process  of  coloration,  and  above  all 
producing  those  chemical  changes  in  the  retina  which 
are  associated  with  vision.  In  the  volume  of  this 
series  which  deals  with  Inventions  due  notice  will  be 
taken  of  photography  (Daguerre,  1838),  which  de- 
pends on  the  chemical  reactions  produced  by  light  on 
a  sensitive  surface.  But  the  retina  was  the  first  sen- 
sitive surface,  and  we  may  therefore  say  that  it  was 
in  the  consideration  of  problems  primarily  physio- 
logical and  secondarily  technical  that  photochemistry, 
like  thermochemistry,  had  its  beginnings. 

We  have  just  mentioned  the  effect  of  light  upon 
the  human  eye,  and  as  an  illustration  from  the  other 


A  CENTURY  OF  CHEMISTRY.  H7 

end  of  the  scale  of  being  we  may  note  the  attraction 
of  some  micro-organisms  to  light.  ThusEngelmann's 
Bacterium  photometricum — rod-like  purple  microbes 
— not  only  crowd  in  a  drop  of  water  under  the  mi- 
croscope to  the  particular  spot  on  which  the  smallest 
possible  beam  of  light  is  focussed,  but  when  a  micro- 
scopic spectrum  is  projected  on  the  field  "  select  ' 
the  area  whose  colour  is  that  which  is  most  absorbed 
by  their  minute  bodies. 

One  other  illustration  of  the  chemical  action  of 
light  upon  living  creatures  may  be  given,  namely,  the 
destructive  effect  of  light  upon  many  kinds  of  mi- 
crobes, both  in  the  air  and  in  culture-solutions.  We 
are  accustomed  to  think  of  light  as  life-giving,  but  it 
also  kills.  And  the  fact  is  significant  and  full  of 
practical  suggestion  that  sunlight  is  the  most  potent, 
universal,  and  economical  antagonist  of  some  of  our 
worst  enemies.  How  exactly  the  light  kills  the  bac- 
teria remains  somewhat  uncertain,  but  it  is  com- 
monly believed  that  it  induces  too  rapid  oxidation, 
that  it  makes  the  minute  organisms  live  so  fast  that 
they  die. 

Photochemical  research  has  been  as  yet  in  great 
part  concerned  with  different  modes  of  measuring 
the  chemical  activity  of  light.  One  of  the  most  suc- 
cessful methods  takes  advantage  of  the  fact  that  light 
induces  a  mixture  of  equal  volumes  of  chlorine  and 
hydrogen  to  form  hydrogen  chloride  (Draper,  1843 ; 
Bunsen  and  Roscoe,  1857).  This  led  to  the  estab- 
lishment of  the  conclusions  that  the  chemical  action 
is  proportional  to  the  light  intensity,  that  equal 
chemical  effects  are  produced  when  the  products  of 
light  intensity  and  time  of  exposure  are  equal,  that 
substances  are  affected  differently  by  different  rays, 
and  so  on.  How  it  is  that  light  induces  chemical 


118    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

change  we  do  not  know,  though  hypothetical  sugges- 
tions have  been  offered. 

Photochemistry  or  the  study  of  the  effects  of 
radiant  energy  (light)  on  chemical  processes  is  still 
incipient;  though  its  results  have  led  to  the  develop- 
ment of  photography,  the  influence  of  light  on  the 
green  leaf  remains  an  unread  riddle. 

Electrochemistry. — It  is  a  familiar  fact  that  if  a 
rod  of  zinc  and  a  rod  of  platinum  "be  immersed  in 
dilute  sulphuric  acid  (which  does  not  attack  either  of 
them  separately),  and  if  the  ends  of  the  two  rods 
projecting  out  of  the  liquid  be  apposed  or  connected 
by  a  metal  wire,  the  zinc  is  dissolved,  the  hydrogen 
of  the  sulphuric  acid  accumulates  on  the  platinum, 
and  there  has  come  into  existence  an  electric  current 
— a  form  of  energy — which  can  be  made  to  do  work. 
The  source  of  this  energy  is  in  the  chemical  process, 
in  the  heat  evolved  by  the  solution  of  the  zinc.  By 
using  heat  as  the  common  standard  of  measurement, 
we  are  able  to  prove  that  a  certain  amount  of  poten- 
tial chemical  energy  available  at  the  outset  is  exactly 
equivalent  to  the  amount  of  electrical  energy  pro- 
duced plus  the  heat  evolved  at  the  seat  of  the  reaction. 

From  the  study  of  comparatively  simple  experi- 
ments like  that  above  referred  to,  always  in  the  light 
of  the  doctrine  of  the  conservation  of  energy,  electro- 
chemistry has  evolved  into  an  important  and  elabo- 
rate department  of  science. 

Faraday  distinguished  bodies,  e.g.,  metals,  which 
conduct  electrical  currents  without  suffering  any 
material  change  beyond  that  of  heating,  from  other 
bodies,  such  as  salts  and  aqueous  solutions  of  acids 
and  bases,  in  which  the  conducted  current  induces 
chemical  change.  "  In  such  conductors  of  the  second 
class,  or  electrolytes,  the  movement  of  electricity 


A  CENTURY  OF  CHEMISTRY.  119 

takes  place  so  that  the  metals  (or  metallic  radicals) 
of  the  salts  and  bases,  and  the  hydrogen  of  the  acids, 
move  from  the  positive  part  of  the  current  to  the 
negative,  while  the  acid  radicals  or  elements,  such  as 
chlorine,  bromine,  iodine,  and  also  the  hydroxyl  of 
bases,  move  in  the  opposite  direction.  These  com- 
ponents, or  ions,  are  set  free  where  the  electrolyte 
is  in  contact  with  metal  conducting  the  current " 
(Ostwald,  op.  cit.  p.  270).  In  1833,  Faraday  for- 
mulated the  general  conclusion,  fundamental  to  sub- 
sequent progress,  that  equal  quantifies  of  electricity 
on  passing  through  different  electrolytes  require 
equivalent  quantities  of  the  ions  for  their  transport. 
This  may  be  called  the  foundation-stone  of  electro- 
chemistry. 

It  would  be  interesting  to  show  how  the  enquiry 
into  the  constitution  of  electrolytes,  which  must  be 
such  that  particles  charged  positively  can  move  in 
one  direction  while  those  charged  negatively  move  in 
the  other,  has  led  through  the  ideas  of  Williamson 
(1851),  Clausius  (1857),  Arrhenius  (1887),  Planck 
(1887),  to  the  theory  that  solutions  of  salts  and  of 
strong  acids  and  bases  contain  these  substances  dis- 
sociated into  ions,  that  a  solution  of  potassium  chlo- 
ride contains  in  great  part  single  potassium  and  chlo- 
rine atoms  with  enormous  electrical  charges  and  with 
their  chemical  properties  thereby  modified.  It  reads 
like  a  romance  in  the  invisible  world — far  more  dar- 
ing than  the  biologist  has  ever  ventured  with  his 
ids  and  biophors — and  yet  it  appears  to  harmonise 
a  large  number  of  observed  facts.  As  Ostwald  says, 
"  The  assumption  that  electrolytes  contain  free  ions 
is  not  only  possible  but  necessary." 

It  would  be  interesting  also  to  show  how  the  elec- 
tric conductivity  of  electrolytes  was  measured  (Kohl- 


120    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

rausch,  1880),  or  how  the  velocity  of  the  migration 
of  the  ions  was  calculated,  or  how  equations  have 
been  worked  out  and  confirmed  (Willard  Gibbs, 
Helmholtz,  Jahn),  showing  the  relation  between  the 
chemical  energy,  the  electrical  energy,  and  the  altera- 
tion of  the  electromotive  force  (i.e.,  potential,  ten- 
sion or  intensity)  with  the  temperature,  such  that 
any  one  of  the  three  can  be  calculated  if  the  other 
two  terms  are  known.  But  we  have  said  enough 
to  suggest  the  fruitfulness  of  the  co-operation  of 
chemistry  and  physics  in  the  department  of  electro- 
chemistry, and  to  suggest  how  well  it  will  repay  the 
reader  to  avail  himself  of  the  pleasure  which  is  af- 
forded by  modern  chemistry,  as  expounded  by  mas- 
ters like  Ostwald. 


THE    CIRCULATION    OF    MATTER. 

Transformations  in  Plants. — We  have  already  al- 
luded to  the  chemist's  power  of  transforming  matter. 
Out  of  coal-tar  he  brings  the  colours  of  the  rainbow 
and  he  makes  the  rubbish  of  twenty  years  ago  a  source 
of  riches  to-day. 

But  any  common  green  plant  is  the  seat  of  trans- 
formations of  matter  not  less  marvellous.  The  ele- 
ments of  soil,  water,  and  air  are  by  the  touch  of  life 
lifted  into  complexity,  united  into  organic  com- 
pounds, forming  part  of  the  capital  of  a  living  crea- 
ture. 

We  are  also  aware  of  what  Mr.  Grove  long  since 
called  the  correlation  of  the  physical  forces,  what 
others  speak  of  as  the  transformations  of  energy.  We 
know  how  the  energy  of  the  mill-race  may  drive  a 
dynamo,  and  we  see  the  energy  again  in  our  electric 


A  CENTURY  OF  CHEMISTRY.  121 

lamp.  We  know  that  heat,  light,  and  electricity  are 
transformable  powers. 

But  any  common  green  plant  is  the  seat  of  trans- 
formations of  energy  not  less  marvellous.  The  ener- 
gies of  the  sunlight — the  undulations  of  the  ethereal 
waves,  according  to  the  student  of  physics — are  so 
used  by  the  plant  that  complex  organic  substances,  of 
which  starch  is  the  first  to  become  visible,  are  built 
up.  The  kinetic  energy  of  the  sunlight  is  changed  in 
the  potential  energy  of  complex  chemical  substances, 
such  as  wood.  We  use  such  potential  energy  to  sup- 
ply power  to  our  life,  to  stoke  our  engines,  to  warm 
our  hearths. 

We  know  of  no  life  which  is  not  life-born,  but  we 
know  that  all  the  world  over,  from  the  red-snow  plant 
of  Arctic  icebergs  to  the  luxuriant  vegetation  of  the 
Tropics,  from  the  seaweed  on  the  shore  to  the  Cali- 
fornian  Wellingtonias,  the  simple  so-called  dead  ele- 
ments of  water,  earth,  and  air  are  being  quickened 
into  life,  that  is  to  say,  are  becoming  part  of  the 
capital  of  living  plants.  On  these  plants  animals 
feed,  and  the  wealth  of  the  plants  is  recoined  to  feed 
muscle  and  nerve,  and  what  was  once  the  dust  of  the 
wayside  may  become  part  and  parcel  of  the  brain  of 
a  Caesar. 

Elements  in  an  Organism, — Let  us  approach  the 
subject  in  another  way.  ISTo  one  knows  the  chemical 
nature  of  living  matter,  for  we  cannot  isolate  what  is 
genuinely  alive  from  associated  not-living  substance. 
Moreover,  the  moment  the  expert  begins  his  analysis 
the  living  matter  is  dead,  and  the  secret  eludes  him. 
But  every  one  now  knows  the  elements  out  of  which 
the  living  body  is  built  up,  though  no  one  can  tell 
how  these  elements  are  arranged  in  really  living 
stuff  nor  how  they  act  as  they  do  when  thus  ar- 


122    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

ranged.  The  elements  cannot  escape  the  chemist,  al- 
though their  intricacy  of  arrangement  in  many  cases 
does. 

If  we  reduce  living  plants  to  ashes,  and  allow 
nothing  to  escape  undetected,  we  find  a  constant  pres- 
ence of  twelve  elements,  carbon,  hydrogen,  oxygen, 
nitrogen,  sulphur,  phosphorus,  chlorine,  potassium, 
sodium,  calcium,  magnesium,  and  iron.  It  may  be 
indeed  that  all  the  twelve  are  not  present  in  some  of 
the  very  simplest  forms  of  life,  where  the  method  of 
ash-analysis  is  inapplicable.  But  for  ordinary  plants 
which  can  be  burned,  the  above  statement  is  true. 
The  twelve  elements  are  always  present.  Had  we 
space,  it  would  be  interesting  to  take  each  of  these 
elements  in  turn,  to  show  in  what  forms  they  exist 
in  inorganic  nature,  to  follow  them  from  their  ab- 
sorption by  root-suckers  to  their  known  combinations 
in  plant,  animal,  or  man,  and  to  show  how  they 
eventually  come  back  to  the  so-called  dead-state  once 
more.  But  since  it  is  better  to  have  one  definite  im- 
pression than  a  hundred  vague  ones,  let  us  confine 
our  attention  to  nitrogen. 

Circulation  of  Nitrogen. — "As  is  well  known,  free 
nitrogen  forms  about  four-fifths  of  the  atmosphere, 
but  the  great  bulk  of  this  takes  no  part  in  vital  proc- 
esses. With  certain  notable  exceptions  it  is  only  in 
the  form  of  compounds  that  nitrogen  can  be  used  by 
living  creatures.  Therefore,  since  nitrogenous  food 
is  essential  both  to  plant  and  animal,  the  amount  of 
life  upon  the  earth  must  depend  on  the  amount  of 
fixed  nitrogen  available.* 

The  commonest  circle  is  the  following:  Nitrogen 
is  obtained  by  the  plant  in  the  form  of  nitrates,  ni- 

*  Bunge,  Text-book  of  Physiological  and  Pathological 
Chemistry,  trans.  1890,  p.  19. 


A  CENTURY  OF  CHEMISTRY.  123 

trites,  or  ammonia ;  these  compounds  are  used  in  the 
elaboration  of  complex  nitrogenous  bodies  such  as 
proteids.  These  proteids  produced  by  the  plant  form 
the  food  of  animals  and  become  part  of  their  vital 
capital.  As  the  animals  live  there  is  a  continual  dis- 
ruption of  the  complex  nitrogenous  substances  and 
the  formation  of  less  complex  nitrogenous  waste 
products.  This  also  takes  place  in  plants,  but  there 
is  this  difference,  that  while  the  plant  retains  its 
nitrogenous  waste,  the  animal  gets  rid  of  it — in  the 
form  of  urea,  uric  acid,  urates,  and  the  like.  These 
waste  products  rapidly  decompose  after  they  have 
been  excreted,  and  ammonia  is  formed — available 
once  more  to  enter  upon  the  cycle. 

If  the  animal  or  plant  die,  the  agency  of  putre- 
factive bacteria  brings  about  decomposition,  and  the 
disruption  of  the  nitrogenous  materials  yields  am- 
monia, nitrates,  and  the  like,  which  may  be  again 
utilised.  The  availability  of  nitrogenous  material 
is  not  thereby  affected.  On  the  other  hand,  as  Bunge 
forcibly  points  out,*  the  burning  of  wood,  the  crema- 
tion of  an  animal,  the  explosion  of  gunpowder,  in- 
volve a  liberation  of  nitrogen  from  its  fixed  or  com- 
pound form,  and  a  consequent  diminution  of  the 
available  supplies. 

"  It  would  appear,  therefore,  that  there  is  a  con- 
tinuous degradation  of  nitrogen  to  the  elementary 
condition — a  very  serious  matter  if  the  nitrogen  so 
degraded  is  finally  removed  from  the  sphere  of  action 
of  organised  beings.  Are  there,  then,  any  other 
agencies  at  work  to  restore  the  balance,  and  enable 
this  apparently  useless  gas  to  return  within  the 
arena  of  physiological  activity  ?  "  f 

*  Bunge,  op.  cit.,  p.  21. 

t  F.  W.  Stoddart,  "  The  Circulation  of  Nitrogen  in  Na- 
ture," Proc.  Bristol  Nat.  Soc..  IX.  (1899),  pp.  57-74. 


124    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

In  the  first  place,  it  has  to  be  borne  in  mind  that 
by  electrical  discharges  in  air  nitrogen  is  united 
with  oxygen  to  form  nitric  acid,  and  in  a  damp  at- 
mosphere the  same  agency  causes  nitrogen  to  combine 
with  water  vapour  to  form  nitrite  of  ammonia  (Ber- 
thelot)-  The  rain  after  the  thunderstorm  brings 
the  products  to  earth. 

In  the  second  place,  it  is  stated  by  Schb'nbein  that 
wherever  evaporation  occurs  minute  traces  of  am- 
monia are  formed  in  the  air. 

In  the  third  place,  the  researches  of  Hellreigel 
and  Willfarth,  repeated  and  confirmed  by  many, 
show  that  leguminous  plants  can  under  the  influence 
of  partner-micro-organisms,  which  form  root-tuber- 
cles, utilise  (indirectly)  the  free  nitrogen  of  the  air. 

In  the  fourth  place,  the  circulation  of  nitrogen  and 
the  increase  of  availability  is  furthered  by  other  lilli- 
putian  agencies;  namely,  those  soil-bacteria  which 
convert  ammonia  into  nitrous  acid,  or  carry  the  oxi- 
dation further  to  the  level  of  nitric  acid. 

Foundation  of  Agricultural  Chemistry. — If  we 
wish  to  associate  any  particular  name  with  the  recog- 
nition of  the  fundamental  fact  of  the  circulation  of 
matter,  it  should  be  the  name  of  Justus  Liebig 
(1803-1873).  Himself  a  student  under  Gay-Lus- 
sac,  he  became  the  master  of  one  of  the  greatest 
schools  of  chemistry,  the  initiator  of  chemical  labo- 
ratories, a  pioneer  of  modern  organic  chemistry,  one 
of  the  prompters  of  chemical  physiology,  the  founder 
of  agricultural  chemistry,  and  the  discoverer  of  many 
important  practical  applications. 

The  circulation  of  elements,  of  nitrogen  for  in- 
stance, from  the  air  or  the  soil  into  plants  and 
thence  into  animals,  and  thence  back  to  the  soil  or 
air  again,  is  a  fact  of  great  interest,  justifying  us 


A  CENTURY  OF  CHEMISTRY.  125 

in  speaking  of  the  circulation  of  matter, — a  fact  to 
be  associated  with  Liebig's  industry — as  not  less  im- 
portant than  Harvey's  theory  of  the  circulation  of 
the  blood.  The  idea  marks  a  new  era. 

CHEMICAL  AFFINITY. 

The  Problem  of  Chemical  Changes. — Chemistry 
has  above  all  to  do  with  changes  in  the  composition 
of  matter,  and  although  in  point  of  time  the  study 
of  chemical  changes  was  prosecuted,  by  the  alche- 
mist, for  instance,  long  before  there  was  any  sound 
knowledge  of  material  composition,  the  understand- 
ing of  the  former  entirely  depends  on  an  understand- 
ing of  the  latter. 

One  of  the  early  results  of  the  careful  study  of 
these  chemical  changes  or  reactions  was  to  show  that 
though  the  number  of  possible  experiments  is  endless, 
the  number  of  kinds  of  experiment  is  limited.  It 
began  to  be  seen  that  substances  could  be  arranged 
in  various  groups,  the  members  of  each  group  acting 
in  a  similar  way  in  similar  circumstances.  Thus 
a  number  of  substances,  like  oil  of  vitriol  (sulphuric 
acid)  and  spirits  of  salt  (hydrochloric  acid)  exhibit 
similar  properties,  or  similar  reactions  in  similar 
conditions,  and  may  be  ranked  together  as  acids; 
another  set  of  substances,  like  spirits  of  hartshorn 
(ammonia)  and  slaked  lime,  are  most  markedly  dif- 
ferent from  the  acids,  and  may  be  ranked  together 
as  alkalis;  a  third  set  of  substances,  like  chalk,  pro- 
ducible by  the  reaction  of  an  acid  and  an  alkali,  may 
be  ranked  together  as  salts.  Thus  there  arose  a  clas- 
sification of  compounds  based  on  similarity  of  reac- 
tion in  similar  conditions.  It  was  merely  a  prelimi- 
nary step  towards  order,  and  it  led  to  many  others 
of  greater  importance. 


126    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

When  two  different  substances  are  brought  to- 
gether it  frequently  happens  that  changes  occur  re- 
sulting in  the  production  of  a  new  substance  or  sub- 
stances. Thus  an  acid  and  an  alkali,  as  noted  above, 
produce  a  salt.  Since  the  indestructibility  of  matter 
was  recognised,  and  since  Dalton  made  the  atomic 
conception  current  coin,  it  has  been  evident  that  the 
change  occurs  through  a  separation  and  re-combina- 
tion of  the  component  particles  of  the  two  substances. 
As  Dalton  said :  "  All  the  changes  we  can  produce 
consist  in  separating  particles  that  are  in  a  state  of 
cohesion  or  combination,  and  joining  those  that  were 
previously  at  a  distance."  But  after  the  phenomena 
of  change  have  been  observed,  the  question  is  bound 
to  arise — why  should  the  atoms  separate  and  re-com- 
bine at  all  ?  Is  the  phenomenon  comparable  to  any- 
thing else  in  our  experience,  or  is  '  chemical  affinity ' 
an  irreducible  fact  ?  Masses  attract  one  another  and 
we  can  measure  the  force;  is  chemical  affinity  also 
measurable  and  does  it  bear  any  analogy  to  gravita- 
tion ?  There  is  also  attraction  due  to  magnetism 
and  different  electrical  states;  has  chemical  affinity 
anything  to  do  with  this  ?  Thus  arises  the  inevitable 
problem  of  chemical  affinity;  it  is  still  unsolved,  but 
we  may  profitably  consider  for  a  little  some  of  the 
suggestions  which  have  been  offered. 

It  is  part  of  the  work  of  chemistry  to  distinguish 
the  different  kinds  of  matter,  and  we  began  this  his- 
torical  sketch  by  alludincf  to  the  search  for  the  ele- 
ments; but  a  more  important  problem  is  to  interpret 
chemical  affinity,  or  the  capacity  of  the  elements  to 
exert  chemical  action. 

Electricity  and  Chemical  Affinity. — In  the  long 
history  of  attempts  to  interpret  the  chemical  activi- 
ties of  different  kinds  of  matter  in  their  relations  to 


A  CENTURY  OF  CHEMISTRY.  127 

one  another,  the  importance  of  electrical  phenomena 
has  bulked  largely.  The  discoveries  of  Galvani 
(1789)  and  Volta  (1792)  on  the  generation  of  elec- 
tricity by  the  use  of  two  metals  were  not  long  in 
being  applied  to  chemistry.  Thus  in  1800  Nichol- 
son and  Carlisle  observed  that  if  an  electrical  cur- 
rent be  passed  through  water,  the  result  is  a  decompo- 
sition into  hydrogen  and  oxygen, — the  two  gases, 
namely,  which  Cavendish,  sixteen  years  before,  had 
shown  (synthetically)  to  be  the  constituents  of 
water.  In  1803  Berzelius  and  Hisinger  published 
the  results  of  similar  experiments  on  many  different 
compounds,  and  showed  that  hydrogen,  metals,  alka- 
lis, metals,  etc.,  possess  positive  electrical  energy, 
while  oxygen,  acids,  etc.,  separate  at  the  positive 
pole. 

Davy. — Meanwhile  Humphry  Davy  had  also 
turned  his  attention  to  similar  enquiries ;  he  con- 
firmed the  results  of  Hisinger  and  Berzelius,  and 
made  the  theoretical  suggestion  that  hydrogen,  alka- 
lis, metals,  etc.,  possess  positive  electrical  energy, 
while  oxygen  and  the  acids  are  correspondingly  nega- 
tive. As  oppositely  electrified  bodies  attract  each 
other,  the  former  substances  come  off  in  electrolysis 
at  the  negative  pole  (cathode),  and  the  latter  at  the 
positive  (anode).  From  this  he  went  on  to  the  mo- 
mentous generalisation  that  chemical  affinity  is  due 
to  difference  in  electrical  condition. 

Pursuing  his  decomposition  experiments,  Davy 
turned  his  attention  to  the  alkalis  (potash  and  soda), 
and  found  that  small  metallic  globules,  burning  with 
brilliancy  in  air,  were  formed  at  the  negative  pole, 
while  oxygen  was  evolved  at  the  other.  He  rightly 
concluded  that  the  substances  he  had  discovered  were 
the  metals  Potassium  and  Sodium,  of  which  the 


128    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

alkalis  are  the  oxides.  This  important  step, 
checked  by  the  French  chemists,  seems  to  have  led 
many  for  a  time  to  a  false  expectation.  "  The  idea 
was  arrived  at  that  the  substances  hitherto  known 
were  only  compounds',  and  that  the  aim  of  chemistry 
was  now  to  discover  the  true  elements,  which  it  was 
supposed  would  resemble  potassium  and  sodium. 
.  .  .  The  galvanic  current,  at  that  period  an  en- 
tirely new  agent,  had  accomplished  this  marvel,  and 
it  was  itself  a  marvellous  thing.  By  its  aid  it  had 
become  possible  to  decompose  compounds  into  their 
true  elements;  hence  it  is  not  surprising  that  this 
agency  was  regarded  as  identical  with  the  one  which 
gave  rise  to  combinations ;  i.e.,  with  affinity." 

Berzelius. — The  ingenious  suggestions  of  Davy 
were  soon  developed  by  Berzelius  into  a  consistent 
theory  which  was  then  used  as  the  foundation  idea 
of  a  chemical  system. 

He  believed,  with  Davy,  that  all  chemical  reac- 
tions are  produced  by  electricity,  which  "  thus  seems 
to  be  the  first  cause  of  the  activity  all  around  us  in 
nature."  But  he  differed  from  Davy  in  his  mode 
of  conceiving  of  the  electrical  distribution.  In  his 
own  words,  "  If  the  electro-chemical  views  are  ac- 
curate, it  follows  that  every  chemical  combination 
depends  wholly  and  only  upon  two  opposite  forces, 
namely,  the  positive  and  negative  electricities,  and 
that  every  compound  must  be  composed  of  two  parts, 
united  by  the  effects  of  their  electro-chemical  reac- 
tions, since  there  is  not  any  third  force.  From  this 
it  follows  that  every  compound  substance,  whatever 
the  number  of  its  constituents  may  be,  can  be  divided 
into  two  parts,  of  which  the  one  is  positively  and  the 
other  is  negatively  electrical." 

*  Ladenburg,  1900,  p.  67. 


A  CENTURY  OF  CHEMISTRY.  129 

But  difficulties  soon  gathered  round  this  electro- 
chemical theory.  Even  as  early  as  1834,  Dumas 
showed,  in  stating  his  "  substitution  "  theory,  that  in 
many  organic  compounds  the  positive  element  hydro- 
gen may  be  replaced  by  the  negative  element  chlorine 
"  without  a  fundamental  alteration  in  the  chemical 
character  of  the  resulting  compound."  This  was 
practically  a  deathblow  to  the  theory  of  Berzelius. 

Faraday. — About  1833,  Faraday  was  led  to  con- 
clude (a)  that  the  chemical  power  of  a  current  of 
electricity  is  in  direct  proportion  to  the  absolute  quan- 
tity of  electricity  which  passes,  and  (6)  that  the 
proportions  of  the  bodies  or  ions  evolved  by  an  elec- 
trolytic action  (the  electro-chemical  equivalents  of 
the  ions)  are  the  same  as  their  ordinary  chemical 
equivalents  or  combining  proportions.  And  he  re- 
turned to  the  theory  of  Davy,  saying  that  "  the  forces 
termed  chemical  affinity  and  electricity  are  one  and 
the  same." 

Sir  Henry  Eoscoe  points  out  that  the  great  prin- 
ciple of  valency  was  foreshadowed  from  a  physical 
point  of  view  in  Faraday's  law  of  electrolysis. 
Faraday  showed  that  the  number  of  atoms  electro- 
lytically  deposited  is  in  the  inverse  ratio  of  their 
valencies;  Helmholtz  in  his  Faraday  lecture  ex- 
plained this  by  the  fact  that  "  the  quantity  of  elec- 
tricity with  which  each  atom  is  associated  is  directly 
proportional  to  its  valency." 

lonisation  Theory. — It  does  not  seem  possible, 
at  present,  to  be  confident  in  affirming  or  denying  the 
idea  that  chemical  combination  is  due  to  the  union 
of  electrically  charged  atoms;  but  it  is  certain  that 
the  question  is  not  so  simple  as  it  appeared  to  Davy, 
Berzelius,  and  Faraday.  To  make  the  matter  in  any 
way  clear  it  would  be  necessary  to  take  account  of 


130    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

many  researches,  notably,  for  instance,  of  those  con- 
cerning the  nature  of  solutions. 

The  reader  should  consult,  for  instance,  the  eighth 
chapter  of  Professor  Tilden's  Short  History,  espe- 
cially with  reference  to  the  theory  of  ionisation  sug- 
gested by  Arrhenius. 

While  the  early  electro-chemical  ideas  of  Berzelius 
have  been  abandoned,  a  new  path  of  enquiry,  es- 
pecially marked  by  the  work  of  Svante  Arrhenius, 
continues  to  be  full  of  promise.  Its  first  milestone 
bears  the  date  1884,  when  Arrhenius  proved  that  def- 
inite and  quantitative  relations  exist  between  elec- 
trical and  chemical  properties. 

But  to  this  we  must  add,  as  suggestive  of  one  of 
the  most  significant  steps  in  modern  chemical  theory, 
another  quotation  from  Ostwald.  "  Research  based 
on  a  well-defined  measure  of  affinity  determinable 
with  numerical  exactness  only  became  possible,  when, 
by  the  development  of  the  electrolytic  theory  of  dis- 
sociation, the  formula  was  found  from  which  a  con- 
stant of  a  general  character  and  independent  of  the 
dilution  could  be  calculated.  This  constant  has  a 
claim  to  serve  as  a  measure  of  affinity." 

While  the  nature  of  chemical  affinity  remains  ob- 
scure, a  mode  of  measuring  it  has  been  attained.  If 
this  step  is  to  be  associated  with  any  particular  name 
it  should  be  with  Ostwald  (1889). 


CHAPTEK  V. 
THE  PKOGBESS  OF  PHYSICS. 

INTRODUCTORY. 

Definition  of  Physics. — "  The  properties  of  matter 
and  energy,  of  energy  and  ether,  and  of  ether  and 
matter,  are  the  subjects  of  investigation  in  physical 
science."  Thus  one  of  the  modern  masters,  Prof. 
G.  F.  Fitzgerald,*  defined  the  scope  of  the  science, 
•whose  progress  in  the  nineteenth  century  will  be  illus- 
trated or  suggested  in  this  chapter. 

Although  we  may  note  Fitzgerald's  statement  that 
physical  science  is  divided  from  chemistry  "  by  being 
the  study  of  each  kind  of  matter  by  itself,  while  chem- 
istry studies  the  actions  of  different  kinds  of  matter 
upon  one  another,"  we  must  also  note  his  acknowledg- 
ment— "  of  course  no  real  line  can  be  drawn." 

The  physicist  has  mainly  to  do  with  transforma- 
tions of  energy,  or,  in  a  word,  with  motion.  Or  per- 
haps it  is  more  accurate  to  say,  with  Professor  J.  J. 
Poynting :  "  The  range  of  the  physicist's  study  con- 
sists in  the  visible  motions  and  other  sensible  changes 
of  matter.  The  experiences  with  which  he  deals  are 
the  impressions  on  his  senses,  and  his  aim  is  to  de- 
scribe in  the  shortest  possible  way  how  his  various 
senses  have  been,  will  be,  or  would  be  affected."  f 

Method  of  Physics. — The  physicist  looks  out  upon 
nature  seeking  for  similarities  of  action — likenesses 

*  Science  Progress,  Vol.  I.,  1894.  p.  3. 
t  Address,  Section  A,  Rep.  Brit.  Ass.  for  1899,  p.  615. 


132    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

of  motion ;  he  groups  these  together  if  they  are 
seen  to  be  really  the  same;  he  uses  instruments 
to  enable  his  senses  to  detect  hidden  motions,  and  to 
measure  these  with  accuracy ;  he  tries  to  find  a  short 
descriptive  formula  of  antecedent  and  sequence  which 
will  fit  the  facts.  The  so-called  laws  of  motion 
are  "  brief  descriptions  of  observed  similarities," 
as  Prof.  J.  J.  Poynting  expresses  it.*  As  his  for- 
mulae increase  in  number  and  precision,  he  often 
finds  it  possible  to  combine  several  of  them  in 
a  more  general  formulae,  which  may  be  so  secure, 
that  is  so  accurate  a  description,  that  it  affords  a 
basis  for  safe  prediction. 

Aim  of  Physics. — "  To  take  an  old  but  never  worn- 
out  metaphor,  the  physicist  is  examining  the  garment 
of  Nature,  learning  of  how  many,  or  rather  of  how 
few,  different  kinds  of  thread  it  is  woven,  finding  how 
each  separate  thread  enters  into  the  pattern,  and 
seeking  from  the  pattern  woven  in  the  past  to  know 
the  pattern  yet  to  come.  How  many  different  kinds  of 
thread  does  Nature  use  ?  So  far,  we  have  recognised 
some  eight  or  nine,  the  number  of  different  forms  of 
energy  which  we  are  still  obliged  to  count  as  distinct. 
But  this  distinction  we  cannot  believe  to  be  real.  The 
relations  between  the  different  forms  of  energy  and 
the  fixed  rate  of  exchange  when  one  form  gives  place 
to  another,  encourage  us  to  suppose  that  if  we  could 
only  sharpen  our  senses  or  change  our  point  of 
view  we  could  effect  a  still  further  reduction.  We 
stand  in  front  of  Nature's  loom  as  we  watch  the  weav- 
ing of  the  garment;  while  we  follow  a  particular 
thread  in  the  pattern  it  suddenly  disappears,  and  a 
thread  of  another  colour  takes  its  place.  Is  this 
a  new  thread,  or  is  it  merely  the  old  thread  turned 

*  Address,  Section  A,  Brit.  Ass.  Report  for  1899,  p.  616. 


THE  PROGRESS  OF  PHYSICS.  133 

round  and  presenting  a  new  face  to  us?  We  can 
do  little  more  than  guess.  We  cannot  get  round 
to  the  other  side  of  the  pattern,  and  our  minutest 
watching  will  not  tell  us  all  the  working  of  the 
loom."11  But  since  we  cannot  rest  with  discon- 
tinuous descriptions,  we  construct  a  hypothetical 
system  as  to  the  constitution  of  matter  and  the 
relation  of  energy  to  it, — a  system  in  line  with  what 
we  do  know  of  visible  motions  and  accelerations, 
— a  system  to  which  we  will  naturally  hold  until  a 
more  complete  knowledge  should  suggest  some  im- 
provement of  it,  or,  it  might  be,  demand  its  rejection. 
SUMMABY. — In  the  main  the  problem  of  the  phys- 
icist is  to  describe  and  formulate  the  likenesses  of 
motion  which  are  observed  in  our  outlook  upon 
nature. 

THE  NEWTONIAN  FOUNDATION. 

At  the  beginning  of  the  nineteenth  century,  chem- 
istry was  just  steadying  itself  on  the  foothold  afforded 
by  the  doctrine  of  the  indestructibility  of  matter,  but 
Physics  had  been  on  sure  ground  since  the  publication 
of  Xewton's  Principia  (1687).  It  seems  necessary 
to  admit  that  the  value  of  the  Xewtonian  foundation 
was  not  fully  appreciated  in  the  eighteenth  century, 
and  that  many  workers  left  it  and  built  short-lived  in- 
dependent structures,  but  for  the  nineteenth  century 
it  does  not  seem  too  much  to  say  that  all  stable  prog- 
ress in  Physics  has  been  dominated  by  Newton's  con- 
clusions. "  In  fact  the  Newtonian  philosophy  can  be 
said  to  have  governed  at  least  one  entire  section  of  the 
scientific  research  of  the  first  half  of  this  period :  only 
in  the  second  half  of  the  period  have  we  succeeded  in 

*  Poynting,  Address,  Section  A,  Rep.  Brit.  Ass.  for  1899, 
p.  618. 


134    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

defining  more  clearly  the  direction  in  which  Newton's 
views  require  to  be  extended  or  modified."  * 

As  to  the  import  of  Newton's  work,  three  points 
may  be  distinguished. 

First,  it  affords  what  is  probably  the  most  striking 
instance  of  the  application  of  scientific  method,  and 
part  of  its  influence  has  been  that  of  an  illustrious 
example.  It  signalised  once  for  all  the  contrast 
between  metaphysical  contemplation  and  scientific 
study. 

Secondly,  in  the  so-called  law  of  gravitation,  which 
describes  "  how  every  particle  of  matter  in  the  uni- 
verse is  altering  its  motion  with  reference  to  every 
other  particle,"  Newton  not  only  enlarged  the  horizon 
of  physics,  but  gave  the  world  perhaps  its  finest  illus- 
tration of  a  focalising  "  thought-economising  "  for- 
mula, whose  universality  and  accuracy  seem  alike 
indisputable.  Here  the  science  passed  beyond  ob- 
servation and  description  to  the  recognition  of  a  uni- 
fying idea. 

Thirdly,  in  his  laws  of  motion  and  other  principles 
Newton  gave  a  marvellous — if  still  imperfect — pre- 
cision to  the  concepts — of  force,  matter,  and  the  like 
— with  which  the  physicist  works.  Some  would  say 
with  Prof.  Ernst  Mach  f  that  Newton  "  completed 
the  enunciation  of  the  principles  of  mechanics,"  or 
with  Thomson  and  Tait  that  "  every  attempt  to 
supersede  them  has  ended  in  utter  failure  " ;  while 
others  would  rather  say  with  Karl  Pearson  that  the 
progress  of  two  centuries  has  given  good  reason  for 
trying  to  modify  and  restate  the  Leges  Motus,  es- 
pecially in  the  direction  of  purifying  them,  if  it  be 

*  J.  T.  Merz,  History  of  European  Thought,  I.,  p.  317. 
\Mechanik  in  ihrer  •'  Entwickehmg,  3d  ed.,    1889,  trans. 
Chicago,  by  J.  T.  McCormack,  1893. 


THE  PROGRESS  OF  PHYSICS.  135 

possible,  from  the  metaphysical  obscurities  which 
lurk  even  in  their  apparent  lucidity.*  But  all  will 
agree  that  Newton  supplied  the  firm  foundation  on 
which,  especially  during  the  last  hundred  years,  phys- 
ical science  has  gradually  grown  into  a  stately  edifice. 

It  is  doubtless  true  that  Xewton  stood  on  the 
shoulders  of  Galilei,  but  his  genius  in  discerning  the 
unity  amid  multiplicity  was  none  the  less  great,  and 
there  is  no  finer  instance  of  a  unifying  idea  than  the 
gravitation-formula.  At  the  same  time,  it  must  be 
recognised  that,  like  other  big  scientific  generalisa- 
tions, the  gravitation-theory  raised  problems  which  it 
did  not  answer. 

What  we  have  is  a  general  formula:  that 
every  particle  or  atom  or  body  in  the  universe  at- 
tracts every  other  with  a  force  proportional  to  their 
masses  taken  conjointly,  and  inversely  proportional 
to  the  square  of  their  distances  apart.  This  may  be 
called  the  law  of  gravitation,  but  is  there  no  theory 
of  the  law  ?  In  this  respect  there  has  been  little  ad- 
vance since  the  beginning  of  the  nineteenth  century. 

It  was  then  that  Lesage  of  Geneva  suggested  that 
in  addition  to  the  gross  particles  of  tangible  or  sensi- 
ble matter,  "  infinite  as  these  are  in  number,  there 
is  an  infinitely  greater  number  of  much  smaller  ones 
darting  about  in  all  directions  with  enormously  great 
velocities.  Lesage  showed  that,  if  this  were  the  case, 
the  effects  of  their  impacts  upon  the  grosser  particles 
or  atoms  of  matter  would  be  to  make  each  two  of 
these  behave  as  if  they  attracted  one  another  with  a 
force  following  exactly  the  law  of  gravity.  In  fact, 
when  two  such  particles  are  placed  at  a  distance  from 
one  another,  each,  as  it  were,  screens  the  other  from 

*  Grammar  of  Science,  Chapter  VIII.,  "  The  Laws  of 
Motion." 

J 


136    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

a  part  of  the  shower  which  would  otherwise  batter 
upon  it.  .  .  It  is  necessary  also  to  suppose  that  par- 
ticles and  masses  of  matter  have  a  cage-like  form,  so 
that  enormously  more  corpuscles  pass  through  them 
than  impinge  upon  them ;  else  the  gravitation  action 
between  two  bodies  could  not  be  as  the  product  of 
their  masses."  *  But  this  speculation  is  only  a  pro- 
visional stop-gap. 

To  the  easy-going  materialists,  if  any  survive,  the 
ignoramus  of  one  of  our  leading  physicists  should 
give  pause : — "  Directly  we  use  the  term  l  weight,' 
we  are  confronted  with  the  fact  that  not  yet  have  we 
any  real  clew  to  that  astonishing  fact  of  universal 
gravitation."  f 

SUMMARY. — The  foundation  of  modern  physics  is 
in  Newton's  Principia  (1687)  whose  value  is  more 
fully  appreciated  at  the  end  than  it  was  at  the  begin- 
ning of  the  nineteenth  century. 

CONSERVATION   OF  ENERGY. 

The  Idea  of  Energy. — Energy  is  a  convenient  term 
for  the  power  of  doing  work  which  is  possessed  by  a 
material  system,  or  by  the  ether  which  modern  phys- 
ics has  invented  as  a  hazy  background  of  matter.  A 
stream  flowing  down  a  valley  illustrates  energy  of 
motion,  it  may  turn  mill-wheels  or  bear  away  bridges ; 
the  reservoir  on  the  plateau  illustrates  energy  of  posi- 
tion, which  intention  or  accident  may  at  any  moment 
bring  into  operation.  These  two  types  of  power  are, 
as  every  one  knows,  called  kinetic  energy  and  poten- 
tial energy.  Whether  the  kinetic  energy  be  expressed 
in  visible  motion,  as  of  the  stream,  or  invisible  mo- 

*  P.  G.  Tait,  Recent  Advances  in  Physical  Science,  1876, 
pp.  299-300. 

t  Prof.  Oliver  J.  Lodge,  "  Modern  Views  of  Matter," 
Jnternat.  Monthly,  I.  (1900),  p.  525. 


THE  PROGRESS  OF  PHYSICS.  137 

tion,  as  in  the  particles  of  a  heated  bar  of  iron ;  wheth- 
er the  potential  energy  be  expressed  in  a  visible  ar- 
rangement of  bodies,  as  in  the  stone  resting  on  the 
roof-edge,  or  in  invisible  arrangements,  as  in  the 
mutual  relations  of  particles  in  an  explosive ;  we  sum 
up  all  the  different  forms  in  the  one  conception  of 
energy  or  power. 

The  convenience  of  this  concept  "  Energy  "  to  sum 
up  groups  of  sense-impressions  is  obvious,  but  it  must 
be  borne  in  mind  that  in  using  the  term  we  are  simply 
making  an  abstraction  which  proves  useful  in  the 
rapid  discussion  of  the  forms  or  modes  of  motion 
which  we  see  and  measure.  Clerk  Maxwell  said  in 
his  remarkable  little  book  Matter  and  Motion:  "  We 
are  acquainted  with  matter  only  as  that  which  may 
have  energy  communicated  to  it  from  other  matter, 
and  which  may  in  turn  communicate  energy  to  other 
matter,"  and  again,  "  Energy,  on  the  other  hand,  we 
know  only  as  that  which  in  all  natural  phenomena 
is  continually  passing  from  one  portion  of  matter  to 
another."  But,  as  Karl  Pearson  points  out,  these 
statements  do  not  carry  us  far.  "  The  only  way  in 
which  we  can  understand  matter  is  through  the  en- 
ergy which  it  transfers.  .  .  .  The  only  way  to  un- 
derstand energy  is  through  matter.  Matter  has  been 
defined  in  terms  of  energy,  and  energy  again  in  terms 
of  matter." 

"  The  activity  of  the  material  universe,"  says  Prof. 
Oliver  Lodge,  "  is  due  to,  or  represented  by,  or  dis- 
played in,  the  continual  interchanges  of  energy  from 
matter  to  ether  and  back  again,  accompanied  by  its 
transformation  from  the  kinetic  to  the  potential  form 
and  vice  versa"  * 

*" Modern  Views  of  Matter,"  Internal.  Monthly,  I.  (1900), 
p.  500. 


138    PROGRESS  OF  SCIENCE  IN  THE  CENTURY, 

Transformations  of  Energy. — Before  methods  of 
measuring  the  different  forms  of  what  we  call  energy 
had  been  elaborated,  it  was  evident  that  one  kind  of 
power  was  continually  being  changed  into  another. 
Carbon  and  oxygen  have  in  separation  potential 
energy — the  energy  of  chemical  affinity  for  one  an- 
other, and  this  is  manifested  by  the  heat  which  they 
give  off  when  they  unite;  the  heat  may  be  in  great 
part  utilised  to  convert  water  into  steam ;  the  "  expan- 
sive force  "  of  the  steam  lifts  the  piston ;  the  wheels 
go  round;  the  energy  re-appears  partly  in  the  poten- 
tial form  of  work  done  and  partly  in  the  heat  which 
results  from  overcoming  friction.  The  energy  of  the 
sunlight  enables  the  plant  to  build  up  complex  food- 
stuffs out  of  simple  raw  materials ;  substances  of  high 
potential  energy  thus  result;  these  become  sources 
of  power  to  man  and  beast.  The  energy  of  chemical 
separation  may  be  transformed  into  heat,  light,  mag- 
netism, electricity,  and  so  on;  or  heat,  light,  and 
electricity  may  be  used  to  effect  chemical  separation. 
Moreover,  all  the  powers  we  can  employ  (except  in 
the  case  of  tidal  currents)  are  directly  or  indirectly 
traceable  to  the  energy  radiated  from  the  sun,  or 
to  stores  of  potential  energy  in  the  earth,  which  again 
we  have  to  thank  the  sun  for. 

Conservation. — These  considerations  lead  us  to 
the  doctrine  of  the  conservation  of  energy,  which  is 
one  of  the  foundations  of  Physics.  It  is  an  induc- 
tion -from  experience  which  states  that  "  the  total 
amount  of  energy  in  a  material  system  cannot  be 
varied,  provided  the  system  neither  parts  with 
energy  to  other  bodies  nor  receives  it  from  them." 
There  may  be  degradation  or  dissipation  of  energy,  as 

*  Article  "  Energy,"  Chambers's  Encyclopedia,  by  Dr. 
W.  Peddle. 


THE  PROGRESS  OF  PHYSICS.  139 

when  heat  passes  into  the  air,  but  destruction  of 
energy  is  unknown. 

Energy  is  the  power  of  doing  work;  work  is  the 
act  of  producing  a  change  of  configuration  in  a  sys- 
tem in  opposition  to  resistance;  and  the  doctrine  of 
the  conservation  of  energy  is  thus  expressed  by  Clerk 
Maxwell :  "  The  total  energy  of  any  material  system 
is  a  quantity  which  can  neither  be  increased  nor 
diminished  by  any  action  between  the  parts  of  the 
system,  though  it  may  be  transformed  into  any  of  the 
forms  of  which  energy  is  susceptible." 

Dissipation  of  Energy. — And  to  this  doctrine  of 
conservation  there  has  to  be  added  the  corollary, 
which  Sir  William  Thomson  (Lord  Kelvin)  first 
focussed  into  lucidity  (1852) — "  the  principle  of  dis- 
sipation or  degradation,"  which  is  "  simply  this,  that 
as  every  operation  going  on  in  nature  involves  a 
transformation  of  energy,  and  every  transformation 
involves  a  certain  amount  of  degradation  (degraded 
energy  meaning  energy  less  capable  of  being  trans- 
formed than  before),  energy  is  becoming  less  and 
less  transformable."  * 

Foundation  of  the  Doctrine  of  the  Conservation  of 
Energy. — Just  as  the  doctrine  of  the  indestructibility 
of  matter  became  stable  with  the  perfecting  of  the 
balance,  so  the  doctrine  of  the  conservation  of  energy 
must  be  associated  with  the  determination  of  the 
mechanical  equivalent  of  heat, — with  the  experiments 
of  Rumford  and  Davy  leading  on  to  those  of  Colding 
and  Joule.  At  the  same  time,  it  should  be  borne  in 
mind  that,  according  to  Thomson  and  Tait,  the  prin- 
ciple is  clearly  implied  in  Newton's  scholium  to  his 
third  law  of  motion, — that  "  if  the  action  of  an  ex- 
ternal agent  is  estimated  by  the  product  of  its  force 
*P.  G.  Tait,  Recent  Advances  (1876),  pp.  145-6. 


140    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

into  its  velocity,  and  the  reaction  of  the  resistance  in 
the  same  way  by  the  product  of  the  velocity  of  each 
part  of  the  system  into  the  resisting  force,  arising 
from  friction,  cohesion,  weight,  and  acceleration,  the 
action  and  reaction  will  be  equal  to  one  another,  what- 
ever be  the  nature  and  motion  of  the  system." 

We  have  placed  the  doctrine  of  the  conservation  of 
energy  before  the  dynamical  theory  of  heat  because 
many  discoveries  were  pointing  towards  the  great 
conclusion  of  the  transf  ormability  and  conservation  of 
energy,  before  Joule's  measurement  of  the  mechanical 
equivalent  of  heat  made  the  vaguely  foreseen  conclu- 
sion an  established  doctrine.  None  the  less,  however, 
would  we  emphasise  that  the  establishment  of  the 
general  doctrine  dates  from  Joule's  success  as  a 
measurer  of  the  relation  between  heat  and  mechanical 
work  in  1843. 

For  it  was  then  that  one  of  the  greatest  scientific 
steps  of  the  century  was  made.  "  Clear  and  unques- 
tionable experimental  proof  was  given  of  the  fact  that 
there  is  a  definite  relation  between  mechanical  work 
and  heat ;  that  so  much  work  always  gives  rise,  under 
the  same  conditions,  to  so  much  heat,  and  so  much 
heat  to  so  much  mechanical  work.  Thus  originated 
the  mechanical  theory  of  heat,  which  became  the  start- 
ing point  of  the  modern  doctrine  of  the  conservation 
of  energy.  Molar  motion  had  appeared  to  be  destroyed 
by  friction.  It  was  proved  that  no  destruction  took 
place,  but  that  an  exact  equivalent  of  the  energy  of  the 
lost  molar  motion  appears  as  that  of  the  molecular 
motion,  or  motion  of  the  smallest  particles  of  a  body, 
which  constitutes  heat.  The  loss  of  the  masses  is  the 
gain  of  their  particles."  * 

*  T.  H.  Huxley,  Essay  on  "  The  Progress  of  Science"  (1887), 
in  Method  and  Results,  1894,  pp.  85-86. 


THE  PROGRESS  OF  PHYSICS. 

While  we  have  given  the  foremost  place  to  Joule 
in  connection  with  the  doctrine  of  energy,  we  must 
also  recognise  the  genius  of  Helmholtz,  as  expressed 
in  his  work  on  Die  Erhaltung  der  Kraft  (the  persis- 
tence of  force),  published  in  1847,  in  which  he 
showed  that  this  great  conclusion  follows  from  New- 
ton's second  interpretation  of  the  third  law  of  motion, 
if  we  make  the  postulate  (sufficiently  justified  exper- 
imentally) of  the  impossibility  of  "  perpetual  motion." 

STTMMABY. — "In  his  determination  of  the  me- 
chanical equivalent  of  heat,  James  Prescott  Joule 
gave  to  the  world  of  science  the  results  of  experiments 
which  placed  beyond  reach  of  doubt  or  cavil  the 
greatest  and  most  far-reaching  scientific  principle  of 
modern  times,  namely,  that  of  the  conservation  of 


energy." 


HEAT  AS  A  MODE  OF  ACTION. 


Old  Theory  of  Heat  as  a  Kind  of  Matter. — The 
theory  that  heat  is  a  subtle  kind  of  matter  was  sug- 
gested by  some  of  the  Greek  philosophers,  and  it  was 
a  dominant  theory  in  the  eighteenth  century.  In 
the  interpretation  of  combustion  defended  by  Stahl 
(1660-1734)  a  burning  body  was  supposed  to  give 
off  a  substance  called  "  phlogiston."  Lavoisier  in- 
cluded heat  in  his  list  of  elements. 

Seventeenth  Century  Theories  of  Heat  as  a  Mode 
of  Motion. — A  more  remarkable  fact,  however,  is 
that  in  the  seventeenth  century  the  modern  view  was, 
to  say  the  least,  clearly  hinted  at.  As  Cajori  notes 
in  his  History  of  Physics,  "  We  are  surprised  to 
find  that  Newton's  immediate  predecessors  had  antici- 
pated our  modern  theory  of  heat.  Heat  a  Mode  of 

*  Sir  Henry  Roscoe,  Pres.  Address,  Rep.  Brit.  Ass..  1887, 
p.  4. 


142    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

Motion  is  the  title  of  Tyndall's  well-known  work 
(1862),  yet  Descartes,  Amontons,  Boyle,  Francis 
Bacon,  Hooke,  and  Newton  already  looked  upon  heat 
as  a  mode  of  motion.  Of  course,  in  the  seventeenth 
century,  this  theory  rested  upon  somewhat  slender 
experimental  evidence,  else  the  doctrine  could  hardly 
have  been  cast  to  the  winds  by  the  eighteenth  cen- 
tury philosophers." 

The  Fiction  of  Imponderable  Matter. — Even  in 
the  eighteenth  century,  it  could  not  but  be  noticed, 
when  the  habit  of  weighing  began,  that  a  body  which 
had  been  heated  was  no  heavier  than  it  was  before. 
Therefore  a  fiction  had  to  be  invented, — the  well- 
known  fiction  of  the  "  imponderables."  Heat,  or 
rather  "  caloric,"  was  a  substance,  but  it  was  an  im- 
ponderable substance.  The  further  difficulty  that 
heat  may  be  produced  in  abundance  apart  from  all 
fire  or  combustion, — even  by  rubbing  two  pieces  of  ice 
together, — and  that  it  may  in  other  cases  disappear 
beyond  trace,  seems  to  the  modern  outlook  quite  fatal 
to  the  material  theory  of  heat,  but  the  difficulty  does 
not  appear  to  have  oppressed  the  natural  philoso- 
phers of  the  eighteenth  century.  It  must  be  recalled 
that  the  doctrine  of  the  indestructibility  of  matter 
dates  from  Lavoisier  and  that  it  was  not  fully  ap- 
preciated till  much  later.  With  this  and  the  doctrine 
of  the  conservation  of  energy  now  clearly  before  us, 
the  materiality  of  heat  seems  like  a  contradiction  in 
terms,  but  this  is  to  be  wise  after  the  event. 

Let  us  therefore  consider  how  the  old  Newtonian 
idea  was  re-habilitated,  how  it  has  come  to  be  an 
elementary  fact  in  physics  that  heat  depends  upon 
motion  of  the  particles  of  a  body,  and  is  a  form  of 
energy,  not  a  kind  of  matter. 

Rumford's  Experiments. — The  first  strong  blow 


THE  PROGRESS  OF  PHYSICS.  143 

which  the  caloric  theory  received  was  dealt  it  by  Ben- 
jamin Thompson,  better  known  as  Count  Rumford, 
who  published  his  observations  on  the  boring  of  can- 
non at  Munich  in  1798.  Surprised  at  the  amount  of 
heat  given  off  in  the  operation,  he  determined  to 
measure  this  by  its  effect  in  raising  the  temperature 
of  surrounding  water.  "At  the  end  of  two  hours 
and  thirty  minutes  the  water  actually  boiled !  "  and 
Count  Rumford  argued :  "  It  is  hardly  necessary  to 
add  that  anything  which  an  insulated  body,  or  system 
of  bodies,  can  continue  to  furnish  without  limitation, 
cannot  possibly  be  a  material  substance,  and  it  ap- 
pears to  me  to  be  extremely  difficult,  if  not  impossible 
to  form  any  distinct  idea  of  anything  capable  of  being 
excited  and  communicated  in  the  manner  in  which 
heat  was  excited  and  communicated  in  these  experi- 
ments, except  it  be  motion" 

The  supporters  of  the  idea  that  heat  is  a  material 
substance  argued  that  the  production  of  heat  by  fric- 
tion or  abrasion  was  due  to  the  fact  that  the  fragmen- 
tation of  the  body  diminished  its  capacity  for  holding 
caloric;  and  if,  as  Prof.  Tait  points  out,  Rumford 
had  seen  his  way  to  a  satisfactory  experiment  which 
would  have  tested  the  capacity  for  heat  of  the  abraded 
metal  and  of  the  metal  before  abrasion,  then  the  fact 
that  heat  is  not  matter  would  have  been  established. 
But  the  essential  experiment — most  readily  a  chem- 
ical one — did  not  suggest  itself,  and  this  is  in  part  the 
reason  why  Rumford's  experiments  published  in  1798 
were  but  little  noticed  until  about  1840. 

Rumford's  argument  was  on  the  main  line  of  prog- 
ress, but  his  measurement  of  the  heat  evolved  by  fric- 
tion was  rough,  and  he  was  unable  to  make  a  definite 
comparison  between  the  energy  expended  and  the 
work  done  anfl  the  heat  dissipated. 


144    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

Davy's  Contribution. — A  more  delicate  experiment 
was  devised  in  IT 9 9  by  Sir  Humphry  Davy,  who  ar- 
ranged a  clockwork  for  rubbing  two  pieces  of  ice 
against  one  another  in  the  vacuum  of  an  air-pump, 
and  observed  that  part  of  the  ice  was  melted,  although 
the  temperature  of  the  receiver  was  kept  below  the 
freezing  point.  From  this  he  concluded  somewhat 
diffidently  that  friction  causes  vibration  of  the  par- 
ticles, which  is  heat ; — a  conclusion  which  he  strength- 
ened in  1812  in  the  statement  that  "  the  immediate 
cause  of  the  phenomenon  of  heat  is  motion  and  the 
laws  of  its  communication  are  precisely  the  same  as 
the  laws  of  the  communication  of  motion."  Thomas 
Young  was  another  of  the  early  supporters  of  Count 
Rumford's  view. 

Work  of  Carnot. — Meanwhile  important  progress 
was  made,  by  Dulong  and  Petit  (1815),  Haugergues 
(1822),  and  others,  on  the  measurement  of  temper- 
atures by  means  of  thermometers;  by  Faraday  and 
others  on  the  liquefaction  of  gases,  and  on  many  other 
subjects  associated  with  heat :  but  the  next  important 
step  in  general  theory  was  made  by  Sadi  Carnot 
(1796-1832),  who,  in  1824,  published  his  estimate 
of  the  amount  of  work  that  can  be  got  from  a  steam- 
engine,  and  introduced  the  fruitful  idea  of  a  revers- 
ible cycle  of  operations.  But  this  was  hardly  known 
until  Sir  William  Thomson  called  attention  to  it  in 
1848. 

"  Without  this  work  of  Carnot's,  the  modern  theory 
of  energy,  and  especially  the  dynamical  theory  of 
heat,  could  never  have  attained  in  so  few  years  its 
now  enormous  development."  * 

"  The  two  grand  things  which  Carnot  introduced, 
which  were  entirely  originated  by  him,  and  which  left 
*  Prof .  P.  G.  Tait's  Recent  Advances  (1876),  p.  95. 


THE  PROGRESS  OF  PHYSICS.  145 

him  in  an  almost  perfect  form,  were  the  idea  of  a 
Cycle  of  Operations  and  the  further  idea  of  a  Re- 
versible Cycle.  In  order  to  reason  upon  the  working 
of  a  heat-engine  (suppose  it  for  simplicity  a  steam- 
engine)  you  must  imagine  a  set  of  operations,  such 
that  at  the  end  of  the  series  you  bring  the  steam  or 
water  back  to  the  exact  state  in  which  you  had  it  at 
starting.  That  is  what  Carnot  calls  a  cycle  of  opera- 
tions, and  of  it  Carnot  says,  then,  and  only  then,  i.e., 
at  the  conclusion  of  the  cycle,  are  you  entitled  to 
reason  upon  the  relation  between  the  work  which  you 
have  acquired,  and  the  heat  which  you  have  spent 
in  acquiring  it."  * 

"  The  other  grand  point  with  reference  to  Carnot 
is  this,  that  he  started  the  notion  of  a  Reversible  En- 
gine,— reversible  not  in  the  ordinary  technical  sense 
of  working  its  parts  backwards,  not  in  the  mere 
sense  of  backing,  but  reversible  in  the  sense  that, 
instead  of  using  heat  and  getting  work  from  it, 
you  can  drive  your  engine  through  your  cycle  the 
other  way  round,  and  by  taking  in  work,  pump  back 
heat  (as  it  were)  from  the  condenser  to  the  boiler 
again — a  reversing  of  the  whole  process, — not  a  mere 
reversing  of  the  direction  in  which  the  engine  is 
driving.  Now,  Carnot  introduced  that  notion,  and 
he  showed  by  perfectly  conclusive  reasoning  that  if 
you  can  obtain  a  reversible  engine,  it  is  the  perfect 
engine;  i.e.,  that  it  is  impossible  to  get  an  engine 
more  perfect  than  a  reversible  one."  f 

Although  he  began  with  a  firm  belief  in  the  caloric 
theory,  Carnot  ended  to  all  intents  and  purposes  as 
an  adherent  to  the  modern  dynamical  view,  and  that 
he  had  grasped  the  principle  of  conservation  is  evi- 
dent from  his  conclusion :  "  Motive  power  is  in 
*  P.  G.  Tait,  loc.  cit.,  p.  97.  t  P.  G.  Tait,  loc.  cit.,  p.  98. 


14:6    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

quantity  invariable  in  nature;  it  is,  correctly  speak- 
ing, never  either  produced  or  destroyed." 

Joule  and  Colding. — Prof.  Tait  notes  that  one 
small  chemical  experiment  would  have  enabled  Rum- 
ford  in  1798  to  prove  that  heat  is  not  matter,  just  as 
a  little  more  conclusive  reasoning  would  have  brought 
Davy  in  1799  securely  to  the  same  conclusion, — 
which  he  eventually  deduced  in  1812. 

What  Seguin  and  Mayer  approached,  but,  by  de- 
parting from  the  scientific  method,  failed  to  attain, 
was  achieved  by  Colding  of  Copenhagen  and  Joule 
of  Manchester,  "  the  true  modern  originators  and  ex- 
perimental demonstrators  of  the  conservation  of 
energy  in  its  generality."  * 

To  Joule  in  particular,  for  his  experiments  were 
more  extensive,  his  measurements  more  exact,  his  con- 
clusions more  generalised  than  those  of  Colding,  we 
owe  a  difficult  proof  of  what  Rumford  and  Davy  had 
foreseen — the  First  Law  of  Thermodynamics.  In 
Tait's.  statement  this  reads :  "  When  equal  quantities 
of  mechanical  effect  are  produced  by  any  means  what- 
ever, from  purely  thermal  sources,  or  lost  in  pure 
thermal  effects,  then  equal  quantities  of  heat  are  put 
out  of  existence  or  are  generated ;  and  for  every  unit 
of  heat  measured  by  the  raising  of  a  pound  of  water 
1  degree  Fahrenheit  in  temperature,  you  have  to  ex- 
pend 772  foot-pounds  of  work."  f 

SUMMARY. — The  idea  that  heat  is  not  material  but 
a  mode  of  motion,  a  form  of  energy,  is  older  even  than 
Newton  s  Principia,  yet  the  foundation  of  the  theory 
may  be  fairly  dated  from  the  experiments  of  Joule. 
But  many  others  contributed  to  the  great  conclusion, 
and  still  more  have  furthered  its  development  and  ap- 
plication. 
*  Tait,  op  cit.,  p.  567.  t  Approximately. 


THE  PROGRESS  OF  PHYSICS.  147 


KINETIC  THEORY  OF  GASES. 

We  have  had  occasion  to  refer  to  this  important 
theory  in  the  chapter  on  Chemistry ;  it  will  be  enough 
to  recall  two  or  three  of  the  steps  in  its  develop- 
ment. 

Diffusion. — Every  one  is  aware  of  the  rapidity 
with  which  an  escape  of  coal-gas  makes  itself  felt 
through  a  house.  Dalton  theorised  this  in  his  sug- 
gestion that  a  gas  consists  of  particles  which  are 
constantly  flying  about  in  all  directions,  spreading  as 
far  as  they  can,  and  inter-penetrating  another  gas, 
or  mixture  of  gases  in  the  case  of  air,  until  equilib- 
rium of  pressure  is  attained. 

A  more  precise  study  of  the  movements  of  gaseous 
particles  was  subsequently  undertaken  by  Graham, 
who  showed  that  the  relative  rates  of  diffusion  of  two 
gases  are  inversely  proportional  to  the  square  roots 
of  their  densities.  Thus  hydrogen  diffuses  four  times 
more  quickly  than  oxygen. 

Joule's  Calculation  of  Velocity  of  Particles. — In 
1848  and  1857,  Joule  took  another  stride  forward  in 
determining  the  mean  translational  velocity  of  the 
particles,  basing  his  calculations  on  the  conclusion 
that  the  pressure  of  a  gas  is  proportional  to  the  energy 
of  motion  of  its  particles.  "  Thus  it  may  be  shown 
that  the  particles  of  hydrogen  at  the  barometrical 
pressure  of  30  inches,  at  a  temperature  of  60°,  must 
move  with  a  velocity  of  6225.54  feet  per  second  in 
order  to  produce  a  pressure  of  14.714  Ibs.  on  the 
square  inch."  In  other  words,  as  Sir  Henry  Roscoe 
expresses  it,  a  molecular  cannonade  or  hailstorm  of 
particles  is  maintained  against  the  bounding  surface 
at  a  rate  far  exceeding  that  of  a  cannon  ball. 


14:8    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

It  seems  that  the  clearness  of  the  Newtonian  view 
of  the  movements  of  the  heavenly  bodies  often  sug- 
gested to  chemists  and  others  who  thought  about 
atoms  and  molecules,  that  these  might  be  bound  to- 
gether in  a  manner  comparable  to  a  planetary  system. 
But  the  behaviour  of  gases  and  the  phenomena  of 
heat  (so  long  regarded  as  a  substance)  made  it  nec- 
essary to  suppose  that  forces  of  repulsion  as  well  as 
attraction  existed  between  particles.  Gradually  the 
intrusion  of  what  Merz  calls  "  the  astronomical 
view  of  nature  "  to  support  the  incipient  "  atomic 
view  of  matter  "  was  found  unavailing.  The  atomic 
view  passed  from  its  static  to  its  kinetic  phase,  and 
we  may  particularly  associate  this  important  step 
with  the  names  of  Joule,  Clausius,  and  Clerk  Max- 
well. 

Although  Bernouilli  (1738),  Herapath,  Waterston 
and  many  others  must  find  their  recognition  in 
learned  histories,  it  was  Joule  who  first  gave  precise 
expression  to  the  theory  that  all  particles  of  gases  may 
be  thought  of  as  being  in  a  natural  state  of  rectilinear 
motion,  changed  only  by  their  mutual  encounters,  or 
by  their  impinging  on  containing  barriers.  It  was 
soon  after  the  half -century  (published  1857)  that 
Joule,  as  we  have  noted,  calculated  the  velocity  of  a 
particle  of  hydrogen  at  ordinary  atmospheric  press- 
ure and  temperature.  The  calculation  presupposed 
the  previous  discovery  by  Eumford,  Davy,  Mayer, 
and  Joule  that  heat  is  not  a  substance  but  a  mode 
of  motion,  and  the  experimental  proof  by  Joule  and 
Thomson  (1853)  that  in  a  gas  allowed  to  expand 
without  doing  work  there  is  a  very  slight  cooling, 
due  to  the  energy  used  up  in  overcoming  the  attract- 
ing forces  of  cohesion. 

The  general  argument  is  simply  that  if  heat  can 


THE  PROGRESS  OF  PHYSICS.  149 

be  transformed  into  the  energy  of  measurable  motion 
of  measurably  large  or  molar  masses,  heat  may  it- 
self be  "  the  energy  of  the  directly  immeasurable 
movements  of  molecular  (immeasurably  small) 
masses." 

Developments. — "By  applying  calculations  simi- 
lar to  those  of  Joule,  but  considerably  extended  by 
the  use  of  more  powerful  mathematical  methods,  such 
as  the  methods  of  the  theory  of  probabilities,  Clausius 
first,  and,  a  little  later,  but  far  more  profoundly, 
Clerk  Maxwell,  and  still  more  recently  Boltzmann, 
have  arrived  at  very  valuable  results  as  to  the  motions 
of  swarms  of  impinging  particles.  One  of  the  results 
arrived  at  is  that  in  a  mass  of  hydrogen  at  ordinary 
temperature  and  pressure,  every  particle  has  on  an 
average  17,700,000,000  collisions  per  second  with 
other  particles ;  that  is  to  say,  17,700,000,000  times 
in  every  second  it  has  its  course  wholly  changed. 
And  yet  the  particles  are  moving  at  a  rate  of  some- 
thing like  70  miles  per  minute.  So  comes  this 
curious  problem — given  that  the  direction  of  motion 
of  a  particle  is  arbitrarily  changed  17,700,000,000 
times  in  every  second,  and  that  the  particle  itself  is 
moving  70  miles  in  a  minute,  where  would  it  be  at 
the  end  of  a  single  minute,  having  started  from  any 
given  place?  .  .  .  The  solution  obtained  is  capable 
of  explaining  almost  everything  that  we  know  with 
reference  to  the  behaviour  of  gases,  and  perhaps 
even  of  vapours."  * 

SUMMAEY. — The  kinetic  theory  of  gases,  the 
brilliant  generalisation  which  harmonised  the  nu- 
merous facts — specific  heat,  diffusion,  friction , 
etc., — known  in  regard  to  the  behaviour  of  bodies  in 
a  gaseous  state,  may  be  regarded  as  a  corollary  of  the 
*  Tail's  Recent  Advances,  1876,  pp.  324-5. 


150    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

dynamical  theory  of  heat.  "  The  fundamental  idea 
that  a  gas  was  an  assemblage  of  moving  particles  had 
been  put  forward  by  D.  Bernouilli  and  by  Herepath, 
and  Joule  had  in  1851  made  a  great  step  in  advance 
by  calculating  the  mean  translational  velocity  of 
these  particles. . .  This  idea,  in  the  hands  of  Kronig 
and  Clausius,  gave  birth  to  the  modern  kinetic  theory 
of  gases,  which  has  been  so  splendidly  worked  out 
by  Clausius  and  Maxwell,  and  since  then  perfected 
in  detail  by  Boltzmann,  0.  E.  Meyer,  Van  der  Waatej 
and  many  others."  * 

UNDULATORY  THEORY  OF  LIGHT. 

The  Emission  Theory. — Throughout  the  eigh- 
teenth century  the  corpuscular  or  emission  theory  of 
light  was  almost  universally  accepted  by  physicists. 
The  theory  was  that  all  luminous  bodies  emit  with 
equal  velocities  inconceivably  minute  elastic  corpus- 
cles which  travel  at  great  speed  in  straight  lines  in  all 
directions. 

The  Modern  View. — Nowadays,  however,  it  is  the 
unanimous  view  of  those  who  are  familiar  with  the 
facts  that  light  is  not  a  material  substance,  but  a 
form  of  energy,  or  a  mode  of  motion,  in  fact  the  re- 
sult of  ethereal  waves.  When  a  body  gives  forth 
light,  we  no  longer  suppose  that  it  emits  corpuscles, 
as  a  grain  of  musk  does  into  the  air ;  we  believe  that 
it  sets  agoing  undulatory  movements  in  the  ether. 
We  believe  furthermore  that  the  phenomena  of  light 
are  essentially  of  the  same  nature  as  those  of  electro- 
magnetic radiation.  The  contrast  of  the  theories  in 
the  two  centuries  is  characteristic,  and  it  is  interest- 
ing to  enquire  how  the  modern  view  was  developed. 

*  E.  von  Meyer,  History  of  Chemistry,  trans.  1891,  p.  414. 


THE  PROGRESS  OF  PHYSICS.  151 

"While  the  corpuscular  theory  served  to  interpret  a 
number  of  the  phenomena  of  light,  it  failed  more  or 
less  markedly  in  regard  to  others — for  instance,  the 
reflection  which  accompanies  refraction,  the  unequal 
refrangibility  of  the  different  colours  of  the  spec- 
trum, double  refraction,  and  so  on.  The  result  was 
that  subsidiary  hypotheses  had  to  be  invented  to  cover 
the  defects  of  the  main  assumption.  Eventually 
it  became  necessary  to  discard  the  main  assumption 
altogether. 

Newton's  Position. — The  central  idea  of  the  un- 
dulatory  theory  was  suggested  by  Hooke  and  others, 
and  was  formulated  as  early  as  1678  by  Huygens, 
who  interpreted  double  refraction,  but  its  establish- 
ment was  due  to  the  work  of  Thomas  Young  and 
Fresnel.  Although  Descartes  had  suggested  that 
light  is  produced  by  waves  excited  in  the  subtle  mat- 
ter which  pervades  the  universe  (analogous  to  but 
different  from  the  non-atomic  ether  of  to-day),  and 
had  also  ventured  the  suggestion  that  the  mechanism 
of  light  and  that  of  gravitation  are  inseparable,  and 
although  Hooke  had  made  the  important  suggestion 
of  substituting  for  the  progressive  wave  of  Descartes 
a  vibrating  one,  we  find  Xewton  weighing  the  merits 
of  the  wave-theory  and  the  emission-theory,  finding 
both  unsatisfactory  and  deliberately  refraining  from 
accepting  either.  Apart  from  his  "  theory  of  fits," — 
in  which  he  states  that  the  phenomena  of  thin  plates 
prove  that  the  luminous  ray  is  put  alternately  in  a 
certain  state  or  fit  of  easy  reflection  and  of  easy 
transmission — he  abstains  from  taking  up  a  definite 
position,  though  "  he  shall  sometimes,  to  avoid  cir- 
cumlocution and  to  represent  it  conveniently,  speak 
of  it  (the  emission)  as  if  he  assumed  it  and  pro- 
pounded it  to  be  believed."  It  does  not  seem  to  be 


152    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

historically  justifiable  to  regard  Newton  as  the 
founder  or  even  upholder  of  the  emission-theory.* 

The  ray  of  light,  on  the  emission-theory,  was  sim- 
ply the  trajectory  of  a  particle  in  rectilinear  motion; 
the  ray  of  light,  as  Newton  described  it,  possesses  a 
regular  periodic  structure,  and  the  period  or  interval 
of  fits  characterises  the  colour  of  the  ray.  This  was 
an  important  result.  It  only  required  a  fitter  inter- 
pretation to  transform  the  luminous  ray  into  a 
vibratory  wave,  but  for  this  there  was  a  century  to 
wait,  and  Dr.  Thomas  Young,  in  1801,  had  the 
honour  of  discovering  it.f 

The  Wave-Theory  of  Young. — Thomas  Young 
(1773-1829),  whose  precocious  genius,  persisting  in 
manhood,  remained,  as  Tyndall  says,  "  hidden  from 
the  appreciative  intellect  of  his  countrymen,"  was  led 
from  a  study  of  the  eye  and  its  optical  properties,  to 
an  enquiry  into  the  phenomena  of  thin  plates  and 
"  interference,"  and  in  the  course  of  this  he  rehabili- 
tated the  undulatory  theory  (1801),  published  in  the 
Philosophical  Transactions  for  1802. 

The  theory  is,  in  general  terms,  that  light  consists 
of  vibrations  in  an  all-pervading  elastic  ether,  and 
that  the  vibrations,  unlike  those  of  sound,  are  in  di- 
rections at  right  angles  to  the  direction  of  propaga- 
tion. So  far  as  Young  went,  the  theory  was,  in 
simple  language,  that  a  homogeneous  ray  of  light  is 
analogous  to  the  wave  produced  by  a  musical  sound, 
and  that  the  vibrations  of  light  ought  to  compose  or 
interfere,  like  those  of  sound.  "  But  his  hypothesis 
found  no  favour;  his  principle  of  interference  led 

*  A.  Cornu,  The  Rede  Lecture:  "The  Wave  Theory  of 
Light:  its  influence  on  Modern  Physics,"  Nature,  July  27, 
1899,  pp.  292-297. 

t  From  Prof.  Cornu's  Rede  Lecture. 


THE  PROGRESS  OF  PHYSICS.  153 

to  this  singular  result  that  light  added  to  light  could, 
in  certain  cases,  produce  darkness,  a  paradoxical  re- 
sult contradicted  by  daily  experience." 

In  spite  of  Young's  step,  the  emission-theory  still 
held  the  field,  and  new  facts,  such  as  the  phenomenon 
of  polarisation  discovered  by  Malus,  lent  support  to 
it  rather  than  to  its  rival. 

Fresnel's  Experiments. — In  1816,  however,  a 
young  engineer,  Augustin  Fresnel  (1788-1827),  re- 
discovered the  principle  of  interference,  applied 
mathematical  analysis  to  the  vindication  of  the  un- 
dulatory  theory,  and  devised  the  famous  two-mirror 
experiment,  by  which  it  was  shown  that  "  two  rays, 
issuing  from  the  same  source,  free  from  any  disturb- 
ance, produced  when  they  met,  sometimes  light,  some- 
times darkness."  Moreover  Fresnel  showed  that 
"  light  is  propagated  in  straight  lines  because  the 
luminous  waves  are  extremely  small,  while  sound  is 
diffused  because  the  lengths  of  the  sonorous  waves 
are  relatively  very  great,"  and  that  "  the  sound 
wave  cannot  be  polarised  because  the  vibrations  are 
longitudinal,  while  light  can  be  polarised  because  the 
vibrations  are  transverse,  that  is  to  say,  perpendicular 
to  the  luminous  ray."  "  Henceforth  the  nature  of 
light  is  completely  established,  all  the  phenomena 
presented  as  objections  to  the  undulatory  theory  are 
explained  with  marvellous  facility,  even  down  to  the 
smallest  details."  f 

To  Fresnel  and  to  Arago,  Young  "  was  first  in- 
debted for  the  restitution  of  his  rights,"  and  it  is 
pleasant  to  notice  the  entire  absence  of  any  discussion 
as  to  priority.  But  the  complete  acceptance  of  the  un- 
dulatory theory  was  still  distant.  There  followed  a 

*  Cornu,  loc.  cit.,  p.  295. 
t  Quotations  from  Cornu. 


154    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

period  in  which  it  had  still  to  struggle  for  existence, 
when  it  had  to  justify  itself  in  application  to  the 
phenomena  of  shadows,  double  refraction,  polarisa- 
tion, colour,  interference,  diffraction  and  so  on. 

With  Young,  Fresnel,  Arago,  and  others  on  the 
winning  side,  with  Laplace,  Biot,  and  Brewster  and 
others  championing  the  older  doctrine,  a  keen,  some- 
times painfully  bitter,  struggle  of  opinions  continued 
till  the  century  had  run  more  than  a  quarter  of  its 
course. 

Joule. — It  should  not  be  forgotten  that  Joule,  who 
contributed  so  much  to  the  foundation  of  the  dy- 
namical theory  of  heat  and  the  kinetic  theory  of 
gases,  and  founded  the  general  doctrine  of  the  con- 
servation of  energy,  also  made  an  important  experi- 
ment (1843)  bearing  on  the  theory  of  Light.  "He 
compared  the  heat  evolved  in  the  wire  conducting  a 
galvanic  current,  when  the  wire  was  ignited  by  the 
passage  of  the  current,  with  that  evolved  when  (with 
an  equal  current,  suppose)  it  was  kept  cool  by  immer- 
sion in  water.  These  experiments  showed  a  small, 
but  unmistakable,  diminution  of  the  heat  when  light 
also  was  given  out."  * 

Foucault. — It  was  not,  however,  till  1850  that  an- 
other crucial  experiment  in  favour  of  the  undulatory 
theory  was  announced  by  Foucault  (1819-1868). 
According  to  the  emission-theory  the  velocity  of 
light  should  be  greater  in  an  optically  denser  me- 
dium ;  according  to  the  undulatory  theory  the  reverse 
should  be  true.  By  an  ingenious  and  now  familiar 
device,  Foucault,  the  inventor  of  the  gyroscope  and 
the  demonstrator  of  the  Earth's  rotation  by  pendulum 
experiments,  gave  the  death-blow  to  the  Newtonian 

*  Tait,     Recent  Advances,  187G,  p.  64. 


THE  PROGRESS  OF  PHYSICS.  155 

theory  by  proving  that  the  velocity  of  light  in  water 
is  less  than  that  in  air. 

Fizeau. — The  determination  of  the  velocity  of 
light,  -which  thus  became  of  importance  in  relation  to 
the  general  theory,  had  been  previously  based,  e.g.,  by 
Romer  and  Bradley,  on  astronomical  data,  derived 
from  aberration-observations,  or  from  timing  the 
eclipses  of  Jupiter's  satellites  when  at  their  greatest 
and  least  distances  from  the  Earth,  but  a  direct  ex- 
perimental method  was  devised  by  Fizeau  (1819- 
1896).  In  1849,  in  the  suburbs  of  Paris,  he  ar- 
ranged a  rapidly  rotating  cog-wheel  which  inter- 
cepted light  at  regular  intervals,  and  found  what 
speed  must  be  given  to  the  wheel  so  that  it  rotated 
one  tooth's  breadth  while  the  light  travelled  to  a 
distant  mirror  and  was  reflected  back  again.  Fou- 
cault  modified  this  method  by  observing  "  the  posi- 
tion ultimately  assumed  by  a  ray  which  travels 
from  a  source  to  a  rotating  mirror,  thence  to  a  dis- 
tant mirror,  and  thence  back  to  the  original  mirror, 
which  by  this  time  has  been  rotated  somewhat."  * 
The  determination  of  the  velocity  of  light  thus 
effected  by  Fizeau  and  Foucault  was  revised  by 
Cornu  in  Paris,  by  James  Young  and  George  Forbes 
in  Britain,  but  the  most  accurate  determinations 
are  said  to  be  those  made  by  Michelson,  Xewcomb, 
and  Holcombe,  in  the  United  States.  A  mean  result 
is  that  light  travels  in  vacuo  at  the  rate  of  186,772 
miles  per  second,  and  in  air  at  a  velocity  less  than 
this  in  the  ratio  of  10,000  to  10,003. 

As  Professor  Alfred  Cornu  points  out  in  his  Rede 
lecture,  to  which  we  have  already  been  much  in- 
debted in  this  section,  the  emission  theory  was  a 
natural  but  primitive  one,  with  its  germ  in  the  ex- 

*  Article  Light,  by  Dr.  Daniell.    Chaiui^r*' 


156     PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

perience  of  throwing  a  stone  or  shooting  an  arrow 
into  "  empty  space."  The  undulatory  theory  is 
subtler,  space  is  filled  with  a  continuous  elastic 
medium,  in  which  particles — no  longer  projectiles — 
were  supposed  to  oscillate  in  the  direction  of  propa- 
gation, like  the  particles  of  water  in  the  ripples  on 
a  pond.  But  this  conception  was  insufficient  and 
gave  place  to  Fresnel's  idea  of  waves  of  transverse 
vibrations  excited  in  an  incompressible  continuous 
medium. 

Electro-magnetic  Theory  of  Light. — The  necessity 
of  admitting  the  existence  of  this  medium  was  made 
clearer  by  Faraday,  and  corroborated  by  his  dis- 
covery of  induction,  and  Clerk  Maxwell  in  his  foot- 
steps ventured  to  forecast,  on  theoretical  grounds, 
that  light  and  electro-magnetic  radiation  are  alike 
due  to  rhythmical  disturbances  in  the  ether,  differ- 
ing only  in  their  wave-lengths — one  of  the  most  uni- 
fying ideas  in  modern  science. 

Experiments  of  Hertz. — "  But  the  abstract  the- 
ories of  natural  phenomena  are  nothing  without  the 
control  of  experiment.  The  theory  of  Maxwell  was 
submitted  to  proof,  and  the  success  surpassed  all 
expectation.  ...  A  young  German  physicist, 
Heinrich  Hertz,  prematurely  lost  to  science,  starting 
from  the  beautiful  analysis  of  oscillatory  discharges 
by  Von  Helmholtz  and  Lord  Kelvin,  so  perfectly 
produced  electric  and  electro-magnetic  waves,  that 
these  waves  possess  all  the  properties  of  luminous 
waves;  the  only  distinguishing  peculiarity  is  that 
their  vibrations  are  less  rapid  than  those  of  light. 
It  follows  that  one  can  reproduce  with  electric  dis- 
charges the  most  delicate  experiments  of  modern 
optics — reflection,  refraction,  diffraction,  rectilinear, 
circular,  elliptic  polarisation,  etc." 

*  Cornu.    Rede  Lecture.    Loc.  cit. ,  p.  200, 


THE  PROGRESS  OF  PHYSICa  157 

We  owe  to  Clerk  Maxwell,  and  to  Hertz,  for 
experimental  corroboration,  the  image  of  a  plane 
wave  of  light  as  a  propagation  of  an  ethereal  dis- 
turbance, in  which  there  is  electric  and,  at  the  same 
time,  magnetic  intensity,  varying  as  a  simple  har- 
monic function  of  the  time.  In  what  may  seem  to 
be  plainer  words,  we  regard  light  as  an  electric  phe- 
nomenon, and  the  term  electric  light  as  a  tautology. 

Invisible  Light. — From  what  has  been  said  it  may 
be  inferred  that  light  has  many  forms,  and  that  it 
is  not  necessarily  visible.  Even  in  sunlight  there 
are  components  which  are  not  visible  to  our  eyes. 

One  of  the  most  recent  additions  (1896)  is  that 
of  an  invisible  radiation  which  Becquerel  discovered 
to  be  emitted  by  many  fluorescent  substances  and 
especially  by  Uranium  salts.  The  radiation  can  be 
polarised  and  by  means  of  it  (as  by  the  Rontgen 
rays)  photographs  can  be  obtained  through  opaque 
bodies.  Moreover,  like  the  Rontgen  rays,  the  Ura- 
nium-radiation causes  an  electrified  body  to  lose  its 
charge,  whether  positive  or  negative.* 

SUIIMAKT. — By  Young  and  Fresnel,  Fizeau  and 
Foucault  and  by  others  the  emission  theory  of  light 
was  replaced  by  the  undulatory  theory.  Light  was 
interpreted  in  terms  of  ethereal  waves,  and  Clerk 
Maxwell  and  Hertz  subsequently  showed  that  it  was 
essentially  similar  to  electro-magnetic  radiations. 

THEOBT  OF  EiZCTEICITT. 

Beginnings. — In  the  last  quarter  of  the  eighteenth 
century,  the  Italian  Galvani — whose  name  has  given 
our  language  several  new  words — had  discovered 

*  See  J.  J.  Thomson.  Address  Section  A,  Rep.  Brit.  Asi. 
for  1896,  p.  703. 


158    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

that  electrical  changes  occurred  in  the  contracting 
muscle  of  the  frog's  leg ;  in  the  last  year  of  the  same 
century  Volta  of  Pavia  had  shown  that  electricity 
may  be  produced  by  the  simple  contact  of  two  metals ; 
but,  for  a  time,  little  resulted  from  the  discoveries 
of  either  of  these  pioneers.  Another  impulse  was 
necessary  before  the  wheels  of  progress  began  to  move, 
and  that  was  afforded  in  1819,  by  Oersted,  who 
brought  the  known  facts  of  electricity  into  touch 
with  those  of  magnetism,  and  initiated  the  movement 
which  has  made  the  word  electricity  almost  as  charac- 
teristic of  the  nineteenth  century  as  the  word  evolu- 
tion. 

Achievements. — Forestalling  the  rest  of  this  sec- 
tion, we  may  briefly  state  that  the  scientific  study  of 
electricity  initiated  by  Oersted  and  also  by  Ampere, 
was  profoundly  influenced  by  the  experimental 
genius  and  scientific  temper  of  Faraday,  found 
mathematical  or  precise  formulation  in  the  work  of 
Thomson  (Lord  Kelvin),  and  was  developed  into  a 
provisional  dynamical  theory  by  the  extraordinary 
insight  of  Clerk  Maxwell.  It  is  perhaps  not  too 
much  to  say  that  what  Newton  did  for  gravitational 
phenomena,  was  done  by  Clerk  Maxwell  for  electrical 
phenomena.  The  study  was  raised  by  him  and  his 
collaborateurs  from  the  observational  and  classi- 
ficatory  level  to  become  an  integral  part  of  a  unified 
Natural  Philosophy. 

Oersted. — Oersted  (1777-1851)  may  be  called 
the  founder  of  the  science  of  electro-magnetism 
because  he  succeeded  in  proving  experimentally 
(1819)  what  had  been  previously  surmised,  for  in- 
stance from  the  effect  of  lightning  on  compasses, — 
that  electrical  and  magnetical  phenomena  are  of  the 
eauie  nature.  In  his  famous  experiment  showing 


THE  PROGRESS  OF  PHYSICS.  159 

the  disturbance  of  the  magnetic  needle  by  the  influ- 
ence of  an  adjacent  electrical  current,  he  not  only 
made  a  step  of  great  theoretical  import,  but  pointed 
forward  (as  we  now  recognise)  to  the  invention  of 
the  telegraph. 

Oersted's  experiment  suggested  the  possibility  of 
measuring  the  strength  of  an  electric  current  by  its 
effect  upon  an  adj  acent  magnet,  and  this  led  Schweig- 
ger  in  1820  to  his  invention  of  the  galvanometer  or 
electrometer,  a  fundamental  instrument  in  electrical 
science.  As  the  history  of  galvanometers  alone  is 
a  long  one,  we  must  be  content  here  to  note  that  after 
modifications  by  Nobili  and  Pouillet  and  others, 
the  measuring  instrument  was  brought  to  great  per- 
fection by  Sir  William  Thomson  (Lord  Kelvin). 

Oersted  observed  the  influence  of  a  current  on  a 
magnet,  and  that  the  latter  always  tends  to  set  itself 
at  right  angles  to  the  direction  of  the  current,  but  a 
further  step  was  soon  taken  by  Ampere  (1775-1836), 
who  showed  (1820)  that  one  current  influences  an- 
other, parallel  currents  in  the  same  direction  being 
attracted,  those  in  opposite  directions  being  repelled 
by  each  other.  His  mathematical  theory  of  these 
phenomena  is  still  referred  to  as  a  masterpiece. 

Ohm. — To  Ohm  (1789-1854)  the  science  was 
greatly  indebted  for  the  precision  which  he  gave  to 
the  conceptions  of  electro-motive  force,  strength  of 
current,  electric  resistance  and  conductivity,  and  for 
the  law  (experimentally  established  in  1826,  mathe- 
matically worked  out  in  1827)  which  states  that 
the  resistance  of  a  conductor  can  be  measured  by  the 
ratio  of  the  electro-motive  force  between  its  two  ends 
to  the  current  flowing  through  it.  It  appears  that 
this  empirical  generalisation  had  been  reached  in 
1781  by  Cavendish,  but  practically  its  recognition 


160    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

must  date  from  Ohm's  work.  "  Since  his  day  it  has 
been  subjected  to  the  severest  experimental  tests  that 
the  scientific  mind  could  imagine,  and  has  stood  them 
all.  It  is  really  the  basis  of  our  whole  system  of 
electrical  measurements,  and  is  to  electric  currents 
what  the  law  of  gravitation  is  to  planetary  mo- 
tions." * 

The  instrumental  measurement  of  resistance  which 
Ohm  initiated  was  subsequently  brought  nearer  per- 
fection, especially  by  those  concerned  in  the  develop- 
ment of  telegraphy.  Thus  Charles  Wheatstone 
(1802-18T5)  invented  what  is  known  as  "  Wheat- 
stone's  bridge."  Here,  as  in  so  many  other  cases, 
practical  requirements  led  to  improvements  which 
stimulated  theoretical  science  and  gave  it  greater 
possibilities  of  precision. 

Faraday. — The  next  great  name  is  that  of  Michael 
Faraday  (1Y91-1867),  who  by  common  consent  is 
ranked  as  the  greatest  experimental  genius  of  the 
nineteenth  century  as  regards  electricity  and  magnet- 
ism. Among  his  numerous  achievements  three  must 
be  specially  mentioned. 

While  Oersted  had  shown  the  deflection  of  the  mag- 
netic needle  by  an  electric  current,  Faraday  suc- 
ceeded in  demonstrating  the  converse;  that  a  magnet 
reacts  upon  an  electric  current.  This  was  the  dis- 
covery of  magneto-electricity  (1831),  and  it  led  him 
on  to  another  of  no  less  importance,  that  of  induced 
currents  (1831), — that  a  wire  through  which  an 
electric  current  is  passing  may  induce  in  another 
adjacent  wire  a  state  similar  to  its  own.  With  Fara- 
day's discoveries  there  must  also  be  associated  the 
entirely  independent  but  synchronous  work  of  the 

*  Prof.  C.  G.  Knott.  Article,  Electricity,  Chambers'  Ency- 
clopaedia. 


THE  PROGRESS  OF  PHYSICS.  161 

American  Joseph  Henry  (1799-1878),  who  also 
detected  the  influence  of  magnetism  upon  electricity 
and  the  phenomenon  of  induction-currents. 

Another  of  Faraday's  achievements  has  already 
been  referred  to  in  the  chapter  on  chemistry, — the 
discovery  of  the  laws  of  electrolysis.  He  showed 
that  the  amount  of  water  decomposed  or  gas  set  free 
is  strictly  proportional  to  the  quantity  of  electricity 
passing  through,  and  that  equal  quantities  of  elec- 
tricity decompose  equivalent  amounts  of  different 
electrolytes. 

In  the  third  place  Faraday  thought  out  a  dy- 
namical theory  of  electricity,  which  replaced  the  old 
two-fluid  theory,  and  has  formed  the  foundation  on 
which  Kelvin,  llaxwell,  Helmholtz,  and  others  have 
reared  an  elaborate  superstructure.  While  Coulomb 
and  others  had  assumed  the  possibility  of  "  action  at 
a  distance,"  and  supposed  that  electric  charges  may 
influence  one  another  without  any  intervening  me- 
dium, Faraday's  ideas  were  distinctly  opposed  to  this 
view,  for  he  supposed  that  electric  attraction  and  re- 
pulsion were  propagated  by  molecular  agitations  in 
the  particles  of  the  insulating  media  which  he  termed 
"  dielectrics."  He  found  reason  to  believe  that  in- 
ductive influence  takes  effect  along  curved  lines 
("  lines  of  force  ")  and  by  the  action  of  adjacent  par- 
ticles in  the  insulating  medium.  As  the  intensity 
of  the  electric  influence  between  two  charged  bodies 
varies  with  the  nature  of  the  "  dielectric,"  he  was  led, 
as  Cavendish  had  been,  to  the  recognition  of  "  specific 
inductive  capacity  " — a  factor  of  fundamental  im- 
portance. As  Cajori  points  out,  Faraday's  theory 
gave  a  death-blow  both  to  the  old  fluid  theory  and  to 
the  assumption  of  action  at  a  distance. 

Uaxwdl. — What  Faraday  had  expressed  in  his 


162    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

symbolism  of  "  lines  of  force,"  was  re-expressed  and 
further  developed  in  the  sterner  language  of  mathe- 
matics by  James  Clerk  Maxwell  (1831-1879),  who 
was  also  led  to  conclude  on  theoretical  grounds  that 
electro-magnetic  phenomena  and  light  phenomena  are 
alike  due  to  waves  of  periodic  displacement  in  the 
same  medium  (the  hypothetical  ether),  and  are,  in 
fact,  identical  in  nature. 

Hertz. — What  Clerk  Maxwell  had  theoretically 
foreseen  was  experimentally  demonstrated  by  Hein- 
rich  Rudolf  Hertz  (1857-1894),  who  detected  tho 
electromagnetic  (electric  and  magnetic)  waves  radi- 
ating into  space  from  the  sparks  of  a  Ley  den  jar  or 
of  a  Holtz  machine,  separated  the  two  components, 
electric  and  magnetic,  and  succeeded  in  reflecting, 
refracting,  diffracting,  and  polarising  the  waves. 
"  The  object  of  these  experiments,"  he  says,  "  was 
to  test  the  fundamental  hypothesis  of  the  Faraday- 
Maxwell  theory,  and  the  result  of  the  experiments  is 
to  confirm  the  fundamental  hypotheses  of  the 
theory."  *  As  Hertz  fully  recognised,  Professors 
Oliver  Lodge  and  G.  F.  Fitzgerald  were  about  the 
same  time  within  sight  of  the  same  discovery  of  the 
electro-magnetic  waves  in  air. 

In  a  review  of  electrical  advance  in  recent 
years,  Mr.  Elihu  Thomson  notes  that  the  work 
of  Hertz  demonstrated  "  the  fact  that  light  of 
all  kinds  and  from  all  sources  is  really  an  electri- 
cal phenomenon,  differing  from  ordinary  alternate- 
current  waves  only  in  the  rate  of  frequency  of  vibra- 
tions. We  produce  electric  waves  of  about  one  hun- 
dred vibrations  per  second  for  alternating  current 
work ;  and  in  the  waves  of  red  light  the  rapidity  is  as 

*  Quoted  by  Cajori  from  Hertz's  Electric  Waves,  trans. 
Ly  Dr.  E.  Jones,  London,  1893. 


THE  PROGRESS  OF  PHYSICS.  163 

high  as  four  hundred  millions  of  millions  of  vibra- 
tions per  second.  Hertz  and  others  used  waves  of 
some  millions  per  second,  and  showed  how  they  could 
transmit  signals  to  distances  without  wires;  these 
invisible  waves  being  recognised  by  suitable  receivers. 
The  recently  announced  Marconi  wireless  telegraph 
is  much  the  same  thing,  with  certain  improvements  in 
detail."  * 

"  Hardly  had  the  work  of  Hertz  and  others  who 
followed  in  his  footsteps  been  assimilated,  before  the 
truly  remarkable,  not  to  say  astounding,  discovery 
by  Professor  Rb'ntgen  of  what  he  called  the  X-rays 
produced  a  profound  impression  not  only  in  the 
scientific  world,  but  upon  the  general  public  as  well. 
The  interest  of  the  scientist  had  a  different  basis 
from  the  popular  one  of  disclosure  of  objects  hidden 
in  opaque  structures;  for  he  saw  in  the  discovery 
a  new  weapon  of  attack  upon  the  secrets  of  nature. 
This  weapon  has  already  proved  to  be  so  serviceable 
as  to  show  that  his  anticipations  were  not  unfounded. 
The  X-rays,  which  became  at  once  indispensable  to 
surgery,  are  the  results  of  electrical  actions  in  certain 
vacuum  bulbs ;  and  the  discovery  is  properly  an  elec- 
trical one."  f 

X  and  other  Rays. — It  has  long  been  known  that 
remarkable  effects  are  produced  when  cathode  rays 
are  passed  through  a  highly  exhausted  vacuum  tube. 
The  glass  shows  bright  "  phosphorescence,"  shadows 
are  thrown  by  opaque  bodies,  and  the  rays  are  de- 
flected by  a  magnet.  Crookes  and  Goldstein  have 
been  prominent  investigators  of  the  phenomena. 

In  1893,  Lenard  used  a  tube  with  a  thin  window 
of  aluminium,  and  found  that  rays  passed  through 

*  Ann.  Rep.  Smithsonian  Inst.,  1897,  p.  135. 
t  Loc.  cit.,  p.  138. 


164    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

this  outside  the  tube,  affecting  photographic  plates 
and  electrified  bodies.  The  rays  are  also  affected 
by  a  magnet,  and  Lenard  regarded  them  as  prolonga- 
tions of  the  cathode  rays. 

In  1895,  Rontgen  found  that  rays  issue  from  the 
tube  which  affect  a  photographic  plate  after  passing 
through  plates,  e.g.,  of  aluminium,  opaque  to  ordi- 
nary light,  which  pass  from  one  substance  to  another 
without  refraction  and  with  little  regular  reflection. 
These  are  apparently  not  affected  by  a  magnet. 
They  are  also  remarkable  in  the  way  in  which  they 
alter  the  properties  (especially  the  electrical  proper- 
ties) of  the  substances  through  which  they  pass. 

Thus,  as  Professor  J.  J.  Thomson  says,*  "  we  may 
conveniently  divide  the  rays  occurring  in  or  near  a 
vacuum  tube  traversed  by  an  electric  current  into 
three  classes ;  without  thereby  implying  that  they  are 
necessarily  distinctly  different  in  physical  character. 
We  have  (1)  the  cathode  rays  inside  the  tube,  which 
are  deflected  by  a  magnet;  (2)  the  Lenard  rays  out- 
side the  tube,  which  are  also  deflected  by  a  magnet; 
and  (3)  the  Rontgen  rays  which  are  not,  as  far  as  is 
known,  deflected  by  a  magnet." 

Two  views  are  held  as  to  the  cathode  rays:  (a) 
that  "  they  are  particles  of  gas  carrying  charges  of 
negative  electricity,  and  moving  with  great  velocities 
acquired  as  they  travelled  through  the  intense  electric 
field  which  exists  in  the  neighbourhood  of  the  nega- 
tive electrode";  or  (&)  that  they  are  waves  in  the 
ether. 

If  the  nature  of  the  cathode  rays  is  uncertain,  so 
much  the  more  is  that  of  Rontgen's.  They  differ 
from  light  in  the  absence  of  refraction,  but  that 
may  be  interpreted  as  due  to  the  exceeding  smallness 

*  Address  to  Section  A,  Rep,  Brit,  Ass,  for  1896,  p.  701. 


THE  PROGRESS  OF  PHYSICS.  165 

of  the  wave-length ;  and  the  same  interpretation  may 
account  for  the  absence  of  conclusive  evidence  of 
polarisation. 

SUMMARY. — Of  what  is  meant  by  an  electric 
charge,  the  nineteenth  century  has  left  us  ignorant, 
but  many  laws  of  electrical  phenomena  have  been 
discovered,  and  that  electrical  radiations  are  best 
interpreted  in  terms  of  ethereal  waves  is  generally 
conceded.  Indeed  it  has  become  a  question  whether 
all  matter  may  not  be  resolvable  into  aggregates  of 
electric  charges  of  opposite  sign.  But  both  as  regards 
theory  and  as  regards  practical  applications,  astound- 
ing as  the  progress  of  these  has  been*  the  twentieth 
century  is  pregnant  with  possibilities  of  development. 

THEORIES   OF  MATTER. 

Very  early  in  the  history  of  science  the  idea  arose 
in  the  minds  of  enquirers  that  matter  might  consist 
of  an  aggregation  of  invisible  particles  separated  by 
interspaces.  This  became  a  precise  scientific  hypo- 
thesis about  a  century  ago,  when  Dalton  developed 
his  Atomic  Theory.  During  the  nineteenth  century 
the  hypothesis  was  in  several  ways  developed  as 
fresh  facts  came  to  light. 

When  we  see  water  becoming  vapour  and  again  be- 
coming ice,  when  we  see  what  is  usually  a  gas  lique- 
fied and  even  solidified,  when  we  watch  the  crystal 
of  sugar  melting  away  in  the  teaspoon  or  a  crystal 
of  alum  growing  in  a  solution  of  alum,  when  we  con- 
sider that  many  bodies,  like  iron,  expand  when  heated 
and  contract  again  as  they  cool,  when  we  observe  that 
a  gas  may  diffuse  through  another  or  even  through  a 

*  A  fascinating  exposition  of  modern  views  will  be  found 
in  an  article  by  Prof.  Oliver  Lodge,  International  Monthly 
I.  (1900),  pp.  483-530. 


166    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

solid;  our  instinctive  desire  to  visualise  what  may 
be  going  on  beyond  the  limits  of  the  visible,  naturally 
leads  us  to  imagine  matter  as  having  a  "  grained 
structure,"  as  being  made  up  of  minute  particles 
separated  by  minute  intervals  which  change  with  the 
state  of  the  substance,  with  conditions  of  temper- 
ature and  pressure. 

The  general  idea  is  simple;  the  details  of  the 
theory  are  profoundly  difficult.  "  Imagine  matter 
to  consist  of  a  crowd  of  separate  particles  with  in- 
terspaces. Contraction  and  expansion  are  then 
merely  a  drawing  in  and  a  widening  out  of  the 
crowd.  Solution  is  merely  a  mingling  of  two  crowds, 
and  evaporation  merely  a  dispersal  from  the  out- 
skirts. The  most  evident  properties  of  matter  are 
then  similar  to  what  may  be  observed  in  any  public 
meeting."  * 

Among  the  many  theories  of  matter,  the  following 
stand  out  prominently. 

Perfectly  Hard  Atoms. — (1)  The  idea  which  was 
expressed  by  Democritus  and  Lucretius,  which  re- 
ceived some  measure  of  approbation  from  Newton, 
was  that  matter  consists  of  perfectly  hard  atoms 
with  void  spaces  between  these.  Newton  used  this 
theory  in  his  interpretation  of  the  propagation  of 
sound. 

Centres  of  Force. — (2)  A  second  view,  which  is 
associated  with  the  name  of  Boscovich,  replaces  the 
perfectly  hard  atom  by  a  centre  of  repulsive  and  at- 
tractive forces.  "  According  to  Boscovich  an  atom 
is  an  indivisible  point,  having  position  in  space, 
capable  of  motion,  and  possessing  mass.  ...  It  has 
no  parts  or  dimensions;  it  is  a  mere  geometrical 

*  J.  J.  Poynting.  Address  Section  A,  Rep.  Brit.  Ass.  for 
1899,  p.  619. 


THE  PROGRESS  OF  PHYSICS.  167 

point  without  extension  in  space;  it  has  not  the 
property  of  impenetrability,  for  two  atoms  can,  it 
is  supposed,  exist  at  the  same  point."  *  A  similar 
view  was  held  by  Faraday. 

Heterogeneousness. — (3)  In  his  Recent  ^Advances 
(1876,  p.  288),  Prof.  P.  G.  Tait  described  "  a  third 
notion — that  the  matter  of  any  body,  where  it  does 
not  possess  pores,  like  those,  for  instance,  of  a  sponge 
(which  obviously  does  not  occupy  the  whole  of  the 
space  which  its  outline  fills),  fills  space  continu- 
ously, but  with  extraordinary  heterogeneousness." 
If  the  moon  were  built  up  of  irregular  stones  and 
mortar,  it  would  seem  homogeneous  to  us  (at  a  dis- 
tance of  250,000  miles),  so  the  drop  of  water  (re- 
moved as  it  were  to  a  distance  by  its  minuteness) 
may  only  be  apparently  homogeneous. 

Vortex  Atoms. — (4)  A  more  fertile  theory,  sug- 
gested in  1867,  is  that  of  Lord  Kelvin — "  that  what 
we"fcall  matter  may  really  be  only  the  rotating  por- 
tions of  something  which  fills  the  whole  of  space; 
that  is  to  say,  vortex-motion  of  an  everywhere  present 
fluid."  f 

The  beautiful  circular  vortex-rings  which  can  be 
so  readily  made  with  tobacco  or  other  smoke  in  air, 
and  with  a  little  ingenuity  in  water,  have  very  inter- 
esting properties  (first  mathematically  deduced  by 
Helmholtz).  Thus  a  vortex  ring  cannot  be  cut;  "  it 
simply  moves  away  from  or  wriggles  round  the  knife, 
and,  in  this  sense,  it  is  literally  an  atom."  $  It  moves 
through  the  air  of  the  room  as  if  it  were  an  independ- 
ent solid  body ;  one  will  pass  through  another  and  al- 
low that  other  to  pass  through  it;  and  it  obviously 
has  an  extraordinary  power  of  persistence. 

*  Glazebrook.    James  Clerk  Maxwell  and  Modern  Physict, 
1896,  p.  108. 
t  Recent  Advances,  p.  20.          t  Recent  Advances,  p.  297. 

L 


168    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

But  "  a  common  vortex  ring  of  air  or  water  con- 
tains within  itself  the  seeds  of  its  own  decease;  it 
is  composed  of  an  imperfect  fluid,  possessing  that  is 
to  say  viscosity,  and  accordingly  its  life  is  short ;  its 
peculiar  energy  being  dissipated,  its  vortex  motion 
declines,  and  as  a  ring  it  perishes.  But  imagine 
a  ring  built  of  some  perfect  fluid,  of  some  medium 
devoid  of  viscosity,  as  the  ether  is;  then  it  may  be 
immortal;  it  can  neither  be  produced  nor  annihi- 
lated by  known  means ;  and  it  is  just  this  property, 
combined  with  other  properties  of  elasticity, 
rigidity,  and  the  like,  that  led  Lord  Kelvin  origi- 
nally to  his  brilliant  and  well-known  hypothesis." 

Thus  if  the  universe  be  filled  with  ether,  and  if 
that  universal  medium  be  a  perfect  fluid,  "  then,  if 
any  portions  of  it  have  vortex-motion  communicated 
to  them,  they  will  remain  forever  stamped  with  that 
vortex-motion;  they  cannot  part  with  it;  it  will  re- 
main with  them  as  a  characteristic  forever,  or  at 
least  until  the  creative  act  which  produces  it  shall 
take  it  away  again.  Thus  this  property  of  rotation 
may  be  the  basis  of  all  that  appeals  to  our  senses  as 
matter"  f 

The  Atomic  View  of  Nature. — Opinions  differ  as 
to  the  fittest  way  in  which  to  express  the  facts  known 
in  regard  to  matter,  but  even  those  who  believe,  for 
instance,  that  "  all  matter  is  resolvable  into  an  ag- 
gregate of  electric  charges  of  opposite  sign,"  will 
admit  their  acceptance  of  the  atomic  view  of  nature, 
though  all  may  not  agree  verbally  with  Prof.  Oliver 
Lodge  when  he  says  "  a  lump  of  matter  is  as  surely 
composed  of  atoms  as  a  house  is  built  of  bricks." 

*  Prof.  Oliver  Lodge.    Modern  Views  of  Matter.    The  Inter- 
national Monthly,  I.  (1900),  p.  501. 
t  Prof.  Tait's  Recent  Advances,  1876,  p.  294. 


THE  PROGRESS  OF  PHYSICS.  169 

"  That  is  to  say,"  he  continues,  "  matter  is  not 
continuous  and  homogeneous,  but  is  discontinuous; 
being  composed  of  material  particles,  whatever  they 
are,  and  non-material  spaces.  There  is  every  reason 
to  be  certain  that  these  spaces  are  full  of  a  connecting 
medium,  full  of  ether;  there  is  no  really  void 
space." 

But  while  the  atomic  view  is  generally  accepted, 
there  is  less  unanimity  as  to  the  fittest  conception  of 
the  atom.  "  No  one  now  believes  that  an  atom  is 
simply  a  vortex  ring  of  ether,  and  that  the  rest  of 
the  ether  is  stagnant  fluid  in  which  the  vortex  rings 
sail  about.  Any  quantity  of  difficulties  surround 
such  an  hypothesis  as  that.  Its  apparently  attrac- 
tive simplicity  is  superficial.  ^Nevertheless  it  is  not 
to  be  supposed  that  every  hydro-dynamical  theory 
of  the  universe  is  thereby  denied.  It  is  quite  con- 
ceivable that  a  single  kind  of  fluid  in  different  kinds 
of  motion — some  kinds  of  motion  not  yet  imagined 
perhaps — may  possibly  be  found  capable  of  explain- 
ing all  the  facts  of  physics  and  chemistry."  * 

"I  hold,"  says  Prof.  Lodge,  "that  the  ether  is 
most  certainly  not  atomic,  not  discontinuous ;  it  is  an 
absolutely  continuous  medium,  without  breaks  or 
gaps  or  spaces  of  any  kind  in  it, — the  universal  con- 
nector,— permeating  not  only  the  rest  of  space,  but 
permeating  also  the  space  occupied  by  the  atoms 
themselves.  The  atom  is  something  superposed  upon, 
not  substituted  for,  the  ether,  it  is  most  likely  a  defi- 
nite modification  of  the  ether,  an  individualisation, 
with  a  permanent  existence  and  faculty  of  locomotion, 
which  the  ether  alone  does  not  possess.  Matter  is  that 
which  is  susceptible  of  motion.  Ether  is  that  which 

*  Modern  Views  of  Matter,  International  Monthly,  I. 
(1900),  pp.  499  and  501. 


170    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

is  susceptible  of  strain.  All  energy  appertains  either 
to  matter  or  to  ether,  and  is  continually  passing  from 
one  to  the  other."  * 

It  is  now  time  to  turn  to  the  actual  progress  of 
scientific  discovery  and  to  note  a  few  of  the  steps 
which  have  led  towards  the  modern  views  of  matter, 
as  above  suggested. 

A.  In  Connection  with  the  Kinetic  Theory  of 
Gases. — In  his  Hydrodynamica  (1738),  Daniel 
Bernouilli  supposed  a  gas  to  consist  of  moving  parti- 
cles, and  argued  that  the  pressure,  if  due  to  the  im- 
pacts of  these,  must  be  proportional  to  the  square  of 
their  velocity. 

In  1816  (published  1821),  Herapath  followed  on 
the  same  tack,  and  in  spite  of  fundamental  errors 
(e.g.,  that  the  temperature  of  a  gas  is  measured  by 
the  momentum  of  each  of  its  particles),  gave  a 
theoretical  justification  of  Boyle's  law  (that  with  con- 
stant temperature  the  product  of  pressure  and  volume 
is  constant). 

In  1846,  Waterston  (whose  work  was  overlooked 
until  disinterred  from  the  archives  of  the  Royal  So- 
ciety of  London  by  Lord  Rayleigh  in  1892)  showed 
that  the  temperature  of  a  gas  "  is  measured  by  the 
mean  kinetic  energy  of  a  single  molecule,  and  that 
in  a  mixture  of  gases  the  mean  kinetic  energy  of 
each  molecule  is  the  same  for  each  gas,"  f  thereby 
furnishing  the  theoretical  basis  for  the  laws  of  Boyle, 
Gay-Lussac,  and  Avogadro. 

In  1848,  Joule  used  Herapath's  results  as  a  basis 
for  calculating  the  mean  velocity  of  the  molecules  of 
a  gas,  and  obtained  from  hydrogen  at  freezing  point 
and  atmospheric  pressure  the  value  of  6,055  feet 

*  Loc.  tit.,  pp.  499-500. 
fGlazebrook.    James  Clerk  Maxwell,  1896,  pp.  118-19. 


THE  PROGRESS  OF  PHYSICS.  171 

per  second,  or  about  six  times  the  velocity  of  sound  in 
air. 

In  1857,  in  his  famous  paper  "  On  the  Kind  of 
Motion  we  call  Heat,"  and  in  his  second  paper  in 
1859,  Clausius  greatly  advanced  the  incipient  kinetic 
theory,  calculating,  for  instance,  the  average  length 
of  the  path  of  a  molecule  in  the  interval  between 
two  "  collisions,"  or  near  approaches  to  another 
molecule. 

In  1859  and  1860,  Clerk  Maxwell  gave  his  "  Illus- 
trations of  the  Dynamical  Theory  of  Gases  "  in  which 
he  demonstrated  "  the  laws  of  motion  of  an  indefinite 
number  of  small,  hard,  and  perfectly  elastic  spheres 
acting  on  one  another  only  during  impact." 

By  the  application  of  an  ingenious  statistical 
method  and  of  general  dynamical  methods  to  molec- 
ular problems,  Maxwell  greatly  advanced  the  theory 
of  gases  and  the  theory  of  matter.  That  he  was  helped 
by  Boltzmann  and  Clausius  and  Kelvin  and  others 
goes  without  saying,  but  it  seems  legitimate  to  asso- 
ciate with  his  name  the  coming  of  age  of  the  molec- 
ular theory  of  matter.  It  matters  not  a  whit  for 
our  general  purpose  how  many  corrections  may  have 
to  be  made  on  his  computation  that  the  length  of  the 
mean  free  path  of  molecules  of  air  is  ^rr.Vinr  of  an 
inch,  or  that  the  number  of  collisions  per  second  ex- 
perienced by  each  molecule  is  about  eight  thousand 
millions;  the  point  is  rather  that  he  justified  a. 
molecular  or  atomic  conception,  harmonising  the  laws 
of  Boyle,  Charles,  and  Avogadro,  and  suggesting  fur- 
ther developments  which  are  still  prompting  re- 
search. 

B.  Cauchy's  Suggestion  of  the  Heterogeneity 
of  Matter. — As  a  second  illustration  of  the  nature 
of  the  argument  which  has  resulted  in  the  modern 


172    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

view  or  views  of  matter  we  may  refer  to  the  inves- 
tigations of  the  French  mathematician,  Cauchy,  as 
to  the  motion  of  light  in  solid  bodies  and  liquids. 
He  showed  "  that  if  matter  were  homogeneous,  there 
might  be  refraction,  but  there  would  be  no  dispersion. 
All  kinds  of  light  would  travel  with  the  same  velocity 
in  glass,  just  as  they  did  in  the  air  outside;  and, 
therefore,  the  mere  fact  that  the  different  kinds  of 
light  can  be  separated  from  one  another  in  passing 
through  a  prism,  gives,  at  least,  a  hint  that  the  mat- 
ter of  the  prism  is  heterogeneous,  is  not  infinitely 
more  fine-grained  than  the  length  of  a  wave  of 
any  of  the  kinds  of  light  which  it  enables  us  to  sepa- 
rate in  their  courses."  *  This  kind  of  argument — 
developed  by  Lord  Kelvin — leads  to  the  result  that 
400,000,000  in  the  inch  is  a  rough  approximation  to 
the  heterogeneity  or  grained  structure  of  matter. 

C.  Other  Methods  of  Estimating  the  Heterogeneity 
of  Matter. — In  his  Recent  Advances  in  Physical 
Science  Prof.  P.  G.  Tait  gave  an  account  of  two 
other  methods  ingeniously  used  by  Lord  Kelvin  in 
forming  an  estimate  of  the  grained  structure  of  mat- 
ter. "  The  second  method  was  founded  upon  con- 
siderations of  the  amount  of  heat  which  would  be 
generated  by  electrical  action  between  particles  of 
different  materials  when  they  were  combined  to- 
gether. The  third  method  was  founded  upon  the 
forces  employed  in  drawing  out  a  film  of  liquid, — 
in  fact  (to  take  the  simplest  case),  in  blowing  a  soap- 
bubble."  The  various  methods  yielded  approxi- 
mately the  same  result,  "  pointing  consistently  to 
something  not  very  largely  differing  from  the  500,- 
000,000th  part  of  an  inch  as  being  the  distance  be- 
tween the  successive  particles  of  matter  in  a  liquid." 
*  P.  G.  Tait.  Recent  Advances,  1876,  p.  304. 


THE  PROGRESS  OF  PHYSICS.  173 

D.  Argument  from   the  Behaviour  of   Gases. — 
Clausius  and  Maxwell  deduced  theoretically  the  con- 
clusion that  the  length  of  the  mean  free  path  of  a 
moving  particle  in  a  gas  (i.e.,  the  distance  which  it 
will  pass  through  between  every  two  successive  colli- 
sions), divided  by  the  diameter  of  any  one  particle,  is 
equal  to  the  ratio  of  the  whole  space  occupied  by  the 
particles  to  about  eight  and  a  half  times  the  bulk  of 
the  whole  particles.*    In  various  ways  it  was  found 
possible  to  form  an  equation  with  approximate  data, 
and  the  result  comes  out  that  the  diameter  of  a  par- 
ticle is  not  very  different  from  ^T^Tnnr.innr  of  an  inch. 

As  a  good-sized  plum  or  a  small  orange  is  to  the 
whole  earth,  so  is  the  coarse-grained  particle  to  a 
drop  of  water  £  of  an  inch  in  diameter. 

The  calculations  of  Joule  and  Clausius,  Maxwell 
and  Boltzmann  lead  to  such  statements  as  the  follow- 
ing:— "  Atoms  are  big  things,  the  thousand  millionth 
of  an  inch  in  diameter,  and  they  cannot  travel  far 
without  mutual  collisions.  They  are  constantly  col- 
liding, even  in  a  very  good  vacuum.  In  ordinary 
air  every  atom  strikes  another  about  six  thousand 
million  times  a  second,  and  it  cannot  travel  even  a 
microscopic  distance  without  collision;  its  free  path 
is  microscopic,  or  on  the  average  ultra-microscopic."  f 

E.  From  Electrical  Phenomena. — As  Prof.  Oliver 
Lodge  says,   "  atoms  are  big  things  " — "  the  thou- 
sand millionth  of  an  inch  in  diameter,  and  they  can- 
not travel  far  without  mutual  collisions."   Much  too 
big  and  cumbrous  these  are  to  figure  in  an  interpre- 
tation of  the  cathode  rays,   the  Lenard  rays,   the 
Eontgen  rays!      For  here  we  are  brought  face  to 

*  See  Recent  Advances,  p.  316. 

t  Oliver  Lodge.  Modern  Views  of  Matter.  International 
Monthly,  I.  (1900),  p.  515. 


PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

face  with  the  astounding  conception  of  fragments  of 
atoms,  of  foundation-stones  of  atoms,  of  a  unifica- 
tion of  all  matter  in  terms  of  corpuscles  of  which  five 
hundred  or  so  go  to  an  atom  of  hydrogen.  But  the 
daring  speculation  carries  us  further — to  doubt 
whether  there  is  any  matter  at  all,  or  rather  whether 
inertia  is  not  fundamentally  electrical. 

Matter  and  Ether. — We  have  previously  spoken 
of  one  of  the  aims  of  science  as  that  of  finding  the 
common  denominator  of  the  fractions  of  reality 
which  we  know.  For  a  time  the  word  Matter  was  a 
conspicuous  part  of  this  common  denominator,  but 
the  nineteenth  century  has  left  us  ignorant  of  its 
real  nature,  and  aware  only  of  some  of  its  many 
properties,  and  even  of  many  of  these  properties  how 
little  we  know.  "  Impenetrability,"  the  text-books 
say,  and  yet  Boscovich  and  Maxwell  seem  to  regard 
it  as  conceivable  that  two  atoms  should  occupy  the 
same  space.  "  Inertia,"  the  text-books  say,  and  yet 
how  little  we  know  of  the  meaning  of  this  term,  how 
doubtful  Lodge  seems  to  be  whether  there  is  any  but 
electric  nl  inertia ! 

The  common  denominator  would  now  read  "  the 
relations  of  matter,  energy,  and  ether."  But  the  fact 
is  that  the  scientific  conception  of  matter  tends  to  be- 
come more  and  more  monistic.  Some  years  ago  we 
thought  of  material  atoms  and  molecules,  floating  in 
ether,  like  the  crowds  of  minute  organisms  in  the 
plankton  of  the  ocean.  But  various  attempts  have 
been  made,  as  Prof.  Poynting  puts  it,  "to  get  rid 
of  the  dualism  " : — Boscovich's  theory  of  point-cen- 
tres surrounded  by  an  infinitely  extending  atmos- 
phere of  force,  Faraday's  theory  of  point-centres  with 
radiating  lines  of  force,  Lord  Kelvin's  theory  of 
atoms  as  vortices  or  whirls  in  a  perfect  fluid  ether, 


THE  PROGRESS  OF  PHYSICS.  175 

Larmor's  theory  of  atoms  as  loci  of  strain  in  the 
ether,  and  so  on.  "  So,  as  we  watch  the  weaving  of 
the  garment  of  Xature,  we  resolve  it  in  imagination 
into  threads  of  ether  spangled  over  with  beads  of 
matter.  We  look  still  closer,  and  the  beads  of  mat- 
ter vanish;  they  are  mere  knots  and  loops  in  the 
threads  of  ether."  * 

An  Analogy. — An  analogy  which  has  often  ap- 
pealed to  our  biological  mind  may  possibly  make  the 
subject  clearer.  In  Biology  we  are  accustomed  to 
speak  of  three  big  facts — organism,  environment,  and 
function.  The  environment  includes  the  world  of 
external  influences;  the  organism  is  the  living  crea- 
ture which  contains  nothing  sensible  that  is  not  also 
in  the  environment;  function  consists  of  action  and 
reaction  between  organism  and  environment.  We  do 
not  know  the  secret  of  the  synthesis  which  has  made 
it  possible  for  the  organism  to  be  a  persistent,  though 
ever  changeful,  a  unified  and  yet  reproductive,  whirl- 
pool in  the  stream  of  the  environment.  But  there 
it  is. 

Now  it  may  be  that  molecules,  atoms,  corpuscles 
are  persistent  unities  individualised  in  the  stream  or 
ocean  of  the  ether,  as  the  organism  is  in  its  environ- 
ment, the  syntheses  being  secrets  in  both  cases.  And 
it  may  be  that  energy  corresponds  to  function, — con- 
sisting of  action  and  reaction  between  matter  and 
ether. 

SUMMAEY. — That  matter  cannot  be  conceived  as 
built  up  of  perfectly  hard  atoms  seems  quite  certain; 
that  it  has  a  heterogeneous  structure  seems  equally 
certain;  some  modification  of  a  theory  of  vortex- 
atoms  would  find  acceptance  as  an  interpretative 

*  J.  J.  Poynting.    Address,  Section  A,  Rep.  Brit.  Ass.  for 
1899,  p.  619." 


176    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

idea;  but  it  may  be  that  what  we  call  matter  will  turn 
out  to  be  conceivable  as  loops  and  knots  in  the  threads 
of  ether. 

THEORY  OF  THE  ETHER. 

Among  the  concepts  which  have  come  to  stay  in 
scientific  thinking,  that  of  the  ether  must  now  be  in- 
cluded. It  is  as  real  as  the  concept  of  "  atom  "  or 
"  molecule,"  but  hardly  more  so.  Perhaps  the  most 
natural  way  of  appreciating  its  validity  is  by  con- 
sidering some  of  the  facts  which  have  made  it  seem  to 
many  a  necessary  hypothesis. 

Premonition  of  the  Idea. — Long  before  the  nine- 
teenth century,  the  scientific  mind,  e.g.,  Newton's, 
seemed  to  feel  the  need  of  supposing  that  there  was 
"  something  "  occupying  space  between  the  heavenly 
bodies. 

It  does  not  seem  very  evident  why  the  extent  of 
distance  should  make  much  difference,  but,  for  his- 
torical purposes  at  least,  it  is  well  to  recall  the  im- 
pression made  by  the  discovery  or  rather  demonstra- 
tion of  the  fact  that  most  of  the  heavenly  bodies  are 
at  a  literally  immense — unmeasurable — distance 
from  the  earth. 

Light  travels  at  a  rate  of  about  186,000  miles  in 
a  second,  and  could  flash  nearly  eight  times  round  the 
earth  in  that  time;  but  if  a  hypothetical  inhabitant 
of  the  nearest  star  could  by  any  means  see  the  earth, 
he  would  see  the  events  of  three  or  four  years  ago. 
Now,  as  we  are  sure  that  light  is  not  any  kind  of 
stuff  or  substance,  but  a  form  of  energy  or  power,  we 
may,  in  some  measure,  understand  why  to  some 
minds  it  has  seemed  necessary  to  suppose  that  there 
is  some  sort  of  something  linking  that  star  to  us. 


THE  PROGRESS  OF  PHYSICS.  177 

If  light  consists  of  waves,  the  question  naturally 
arises:  "Waves  in  what?"  Especially  when  the 
study  of  polarisation  and  double  refraction  showed 
that  the  elastic  properties  of  air  or  water  which  act 
as  media  for  sound,  will  not  work  when  applied  to 
the  interpretation  of  light-phenomena,  the  conception 
of  the  ether  f oreed  itself  upon  physicists. 

At  first  it  seems  to  have  been  thought  of  as  an  ex- 
ceedingly rare  form  of  matter  pervading  space  and 
composed  of  discrete  particles;  and  it  was  of  course 
invested  with  the  requisite  elastic  qualities.  But 
gradually  the  conception  became  subtler. 

Identification  of  Luminiferous  and  Electro-mag- 
netic Ether. — The  luminiferous  ether  was  invented 
as  a  conception  which  fitted  the  facts  known  in  re- 
gard to  light.  Similarly  Faraday  and  Clerk  Max- 
well postulated  a  special  ether  for  electrical  and 
magnetic  phenomena.  But  when  Clerk  Maxwell 
made  the  further  step  of  showing  that  one  hypo- 
thetical medium  would  suffice  for  the  interpretation 
of  luminous,  electric,  and  magnetic  radiations,  the 
case  for  the  ether  became  much  stronger. 

That  the  ether  is  a  necessary  conception  in  modern 
physics  seems  to  be  unanimously  admitted  by  experts, 
but  how  exactly  the  ether  is  to  be  conceived  of  re- 
mains quite  uncertain. 

For  some  imagine  it  as  an  elastic  solid,  others  as 
a  labile  fluid,  others  as  a  vortex  sponge  (a  phrase 
which  we  cannot  pretend  to  explain),  and  others 
otherwise. 

The  modern  conception  of  the  ether  is  that  of  an 
absolutely  continuous  medium,  "  without  breaks  or 
gaps  or  spaces  of  any  kind  in  it,"  "  a  universal  con- 
nector," permeating  space  whether  otherwise  occu- 
pied or  not,  susceptible  of  stress,  but  not  of  locomo 


178    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

tion,  probably  full  of  vorticity,  but  in  any  case  not 
a  stagnant  homogeneous  fluid,  the  seat  of  waves  which 
we  call  "  light "  and  of  others  which  we  call  "  electro- 
magnetic phenomena,"  on  the  whole  the  most  marvel- 
lous scientific  concept  which  the  mind  of  man  has 
conceived ! 

Value  of  these  Hypotheses. — We  can  well  imagine 
a  practical  man  saying  that  all  this  talk  of  atom  and 
molecule  and  ether  is  unreal  and  unverifiable,  and  in 
a  certain  sense  he  is  undoubtedly  right.  These 
molecular  and  ethereal  hypotheses  are  human  imagin- 
ings,— and  nothing  more;  they  are  constructed  in 
terms  of  one  sense,  that  of  sight;  they  are  attempts 
to  see  that  which  is  invisible,  to  invent  a  machinery 
of  Nature  since  the  real  mechanism  is  beyond  our 
ken;  but  it  must  be  observed  that  these  hypotheses 
are  not  vain  imaginings,  for  they  prove  themselves 
yearly  most  effective  tools  of  research,  and  that  they 
are  not  random  guesses,  for  they  are  constructed 
in  harmony  with  known  facts. 


CRAPTEE  VI. 
ADVANCE  OF  ASTRONOMY. 

FEOM   COPEENICUS   TO  NEWTON. 

^Astronomy  an  Ancient  Science. — Astronomy  is 
usually  ranked  as  the  most  ancient  of  the  concrete 
sciences,  and  this  at  least  is  certain  that  evidence  of 
astronomical  observation  is  furnished  by  the  posi- 
tion of  buildings  which  are  much  older  than  all 
written  records.  Perhaps  one  of  the  first  scientific 
discoveries  to  become  clear  and  definite  was  the  dis- 
covery of  the  year,  with  its  fine  demonstration-lesson 
of  recurrent  sequences.  From  that  unknown  date  to 
the  latest  announcements  from  the  observatories  of 
Greenwich  and  Potsdam,  Harvard  and  Lick,  there 
extends  a  long  procession  of  discoveries,  sometimes 
almost  monotonous  in  their  continuity  and  sameness, 
but  relieved  at  intervals  by  some  great  and  novel 
achievement  which  has  given  a  new  meaning  to  the 
whole. 

That  astronomy  reached  a  stable  position  sooner 
than  the ^ other  sciences  was  partly  because  the  sub- 
lime subject  attracted  men  of  genius  who  "  attended 
their  minds  thereunto,"  and  partly  because  a  great 
part^of  astronomy  is  concerned  with  simple  relations 
of  distance,  mass,  and  motion. 

Three  Main  Chapters. — Balfour  Stewart  has 
summed  up  the  long  history  of  astronomy  in  three 


180    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

main  chapters.  First  it  passed  through  an  observ- 
ing-period  lasting  through  thousands  of  years  of 
nightly  study  by  watchers  in  the  plains  of  the  East 
to  its  culmination  in  the  discoveries  of  Copernicus 
and  Keppler.  It  then  passed  into  a  stage  of  analysis 
and  generalisation,  when  the  genius  of  Newton 
rationalised  a  huge  mass  of  facts  in  the  formula 
of  gravitation.  "  God  said,  Let  Newton  be,  and 
there  was  light."  It  finally  reached  a  stage  of  deduc- 
tion, which,  from  a  knowledge  of  the  positions  and 
movements  of  the  heavenly  bodies,  predicts  their  fu- 
ture courses.  This  might  also  be  called  the  evolu- 
tionary period,  since  one  of  its  dominant  aims  has 
been  to  show  how  the  solar  and  other  systems  have 
come  to  be  what  they  are. 

The  Succession  of  Systems. — The  Ptolemaic  sys- 
tem— which  placed  the  earth  immovable  in  the  centre 
of  the  universe — was  superseded  by  the  system  of 
Copernicus  (14T3--1543),  which  made  the  sun  the 
immovable  centre.  This  again  was  reformed  by 
Keppler  (1571--1630),  who  stated  the  famous  laws 
or  descriptive  formulae  of  the  movements  of  the 
planets  in  their  orbits,  but  was  impelled  to  call  in 
the  service  of  guiding  spirits  to  account  for  them. 
Galileo  Galilei  (1564-1642)  was  the  first  to  use  for 
systematic  study  the  telescope  which  the  Dutchman, 
Hans  Lippersheim,  had  invented,  and  in  spite  of  his 
revelation  of  some  of  the  wonders  of  the  heavens — 
the  broken  surface  of  the  moon,  the  countless  stars 
of  the  Milky  Way,  the  satellites  of  Jupiter,  and  the 
spots  on  the  sun — was  almost  made  a  martyr  for  his 
dogged  adherence  to  Copernican  doctrine.  But  we 
must  not  do  more  than  mention  these  great  names, 
which  are  separated  by  a  long  interval  from  the  nine- 
teenth century. 


ADVANCE  OF  ASTRONOMY.  181 

The  Gravitation  Law. — It  is  necessary,  however, 
to  dwell  for  a  little  on  what  is  perhaps  the  greatest 
of  all  scientific  achievements — Newton's  formulation 
of  the  Gravitation  Law  (1687), — the  foundation  of 
what  has  been  called  the  astronomical  view  of  nature. 
"  Every  particle  of  matter  in  the  universe  attracts 
every  other  particle  with  a  force  whose  direction  is 
that  of  the  straight  line  joining  the  two,  and  whose 
magnitude  is  proportional  directly  as  the  product  of 
their  masses,  and  inversely  as  the  square  of  their 
mutual  distance  " — this  is  the  generalisation  known 
as  the  Law  of  Gravitation.*  Another  way  of  phras- 
ing it  may  be  quoted : — "  The  law  of  gravitation 
states  that  to  each  portion  of  matter  we  can  assign 
a  constant — its  mass — such  that  there  is  an  accelera- 
tion towards  it  of  other  matter  proportional  to  that 
mass  divided  by  its  distance  away.  Or  all  bodies 
resemble  each  other  in  having  this  acceleration  to- 
wards each  other."  f  The  fundamental  concept  is 
that  of  mutual  acceleration. 

This  formula  applies  with  equal  accuracy  to  a 
stone  falling  to  the  ground  and  to  the  motion  of  the 
earth  round  the  sun.  As  far  as  we  know,  it  is  uni- 
versally true.  It  may  not  be  possible  to  trace  the 
logical  processes  of  genius,  but  it  should  be  noted  that 
just  as  Keppler  deduced  his  three  laws  from  the 
observations  of  Tycho  Brahe,  so  Keppler's  laws 
formed  a  basis  of  deduction  for  Newton. 

SUMMARY. — The  science  of  astronomy,  most  an- 
cient in  its  origin,  may  be  said  to  have  passed 
through  three  main  phases — (a)  of  observation, 
(b)  of  analysis  and  generalisation,  and  (c)  of  deduc- 

*  Cited  from  Chambers's  Encyclopedia. 
t  Prof.  Poynting,  Pres.     Address,  Section  A.,  Rep.  Brit. 
Ass.  for  1899,  p.  616. 


182    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

tion;  but  activity  continues  on  each  of  these  lines, 
and  it  may  be  more  accurate  to  say  that  the  suc- 
cession of  astronomical  systems — Ptolemaic,  Co- 
pernican,  Kepplerian,  Newtonian,  etc.,  implies 
mainly  a  progress  in  the  lucidity,  validity,  brevity, 
and  universality  of  descriptive  formulce. 

APPLICATIONS  OF  THE  GKAVITATION-FOKMULA. 

A  great  part  of  astronomy  is  concerned  with  appli- 
cations of  the  gravitation-formula  to  the  phenomena 
of  the  heavens;  another  department  has  to  do  with 
topographical  relations,  with  mapping  out  positions 
and  orbits ;  while  a  third  kind  of  enquiry  deals  with 
the  physical  and  chemical  nature  of  the  celestial 
bodies.  Laplace,  Bradley,  and  Herschel  may  be 
named  as  representative  great  masters  in  these 
three  departments,  which  have  been — not  very  hap- 
pily— distinguished  as  "  gravitational,"  "  observa- 
tional," and  "  descriptive."  Adopting  this  classifica- 
tion, Mr.  Berry  notes  in  his  Short  History  of  As- 
tronomy *  that  "  gravitational  astronomy  and  exact 
observational  astronomy  have  made  steady  progress 
during  the  nineteenth  century,  but  neither  has  been 
revolutionised,  and  the  advances  made  have  been 
to  a  great  extent  of  such  a  nature  as  to  be  barely 
intelligible,  still  less  interesting,  to  those  who  are 
not  experts.  .  .  .  Descriptive  astronomy,  on  the 
other  hand,  which  can  be  regarded  as  being  almost 
as  much  the  creation  of  Herschel  as  gravitational  as- 
tronomy is  of  Newton,  has  not  only  been  greatly  de- 
veloped on  the  lines  laid  down  by  its  founder,  but 
has  received — chiefly  through  the  invention  of  spec- 
trum analysis — extensions  into  regions  not  only  un- 
thought  of,  but  barely  imaginable  a  century  ago." 
*  P.  355. 


ADVANCE  OF  ASTRONOMY.  183 

In  illustrating  the  century's  confirmations  and  ex- 
tensions of  the  gravitational  theory,  account  should 
be  taken  of  re-estimates  of  the  sun's  distance,  re- 
investigations  of  the  movements  of  the  moon  and  the 
planets,  further  elaboration  of  the  theory  of  the 
tides,  and  so  on.  We  have  confined  ourselves  to  a 
brief  notice  of  the  discovery  of  the  minor  planets, 
the  discovery  of  Neptune,  and  the  study  of  comets. 

Discovery  of  the  Minor  Planets. — Kant  had  sug- 
gested that  the  zone  in  which  a  planet  moves  might 
be  regarded  as  the  empty  area  from  which  its  ma- 
terials had  been  derived,  and  that  some  definite  re- 
lation should  therefore  be  found  between  the  masses 
of  the  planets  and  the  intervals  between  them.  In 
1772  Titius  pointed  out  that  the  distances  from 
the  sun  of  the  six  planets  then  known  might  be 
represented  by  a  certain  numerical  series,  except  that 
there  was  nothing  to  correspond  to  the  term  succeed- 
ing the  one  which  corresponds  to  the  orbit  of  Mars. 
Johann  Elert  Bode,  astronomer  in  Berlin,  filled  the 
gap  with  a  hypothetical  planet,  and  the  search  for 
it  began.  In  1801  Piazzi  discovered  Ceres,  and  with 
the  help  of  Gauss's  mathematical  genius  (used  to  pre- 
dict where  the  planet  should  be  at  certain  dates)  von 
Zach  and  Olbers  were  soon  able  to  confirm  Piazzi. 
In  spite  of  Hegel's  protest  that  the  number  of  planets 
could  not  exceed  the  sacred  number  seven,  a  second 
(Pallas)  was  soon  discovered  (1802)  by  Olbers, 
and  in  1807  four  were  known.  Three  of  these  "  as- 
teroids," as  Sir  W.  Herschel  called  them,  corre- 
sponded approximately  with  the  requirements  of  the 
series  indicated  by  Titius  and  usually  referred  to  as 
"  Bode's  Law,"  and  the  idea  commended  itself  that 
these  bodies  were  the  remains  of  an  exploded  planet. 

As  we  now  know,  neither  Bode's  Law  nor  the  no- 
li 


184:    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

tion  of  an  exploded  planet  can  be  regarded  as  tenable, 
but  both  served  a  useful  purpose  in  prompting  re- 
search. They  led  to  the  recognition  of  the  minor 
planets,  now  known  to  be  very  numerous  (over  five 
hundred)  and  the  discovery  must  have  served  as  a 
useful  hint  of  the  complexity  of  relations  which  fur- 
ther study  of  the  heavens  was  to  reveal.  The  story  is 
of  interest  in  illustration  of  a  scientific  prophecy 
which  was  rewarded  even  more  richly  than  its  basis 
deserved. 

In  1857  Clerk  Maxwell  proved  the  truth  of  what 
had  been  several  times  suggested — that  the  rings 
around  Saturn  could  not  be  continuous  solid  bodies 
nor  liquid  zones,  but  that  they  behaved  as  if  they 
were  composed  of  a  multitude  of  small  solid  bodies 
revolving  independently  around  the  planet,  somewhat 
as  the  minor  planets  do  around  the  sun.  This  has 
received  corroboration  from  telescopic  and  spectro- 
scopic  observations,  and  is  one  of  the  facts  which 
lend  countenance  to  the  hypothesis  of  the  meteoric 
constitution  of  the  heavenly  bodies: — that  meteoric 
dust,  shooting  stars,  meteor  rings,  Saturn's  rings, 
comets,  minor  planets,  nebulae,  and  so  on,  are  all,  as 
it  were,  terms  in  an  evolution-series. 

Discovery  of  Neptune. — There  are  few  chapters 
in  the  history  of  astronomy  more  familiar,  and,  at 
the  same  time,  more  instructive,  than  the  story  of  the 
discovery  of  Neptune.  It  illustrates  the  method  of 
science, — discovering  an  anomaly,  tracing  out  the 
reason  for  it,  and  thereby  corroborating  a  general  con- 
clusion. 

In  the  first  quarter  of  the  century  it  was  repeat- 
edly remarked  that  the  real  orbit  of  Uranus  (which 
Herschel  had  removed  from  among  the  fixed  stars 
to  a  place  among  the  planets)  was  not  (to  the  astro- 


ADVANCE  OF  ASTRONOMY.  185 

nomical  eye)  in  harmony  with  its  theoretical  path  as 
deduced  from  the  gravitation-formula.  To  explain 
these  puzzling  discrepancies  of  orbit,  it  was  suggested 
by  several  astronomers  that  they  must  be  due  to  the 
influence  of  some  undetected  exterior  body.  But 
precision  was  first  given  to  this  suggestion  in  1845, 
when  John  Couch  Adams  succeeded  in  calculating 
out  the  probable  mass  and  position  of  the  hypothetical 
planet.  In  the  same  year  Leverrier  (b.  1811)  began 
a  similar  quest  by  a  different  method ;  in  1846  he  de- 
termined the  probable  position  of  the  supposed  cause 
of  the  disturbance;  in  the  same  year  he  announced 
that  it  should  be  visible  in  a  certain  place.  He  wrote 
to  Galle  of  the  Berlin  observatory,  told  him  where  to 
look,  and  Xeptune  was  discovered.  In  the  same 
month  (September,  1846)  the  discovery  was  con- 
firmed by  Challis  of  Cambridge,  who  had  been  ad- 
vised by  Adams.  It  is  almost  needless  to  remark 
on  the  importance  of  the  discovery  as  a  confirmation 
of  the  gravitational  formula ;  here,  if  anywhere,  the 
exception  proved  the  rule.  It  should  be  noted,  how- 
ever, as  S.  C.  Walker  first  showed,  that  Xeptune 
had  been  observed  as  a  fixed  star  by  Lalande  in  1795, 
and  furthermore  that  "  the  planet  was  found  to  have 
a  different  orbit  from  that  assigned  by  the  calculators. 
Their  (hypothetical)  planets  were  not  identical,  nor 
were  they  the  (real)  planet  Xeptune.  But  they 
must  ever  have  credit  for  the  sagacity  and  ability 
with  which,  aiming  at  so  indefinite  a  target,  they  so 
nearly  struck  the  centre."  * 

The  prophetic  recognition  of  the  existence  of  Nep- 
tune and  its  verification  may  be  taken  as  one  of  the 

*E.  B.  Kirk.     Article,  Astronomy,  Chambers's  Encyclo- 
padia,  vol.  I.  p.  528. 


186    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

^finest  illustrations  of  the  stability  of  the  gravitational 
theory. 

Comets. — Another  series  of  confirmations  of  New- 
tonian laws  is  concerned  with  comets.  For,  although 
Newton  had  shown  that  their  movements  were  in  har- 
mony with  his  general  formula,  he  had  few  data  at 
his  command,  and  a  clearer  demonstration  was  given 
by  Halley,  who,  from  a  basis  of  calculations,  accu- 
rately predicted  the  return  of  "  Halley's  comet "  in 
1758-9. 

The  physician  Olbers  (d.  1840)  introduced  a  sim- 
plification in  the  method  of  computing  the  paths  of 
comets,  and  for  half  a  century  was  one  of  the  most 
assiduous  and  successful  students  of  these  periodic 
visitants.  Among  the  many  whom  he  helped  and 
stimulated  during  his  long  life  was  Encke,  a  pupil 
of  Gauss,  one  of  those  who  have  passed  through  the 
portal  of  mathematics  to  the  study  of  the  stars. 
Sixty-three  years  after  Halley's  prediction  was  veri- 
fied, Encke  in  1822  had  a  similar  success  with  a 
comet  "  of  short  period,"  which  revolves  round  the 
sun  in  about  three  and  a  quarter  years. 

More  than  200  comets  have  been  studied  in  the 
nineteenth  century;  and  by  means  of  the  spectro- 
scope, applied  to  the  study  of  comets  by  Donati  in 
1864  and  by  Huggins  in  1868,  it  has  been  possible 
to  advance  a  little  beyond  the  computation  of  paths 
and  periods,  and  to  prove,  for  instance,  that  at  least 
some  comets  are  in  part  self-luminous,  while  others, 
especially  those  of  short  period,  appear  to  owe  most 
of  their  brilliance  to  light  reflected  from  the  sun. 
Professor  Tait  seems  to  have  been  the  first  to  give 
definite  expression  to  the  idea  (expounded  by  Lord 
Kelvin  in  1871)  that  the  light  of  comets,  and  of 
nebula?  as  well,  may  be  due  to  flashes  of  ignited  gas 


ADVANCE  OF  ASTRONOMY.  187 

induced  by  the  encounters  amid  the  swarms  of  me- 
teoric stones. 

It  is  impressive  to  read  how  the  comet  of  1811 
was  assigned  an  orbit  requiring  3065  years  for  its 
completion,  such  that  "  when  it  last  visited  our 
neighbourhood,  Achilles  may  have  gazed  on  its  im- 
posing train  as  he  lay  on  the  sands  all  night  bewail- 
ing the  loss  of  Patroclus;  and  when  it  returns,  it 
will  perhaps  be  to  shine  upon  the  ruins  of  empires 
and  civilisations  still  deep  buried  among  the  secrets 
of  the  coming  time."  It  is  impressive  to  note  the 
measurements  of  some  of  the  great  comets  whose 
highly  rarefied  emanations  or  "  tails  "  may  extend 
for  several  millions  of  miles,  but  the  behaviour  of 
the  tail  points  to  the  conclusion  that  it  is  but  "  a 
stream  of  matter  driven  off  from  the  comet  in  some 
way  by  the  action  of  the  sun,"  and  the  density  must 
be  small  indeed,  since  the  earth  has  passed  through 
a  tail  at  least  twice  in  the  century  without  the  fact 
being  known  until  afterwards.  Indeed  the  progress 
of  knowledge  has  robbed  comets  of  some  of  their 
dignity,  for  since  the  middle  of  the  century  it  has 
been  generally  recognised  that,  with  the  possible  ex- 
ception of  the  bright  central  "  nucleus,"  a  comet  is 
small  in  mass,  and  in  a  state  of  great  tenuity,  unable 
to  affect  the  motion  of  the  planet  it  approaches,  and 
allowing  the  light  of  a  star  to  pass  even  through  its 
"  head." 

Numerous  interesting  observations  point  to  some 
close  connection  between  comets  and  meteors  or 
"  shooting  stars."  Thus  Biele's  comet  (with  a  period 
of  sixty-seven  years),  which  scared  the  popular  im- 
agination in  1832,  was  first  seen  to  become  double, 
and  was  afterwards  lost  altogether,  while  on  two  sub- 


188    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

sequent  occasions  (1872  and  1885),  as  the  earth  was 
crossing  the  path  of  the  comet  when  it  (if  it  had 
persisted)  was  nearly  due  at  the  same  place,  there 
was  an  unusually  brilliant  shower  of  meteors. 
Meteors  may  be  fragments  of  a  broken-up  comet,  or 
a  comet  may  be  a  swarm  of  meteors. 

In  the  study  of  comets  the  accuracy  of  the  gravi- 
tational formula  has  been  beautifully  illustrated,  and, 
during  the  latter  half  of  the  century,  considerable 
progress  was  made  towards  an  understanding  of  their 
physical  nature. 

THE  STUDY  OF  THE  STARS. 

Almost  until  the  end  of  the  eighteenth  century, 
it  was  the  general  belief,  even  among  astronomers, 
that  the  stars  were  fixed  and  unchanging.  As  Miss 
Clerke  says,  "  their  recognised  function,  in  fact,  was 
that  of  milestones  on  the  great  celestial  highway 
traversed  by  the  planets."  Gradually,  however,  it 
became  evident  that  this  emphatically  static  image 
was  far  from  being  true.  What  Giordano  Bruno 
had  imagined,  was  confirmed  by  Halley  in  1718, 
when  he  showed  that  Sirius,  Aldebaran,  Betelgeuse, 
and  A  returns  had  changed  their  positions  in  the  sky 
since  Ptolemy  marked  these  out.  Many  similar  facts 
came  to  light,  and  in  the  last  quarter  of  the  eigh- 
teenth century,  sidereal  astronomy  included  "  three 
items  of  information — that  the  stars  have  motions, 
real  or  apparent;  that  they  are  immeasurably  re- 
mote ;  and  that  a  few  shine  with  a  periodically  varia- 
ble light."  * 

William  Eerschel. — It  was  about  the  beginning  of 


*  Agnes  M.   Clerke.     A  popular  History  of  Astronomy 
During  the  Nineteenth  Century,  1885,  p.  13. 


ADVANCE  OF  ASTRONOMY.  189 

the  last  quarter  of  the  eighteenth  century  that  Wil- 
liam Herschel  (1738-1822)  began  to  realise  his 
ambition  of  obtaining  "  a  knowledge  of  the  construc- 
tion of  the  heavens,"  and  rapidly  passed  from  being 
"  a  star-gazing  musician  "  to  the  post  of  royal  astron- 
omer. 

He  made  clear,  what  had  been  suspected  by  some, 
that  there  were  systems  of  stars,  in  some  measure 
comparable  to  the  planetary  system,  but  varying 
greatly  in  the  periods  and  forms  of  their  revolutions. 
A  double  star  had  been  usually  regarded  as  an  opti- 
cal phenomenon  due  to  the  fact  that  two  stars  which 
might  be  very  far  apart,  happened  to  be  nearly  in  the 
same  line  of  sight  from  the  earth;  Herschel  proved 
that  many  double  stars  were  real  binary  combina- 
tions, "  intimately  held  together  by  the  bond  of  mu- 
tual attraction."  In  the  apparent  motions  of  the 
stars  he  distinguished  one  component  due  to  a  trans- 
lation of  our  planetary  system  towards  a  point  in 
the  constellation  Hercules,  and  another  component 
due  to  a  real  movement  of  the  stars  themselves.  In 
his  study  of  nebula?  he  was  gradually  forced  to  the 
conclusion  that  there  were  nebulosities  which  could 
not  be  resolved  in  stars,  but  consisted  of  a  "  shining 
fluid  "  or  "  self-luminous  matter  "  diffused  in  space, 
and  "  more  fit  to  produce  a  star  by  its  condensation, 
than  to  depend  on  the  star  for  its  existence."  This 
led  him  about  1791  to  a  theory  of  the  nebular  origin 
of  stars,  apparently  in  complete  independence  of  thie 
nebular  theory  of  Laplace  (1796). 

Two  main  contributions,  then,  must  ~be  traced  io 
Herschel, — that  fie  extended  Neuionian  methods  to 
the  study  of  the  stars,  and  that  he  made  the  whole 
scientific  picture  of  the  heavens  vividly  kinetic.  On 
the  one  hand,  he  extended  the  range  of  precise 


190    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

measurement  and  calculation;  on  the  other  hand, 
he  emphasised  the  idea  of  change  or,  one  may  almost 
say,  of  evolution.  The  heavens  no  longer  seemed 
fixed  and  unchanging,  when  it  was  shown  that  new 
systems  were  being  formed  and  that  others  were  dying 
away. 

Herschel's  work  was  continued  at  Konigsberg  by 
Bessel;  at  the  Russian  observatory  of  Pulkowa  by 
Struve,  succeeded  in  1858  by  his  son  Otto;  and  by 
many  other  illustrious  workers.  In  Britain  the 
father  found  an  intellectual  heir  in  the  son,  John 
F.  W.  Herschel  (1792-1871),  whose  Cape  observa- 
tions (1834-38)  did  for  the  Southern  heavens  what 
had  been  done  for  the  Northern.  Published  in  1847, 
they  represent  the  state  of  sidereal  astronomy  at  the 
middle  of  the  century.  "  Not  only  was  acquaint- 
ance with  the  individual  members  of  the  cosmos 
vastly  extended,  but  their  mutual  relations,  the  laws 
governing  their  movements,  their  distances  from  the 
earth,  masses,  and  intrinsic  lustre,  had  begun  to  be 
successfully  investigated."  * 

Improvements  in  telescopes  and  other  instruments 
aided  in  the  progress  of  the  sidereal  astronomy  to 
which  Herschel  had  given  so  much  impetus,  and  with' 
improved  mechanical  means  was  associated  a  re- 
formed method  of  observation.  Friedrich  Wilhelm 
Bessel  (1784-1846),  who  made  himself  famous  at 
the  age  of  twenty  by  calculating  an  orbit  for  Halley's 
comet,  did  a  gigantic  piece  of  work  by  instituting 
'(1813,  1830)  a  uniform  system  of  "  reduction  "  (or, 
correction  of  observations)  which  lengthened  out  the 
period  of  exact  astronomy  by  half  a  century.  In 
other  words  he  made  a  uniform  correction  of  Brad- 
ley's  Greenwich  observations,  making  allowances  for 
*  A.  M.  Clerke.  History,  1885,  p.  65. 


ADVANCE  OF  ASTRONOMY.  191 

precession,  aberration,  refraction,  and  instrumental 
errors.  And  the  edition  of  Bradley's  results  was 
only  a  prelude  to  fresh  catalogues  of  his  own,  exe- 
cuted between  1821  and  1833,  and  including  about 
62,000  stars.  It  is  hardly  necessary  to  say  that 
Bradley's  work  was  continued  through  the  century 
by  many  illustrious  astronomers. 

Measuring  the  Distance  of  a  Star. — To  the  an- 
cients the  stars  remained  altogether  mysterious; 
they  were  points  of  fire  set  in  the  concave  vault  of 
the  firmament  and  borne  by  it  in  daily  revolution 
around  the  fixed  earth.  Keppler  seems  to  have  been 
the  first  to  dare  to  deduce  from  the  Copernican  sys- 
tem the  conclusion  that  the  stars  are  extremely  dis- 
tant suns, — so  distant  that  most  of  them  appear  un- 
affected in  direction  throughout  the  year ;  e.  g.,  when 
viewed  from  opposite  ends  of  the  earth's  orbit.  If 
so  distant  and  yet  so  clearly  visible,  they  must  be 
sunlike ;  i.  e.,  great  sources  of  radiant  energy.  This 
conclusion  was  less  hesitatingly  accepted  by  Galilei. 

But  while  it  came  to  be  generally  recognised  that 
the  stars  were  unthinkably  distant  suns,  it  was  not 
till  1838  that  the  distance  of  any  star  was  measured. 
In  that  year,  Friedrich  Wilhelm  Bessel  (1784- 
1846),  using  Fraunhofer's  heliometer,  or  "  divided 
object-glass  micrometer,"  was  able  to  determine  the 
parallax,  and  thus  to  deduce  the  distance  of  a  small 
star  in  the  constellation  of  the  Swan  (61  Cygni). 
Soon  afterwards  analogous  results  were  published  by 
Thomas  Henderson  for  a  Centauri  (1839),  and  by 
Struve  (1840)  for  Vega. 

The  method  of  estimating  the  distance  of  a  star 
is  simple  in  theory.  Suppose  that  the  direction  of  a 
star  is  observed  at  a  certain  time  with  all  possible 
accuracy;  suppose  that  the  same  star  is  observed 


192    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

six  months  later  when  the  earth  has  travelled  over 
one-half  of  its  orbit,  another  direction-line  may  be 
observed;  suppose  the  two  direction-lines  produced 
till  they  meet,  the  point  of  intersection  must  be  the 
position  of  the  star.  Then  we  have  a  triangle  whose 
base  is  the  diameter  of  the  earth's  orbit,  and  a  geo- 
metrical calculation  enables  us  to  determine  the  pro- 
portion that  the  sides  bear  to  this. 

The  method  of  determining  parallax  is  theoreti- 
cally so  simple  that  it  could  not  but  be  known  to 
Copernicus  and  his  followers.  Indeed  for  three  hun- 
dred years  before  Bessel's  success  there  were  pains- 
taking attempts  to  apply  it,  attempts  which  invaria- 
bly ended  in  the  disappointing  result  that  the  two 
direction-lines  from  opposite  ends  of  the  earth's  orbit 
always  seemed  to  be  parallel.  We  know  this  to  mean 
that  the  star  observed  was  too  distant,  or  that  the 
instruments  used  were  not  precise  enough,  to  show 
appreciable  parallax. 

As  we  have  noted,  Bessel  succeeded  and  the  im- 
portance of  the  step  thus  taken  is  not  affected  by  the 
fact  that  his  estimate  of  the  distance  of  61  Cygni 
as  600,000  times  that  of  the  Sun  is  now  reduced  to 
440,000. 

A  few  months  after  Bessel  announced  his  dis- 
covery, Henderson  of  Edinburgh  published  his  esti- 
mate of  the  distance  of  «  Centauri,  which  is,  so  far 
as  we  know,  the  star  nearest  the  solar  system.  Hen- 
derson calculated  its  distance  at  180,000  times  that 
of  the  Sun,  this  has  now  been  extended  to  270,000 
times. 

Writing  in  1885,  Miss  Clerke  says:  "The  same 
work  has  since  been  steadily  pursued,  with  the  gen- 
eral result  of  showing  that  as  regards  their  over- 
whelming majority,  the  stars  are  far  too  remote  to 


ADVANCE  OF  ASTRONOMY.  193 

show  even  the  slightest  trace  of  optical  shifting  from 
the  revolution  of  the  earth  in  its  orbit.  In  about  a 
score  of  cases,  however,  small  parallaxes  have  been 
determined,  some  certainly  (that  is,  within  moderate 
limits  of  error),  others  more  or  less  precariously." 

Dr.  Fison  notes  that  for  forty  years  after  Bessel's 
discovery  the  record  is  chiefly  one  of  accumulation 
of  experiences ;  "  and  when  in  1881  Dr.  Gill  and 
Dr.  Elkin  commenced  a  series  of  observations  at 
the  Cape  of  Good  Hope,  the  parallaxes  of  not  more 
than  half  a  dozen  stars  had  been  detected  with  cer- 
tainty. Since  that  date,  however,  parallax  hunters 
have  been  better  rewarded,  though  up  to  the  present 
time  (1898)  it  is  doubtful  whether  success  has  been 
achieved  in  more  than  fifty  instances."  f 

The  distances  of  the  stars  whose  remoteness  is 
measurable  are  so  enormous  that  they  produce  almost 
no  impression  on  the  ordinary  mind. 

"  It  follows,"  said  Bessel,  "  that  the  distance  of 
61  Cygni  from  the  sun  is  657,700  times  the  half 
diameter  of  the  earth's  orbit.  The  light  from  the 
star  takes  ten  years  to  traverse  this  enormous  dis- 
tance. It  is  so  vast,  that  though  it  may  be  conceived, 
it  cannot  be  visualised.  All  attempts  to  realise  it, 
fail  either  because  of  the  size  of  the  unit  of  measure- 
ment or  because  of  the  number  of  repetitions  of  the 
unit.  The  distance  which  light  traverses  in  a  year 
is  not  more  realisable  than  that  traversed  in  ten 
years.  Or  if  we  choose  a  realisable  unit,  such  as 
the  distance  of  200  miles  which  a  locomotive  (bicycle, 
we  should  say)  travels  in  a  day,  it  would  require 
68,000  millions  of  such  daily  journeys,  or  about  200 

*  A.  M.  Clerke.     History,  1885,  p.  48. 
t  Recent  Advances  in  Astronomy,  1898,  p.  7. 


194    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

millions  of  yearly  journeys  to  reach  the  star  in  ques- 
tion." * 

It  seems  on  the  whole  most  convenient  to  use,  as 
Bessel  suggested,  as  a  unit  "  the  light  journey  of  one 
year."  The  velocity  of  light  is  186,300  miles  a 
second,  about  six  billion  miles  a  year.  "  Light  takes 
four  years  and  four  months  to  reach  the  earth  from 
a  Centauri,  yet  a  Centauri  lies  some  ten  billions  of 
miles  nearer  to  us  (so  far  as  is  yet  known)  than  any 
other  member  of  the  sidereal  system !  "  f  In  other 
words,  we  see  a  Centauri,  not  as  it  is  now,  but  as  it 
was  more  than  four  years  ago.  Similarly,  light  takes 
more  than  six  years  to  reach  us  from  61  Cygni. 

Given  a  determination  of  the  parallax  and  distance 
of  two  stars  in  a  system,  and  a  knowledge  of  their 
period  of  revolution,  it  became  possible  to  calculate 
their  combined  mass  in  terms  of  that  of  the  sun ;  and 
the  process  of  weighing  the  stars  began. 

Herschel's  conclusion  as  to  movement  of  the  solar 
system  as  a  whole,  often  doubted,  was  repeatedly 
confirmed ;  the  general  direction  was  more  carefully 
stated ;  and  even  the  rate  has  been  guessed  at.  F.  G. 
W.  Strove  (1793-1864)  continued  Herschel's  study 
of  double  stars,  and  published  in  1837  his  monumen- 
tal Mensurce  Micrometricce,  which  "  will  for  ages 
serve  as  a  standard  of  reference  by  which  to  detect 
change  or  confirm  discovery." 

The  distances  of  some  of  the  nearer  stars  can  lie 
calculated  by  the  determination  of  annual  parallax, 
a  method  first  successfully  employed  by  Bessel 
(1838),  Henderson  (1839),  and  Struve  (1840); 
this  is  historically  important  as  a  confirmation  of 

*  Freely  translated  from  Dannemann's  Grundriss  einer 
Oeschichte  der  Nalurwissenschaften,  vol.  1,  1896,  p.  825. 
t  A.  M.  Clerke.    History,  1885,  p.  49. 


ADVANCE  OF  ASTRONOMY.  195 

{he  Copernican  system  and  as  a  suggestion  of  the 
sunlike  nature  of  the  stars. 

Life  of  Stars. — If  the  view  be  accepted  that  the 
sun  was  once  a  diffused  body  of  gas  extending  be- 
yond the  present  limits  of  the  solar  system,  and  that 
it  has  slowly  shrunk,  giving  rise  to  the  present  phase 
of  things,  and  if  the  stars  be  regarded  as  sunlike,  we 
should  expect  to  find  in  the  immensity  of  the  heavens 
some  confirmatory  evidence.  In  other  words,  we 
should  expect  to  see  stars  a-making  and  others  a-dy- 
ing.  The  former  are  now  familiar  to  astronomers, 
and  the  existence  of  dead  stars  is  generally  admitted. 

Nebulce. — It  is  generally  agreed  that  the  faint 
clouds  of  light  called  nebulae,  which  occur  scattered 
in  the  sky,  are  in  many  cases  at  least  early  stages  of 
star-making, — embryo  stars  in  an  undifferentiated 
state.  Two  of  these  nebulae  are  visible  to  the  un- 
aided eye  on  clear  dark  nights,  namely,  in  the  con- 
stellations of  Orion  and  of  Andromeda. 

In  the  seventeenth  century,  after  Galilei  had  intro- 
duced the  use  of  the  telescope,  many  nebula?  were  de- 
tected, but  they  were  generally  passed  over  quickly 
as  "  diffusions  of  self-luminous  matter,"  or  "  shining 
fluid,"  or  "  fire-mist,"  and  so  forth.  Towards  the 
end  of  the  eighteenth  century  (1780)  William  Her- 
schel  began  his  study  of  nebula?,  and  not  only  in- 
creased the  list  from  150  to  2,500  in  about  a  score 
of  years,  but  showed  that  many  of  them  had  a  de- 
tailed structure.  At  first  he  regarded  nebula?  as 
clusters  of  stars,  and  stated  the  evolutionary  idea 
that  stars  and  clusters  of  stars  arose  from  nebular 
condensations.  Subsequently,  however,  he  reverted 
to  the  older  view  in  regard  to  many  nebula?,  includ- 
ing that  of  Orion.  In  the  first  half  of  the  nineteenth, 
century  it  was  Herschel's  earlier  view  that  prevailed ; 


196    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

improved  telescopes,  such  as  that  constructed  by  Lord 
Rosse  at  Parsonstown  in  Ireland,  resolved  one  nebula 
after  another  into  collections  of  stars.  Indeed  imag- 
ination far  outstripped  the  evidence,  and  it  was  wide- 
ly supposed  that  nebulae  were  systems  of  suns,  multi- 
ples, as  it  were,  of  the  architectural  unit  which  our 
solar  system  was  believed  to  display. 

So  far  telescopic  analysis  had  alone  been  possi- 
ble, but  the  next  great  step  was  taken  in  1864, 
when  Sir  William  Huggins  applied  the  spectroscope 
to  the  study  of  a  small  but  bright  nebulae  in  the  con- 
stellation of  the  Dragon.  The  spectrum  (yielding 
no  continuous  band)  was  like  that  of  a  glowing  gas, 
and  therefore  it  was  concluded  that  this  nebula?  was 
not  a  galaxy  of  stars,  but  a  vast  area  of  incandescent 
gas.  In  the  next  few  years  many  others,  including 
the  Great  Nebulae  of  Orion,  were  shown  to  be  gaseous 
while  others  (yielding  "continuous"  spectra)  seemed 
to  be  either  star  clusters  or  gases  in  process  of  con- 
densation. 

It  is  important  to  notice  that  the  growth  of  ther- 
modynamics has  led  to  a  rejection  of  the  old  view 
that  nebulous  stuff  was  originally  or  is  still  "  instinct 
with  fire."  The  essay  of  Helmholtz  in  1854  made  it 
plain  that  this  supposition  is  unnecessary,  "  since  in 
the  mutual  gravitation  of  widely  separated  matter  we 
have  a  store  of  potential  energy  sufficient  to  gener- 
ate the  high  temperature  of  the  sun  and  stars.  We 
can  scarcely  go  wrong  in  attributing  the  light  of  the 
nebulae  to  the  conversion  of  the  gravitational  energy 
of  shrinkage  into  molecular  motion.''  * 

"  It  is  difficult  not  to  see  in  the  gaseous  nebulae 
the  stuff  of  which  future  stars  will  be  made.  Grant- 
ing that  their  substance  is  subject  to  the  law  of  gmvir 
*  Huggins.  Rep,  Brit.  Ass.  for  1891,  p.  22. 


ADVANCE  OF  ASTRONOMY.  197 

tat  ion,  it  appears  certain  that  in  coming  ages  their 
glowing  matter  must,  under  its  influence,  be  drawn 
towards  centres  of  condensation;  the  smaller  and 
more  symmetrical  of  the  nebulae  possibly  developing 
into  single  stars,  but  such  majestic  collections  of 
cloudy  structures  as  are  revealed  in  Orion  being  more 
probably  the  origin  of  hosts  of  separate  suns/' 

Dead  Stars. — While  some  nebulae  are  plausibly 
interpreted  as  stars  a-making,  there  are  also  phe- 
nomena which  indicate  stars  dying  or  dead,  or  in 
other  words,  dark.  It  is  obvious  that  the  existence 
of  a  dark  star  cannot  be  demonstrated  to  the  eye ;  but 
it  may  be  inferred  (a)  from  the  occurrence  of  the 
total  or  partial  eclipse  of  a  bright  star,  or  (fc)  from 
disturbances  in  the  movement  of  a  bright  star  such 
as  the  gravitational  influence  of  a  dark  neighbour 
would  explain.  In  both  these  ways  the  existence  of 
dark  stars  has  been  indirectly  proved. 

The  regularity  in  the  variations  of  the  light  of 
Algol — the  best-known  of  the  variable  stars — was 
hypothetically  interpreted  by  Goodriche  (1782)  as 
due  to  the  revolutions  of  a  dark  companion  star 
which  caused  partial  eclipse;  and  the  researches  of 
E.  C.  Pickering  of  Harvard  (1888)  and  of  Yogel  of 
Potsdam  (1888-1891)  have  justified  the  hypothesis. 

"  The  possibility  of  an  unseen  system  of  stars  per- 
meating the  seen  is  beyond  doubt"  * 

Condensing  Dr.  Fison's  account  of  the  subject,  we 
may  sum  up  the  possible  history  of  a  nebula.  A 
diffused  area  of  gases,  perhaps  comparatively  cool, 
perhaps  holding  part  of  its  contents  in  the  form  of 
solid  or  liquid  particles;  gravitational  attraction 
brings  about  a  spherical  form;  heat  is  lost  by  radi- 
ation and  the  parts  of  the  area  draw  together;  tem- 
*Fison.  Recent  Advances,  p.  35. 


198    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

perature  rises  and  the  nebula  becomes  more  thor- 
oughly gaseous,  if  it  was  not  so  at  the  start;  as  the 
outer  parts  cool  they  condense  into  the  clouds  of  a 
photosphere  and  the  nebula  becomes  a  sun;  for  a 
time,  as  shrinkage  increases,  the  temperature  rises; 
but  the  limits  to  this  must  be  reached  sooner  or  later 
and  the  sun,  passing  the  zenith  of  its  splendour,  grad- 
ually sinks  into  dark  coldness. 

"  Fixed  Stars." — One  of  the  many  instances  of 
the  characteristic  nineteenth  century  transition  from 
static  to  kinetic  conceptions,  may  be  found  in  the 
hesitancy  with  which  astronomers  now  speak  of 
"  fixed  stars."  In  many  cases  it  has  been  shown 
that  their  positions  relative  to  one  another  change  in 
the  course  of  years,  and  the  displacement,  though  ap- 
parently very  minute,  indicates  an  enormous  velocity 
of  movement.  "  Sirius  drifts  over  the  face  of  the  sky 
with  such  speed  that  in  1,400  years  its  position  will 
be  removed  from  its  present  one  by  a  distance  that 
would  just  be  covered  by  the  diameter  of  the  full 
moon.  ...  To  do  this  it  must  travel  athwart  the 
direction  of  vision  with  a  speed  of  over  ten  miles  per 
second,  more  than  one-half  of  that  of  the  Earth  in  its 
orbit;  and  this  takes  no  account  of  any  velocity  the 
star  may  possess  in  the  direction  of  the  line  of  vision, 
a  displacement  in  which  direction  would  obviously 
not  affect  its  position  upon  the  face  of  the  heavens." 

Similarly,  to  take  the  most  rapid  known  dis- 
placement, a  star  in  the  Great  Bear  named  Groom- 
bridge,  1830,  would  move  in  257  years  over  the 
moon's  diameter,  and  this  at  a  distance  of  2,300,000 
times  that  of  the  sun  implies  a  rate  of  227  miles  per 
second.  JsTor  should  we  forget  here  that  the  sun  itself 
is  travelling  in  a  line  directed  towards  the  star  Vega, 
*  Fison,  p.  46. 


ADVANCE  OF  ASTRONOMY.  199 

at  a  rate  which  some  estimate  at  12-18  miles  per 
second.  There  has  been  no  justification  of  the  hope 
of  a  century  ago  that  some  star  (Sirius  was  suggested 
by  Kant)  or  some  point  (in  the  Pleiades,  according 
to  Madler)  would  turn  out  to  be  the  hub  of  the  uni- 
verse, the  centre  to  which  all  the  heavenly  bodies  are 
related;  the  system  or  goal  of  the  grandest  of  all 
movements  is  unknown. 

EXTENSION  AND  INTENSIFYING  OF  OBSERVATION. 

Extension  of  Observational  Astronomy. — In  as- 
tronomy, as  in  other  sciences,  a  large  part  of  the 
available  intellectual  energy  has  gone  and  must  go 
to  extend  the  area  of  observation,  or  to  revise  with 
intensified  carefulness  what  has  been  already  ob- 
served. It  is  difficult  to  give  any  account  of  this 
ungeneralised  work,  whose  value  is  in  the  future 
rather  than  in  the  present.  Numbering  the  stars  is 
like  cataloguing  Eadiolarians  or  Diatoms,  a  means 
not  an  end;  and  a  telescopic  photograph  of  a  corner 
of  the  Milky  Way  is  like  a  similar  picture  of  a  micro- 
scopic section — interesting  and  marvellous,  of  course, 
for  everything  is — but  not  attaining  full  interest 
until  it  can  be  used  as  an  item  in  some  generalisa- 
tion. 

The  Milky  Way. — To  take  an  instance :  The  Milky 
Way — the  high  road  to  Olympus — has  been  the  sub- 
ject of  imaginings  since  men  first  saw  the  stars.  Its 
poetical  interpretations  are  many,  but  as  to  its  sci- 
entific interpretations  there  has  been  little  progress 
since  Galilei's  telescope  confirmed  the  conjecture  of 
Pythagoras  that  the  haze  of  the  dimly  luminous  arch 
was  "  the  combined  shimmer  of  hosts  of  stars,  each 
one  too  faint  by  itself  to  be  distinguished  by  the 
unaided  eye." 

N 


200    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

Both  the  Herschels,  Struve,  Proctor,  and  others 
sought  to  explain  the  appearance  of  this  majestic 
way  of  light  as  due  to  perspective  effect  or  optical 
projection,  but  there  seems  to  have  been  a  complete 
acceptance  of  "  the  more  simple  and  direct  view, 
that  the  Milky  Way  is  a  definite  and  complicated 
structure,  and  that  its  bifurcation,  its  vacuities,  its 
gaps,  and  its  other  irregularities,  are  definite  physi- 
cal facts."  * 

The  great  "  Bonn  Durchmusterung "  compiled 
(1859-1862)  under  the  supervision  of  Argelander, 
the  more  recent  Harvard  catalogue  by  Pickering,  and 
Gould's  list  of  the  stars  visible  from  the  southern 
hemisphere,  illustrate  supreme  patience  and  care- 
fulness, but  as  yet  we  remain  unaware  of  any 
securely  established  or  intelligible  generalisations 
as  to  the  stellar  distribution.  The  Bonn  list  in- 
cludes 324,198  stars  down  to  a  certain  (9.5)  mag- 
nitude (estimated  in  terms  of  brightness),  but  mere 
number  does  not  impress  the  imagination,  especi- 
ally since  the  sight  of  the  starlit  sky  suggests  le- 
gions upon  legions  of  luminaries  visible  to  the  un- 
aided eye, — a  suggestion  very  far  from  the  truth. 
The  more  impressive  aspect  is  that  which  remains 
vague,  of  which,  indeed,  we  have  as  yet  only  sug- 
gestions, that  there  is  probably  a  system  of  the  stars, 
— hidden  from  our  gaze  not  only  by  distance,  but  by 
its  inherent  complexity. 

A  quotation  from  one  of  the  modern  masters  may 
serve  to  suggest  the  present  tentative  position: — 
"  The  heavens  are  richly  but  very  irregularly  in- 
wrought with  stars.  The  brighter  stars  cluster  into 
well-known  groups  upon  a  background  formed  of  an 
enlacement  of  streams  and  convoluted  windings  and 
*  Fison,  Recent  Advances,  1898,  p.  85. 


ADVANCE  OF  ASTRONOMY.  201 

intertwined  spirals  of  fainter  stars,  which  become 
richer  and  more  intricate  in  the  irregularly  rifted 
zone  of  the  Milky  Way. 

"  We,  who  form  part  of  the  emblazonry,  can  only 
see  the  design  distorted  and  confused ;  here  crowded, 
there  scattered,  at  another  place  superposed.  The 
groupings  due  to  our  position  are  mixed  up  with  those 
which  are  real. 

"  Can  we  suppose  that  each  luminous  point  has  no 
other  relation  to  those  near  it  than  the  accidental 
neighbourship  of  grains  of  sand  upon  the  shore,  or 
of  particles  of  wind-blown  dust  of  the  desert  ?  Surely 
every  star  from  Sirius  and  Vega  down  to  each  grain 
of  the  light-dust  of  the  Milky  Way  has  its  present 
place  in  the  heavenly  pattern  from  the  slow  evolving 
of  its  past.  We  see  a  system  of  systems,  for  the  broad 
features  of  clusters  and  streams  and  spiral  windings 
which  mark  the  general  design  are  reproduced  in 
every  part.  The  whole  is  in  motion,  each  point 
shifting  its  position  by  miles  every  second,  though 
from  the  august  magnitude  of  their  distances  from 
us  and  from  each  other,  it  is  only  by  the  accumulated 
movements  of  years  or  of  generations  that  some  small 
changes  of  relative  position  reveal  themselves. 

"  The  deciphering  of  this  wonderfully  intricate 
constitution  of  the  heavens  will  be  undoubtedly  one 
of  the  chief  astronomical  works  of  the  coming  cen- 
tury." * 

One  interesting  result  as  to  method  should  be 
noted,  namely,  the  development  of  stellar  photogra- 
phy. When  even  the  trained  eye,  with  the  telescope 
to  help,  cannot  detect,  the  photographic  plate  may 
reveal.  The  invention  and  improvement  of  the  gela- 

*  Sir  William  Huggins.  President's  Address,  Rep.  Brit. 
Ass.  for  1891,  pp.  35-36. 


202    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

tine  dry  plate,  which  on  sufficiently  long  exposure 
will  register  an  image  of  a  body  whose  luminosity 
falls  far  below  the  limit  of  visibility  to  our  eyes, 
has  meant  a  remarkable  extension  of  our  sense  of 
sight.  It  has  meant  seeing  the  invisible ! 

Of  some  importance,  too,  has  been  the  develop- 
ment of  more  exact  methods  of  measuring  star  bright- 
ness (photometry),  and  the  resulting  classification 
(first  suggested  by  Pogson  in  1856)  into  definite  de- 
grees of  "  magnitude."  Thus  a  star  of  the  sixth 
magnitude  is  one  hundred  times  fainter  than  one  of 
the  first  magnitude. 

Intensifying  of  Observation. — Inspection  of  the 
recent  moon-maps  and  photographs,  as  seen,  for  in- 
stance, at  the  Paris  Exposition  (1900),  will  illus- 
trate what  is  meant  by  an  intensifying  of  observa- 
tion. 

The  Moon. — The  large  size  of  our  satellite  (2,160 
miles  in  diameter),  and  its  relative  nearness  to  us 
(238,833  miles  from  the  earth's  centre),  facilitated 
the  careful  study  of  its  superficial  characters,  at 
least  of  that  side  which  is  alone  presented  to  our 
view.  The  systematic  and  interpretative  study  of 
the  moon's  face  practically  began  with  the  century, 
for  it  dates  from  Schroter's  Solenotopographische 
Fragmente  (1791-1802).  Lohrmann  and  Schmidt, 
Beer  and  Madler,  Nasmyth  and  Carpenter,  Neison 
and  Secchi,  and  many  more  have  added  detail  to  de- 
tail, so  that  it  is  safe  to  say  there  is  no  country 
mapped  so  nearly  up  to  the  present  limits  of  possible 
precision.  The  heights  of  some  of  its  mountain 
ranges  have  been  computed  from  their  shadows  and 
the  depths  of  some  of  its  extinct  craters  have  been 
sounded.  We  have  certainly  advanced  far  from  the 
older  view,  which  even  Herschel  did  not  entirely  get 


ADVANCE  OF  ASTRONOMY.  203 

rid  of,  that  the  moon  might  be  habitable  like  the 
earth,  and  yet  there  seems  no  unanimous  answer  to 
the  question: — Has  the  moon  no  atmosphere,  or  one 
of  extreme  tenuity  ?  We  have  got  far  from  the  belief 
of  Schrb'ter,  who  imagined  he  had  discovered  a  lunar 
city  ;  what  were  called  seas  are  now  said  to  be  cov- 
ered with  dry  rock ;  what  are  called  rills  are  now  said 
to  be  great  clefts  or  gorges  certainly  waterless,  but  we 
remain  in  doubt  as  to  the  meaning  of  the  broad  white 
rays  which  diverge  for  hundreds  of  miles  from  some 
of  the  principal  "  ring-plains,"  and  there  are  many 
who  attribute  to  glaciation  what  others  confidently 
interpret  as  due  to  volcanic  action.  Perhaps  the 
most  interesting  observations  are  the  few  which  point 
— though  with  insufficient  security — to  some  slight 
changes  on  the  moon's  apparently  changeless  face. 

Similarly,  there  are  maps  of  Mars  now  in  circu- 
lation, which  surpass  in  detail  those  available  in  re- 
gard to  Africa  a  century  ago.  And  though  the  pre- 
cision of  these  Martian  maps  may  be  fallacious  the 
same  is  true  of  many  of  the  early  maps  of  Africa, 
and  we  cannot  gainsay  the  impression  of  a  greatly 
increased  intensity  of  observation.  To  what  is  this 
due  ?  To  more  powerful  telescopes,  to  the  use  of  the 
spectroscope  and  polariscope,  to  the  development  of 
photography,  and  to  an  exact  knowledge  of  the  times 
(in  "  opposition  "  to  the  sun,  i.  e.,  nearest  the  earth) 
when  Mars  can  be  studied  to  best  advantage. 

The  study  of  Mars  illustrates  the  growing  intensity 
of  observational  study,  while  the  imaginary  super- 
structure reared  by  some  on  the  supposed  existence  of 
an  intricate  system  of  canals  illustrates  the  danger 
of  outstripping  the  evidence. 

PHYSICAL  AND  CHEMICAL  PKOBLEMS. 

Beginnings    of   Physical   Astronomy. — In    1610, 


204:    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

Fabricius  and  Galilei  discovered  sun-spots,  which  are 
still  of  fascinating  interest  to  astronomers.  In  early 
days,  some  regarded  them  as  due  to  the  transits  of 
small  planets  across  the  sun's  disc,  others  thought  of 
them  as  clouds,  others  as  masses  of  cindery  slag  in 
process  of  being  sloughed  off,  and  so  on.  In  1774, 
Prof.  Alexander  Wilson  of  Glasgow  was  able  to  give 
geometrical  definiteness  to  the  suggestion,  which  had 
been  repeatedly  made,  that  the  spots  were  due  to 
great  excavations  in  the  sun's  substance.  He  also 
expounded  the  idea,  which  William  Herschel  elabo- 
rated, that  the  sun  was  like  an  earth  within,  but  sur- 
rounded by  an  aurora  of  resplendent  clouds.  Some 
estimate  of  the  state  of  knowledge  in  regard  to  the 
physical  constitution  of  the  sun  may  be  got  from 
Sir  William  Herschel's  eloquent  descriptions  about 
the  beginning  of  the  nineteenth  century.  It  was  to 
him  a  sort  of  glorified  earth,  with  hills  and  valleys, 
luxuriant  vegetation,  and  a  population,  protected  by 
a  cloud-canopy  from  a  radiant  outer  shell  some  thou- 
sands of  miles  in  thickness.  This  "  was  nothing  less 
than  the  definite  introduction  into  astronomy  of  the 
paradoxical  conception  of  the  central  fire  and  hearth 
of  our  system  as  a  cold,  dark,  terrestrial  mass,  wrapt 
in  a  mantle  of  innocuous  radiance — an  earth,  so  to 
speak,  within — a  sun  without."  *  Herschel's  author- 
ity gave  vitality  to  this  conception,  whose  main  util- 
ity was  that  it  helped  to  definitise  error — often  the 
first  step  to  its  demolition.  But  it  would  be  histor- 
ically unjust  to  ignore  the  fact  that  although  Her- 
schel's main  idea  was  quite  erroneous,  it  was  the  peg 
to  which  a  number  of  accurate  observations  were  tem- 
porarily attached. 

*  A.  M.  Clerke.    History,  1885,  p.  71. 


ADVANCE  OF  ASTRONOMY.  205 

William  Herschel's  picture  of  the  sun  seems  to 
have  been  generally  accepted  for  about  seven  decades. 
His  son,  Sir  John  Herschel,  while  working  at  the 
Cape,  was  probably  beginning  to  doubt  its  validity 
when  he  maintained  that  the  sun's  rotation  was  inti- 
mately concerned  with  the  formation  of  sun-spots; 
and  the  attention  which  he,  Baily,  Airy,  Arago, 
Struve,  and  others  paid  to  the  corona,  chromosphere, 
and  other  luminous  appendages  of  the  sun  observed 
during  the  eclipses  of  1842  and  1857,  led  to  further 
suspicions. 

The  careful  patience  of  an  amateur — Heinrich 
Schwabe  (d.  1875) — made  the  next  step  possible, 
for  by  the  observations  of  a  quarter  of  a  century  he 
showed,  about  1850,  that  there  was  a  periodicity  in 
the  appearance  of  sun-spots.  But  this,  in  itself  in- 
teresting, acquired  additional  importance  when  the 
magnetic  observations  which  the  enthusiasm  of  Hum- 
boldt,  Gauss,  and  others  had  secured  in  five  conti- 
nents led  Dr.  John  Lamont  and  Sir  Edward  Sabine 
(1852)  independently  to  the  conclusion  (based  on 
different  sets  of  data),  that  there  was  a  remarkable 
harmony  between  periods  of  disturbance  in  terrestrial 
magnetism  and  the  periods  of  the  sun-spots.  The 
congruence  was  confirmed  in  the  same  year  (1852) 
by  Eudolph  Wolf  and  by  A.  A.  Gautier,  and  although 
Sir  William  Herschel's  association  of  the  price  of 
bread,  periods  of  sunny  weather,  and  frequency  of 
sun-spots  was  not  borne  out,  the  influence  of  fhe  sun 
on  the  earth's  magnetism  was  henceforth  recognized 
as  a  fact. 

It  is  now  generally  believed  that  the  sun  is  sur- 
rounded by  a  halo  of  incandescent  clouds — the  photo- 
sphere— outside  of  which  there  is  a  solar  atmosphere 
composed  of  vapours  of  hydrogen,  calcium,  iron,  and 


206    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

other  metals,  besides  a  few  non-metallic  elements. 
The  clouds  of  the  photosphere  may  be  due  to  fog-pre- 
cipitates from  the  cooling  atmosphere,  while  depres- 
sions or  gaps  in  the  photosphere  probably  give  rise  to 
the  phenomena  of  sun-spots.  Herschel's  idea  of  a 
solid  core — cool  and  even  habitable — gave  place  to  the 
idea  of  an  ocean  of  molten  matter,  but  this,  with 
fuller  knowledge  of  the  conditions  of  the  various 
states  of  matter,  has  given  place  to  the  generally  ac- 
cepted view  that  the  sun  is  in  the  main  or  wholly 
gaseous. 

The  Sun's  Heat. — About  1836,  Sir  John  Herschel 
at  the  Cape  and  Pouillet  in  France  took  a  step  which 
meant  much  to  the  progress  of  physical  astronomy. 
It  is  hardly  necessary  to  say  that  the  step  was  one 
of  measurement.  They  tried  to  measure  how  much 
of  the  sun's  radiant  energy  is  intercepted  by  the 
earth — a  mere  speck  in  the  heavens  (one  part  in  two 
thousand  millions!)  Although  their  estimates  were 
afterwards  shown,  by  the  work  of  Young,  of  Lang- 
ley  (1880-81),  of  Janssen  (1897),  and  others  to  be 
far  under  the  mark,  they  were  sufficient  to  indicate 
the  magnitude  of  the  flood  of  energy  which  pours 
forth  from  the  hearth  of  our  system. 

Herschel  calculated  that  the  heat  received  by  the 
earth  in  a  year  (including  that  caught  in  .the  atmos- 
phere) would  suffice  to  melt  a  covering  of  ice  120  feet 
thick  over  the  whole  surface  of  our  planet;  Young's 
estimate  leads  to  the  result  that  "  each  square  metre 
of  the  Sun's  surface  pours  out  enough  heat  to  main- 
tain about  half  a  dozen  mighty  Atlantic  steamers  at 
their  utmost  speed  night  and  day,  from  year's  end  to 
year's  end  ; "  *  Langley  remarks  that  "  though  there 

*Sir  Robert  Ball,  The  Story  of  the,  Sun,  1893,  p.  263. 


ADVANCE  OF  ASTRONOMY.  207 

is  coal  enough  in  the  State  of  Pennsylvania  to  sup- 
ply the  wants  of  the  United  States  for  many  centuries 
to  come,  yet  the  heat  which  could  be  generated  by 
the  combustion  of  all  the  coal  in  Pennsylvania  would 
not  be  sufficient  to  supply  the  sun's  radiation  for  the 
thousandth  part  of  a  single  second."  * 

From  experiments  on  the  intensity  of  the  radi- 
ation emitted  by  an  incandescent  body,  Le  Chatelier 
has  argued  (1892)  that  the  temperature  of  the  sun 
cannot  be  less  than  7,600°C.,  and  probably  much 
more.  These  and  similar  figures  convey  little  mean- 
ing in  themselves,  but  they  are  significant  in  rela- 
tion to  the  problem  of  how  the  supply  of  energy  is 
sustained. 

Maintenance  of  Solar  Energy. — Especially  after 
the  formulation  of  the  doctrine  of  the  conservation 
of  energy  (about  1843),  the  problem  of  the  main- 
tenance of  the  sun's  heat  urgently  claimed  atten- 
tion. It  soon  became  evident  that  it  is  impossible 
to  think  of  the  sun  as  like  an  enormous  fire  giving 
out  heat  by  combustion.  "  Massive  as  the  sun  is, 
if  its  materials  had  consisted  even  of  the  very  best 
materials  for  giving  out  heat  by  what  we  understand 
on  the  terrestrial  surface  as  combustion,  that  enor- 
mous mass  of  some  400,000  miles  in  radius  could 
have  supplied  us  with  only  about  5000  years  of  the 
present  radiation."  f  From  what  we  know  of  the 
sun's  age  and  the  amount  of  its  radiation,  it  is  cer- 
tain that  its  heat  cannot  be  mainly  due  to  chemical 
processes  at  present  known  to  us. 

Setting  aside  the  chemical  solution  of  what  Sir 
John  Herschel  called  "  the  great  secret,"  we  find  two 

*  Sir  Robert  Ball,  The  Story  of  the  Sun,  1893,  p.  265. 
tP.  G.  Tait,  Recent  Advances,  1876,  p.  151. 


208    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

other  suggestions.  About  1848,  Mayer,  who  shared 
in  stating  the  idea  of  the  conservation  of  energy, 
brought  forward  a  "  meteoric  hypothesis  "  according 
to  which  it  was  supposed  that  the  meteorites  swarm- 
ing around  the  sun  engendered  heat  by  impact  with 
it, — thus  furnishing  a  supply  of  heat  many  thousand 
times  greater  than  if  they  underwent  complete  com- 
bustion. This  view,  also  suggested  by  Waterston,  was 
developed  in  1853  by  Sir  William  Thomson  (Lord 
Kelvin)  and  was  supported  by  Tyndall  and  Tait. 
The  latter  says :  "  We  find,  by  calculations  in  which 
there  is  no  possibility  of  large  error,  that  this  hypoth- 
esis is  thoroughly  competent  to  explain  100,000,000 
of  years'  solar  radiation  at  the  present  rate,  perhaps 
more;  and  it  is  capable  of  showing  us  how  it  is 
that  the  sun,  for  thousands  of  years  together,  can 
part  with  energy  at  the  enormous  rate  at  which  it 
does  still  part  with  it,  and  yet  not  apparently  cool 
by  perhaps  any  measurable  quantity."  * 

On  the  other  hand,  while  the  infall  of  meteorites 
and  the  heat  they  produce  by  impact  may  be  re- 
garded as  certain,  it  is  urged  by  competent  au- 
thorities that  the  "  intra-planetary "  supply  is  too 
scanty  to  be  more  than  a  makeshift,  while  Lord 
Kelvin  himself  excluded  an  "  extra-planetary " 
supply  on  the  ground  that  if  it  were  true  the  year 
would  be  shorter  now  by  six  weeks  than  at  the  open- 
ing of  the  Christian  era.f 

In  1854,  Helmholtz  gave  the  answer  which  is 
now  generally  accepted.  If  we  start  with  the  reason- 
able assumption  of  a  once  larger  and  less  condensed 
sun,  we  can  understand  that  as  the  sun  shrank 
there  was  thereby  accumulated  a  great  thermal  store 

*  Recent  Advances,  1876,  pp.  153-54. 

f  See  Miss  Clerke's  History,  p.  352. 


ADVANCE  OF  ASTRONOMY.  209 

— the  direct  result  of  the  condensation.  Most  of 
this  has  already  been  lost ;  but  as  the  cooling  proceeds, 
further  condensation  of  the  interior  (gases)  ensues, 
and  this  implies  further  evolution  of  heat.  Thus 
as  the  sun  parts  with  heat  it  compensates  for  its 
loss  by  evolving  more.  In  brief,  gravitational  energy 
is  exchanged  for  radiant  energy.  Ho\v  long  it  can 
continue  to  do  so  before  ceasing  to  glow,  before  fad- 
ing away  into  a  dark  star,  is  really  indeterminable 
in  the  present  state  of  our  knowledge  of  the  sun's 
physical  constitution,  but  some  rough  calculations 
have  been  made.  Helmholtz  estimated  the  rate  of 
the  sun's  contraction  at  about  220  feet  a  year,  and 
granted  a  lease  of  life  for  many  millions  of  years  to 
come. 

Whether  the  sun  is  at  present  becoming  actually 
cooler  we  do  not  certainly  know,  but  it  is  interesting 
to  take  note  of  Lane's  theorem  (1870),  which,  on  the 
assumption  that  the  sun  is  gaseous  and  behaves  as 
a  perfect  gas  (one  whose  relations  of  volume  to  pres- 
sure are  indicated  by  Boyle's  Law),  seeks  to  show 
that  the  temperature  must  be  increasing,  not  decreas- 
ing. As  we  cannot  assert  that  the  behaviour  of  gases 
in  the  sun's  interior  is  such  as  Boyle's  Law  indicates, 
we  cannot  at  present  decide  whether  the  sun  has  yet 
attained  its  maximum  splendour  or  whether  it  has 
now  begun  to  wane. 

Collisions  and  Impacts. — From  what  has  been 
said  it  is  evident  that  the  picture  of  the  sun's  origin 
which  astronomers  incline  to  give,  is  that  of  a  vast 
primitive  nebula,  with  a  great  store  of  energy  in  the 
mutual  gravitation  of  its  parts.  We  have  also 
noted  the  importance  of  the  suggestion  due  to  Helm- 
holtz— that  cooling  induced  shrinkage,  and  that  this 
in  turn  evolved  more  heat  But  another  possible 


210    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

factor  in  the  production  of  the  sun's  heat  has  been 
suggested  by  several  astronomers. 

Sir  Robert  Ball  illustrates  this  by  the  story  of  the 
new  star  in  Auriga,  whose  appearance  was  observed 
in  February,  1892.  Where  a  few  days  before  the 
photographic  plates  had  shown  nothing,  a  bright 
star  suddenly  became  apparent.  "  Everything  we 
have  learned  about  the  matter  suggests  that  the  new 
star  in  Auriga  during  the  time  of  its  greatest  bril- 
liance dispersed  a  lustre  not  inferior  to  that  of  our 
own  sun.  ...  It  became  clear  that  the  brightness 
of  the  new  star  in  Auriga  was  the  result  of  a  collision 
which  had  taken  place  between  two  previously  ob- 
scure bodies.  Perhaps  it  would  hardly  be  right  to 
describe  what  happened  as  an  actual  collision.  It 
is,  however,  perfectly  clear  from  the  evidence  that 
two  objects,  whose  relative  velocities  were  some 
hundreds  of  miles  to  a  second,  came  into  such  close 
proximity  that  by  their  mutual  action  a  large  part 
of  their  energy  of  movement  was  transformed  into 
heat,  and  a  terrific  outburst  of  incandescent  gases 
and  vapours  proclaimed  far  and  wide  throughout 
the  universe  the  fact  that  such  an  encounter  had 
taken  place."  * 

From  the  analogy  of  Nova  Auriga — which  is  no 
isolated  instance — it  has  been  conjectured,  by  Lord 
Kelvin  among  others,  that  our  sun  may  have  arisen 
from  the  collision  of  two  bodies  which  attracted 
each  other  until  they  became  a  single  sun  with  an 
enormous  store  of  heat  derived  from  the  crash  of 
their  impact. 

This  speculation  is  of  interest  when  we  look 
forward  to  the  time  in  the  life  of  a  sun  or  star,  when 
further  compression  no  longer  compensates  for  the 

*  Sir  Robert  Ball,  loc.cit.,  p.  277. 


ADVANCE  OF  ASTRONOMY.  211 

loss  of  heat  by  radiation.  There  seems  then  no  possi- 
bility of  the  star  recovering  itself,  unless  through 
a  collision  with  another.  For  it  is  possible  that  the 
heat  produced  by  the  impact  might  restore  them  to 
the  primitive  nebulous  state.  If  the  two  colliding 
bodies  were  solid  the  result  might  be  a  shattering 
into  fragments  which  would  be  projected  with  high 
velocities  into  space;  but  if  the  stars  had  not  cooled 
enough  to  be  solid,  fragmentation  would  be  less  like- 
ly, and  the  collision  might  lead  to  rejuvenescence. 

The  establishment  of  stellar  physics  practically 
dates  from  the  application  of  the  spectroscope  to  the 
investigation  of  the  composition  of  the  sun,  the  plan- 
ets, and  the  stars.  The  facts  illustrate  what  has 
been  repeatedly  true  in  the  history  of  science,  that 
the  application  of  a  new  instrument  or  method,  may 
lead  to  development  at  a  rate  and  in  a  direction  which 
no  one  would  have  ventured  to  predict. 

SPECTRUM  AXAJLYSIS. 

The  spectroscope  is  a  combination  of  prisms  (or 
equivalent  structures  such  as  a  "  diffraction- 
grating")  by  means  of  which  the  various  rays  com- 
posing a  particular  kind  of  light  can  be  separated 
out  and  arranged  in  a  line,  the  differences  of  wave- 
length showing  themselves  as  differences  of  colour. 
Thus  the  presence  or  absence  of  certain  kinds  of 
light  can  be  seen  at  a  glance.  The  use  of  the  instru- 
ment in  astronomy  is  based  on  the  facts  (1)  that  the 
quality  of  light  is  not  affected  by  distance;  (2)  that 
each  element  when  in  a  glowing  state  emits  charac- 
teristic rays  of  light  or  has  a  definite  discontinuous 
spectrum;  and  (3)  on  what  is  known  as  Kirchhoff's 
law  of  selective  absorption.  Thus  the  spectroscope 


212    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

furnishes  a  means  of  showing  that  certain  kinds  of 
glowing  matter — known  to  our  terrestrial  experience 
— also  occur  in  sun  and  stars.  But  the  recognition 
of  the  importance  of  this  new  organon  came  about 
very  gradually. 

Gradual  Discovery. — In  1672  Sir  Isaac  Newton 
made  the  simple  but  beautiful  experiment  (which 
Kepler  had  also  tried  less  effectively)  of  using  a 
prism  to  split  up  a  ray  of  sunlight  which  entered 
a  darkened  room  through  a  round  hole  bored  in  the 
shutter.  He  thereby  produced  a  spectrum  or  image 
of  the  differently  coloured  constituents  of  light,  due, 
as  he  showed,  to  the  fact  that  these  constituents  (rays 
of  different  wave-length,  as  we  now  say)  have  differ- 
ent refrangibilities.  This  was  the  beginning  of  the 
analysis  of  sunlight,  which  was  destined  to  have  such 
a  remarkable  future. 

The  historians  tell  us  that  a  young  Scotchman 
Thomas  Melvil  (d.  1753)  began  the  study  of  the 
spectra  of  salts,  and  the  spectroscope  was  certainly 
a  chemist's  instrument  before  its  astronomical  value 
was  recognised.  It  may  be  recalled  that  several 
elements — caesium,  rubidium,  thallium,  indium,  gal- 
lium, and  scandium  were  discovered  by  means  of 
the  spectroscope.  In  1802,  Wollaston  replaced  "  the 
round  hole  in  the  shutter  "  by  a  fine  slit  parallel 
to  the  edge  of  the  prisms,  showed  that  there  were 
gaps  in  the  solar  spectrum,  and  made  the  further  im- 
portant step  of  contrasting  the  spectrum  of  sunlight 
with  that  of  a  candle  flame. 

Mechanical  improvements  were  soon  introduced 
by  Fraunhofer  (1814)  and  Simms  (1839).  Fraun- 
hofer,  independently  of  Wollaston,  also  mapped  out 
a  large  number  of  the  dark  lines  in  the  spectrum  of 
sunlight,  and  called  particular  attention  to  the  fact 


ADVANCE  OF  ASTRONOMY.  213 

that  two  adjacent  yellow  lines  in  the  spectrum  of  a 
candle  flame  (now  known  to  be  due  to  sodium)  coin- 
cided with  a  pair  of  dark  lines  in  the  solar  spectrum. 
Similarly  Brewster  showed  that  the  potassium  lines 
coincide  with  other  Fraunhofer  lines. 

In  1822  Sir  John  Herschel  noted  the  bright  lines 
of  flames  in  which  certain  metallic  salts  are  burnt, 
and  in  1825,  along  with  Talbot,  he  suggested  the 
importance  of  using  the  spectroscope  to  detect  the 
presence  of  minute  quantities  of  certain  substances 
in  minerals.  In  1826  Talbot  almost  reached  the  fun- 
damental conclusion  that  the  presence  of  a  certain 
line  in  the  spectrum  tells  unerringly  that  a  certain 
substance  is  glowing  in  the  fire  of  the  luminous  body. 
Brewster  followed  on  the  same  track,  and  William 
Swan  noted  the  delicacy  of  the  spectroscopic  test  in 
detecting  the  presence  of  various  substances,  such  as 
common  salt. 

As  we  have  already  hinted,  gaps  or  dark  lines  in 
the  solar  spectrum  mean  that  rays  of  a  certain  re- 
frangibility  (which  depends  upon  wave-length)  are 
absent.  It  is  plain  that  they  may  be  absent  from, 
the  start  or  simply  because  they  are  absorbed  in 
passing  through  the  earth's  atmosphere.  Thus  it 
was  an  important  step  when,  in  1832,  Sir  David 
Brewster  noted  that  some  of  the  dark  lines  which 
Fraunhofer  had  mapped  out  on  the  solar  spectrum, 
were  intensified  when  the  sun  was  near  the  horizon, 
that  is  to  say  when  its  rays  have  a  longer  path  through 
the  earth's  atmosphere  and  are  therefore  more  liable 
to  absorption.  Gaps  thus  due  to  absorption  by  the 
earth's  atmosphere  are  called  "  telluric  lines." 

The  coincidence  noted  by  Fraunhofer  between 
two  yellow  lines  on  the  sodium  spectrum  and  a  pair 
of  dark  (D)  lines  in  the  solar  spectrum,  was  carefully 


214    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

tested  by  Professor  Miller;  and  Sir  Gabriel  Stokes 
suggested  in  1850,  as  Angstrom  did  in  1853,  that 
the  double  D  line  must  be  due  to  the  absorptive 
action  of  sodium  vapour  in  the  sun's  atmosphere. 
Interesting  also  in  this  connection  was  Swan's  ex- 
planation that  the  appearance  of  the  two  yellow 
sodium  lines  in  all  sorts  of  flames  was  due  to  the 
almost  universal  distribution  of  common  salt  (sodium 
chloride)  in  the  earth's  atmosphere. 

In  1849  Foucault  had  shown,  without  seeing  the 
importance  of  the  fact,  that  the  D  lines  were  dark- 
ened when  the  sunlight  was  passed  through  an  elec- 
tric arc  which  gave  bright  sodium  lines  in  its  spec- 
trum. It  was  reserved  for  Kirchhoff  ten  years  later 
to  show  clearly  what  this  meant. 

Thus  spectrum  analysis  "  has  grown  out  of  some 
apparently  insignificant  and  disconnected  observa- 
tions made  by  Marcgraf,  Herschel,  and  others  upon 
the  light  emitted  by  flames  coloured  by  certain  salts. 
The  spectra  of  such  flames  were  investigated  by 
various  physicists,  among  whom  Talbot,  Miller,  and 
Swan  deserve  first  mention;  but  it  was  only  after 
Kirchhoff  (in  1860)  had  made  and  proved  the  def- 
inite statement  that  every  glowing  vapour  emits  rays 
of  the  same  degree  of  refrangibility  that  it  absorbs, 
— that  spectrum  analysis  became  developed  by  Bun- 
sen  and  himself  into  one  of  the  great  branches  of 
science."  *  Again  we  find  an  illustration  of  the 
historical  fact  that  apparently  trivial  beginnings 
often  lead  to  great  issues,  and  should  never  be  judged 
hastily. 

Bunsen  and  Kirchfioff. — These  two  investigators 
were  the  first  to  show  conclusively  that  definite 

*  E.  von  Meyer.  History  of  Chemistry.  Trans.  1891, 
p.  445. 


ADVANCE  OF  ASTRONOMY.  215 

bright  lines  in  the  spectra  of  various  flames  are  due 
to  the  presence  of  definite  glowing  vapours  in  these 
flames.  In  other  words  the  presence  of  certain 
lines  in  the  spectrum  is  a  sure  index  of  the  presence 
of  certain  elements  in  the  luminous  body. 

In  a  famous  experiment,  Kirchhof?  and  Bunsen 
interposed  the  flame  of  a  spirit  lamp,  on  whose  wick 
some  salt  had  been  sprinkled,  in  the  line  of  the  rays 
from  a  lime-light,  and  found  that  on  what  would 
have  been  a  continuous  spectrum  there  were  two  dark 
sodium  lines — the  phenomenon  of  "  reversal."  Yet 
when  the  salted  flame  of  a  Bunsen  burner  was  sub- 
stituted for  that  of  the  spirit  lamp,  the  "  reversal " 
phenomenon  did  not  occur,  but  a  bright  yellow  pair 
of  lines  was  superposed  on  the  lime-light  spectrum. 
Thence  they  inferred  that  to  effect  "  reversal "  the 
temperature  of  the  vapour  through  which  the  light 
passes  must  be  less  than  that  of  the  radiating  source 
— a  conclusion  afterwards  developed  by  Balfour 
Stewart,  and  of  great  importance  in  the  study  of  the 
eolar  spectrum.  For  it  led  investigators  to  recog- 
nise that  the  appearance  of  dark  lines  in  the  spec- 
trum of  the  sun  implies  that  the  gases  in  the  sun's 
atmosphere  must  be  at  a  lower  temperature  than  those 
in  the  photosphere  behind. 

Kirchhoff's  Law. — The  experiment  of  the  reversal 
of  the  lines  was  the  concrete  proof  of  what  Kirchhoff 
had  reached  mathematically — the  law  of  selective 
absorption — which  was  also  approached  by  Ang- 
strom and  Balfour  Stewart. 

"  The  law  states  that  the  ratio  between  the  emissive 
power  and  the  absorptive  power  is  the  same  for  all  sub- 
stances at  the  same  temperature  for  rays  of  the  same 
wave-length.  From  this  it  follows  that  all  opaque  sub- 
stances begin  to  glow  at  the  same  temperature — that  is, 


216    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

that  they  give  out  light  of  the  same  wave-length — and 
that  incandescent  substances  only  absorb  such  rays  as 
they  themselves  emit.  Since,  however,  incandescent 
gases  possess  maxima  and  minima  of  light  intensity, 
while  solid  and  liquid  substances  emit  light  of  every 
kind  when  sufficiently  heated,  the  former  must  also 
possess  a  selective  absorptive  power,  and  this  is  not  the 
case  in  general  with  the  latter.  The  Fraunhofer  lines 
are  thus  explained  as  consequent  upon  absorptions  by 
incandescent  vapours."* 

Applications. — From  the  coincidence  of  the  two 
yellow  sodium  lines  in  the  spectrum  of  a  candle 
flame  with  two  of  Fraunhofer's  dark  lines  in  the 
solar  spectrum,  Kirchhoff  concluded  that  sodium 
was  present  in  the  sun's  atmosphere;  and  the  same 
kind  of  argument  was  used  over  and  over  again. 
The  method  is  to  find  in  the  spectra  of  terrestrial 
elements  bright  lines  which  exactly  coincide  with  the 
dark  lines  in  the  sun's  spectrum.  Thus  Kirchhoff 
showed  that  besides  sodium,  the  sun's  atmosphere 
contained  iron,  calcium,  magnesium,  nickel,  barium, 
copper,  zinc,  and  chromium,  while  others  such  as 
gold  and  silver  were  similarly  shown  to  be  absent. 
In  1852  Angstrom  added  hydrogen  and  others  to  the 
list;  in  1872-1876  Lockyer  increased  the  number 
from  14  to  34;  in  1887  Trowbridge  and  Hutchins 
demonstrated  the  presence  of  carbon;  in  1891  Eow- 
land  detected  silicon.  The  absence  of  some  elements, 
notably  of  oxygen,  is  as  remarkable  as  the  presence 
of  others,  but  there  is,  as  Lockyer  and  others  have 
shown,  some  reason  to  suspect  that  elements  may  be 
present  when  they  are  apparently  absent;  that  is  to 
say  they  may  exist  under  physical  conditions  which 

*  Ladenburg.  History  of  Cliemistry.  Trans,  by  Dobbin, 
1900,  pp.  317  to  318. 


ADVANCE  OF  ASTRONOMY.  217 

disguise  or  modify  their  spectrum,  or  they  may  per- 
haps be  "  dissociated  "  into  more  elementary  forms 
of  matter. 

In  short,  the  date  1859  or  1860  marks  the  widen- 
ing of  astronomy  from  being  a  science  descriptive 
of  movements  to  be  also  a  science  descriptive  of  the 
chemical  constitution  and  changes  of  the  heavenly 
bodies. 

Extension  to  the  Stars. — There  is  no  greater 
triumph  of  scientific  analysis  than  that  by  which  a 
minute  beam  of  sunlight  has  been  made  to  disclose 
the  chemical  constitution  of  the  sun's  atmosphere, 
and  this,  as  we  have  seen,  was  the  first  general  result 
of  the  application  of  the  spectroscope  to  astronomy. 
But  what  can  be  done  with  sunlight  can  also  be  done 
in  some  measure  with  starlight,  and  the  application 
of  the  spectroscope  to  the  stars  has  been  one  of  the 
characteristic  features  of  the  astronomical  work  of 
the  second  half  of  the  nineteenth  century. 

As  early  as  1814,  Fraunhofer  observed  that  the 
dark  lines  of  stellar  spectra,  though  sometimes  agree- 
ing with  those  in  the  sun's  spectrum,  were  oftener 
different,  both  in  arrangement  and  intensity;  but 
it  was  with  Kirchhoff  s  researches  that  the  spectro- 
scopic  study  of  the  stars  began  in  earnest.  About 
1863  Sir  William  Huggins  and  Dr.  Miller  began 
the  systematic  study  of  stellar  spectra,  and  the  former 
extended  his  observations  to  nebulae,  showing  that 
some  of  these  (with  a  spectrum  of  bright  lines)  are 
not  star-clusters  but  areas  of  incandescent  gas.  As 
early  as  1864,  Huggins  was  able  to  identify  some  of 
the  dark  lines  in  the  spectra  of  stars  with  those  of 
known  elements,  such  as  hydrogen,  iron,  sodium, 
and  calcium, — a  kind  of  work  which  has  since  been 
vigorously  prosecuted. 


218    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

But  while  the  use  of  the  spectroscope  revealed  the 
presence  of  certain  chemical  elements  in  the  stars, 
and  distinguished  gaseous  from  star-cluster  nebulae, 
it  led  to  an  even  more  important  achievement — the 
detection  and  measurement  of  the  motion  of  certain 
stars  in  the  line  of  sight.  We  cannot  briefly  explain 
the  suggestion  of  Christian  Doppler  (1848)  that 
"  the  colour  of  an  object  should  be  affected  by  the 
motion  of  the  source,  becoming  more  violet  as  the 
object  approached,  and  inclining  toward  red  as  it 
receded  from,  the  observer,"  *  or  the  method  of 
Fizeau  (1848)  by  which  the  displacement  of  the  dark 
lines  in  the  spectrum  was  used  as  an  index  of 
approach  or  recession.  These  led  to  the  work  of  Sir 
William  Huggins  who  announced  in  1868  that  he 
had  found  spectroscopic  evidence  (a  minute  displace- 
ment of  a  dark  hydrogen  line)  of  the  recession  of 
Sirius  and  estimated  the  rate  of  this  recession  (from 
the  sun)  at  29^  miles  per  second.  He  extended  the 
discovery  to  thirty  other  stars  and  confirmed  the 
method  by  the  spectroscopic  study  of  Venus  at 
different  times — when  the  planet  was  known  to  be 
moving  towards  or  away  from  the  earth. 

It  is  interesting  to  notice  that  displacement  of 
lines  has  also  been  detected  in  the  observation  of  sun- 
spots,  and  has  led  to  the  conclusion  that  these  are 
due  to  downrushes  of  gases. 

From  1870  onwards,  the  splendid  work  of  Huggins 
was  continued  by  Hermann  Vogel,  at  Potsdam,  who 
in  1887  availed  himself  of  the  valuable  aid  afforded 
by  the  dry  gelatine  plate  and  the  microscopic  ex- 
amination of  its  photographic  record  of  the  spectrum. 
The  motions  of  approach  and  recession  of  many 
stars  were  thus  calculated  with  great  accuracy,  and 
*  Fison,  Recent  Advances,  1898,  p.  200. 


ADVANCE  OF  ASTRONOMY.  219 

this  is  only  one  of  many  results  with  which  spectrum 
analysis  has  enriched  astronomy.  Thus  we  might 
refer  to  the  remarkable  argument  from  spectroscopy 
which  led  Pickering  of  Harvard  in  1889  to  infer  that 
a  certain  star  in  Ursa  was  really  double,  or  Vogler 
to  confirm  the  suggestion  that  the  variability  of 
Algol  was  due  to  its  being  periodically  eclipsed  by 
a  dark  or  nearly  dark  companion  star.  In  short, 
besides  chemical  information,  the  spectroscope  affords 
a  means  of  determining  celestial  motions  in  the  line 
of  sight,  and  has  detected  binary  which  the  telescope 
could  never  have  revealed. 

Sir  William  Huggins  writes :  "  In  no  science, 
perhaps,  does  the  sober  statement  of  the  results  which 
have  been  achieved  appeal  so  strongly  to  the  imagina- 
tion, and  make  so  evident  the  almost  boundless 
powers  of  the  mind  of  man.  By  means  of  its  light 
alone  to  analyse  the  chemical  nature  of  a  far  dis- 
tant body ;  to  be  able  to  reason  about  its  present  state 
in  relation  to  the  past  and  future ;  to  measure  within 
an  English  mile  or  less  per  second  the  otherwise  invis- 
ible motion  which  it  may  have  towards  us  or  from 
us ;  to  do  more,  to  make  even  that  which  is  darkness 
to  our  eyes  light,  and  from  vibrations  which  our 
organs  of  sight  are  powerless  to  perceive,  to  evolve  a 
revelation  in  which  we  see  mirrored  some  of  the 
stages  through  which  the  stars  may  pass  in  the 
slow  evolutional  progress — surely^  the  record  of  such 
achievements,  however  poor  the  form  of  words  in 
which  they  may  be  described,  is  worthy  to  be  re- 
garded as  the  scientific  epic  of  the  century.  "  * 

The  extension  of  spectrum  analysis  to  the  stars 
has  yielded  information  as  to  the  chemical  elements 
which  occur  in  them,  has  distinguished  gaseous  neb- 

*  President's  address.    Rep.  Brit.  Ass.  for  1891,  p.  4. 


220    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

ulce  from  star-clusters,  has  afforded  a  method  of 
measuring  the  motions  of  stars  in  the  line  of  sight, 
and  has  led  to  many  other  results  which  afford  fine 
historical  illustration  of  the  value  of  co-operation 
between  sister-sciences. 

THE  EVOLUTION-IDEA  IN  ASTRONOMY. 

The  evolution-idea  has  asserted  itself  in  astron- 
omy especially  in  connection  with  what  is  called  the 
nebular  hypothesis, — an  attempt  to  give  an  account 
of  the  origin  of  a  solar  system.  It  is  said  to  have 
arisen  as  a  transcendental  conception  in  the  mind 
of  Swedenborg;  it  was  suggested  on  general  grounds 
by  Kant;  it  was  formulated  in  mechanical  terms  by 
Laplace;  and  it  has  been  the  subject  of  much  dis- 
cussion— on  the  whole  unfavourable  to  its  details, 
though  confirmatory  of  the  general  idea. 

It  was  in  1755  that  Immanuel  Kant  (1724-1804) 
published  his  General  Natural  History  and  Theory 
of  the  Heavens,  more  than  a  quarter  of  a  century 
before  his  Critique  of  Pure  Reason.  Based,  as  its 
title  indicates,  on  Newton's  Principia,  the  essay  pic- 
tures a  possible  mode  of  origin  for  the  sun  and  the 
planets  from  a  homogeneous  distribution  of  vaporous 
particles  in  the  space  now  occupied  by  the  solar  sys- 
tem. 

A  more  important  step  was  taken  in  1796  when 
Laplace  presented  his  "  Nebular  Hypothesis."  Start- 
ing from  a  vast  fluid  nebula  in  slow  rotation,  he 
supposed  that  as  this  cooled  it  contracted,  that  as  it 
contracted  its  rate  of  rotation  increased,  that  event- 
ually the  "  centrifugal  force  "  of  the  great  nebular 
sphere  exceeded  the  centripetal  gravitational  attrac- 
tion, and  a  nebulous  ring  was  separated  off  from  the 


ADVANCE  OF  ASTRONOMY.  221 

equatorial  regions.  This  ring  afterwards  broke  up, 
but  its  parts  condensed  to  form  the  furthest  planet. 
With  further  shrinkages  and  accelerations  of  the 
parent  nebular  mass,  the  various  planets  were  thrown 
off  in  succession,  themselves  to  repeat  the  process 
in  forming  rings  like  Saturn's,  or  satellites  like  those 
of  Jupiter. 

One  of  the  chief  reasons  which  led  Laplace  to 
think  out  a  possible  unity  of  origin  for  the  solar 
system,  was  that  the  planets  and  their  satellites 
revolve  and  rotate  in  the  same  direction  as  that  in 
which  the  sun  rotates, — a  coincidence  of  many  (40  or 
more)  motions  which  almost  suggests  a  common 
origin.  We  now  know  that  the  satellites  of  Uranus 
and  Neptune  move  in  the  opposite  direction,  and  that 
there  are  other  exceptions,  e.g.,  that  the  inner 
Martian  moon  revolves  in  a  shorter  time  than  Mars, 
to  the  uniformity  which  Laplace  proposed;  on  the 
other  hand  we  know  that  there  are  many  more  in- 
stances of  uniformity  of  motion  than  he  was  aware 
of. 

There  are  many  other  sets  of  facts  which  favour 
the  general  idea  of  the  nebular  hypothesis.  Thus 
we  have  a  rapidly  increasing  mass  of  information 
in  regard  to  the  nebulae  which  Herschel  was  the 
first  to  begin  to  study  in  earnest,  some  of  which  look 
like  the  primeval  nebula  which  Laplace  postulated, 
while  others  present  appearances  suggestive  of 
systems  in  process  of  being  made.  The  great  Nebula 
in  Andromeda,  as  photographed  by  Roberts, 
"  suggests,"  as  Huggins  says,  "  a  stage  in  a  succes- 
sion of  evolutional  events  not  inconsistent  with  that 
which  the  nebular  hypothesis  requires." 

That  the  same  substances  occur  (as  the  spectro- 
scope proves)  in  sun  and  planets  is  another  fact  which 


222    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

would  fit  in  well  with  the  evolutionary  theory,  being 
suggestive  of  community  of  origin. 

Corroboration  may  also  be  found  in  Helmholtz's 
shrinkage  theory  (previously  noted)  of  the  origin 
and  maintenance  of  solar  energy,  for  it  leads  us 
back  to  a  larger  and  less  condensed  sun,  and  thence 
to  one  larger  still,  until  finally  we  approach  some- 
thing like  Laplace's  primitive  nebula.  "  We  can 
reason  back  to  the  time  when  the  sun  was  sufiiciently 
expanded  to  fill  the  whole  space  occupied  by  the  solar 
system  and  was  reduced  to  a  great  glowing  nebula. 
Though  man's  life,  the  life  of  the  race  perhaps,  is 
too  short  to  give  us  direct  evidence  of  any  distinct 
stages  of  so  august  a  process,  still  the  probability  is 
great  that  the  nebular  hypothesis,  especially  in  the 
more  precise  form  given  to  it  by  Roche,  does  repre- 
sent broadly,  notwithstanding  some  difficulties,  the 
succession  of  events  through  which  the  sun  and  plan- 
ets have  passed."  * 

"  So  little  is,  however,  known  of  the  behaviour  of  a 
body  like  Laplace's  nebula  when  condensing  and  rotat- 
ing that  it  is  hardly  worth  while  to  consider  the  details 
of  the  scheme,  and  that  Laplace  himself  did  not  take 
his  hypothesis  nearly  so  seriously  as  many  of  its  ex- 
pounders, may  be  inferred  from  the  fact  that  he  only 
published  it  in  a  popular  book,  and  from  his  remarkable 
description  of  it  as  '  these  conjectures  on  the  formation 
of  the  stars  and  of  the  solar  system,  conjectures  which 
I  present  with  all  the  distrust  which  everything  which 
is  not  a  result  of  observation  or  of  calculation  ought 
to  inspire.' "  f 

Meteoritic  Hypothesis. — We  have  already  alluded 
to  the  speculation,  which  is  now  particularly  asso- 

*  Sir  W.  Hupgins.    Rep.  Brit.  Ass.  for  1891,  p.  20. 

f  Arthur  Berry.  Short  History  of  Astronomy,  1898,  p.  322. 


ADVANCE  OF  ASTRONOMY.  223 

elated  with  the  names  of  Faye  and  Sir  J.  Norman 
Lockyer,  that  crowds  of  discrete  meteoric  bodies 
drawn  together  into  aggregates  by  gravitational  at- 
traction, and  evolving  heat  by  collisions,  may  have 
given  rise  to  nebula?,  with  further  condensation  to 
luminous  stars,  and  eventually  to  dark  planets,  whose 
vitality  is  at  an  end  unless  a  collision  make  it  possi- 
ble for  the  evolutionary  process  to  recommence.  But 
this  remains  in  the  speculative  phase. 

The  possibility,  however,  must  be  borne  in  mind 
that  some  of  the  existing  nebulae  may  have  originated 
in  the  collisions  of  dark  suns,  and  are  thus  the  chil- 
dren, as  it  were,  of  a  later  generation.  "  During 
the  short  historic  period,  indeed,  there  is  no  record 
of  such  an  event;  still  it  would  seem  to  be  only 
through  the  collision  of  dark  suns,  of  which  the 
number  must  be  increasing,  that  a  temporary  reju- 
venescence of  the  heavens  is  possible,  and  by  such 
ebbings  and  Sowings  of  stellar  life  that  the  inevita- 
ble end  to  which  evolution  in  its  apparently  uncom- 
pensated  progress  is  carrying  us  can,  even  for  a 
little,  be  delayed.  .  .  .  We  cannot  refuse  to  admit 
as  possible  such  an  origin  for  nebulse." 

Tidal  Friction. — An  interesting  recent  contribu- 
tion to  the  theory  of  the  evolution  of  planetary  sys- 
tems, and  of  satellites  in  particular,  has  been  made 
by  Mr.  G.  H.  Darwin,  in  his  papers  on  the  influence 
of  tidal  friction,  but  the  subject  is  too  intricate  for 
discussion  within  our  limits. 

SUMMARY. — A  cautious  summary  forms  the  last 
paragraph  of  Berry's  Short  History  of  Astronomy, 
and  this  we  venture  to  quote: — "  Speaking  generally , 
we  may  say  that  the  outcome  of  the  nineteenth-cen- 
tury study  of  the  problem  of  the  early  history  of  the 
*  Sir  W.  Huggins.  Rep.  Brit.  Ass.  for  1891,  p.  24. 


224:    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

solar  system  has  been  to  discredit  the  details  of  La- 
place's hypothesis  in  a  variety  of  ways,  but  to  estab- 
lish on  a  firmer  basis  the  general  view  that  the  solar 
system  has  been  formed  by  some  process  of  condensa- 
tion out  of  an  earlier  very  diffused  mass  bearing  a 
general  resemblance  to  one  of  the  nebulce  which  the 
telescope  shows  us,  and  that  stars  oilier  than  the  sun 
are  not  unlikely  to  have  been  formed  in  a  somewhat 
similar  way;  and,  further,  the  theory  of  tidal  friction 
supplements  this  general  but  vague  theory,  by  giving 
a  rational  account  of  a  process  which  seems  to  have 
been  the  predominant  factor  in  the  development  of 
the  system  formed  by  our  own  earth  and  moon,  and 
to  have  had  at  any  rate  an  important  influence  in  a 
number  of  other  cases." 


CHAPTER  VII. 
GROWTH  or  GEOLOGY.* 

CATACLYSMAL,  UNIFOBMITABIAN,  EVOLTTTIONABY. 

THESE  are  cumbrous  words  for  the  heading  of  a 
paragraph,  and  yet  they  are  serviceable  to  sum  up 
the  three  chief  phases  of  geology  during  the  nine- 
teenth century.  For  if  it  be  borne  in  mind  that 
phases  of  science  do  not  end  abruptly  like  the  reigns 
of  kings,  but  overlap  and  dovetail,  the  words  cata- 
clysmal, uniformitarian,  and  evolutionary  may  serve 
with  some  usefulness  to  emphasise  the  changes  of 
outlook  in  the  geology  of  the  period  under  discussion. 

Cataclysmal. — The  nickname  cataclysmal  or  catas- 
trophic applies  to  those  who  saw  no  way  of  explain- 
ing the  features  of  the  earth's  face — its  ridges, 
wrinkles,  dents,  and  scars — without  postulating  con- 
vulsions and  cataclysms,  fires  and  flood,  not  only  on 
a  scale  vastly  greater  than  any  analogous  occurrences 
now  to  be  observed  on  our,  on  the  whole,  very  sedate 
earth,  but  even  different  in  kind.  Cuvier,  and  to 
some  extent  Buffon,  may  be  named  as  champions  of 
the  catastrophic  theory. 

Uniformitarian. — From  this  way  of  looking  at 
things  a  recoil  was  inevitable  when  a  growing  appre- 
ciation of  scientific  method  made  it  clear  that  in 
geological  interpretation,  as  elsewhere,  we  must  not 

*  The  history  of  geology  relied  on  is  Karl  Alfred  von 
Zittel's  Geschichte  der  Geologic  und  PaWontologie,  1899; 
translated  (1901)  by  Dr.  Maria  Ogilvie-Gordon. 


226    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

invent  hypothetical  agencies;  that  we  must  exhaust 
the  full  potency  of  known  and  verifiable  causes  before 
we  admit  even  the  Tjeed  of  postulating  others  which 
are  unknown  and  unverifiable. 

The  uniformitarian  view,  well  expressed  by  Hut- 
ton  and  Playfair,  was  right  when  it  insisted  that  we 
must  in  our  interpretation  exhaust  the  possibilities 
of  actually  observable  factors,  but  it  was  wrong  if 
it  assumed  that  these  were  necessarily  all  the  factors, 
or  that  they  had  never  changed  in  the  rate  or  amount 
of  their  influence. 

In  the  hands  of  Lyell  (1797-1875)  the  uniformi- 
tarian interpretation  found  its  best  expression,  and  at 
the  same  time,  as  many  think,  signed  its  own  death- 
warrant.  For  in  spite  of  the  progress  of  physics  and 
'astronomy  since  the  time  of  Hutton,  Lyell  deliber- 
ately shut  out  the  light  of  the  evolution-idea — the 
thought  of  a  beginning  and  of  an  end  to  the  earth 
which  the  theory  of  energy  presses  home.  "  He  con- 
sistently refused  to  extend  his  gaze  beyond  the  rocks 
beneath  his  feet,  and  was  thus  led  to  do  a  serious 
injury  to  our  science ;  he  severed  it  from  cosmogony, 
for  which  he  entertained  and  expressed  the  most  pro- 
found contempt,  and  from  the  mutilation  thus  in- 
flicted geology  is  only  at  length  making  a  slow  and 
painful  recovery."  * 

A  reaction  from  extreme  uniformitarianism  was 
inevitable.  It  began  to  be  felt  that  although  "  Lyell, 
in  his  great  work,  proved  that  the  agents  now  in 
operation,  working  with  the  same  activity  as  that 
which  they  exhibit  at  the  present  day,  might  produce 
the  phenomena  exhibited  by  the  stratified  rocks, 

*W.  J.  Sollas,  Pres.  Address,  Sec.  C,  Rep.  Brit.  Ass.,  1900; 
Nature,  Sept.  13,  1900,  p.  481. 


GROWTH  OF  GEOLOGY.  227 

.  .  .  that  is  not  the  same  thing  as  proving  that  they 
did  so  produce  them."  *  Such  proof  can  only  be 
afforded  by  a  detailed  study  of  the  strata,  more  ex- 
tensive and  intensive  than  even  now  exists. 

But  as  this  detailed  study  has  proceeded,  it  has 
become  more  and  more  clear  not  only  that  the  earth 
has  evolved  from  a  very  different  primitive  state  to 
its  present  form,  but  furthermore  that  through  the 
immense  expanse  of  its  history  there  have  been  nota- 
ble changes  in  the  earth-sculpturing  factors.  The 
indisputable  proof  of  great  Ice-Ages  and  of  enormous 
thrust-movements  may  serve  to  show  that  uniformi- 
tarianism  recoiled  too  far  from  catastrophism.  To 
try  to  explain  the  phenomena  of  glaciation  without 
glaciers  strained  the  uniformitarian  theory  to  the 
breaking-point. 

Evolutionary. — The  cataclysmal  geology  was  un- 
scientific, for  it  invoked  the  aid  of  undemonstrable 
factors ;  the  uniformitarian  geology  was  inconsistent, 
for  while  it  sought  to  interpret  the  past  in  terms  of 
the  present,  it  rejected  the  evolution  idea  which  sums 
up  the  whole  history  as  a  process  of  becoming;  the 
modern  evolutionary  geology  has  inherited  the 
strength  of  the  uniformitarian  school  and  has  given 
this  fresh  virility  by  recognising  that  the  history  of 
the  earth  is  a  natural  development  in  which  at  every 
stage  the  present  is  the  child  of  the  past  and  the  par- 
ent of  the  future.  The  evolutionist  school  differs 
from  the  uniformitarian,  (a)  in  admitting  in  its  full- 
est sense  the  hypothesis  that  the  earth  has  had  a 
natural  history  from  a  nebular  or  molten  mass  down 
to  the  twentieth  century,  and  (6)  in  admitting  the 
likelihood  that  in  the  course  of  the  evolution  there 

*  J.  E.  Marr,  Address  Section  C,  Rep.  Brit.  Ass.,  1896. 


228    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

may  have  been  rhythms  and  changes  in  the  action 
of  the  known  factors."  * 

SUMMARY. — "  From,  Steno  onward  the  spirit  of 
geology  was  catastrophic;  from  Hutton  onward  it 
grew  increasingly  uniformitarian;  from  the  time  of 
Darwin  and  Kelvin  it  has  become  evolutional."  f 
"  The  Catastrophists  had  it  all  their  own  way  until 
the  Uniformitarians  got  the  upper  hand,  only  to  be 
in  turn  displaced  by  the  Evolutionists/'  $ 

FOUNDATION   STONES   OF   GEOLOGY. 

Even  in  the  later  decades  of  the  eighteenth  century 
geology  as  a  distinct  science  did  not  exist,  but  its  sure 
foundations  were  being  laid.  Thus  Sir  Archibald 
Geikie  has  rescued  from  undeserved  oblivion  (in 
Britain  at  least)  the  name  of  Jean  fitienne  Guettard 
(1715-1786) — "the  first  to  construct,  however  im- 
perfectly, geological  maps,  the  first  to  make  known 
the  existence  of  extinct  volcanoes  in  Central  France, 
and  one  of  the  first  to  see  the  value  of  organic  re- 
mains as  geological  monuments,  and  to  prepare  de- 
tailed descriptions  and  figures  of  them.  To  him  also 
are  due  some  of  the  earliest  luminous  suggestions  on 
the  denudation  of  the  land  by  the  atmospheric  and 
marine  agents."  ** 

Another  illustrious  pioneer  was  Nicholas  Desmar- 
est  (1725-1815),  who  amid  the  labours  of  a  life 
devoted  to  fostering  the  industries  of  France,  found 
time  to  map  the  volcanic  rocks  of  Auvergne,  to  work 
out  a  theory  of  the  volcanic  origin  of  basalt,  to  trace 

*    See  J.  E.  Marr.     Address  Section  C,  Rep.  Brit.  Ass., 
1896,  p.  775. 
t  Sollas,  loc.  cit. 

$  Geikie.    Founders  of  Geology,  1897,  p.  288. 
**  Sir  Archibald  Geikie.    Founders  of  Geology,  1897,  p.  46. 


GROWTH  OF  GEOLOGY.  229 

with  persistent  patience  the  various  effects  of  denu- 
dation on  beds  of  lava,  to  propound  the  doctrine  of 
the  origin  of  valleys  by  the  erosive  action  of  the 
streams  which  flow  in  them,  and  in  short,  to  lay, 
not  one  but  several  of  the  foundation-stones  of  modern 
geology. 

In  Sir  Archibald  Geikie's  fascinating  account  of 
the  founders  of  geology,  the  next  two  names  are  Peter 
Simon  Pallas  (1741-1811)  and  Horace  Benedict  de 
Saussure  (1740-1799).  Pallas  was  in  charge  of  a 
famous  Russian  expedition  (1768-1774)  ordered  by 
the  Empress  Catherine  II.,  primarily  with  the  object 
of  observing  the  Transit  of  Venus,  but  also  with  in- 
structions to  make  a  complete  regional  survey  of 
everything  from  mountains  to  man.  Geologically, 
the  expedition  was  signalised  by  the  discovery  of  the 
widespread  remains  of  mammoth,  rhinoceros,  and 
buffalo  in  the  Siberian  basins,  and  by  Pallas's  re- 
searches on  the  origin  and  history  of  mountains. 
Far  beyond  the  limits  of  geology,  the  work  of  Pallas 
has  an  acknowledged  importance. 

"  The  labours  of  De  Saussure  among  the  Alps 
mark  an  epoch,  not  only  in  the  investigation  of  the 
history  of  the  globe,  but  in  the  relations  of  civilised 
mankind  to  the  mountains  which  diversify  the  sur- 
face of  the  land."  He  broke  down  a  strange  tradi- 
tional prejudice  against  the  horror  of  the  great  hills 
and  inspired  the  modern  enthusiasm  for  mountain- 
eering; he  began  experiments  in  rock-making;  he 
furnished  a  model  of  how  mountain  ranges  should 
be  studied  and  described ;  and  he  seems  to  have  been 
the  first  to  adopt  the  terms  Geology  and  Geologist* 

When  theoretical  critics  came  to  Desmarest  with 
objections,  he  used  to  say  "  Go  and  see  " ;  and  if  it 
*  See  Geikie,  p.  88. 


230    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

be  true  that  any  vindication  of  the  necessity  for  an 
observational  basis  in  science  is  now  an  anachronism, 
we  should  not  forget  the  early  struggles  towards  this 
essential  virtue.  Desmarest's  conclusion  as  to  the 
igneous  origin  of  basalt  may  seem  a  small  result  for 
years  of  patience,  but  we  have  only  to  contrast  it 
with  the  old  idea  that  basaltic  columns  were  petri- 
fied bamboo  stems  to  see  its  historical  importance. 
It  may  not  be  easy  to  cite  any  particular  conclusion 
of  De  Saussure's  which  is  now  part  of  the  frame- 
work of  tektonic  geology,  but  his  lifework  was  none 
the  less  a  vindication  of  the  precept  "  Go  and  see." 

Nowadays,  no  one  who  is  interested  in  the  nature 
and  origin  of  the  sculptured  earth  around  him  can 
"  go  and  see  "  without  bearing  with  him  the  idea  that 
the  earth's  crust  is  a  great  history-book,  that  the 
various  layers  and  strata  are  pages  recording  particu- 
lar processes,  and  that  there  has  been  a  "  geological 
succession "  still  to  be  deciphered  though  he  who 
runs  may  not  read  it.  Yet  this  familiar  and  ele- 
mentary idea  of  a  geological  succession  had  a  long 
history ! 

Werner. — Sir  Archibald  Geikie  refers  to  Leh- 
mann,  Fuchsel,  and  Werner  as  three  observers  who 
advanced  the  idea  of  geological  succession  during  the 
latter  half  of  the  eighteenth  century.  Of  the  three, 
Werner  was  the  most  important.  He  tried  to  put 
minerals  in  order,  as  Linnaeus  had  done  for  plants; 
he  was  one  of  the  first  to  expound  the  general  idea  of 
the  sequence  of  geological  formations ;  and  he  was  an 
influential  teacher  of  great  personal  charm. 

Hutton. — In  1Y85,  after  years  of  travel  and 
thought,  James  Hutton  communicated  to  the  Royal 
Society  of  Edinburgh  the  first  outlines  of  his  Theory 
of  the  Earth. 


GROWTH  OF  GEOLOGY.  231 

For  the  main  purpose  of  this  volume,  which  is  to 
illustrate  the  working  of  the  scientific  mood,  the 
theory  of  the  earth  which  Hutton  suggested  is  full 
of  significance.  Significant,  because  its  author  had 
so  clearly  grasped  the  scientific  method  of  seeking  to 
appreciate  the  full  force  of  known  factors  instead  of 
invoking  the  aid  of  others  whose  reality  is  hypotheti- 
cal. Waters  wear  the  stones,  the  solid  earth  melts 
away,  the  mountain  is  transplanted  piece-meal  to  the 
sea,  there  is  a  ceaseless  decay  of  continents;  on  the 
other  hand,  underground  forces  cause  upheaval,  con- 
solidated debris  is  once  more  brought  to  light,  and 
molten  masses  are  here  and  there  thrust  upward  to 
form  eruptive  rock.  What  is,  has  been,  and  that 
through  a  vast  antiquity  of  ages,  so  that  "  little 
causes,  long  continuing,"  have  wrought  great 
changes.  The  present  is  the  child  of  the  past  and  the 
parent  of  the  future.  In  short  it  was  the  idea  of 
development  that  Hutton  had,  perhaps  subcon- 
sciously, in  mind.  The  keynote  of  his  work  may  be 
found  in  his  sentence :  "  !N"o  powers  are  to  be  em- 
ployed that  are  not  natural  to  the  globe,  no  action  to 
be  admitted  of  except  those  of  which  we  know  the 
principle,  and  no  extraordinary  events  to  be  alleged 
to  explain  a  common  appearance."  * 

Unlike  Werner,  Hutton  started  from  observations 
not  from  preconceptions.  He  studied  the  present,  and 
in  the  process  now  occurring  found  the  key  to  the 
history  of  the  past  Among  his  conclusions  we  may 
note : — The  aqueous  origin  of  sedimentary  rocks,  the 
influence  of  subterranean  force  (essentially  due  to 
heat)  in  contorting  strata,  the  theory  of  subterranean 
intrusions  of  molten  matter  forming  veins  or  dykes 

*  Theory  of  the  Earth,  Vol.  II.  p.  547.  Quoted  by  Sir  A, 
Geikie,  Founders  of  Geology,  p.  182. 


232    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

of  "  whinstone  "  and  the  like,  the  idea  of  the  meta- 
morphism  of  rocks  under  the  influence  of  new  condi- 
tions, and  the  doctrine  of  earth-sculpture  by  denuda- 
tion (through  rain,  rivers,  glaciers,  etc.). 

Neptunists  and  Plutonists. — The  masterly  and 
lucid  Illustrations  of  the  Huttonian  Theory  by 
Hutton's  friend  and  disciple  John  Playfair,  did 
much  to  help  the  new  theory  of  the  earth  towards 
acceptance.  But  this  was  further  delayed  by  the 
bitterness  of  the  strange  controversy  which  sprang 
up  between  Hutton's  followers — nicknamed  Plu- 
tonists— and  those  of  Werner,  who  were  similarly 
called  Neptunists.  Hutton  had  emphasised  the  im- 
portance of  subterranean  heat  in  consolidating  and 
upheaving  sedimentary  deposits ;  Werner  had  almost 
exclusively  emphasised  the  agency  of  water,  believ- 
ing that  the  rocks  had  arisen  for  the  most  part  as 
precipitates  in  a  primeval  ocean.  To  one  looking 
backward  it  does  not  seem  an  instructive  controversy, 
and  it  is  perhaps  enough  to  say  that  the  more  stable 
doctrines  of  Hutton  were  those  that  survived. 

Hall. — The  Neptunists  had  urged  against  the  Plu- 
tonists that  if  basalt  and  the  like  had  really  arisen 
from  molten  masses,  they  ought  to  be  found  as  glasses 
or  slags.  To  this  Sir  James  Hall  retorted  by  ex- 
periment, showing  that  basalt  could  be  fused  and 
vitrified,  and  that  if  a  portion  of  this  basalt-glass  was 
re-fused  and  allowed  to  cool  very  slowly,  it  resumed 
its  familiar  stony  textures.  From  pounded  chalk, 
fused  under  pressure,  he  obtained  a  substance  resem- 
bling marble.  In  another  direction  he  also  experi- 
mented most  suggestively,  for  he  arranged  a  mechan- 
ical device  for  contorting  layers  of  clay  (by  lateral 
compression  under  considerable  vertical  pressure), 
and  showed  that  the  foldings  of  strata  could  thus  be 


GROWTH  OF  GEOLOGY.  233 

imitated.  These  and  other  experiments  may  be 
justly  regarded  as  the  foundation  of  experimental 
geology. 

William  Smith. — While  the  Xeptunists  and  Plu- 
tonists  were  bickering  in  Edinburgh — which  has 
been  a  centre  of  geological  activity  through  the  cen- 
tury— the  land-surveyor  and  engineer  William 
Smith  (1769-1839),  was  walking  through  the  coun- 
ties of  England,  and  working  out  his  momentous 
conclusion  that  the  stratified  rocks  occur  in  defi- 
nite sequence,  and  that  each  well-marked  group 
can  be  recognised  and  tracked  by  its  characteristic 
fossils.  In  1815  he  published  his  epoch-making  Geo- 
logical Map  of  England,  and  this  he  followed  up 
during  the  succeeding  nine '  years  by  twenty-one 
county  maps,  in  the  execution  of  which  he  was 
helped  by  his  nephew  and  pupil,  John  Phillips.  This 
was  the  foundation  of  stratigraphical  geology. 

In  regard  to  the  importance  of  William  Smith's 
work,  the  verdict  of  one  of  the  foremost  living  geolo- 
gists may  be  cited.  "  No  single  discovery,"  says  Sir 
Archibald  Geikie,  "  has  ever  had  a  more  momen- 
tous and  far-reaching  influence  on  the  progress  of  a 
science  than  that  law  of  organic  succession  which 
Smith  established.  At  first  it  served  merely  to  de- 
termine the  order  of  the  stratified  rocks  of  England. 
But  it  soon  proved  to  possess  a  world-wide  value, 
for  it  was  found  to  furnish  the  key  to  the  structure 
of  the  whole  stratified  Crust  of  the  earth.  It  showed 
that  within  that  crust  lie  the  chronicles  of  a  long 
history  of  plant  and  animal  life  upon  this  planet, 
it  supplied  the  means  of  arranging  the  materials 
for  this  history  in  true  chronological  sequence,  and 
it  thus  opened  out  a  magnificent  vista  through  a  vast 
series  of  ages,  each  marked  by  its  own  distinctive 


234    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

types  of  organic  life,  which  in  proportion  to  their  an- 
tiquity, departed  more  and  more  from  the  aspect  of 
the  living  world."  * 

Along  with  the  achievements  of  William  Smith, 
we  must  place  the  researches  of  Cuvier  and  Brongni- 
art,  and  of  others  who  early  realised  the  value  of 
fossils  as  indices  in  determining  the  sequence  of 
strata. 

The  idea  of  interpreting  the  history  of  the  past  in 
terms  of  changes  observed  in  occurrence  in  the  pres- 
ent; the  conception  of  the  sequence  of  strata;  the 
recognition  of  the  value  of  fossils  as  indices,  are  three 
of  the  foundation-stones  of  geology  which  were  laid 
at  the  beginning  of  the  nineteenth  century. 

THE  EVOLUTION-IDEA  IN  GEOLOGY. 

At  various  dates  we  find  exceptional  recognition  of 
the  Evolution-Idea  as  applied  to  the  Earth.  It  fas- 
cinated a  few  long  before  Darwin  brought  it  home 
to  all.  Thus  Descartes  propounded  a  scheme  of  the 
Earth's  development  from  a  globe  of  molten  liquid, 
and  Leibnitz's  Protogcea  (published  long  after  his 
death,  about  the  middle  of  the  eighteenth  century) 
contained  a  similar  attempt.  Buffon,  too,  starting 
with  the  bold  idea  that  the  Earth,  like  the  planets, 
was  detached  from  the  mass  of  the  sun  by  a  cometary 
shock,  sketched  with  a  free  hand  the  successive 
chapters  of  a  problematical  history  in  his  Epochs  of 
Nature  (17T8). 

Even  when  uniformitarianism  was  in  its  full 
strength, — inquiring  minds  here  and  there  were  be- 
ginning to  suspect  that  there  was  something  to  be 
said  for  the  heresies  of  Buffon,  Lamarck,  Erasmua 
*  Op.  cit.,  1892,  pp.  9-10. 


GROWTH  OF  GEOLOGY.  235 

Darwin,  and  other  pioneers  who  spoke  of  a  progres- 
sive evolution  of  plants  and  animals.  The  evolution- 
idea  was  whispered  by  many,  and  a  few  proclaimed 
it  prematurely  on  the  house-tops. 

The  cosmological  speculations  of  Kant  and  Laplace 
as  to  the  possible  evolution  of  suns  and  their  sys- 
tems did  not  apparently  much  excite  the  geologists, 
but  they  must  have  raised  some  disquieting  thoughts. 
Sir  William  Thomson's  early  insistence  (1862- 
1868)  on  the  secular  loss  of  heat  from  both  earth  and 
sun  brought  the  question  nearer  home,  for  the  con- 
clusion was  inevitable  that  the  present  state  of  affairs 
could  not  have  lasted  forever. 

Without  going  back  to  a  nebular  mass  we  must 
at  least  think  of  a  time  when  the  earth  was  much 
hotter  than  now,  when  the  waters  of  our  ocean 
formed  part  of  a  hot  atmosphere,  and  we  may  also 
look  forward  to  a  time  when  the  earth  will  be 
much  colder  than  now,  and  again  without  an  ocean 
unless  it  be  one  of  liquid  air.  In  neither  of  these 
conditions  could  life,  as  we  know  it,  exist.  "  Some- 
where between  these  two  indefinite  points  of  time  in 
the  evolution  of  our  planet  it  is  our  privilege  to  live, 
to  investigate,  to  speculate  concerning  the  antecedent 
and  future  conditions  of  things."  *  This  is  the  evo- 
lutionist attitude. 

It  is  interesting,  however,  to  pause  to  notice  a  few 
of  the  lines  of  inquiry  which  led  to  the  transition 
from  Uniformitarian  to  what  may  be  called  Evolu- 
tionist geology. 

From  the  early  works  of  Fourier  (1820),  Poisson 
(1835),  and  Hopkins  (1839),  down  to  the  more  mod- 
ern researches  of  Thomson  and  Tait  and  Helmholtz, 
there  has  been  a  prolonged  attempt  to  map  out  the 
*  Sir  John  Murray,  Rep.  Brit.  Ass.,  1899,  p.  796. 


236    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

great  steps  in  the  early  history  of  the  Earth  before 
it  became  fit  to  be  a  home  of  life,  and  also  to  reach 
from  physical  and  astronomical  data  some  secure 
conclusion  as  to  the  present  physical  state  of  the 
Earth's  interior. 

Chapters  in  the  Ancient  History  of  the  Earth. — 
The  Earth  probably  had  its  beginning  as  one  of  the 
many  rings  swirled  off  from  the  great  nebular  mass 
which  gradually  condensed  into  our  sun ;  but  other 
origins  are  conceivable.  In  any  case,  it  had  a  be- 
ginning as  a  rapidly  rotating  molten  planet  It  solid- 
ified about  the  centre  into  a  metallic  nucleus,  which 
was  probably  composed  in  great  part  of  iron ;  it  was 
surrounded  by  a  deep  atmosphere,  the  larger  part  of 
which  has  been  condensed  into  the  waters  of  our 
present  seas.  Its  molten  ocean  was  profoundly  dis- 
turbed by  solar  tides,  for  there  was  as  yet  no  moon, 
and  it  was  perhaps  a  particularly  high  tide  which 
made  the  earth  give  birth  to  its  satellite. 

"  This  event  may  be  regarded  as  marking  the  first 
critical  period,  or  catastrophe  if  we  please,  in  the 
history  of  our  planet.  The  career  of  our  satellite, 
after  its  escape  from  the  earth,  is  not  known  till  it 
attained  a  distance  of  nine  terrestrial  radii;  after  this 
its  progress  can  be  clearly  followed.  At  the  eventful 
time  of  parturition  the  earth  was  rotating,  with  a 
period  of  from  two  to  four  hours,  about  an  axis  in- 
clined at  some  11°  or  12°  to  the  ecliptic.  The  time 
which  has  elapsed  since  the  moon  occupied  a  position 
nine  terrestrial  radii  distant  from  the  earth  is  at  least 
fifty-six  to  fifty-seven  millions  of  years,  but  may  have 
been  much  more."  * 

"  The  outer  envelope  of  the  earth  drawn  off  to 
form  the  moon  was  charged  with  steam  and  other 

*W.  J.  Sollas,  Pres.  Address,  Sec.  C,  Hep.  Brit.  Ass.,  1900; 
Nature,  13th  Sept.,  1900,  p.  482. 


GROWTH  OF  GEOLOGY.  237 

gases  under  a  pressure  of  5,000  Ibs.  to  the  square 
inch;  but  as  the  satellite  wandered  away  from  the 
parent  planet  this  pressure  continuously  diminished. 
Under  these  circumstances  the  moon  would  become 
as  explosive  as  a  charged  bomb,  steam  would  burst 
forth  from  numberless  volcanoes,  and  while  the  face 
of  the  moon  might  thus  have  acquired  its  existing 
features,  the  ejected  material  might  possibly  have 
been  shot  so  far  away  from  its  origin  as  to  have  ac- 
quired an  independent  orbit,"  *  and  some  of  the 
meteorites  which  now  descend  upon  the  earth  may  be 
returned  portions  of  the  early  envelope. 

Soon  after  the  birth  of  the  moon,  the  earth  became 
consolidated  (with  a  surface  temperature  of  about 
1170°C.),  and  the  moon  may  have  been  influential 
in  determining  high-pressure  areas  where  the  crust 
was  depressed,  and  low-pressure  areas  where  it  was 
lowered.  This,  as  Sollas  says,  was  the  second  critical 
period  in  the  history  of  the  earth,  the  stage  of  the 
"  consistentior  status."  Since  this  epoch,  on  Lord 
Kelvin's  estimate,  twenty  to  forty  millions  of  years 
may  have  elapsed. 

Below  the  surface  the  temperature  increased,  as  it 
still  does;  at  a  depth  of  twenty-five  miles,  it  would 
be  (according  to  Lord  Kelvin's  calculations)  about 
1430 °C.,  or  260°C.  above  the  fusion  point  of  the 
matter  forming  the  crust.  But  the  great  pressure  at 
this  depth  would  counteract  the  heightened  temper- 
ature, and  still  keep  the  crust  solidified  even  at  a 
depth  of  twenty-five  miles. 

When,  with  continued  cooling,  the  temperature 
of  the  surface  fell  to  370 °C.,  the  steam  in  the  atmos- 
phere would  begin  to  liquefy,  and  this  was  the  first 
step  in  the  origin  of  the  oceans.  Supposing,  as 
*  Sollas,  loc.  cit. 


238    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

Sollas  suggests,  a  localisation  of  the  water  in  primi- 
tive faint  depressions  (anti-cyclonic  areas),  and  a 
corresponding  reduction  of  pressure  on  the  incipient 
continental  areas,  there  might  result  an  expansion  of 
the  underlying  rock  of  these  areas,  "  for  a  great 
change  of  volume  occurs  when  the  material  of  igneous 
rocks  passes  from  the  crystalline  state  to  that  of 
glass."  In  some  such  way,  the  ocean  basins  might  be 
deepened  and  the  continental  areas  raised.  The  hot 
water  of  the  primeval  ocean  would  act  energetically 
on  the  silicates  of  the  primitive  crust ;  it  would  begin 
to  be  "  salt "  with  saline  solutions  and  to  precipitate 
deposits.  Since  the  condensation  of  the  oceans, 
Prof.  Joly  suggests  a  lapse  of  eighty  to  ninety  mil- 
lions of  years. 

To  sum  up  dogmatically  would  be  absurd,  but  it 
may  be  said  that  a  nebular  mass  probably  gave  rise 
to  a  rapidly  rotating  molten  planet;  that  after  central 
solidification,  this  may  have  given  birth  to  the  moon; 
and  that  as  cooling  slowly  continued,  there  followed 
the  consolidation  of  the  crust  and  the  beginning  of 
the  distinction  between  ocean  basins  and  continental 
areas. 

Through  phases  more  or  less  like  those  outlined 
above  the  Earth  has  reached  its  present  state.  The 
vast  nucleus  or  "  centrosphere  "  is  practically  solid, 
the  melting-point  of  the  metals  and  metalloids  being 
raised  by  the  immense  pressure.  Outside  the  cen- 
tral mass  there  is  "  a  shell  of  materials  bordering 
upon  fusion,"  that  which  Sir  John  Murray  calls 
the  "  tektosphere."  On  this  plastic  shell  there  rests 
the  heterogeneous  and  wrinkled  crust  or  lithosphere, 
always  slightly  pulsating. 

Wrinkling  of  the  Lithosphere. — How  the  crust  or 
lithosphere  has  come  to  be  elevated  into  continental 


GROWTH  OF  GEOLOGY.  239 

areas,  on  an  average  three  miles  above  the  ocean 
floor  and  to  be  folded  into  mountain  chains,  is  one 
of  the  most  difficult  of  geological  problems,  but  there 
are  several  factors  on  which  the  evolutionary  geolo- 
gist relies.  Perhaps  the  most  important  is  the 
contraction  of  the  centrosphere.  But,  before  noting 
a  few  opinions  of  experts  on  this  subject,  it  may  be 
useful  to  recall  that,  stupendous  as  mountain-chains 
are,  their  height  is  minute  when  compared  with  the 
radius  of  the  earth.  Indeed,  it  has  been  pointed 
out  that  on  an  artificial  globe  a  foot  in  di- 
ameter, they  should  not  stand  out  more  than  the 
slight  elevations  which  might  result  where  the  edges 
of  the  covering  paper-slips  overlap. 

"As  the  solid  centrosphere  slowly  contracted  from 
loss  of  heat,  the  primitive  lithosphere,  in  accommodat- 
ing itself — through  changes  in  the  tektosphere — to 
the  shrinking  nucleus,  would  be  buckled,  warped,  and 
thrown  into  ridges.  .  .  .  The  compression  of  moun- 
tain chains  has  most  probably  been  brought  about  in 
this  manner,  but  the  same  cannot  be  said  of  the  eleva- 
tion of  plateaus,  of  mountain  platforms,  and  of  con- 
tinents." * 

"  It  was  at  first  imagined  that  during  the  flow  of 
time  the  interior  of  the  earth  lost  so  much  heat,  and 
suffered  so  much  contraction  in  consequence,  that  the 
exterior  in  adapting  itself  to  the  shrunken  body, 
was  compelled  to  fit  it  like  a  wrinkled  garment.  This 
theory,  indeed,  enjoyed  a  happy  existence  till  it  fell 
into  the  hands  of  mathematicians,  when  it  fared  very 
badly,  and  now  lies  in  a  pitiable  condition,  neglected 
of  its  friends."  f  The  mathematicians  maintained 

*  Sir  John  Murray,  Rep.  Brit.  Ass.,  1899,  p.  797. 
tSollas,  Rep.  Brit.  Ass.,  1900.     See  Mature,  Sept.  13,  1900, 
p.  487. 


240    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

that  the  amount  of  contraction  was  altogether  inade- 
quate to  explain  the  wrinkling,  but  Prof.  Sollas  finds 
sufficient  flaws  in  the  data  to  warrant  him  in  still 
maintaining  the  theory  of  contraction.  "  The  con- 
traction of  the  interior  of  the  earth,  consequent  on 
its  loss  of  heat,  causes  the  crust  to  fall  upon  it  in 
folds,  which  rise  over  the  continents  and  sink  under 
the  oceans,  and  the  flexure  of  the  area  of  sedimenta- 
tion is  partly  a  consequence  of  this  folding,  partly 
of  overloading."  * 

Another  factor  may  be  chiefly  alluded  to.  Since 
the  floor  of  the  ocean  has  a  temperature  about  zero, 
and  is  some  three  miles  below  the  continental  level, 
surfaces  of  equal  internal  temperature  will  not  be 
spherical,  but  will  rise  beneath  the  continents  and 
sink  beneath  the  ocean,  and  the  effect  will  be  to  ren- 
der the  continents  mobile  as  regards  the  ocean  floor ; 
or  vice  versa  (Sollas). 

We  have  cited  enough  to  illustrate  a  kind  of  in- 
quiry eminently  characteristic  of  the  end  of  the 
nineteenth  century  which  the  new  century  is  certain 
to  develop  to  more  stable  and  precise  results. 

The  general  result  may  ~be  summed  up  in  a  sen- 
tence; the  contraction  of  the  interior  probably  ac- 
counts for  much  of  the  folding  and  crumpling  of  the 
exterior;  other  physical  factors  are  and  have  been 
at  work;  and  the  transforming  influences  of  water, 
of  the  atmosphere,  and  of  life  have  been  continuous 
and  momentous  since  they  first  began  to  act. 

It  must  not  be  supposed  that  the  evolution-idea  in 
Geology  has  been  restricted  in  application  to  the 
recondite  problem  of  the  Earth's  early  phases;  the 
idea  has  influenced  the  whole  science  and  is  illus- 
trated in  the  modern  treatment  of  river-development, 
or  of  coral  reefs,  or  of  details  of  scenery,  and  so  on, 
*  Sollas,  Joe.  tit* 


GROWTH  OF  GEOLOGY.  241 

just  as  markedly  as  in  connection  with  the  big  ques- 
tion of  the  history  of  the  Earth  as  a  whole. 

AGE  OF  THE  EAKTH. 

In  the  early  days  of  geological  science,  the  preva- 
lent opinion  seems  to  have  been  that  the  earth  was 
about  6,000  years  old.  But  this  belief  was  for  the 
most  part  an  outcome  of  "  wresting  the  Scriptures  " 
from  their  proper  use,  and  is  quite  irrelevant  in 
scientific  discussion. 

The  Age  of  the  Earth  as  Realised  ~by  Uniformi- 
tarians. — When  James  Hutton  (1726-1797)  began 
to  show  that  the  present  supplies  the  key  to  the  inter- 
pretation of  the  past,  and  saw  "  the  ruins  of  an  older 
world  in  the  present  structure  of  the  globe,"  it  be- 
came plain  to  inquiring  minds  that  the  earth  must 
be  old  beyond  all  telling. 

William  Smith's  revelation  of  the  succession  of 
strata  in  England — the  vision  of  age  before  age 
stretching  back  into  an  inconceivably  distant  past ; 
the  founding  of  palaeontology  by  Cuvier  and  others, 
and  the  suggestion  of  successive  faunas  and  floras 
leading  us  back  and  back  to  the  mist  of  life's  begin- 
nings; the  publication  of  John  Playfair's  Illustra- 
tio?is  of  the  Huttonian  Theory  (1802);  and  other 
great  events  led  to  an  accentuation  of  the  idea  of  an- 
tiquity. Indeed,  Playf air  went  so  far  as  to  deny  that 
either  earth  or  cosmos  furnished  tangible  hint  of  any 
beginning  at  all.  Thus  the  earth,  which  had  not 
long  before  been  credited  with  a  short  duration  of 
6,000  years,  was  at  the  beginning  of  the  century  con- 
ceived of  as  a  sort  of  inanimate  Methuselah,  "  with- 
out beginning  of  days  or  end  of  years." 

Recognitions  of  Limits. — A  reaction  began  in  1862, 
when  Lord  Kelvin  (then  Sir  William  Thomson)  sent 


242    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

his  first  shell  into  the  camp  of  the  geologists,  which 
he  has  not  since  ceased  to  bombard.  From  that  date 
the  history  has  been  this, — the  physicists  have  calcu- 
lated out  certain  limits;  the  geologists  have  agreed 
that  they  do  not  require  eternity,  but  yet  much  more 
than  the  physicists  will  grant  them;  there  has  been 
much  criticism  of  data  and  calculations  and  some 
reconsideration  on  both  sides;  of  late  the  biologists 
have  also  insisted  on  being  heard. 

(a)  Physical  Arguments. — The  chief  arguments 
of  the  physicists  as  to  the  age  of  the  earth  are  based 
(1)  on  the  downward  increase  of  terrestrial  temper- 
ature, (2)  on  the  retardation  of  the  earth's  angular 
velocity  by  tidal  friction,  and  (3)  on  the  limitation 
of  the  sun's  age.  Lord  Kelvin  began  by  declaring 
that  the  age  of  the  earth  must  be  more  than  twenty 
millions  of  years,  and  less  than  four  hundred  mil- 
lions ;  but  he  subsequently  cut  down  his  maximum  to 
the  former  minimum,  and  Professor  Tait  would  not 
allow  even  half  as  much.  In  one  of  his  last  utter- 
ances on  the  subject,  Lord  Kelvin  states  "  it  was  more 
than  twenty  and  less  than  forty  million  years,  and 
probably  much  nearer  twenty  than  forty."  * 

That  the  physicists  are  far  from  being  agreed 
among  themselves  may  be  inferred  from  the  frank 
statement  of  Professor  George  Darwin :  "  At  pres- 
ent our  knowledge  of  a  definite  limit  to  geological 
time  has  so  little  precision  that  we  should  do  wrong 
to  summarily  reject  any  theories  which  appear  to 
demand  longer  periods  of  time  than  those  which  now 
appear  allowable."  f 

(&)   Geological   Arguments:     From    the   rate    of 

deposition   of   rock-forming   materials. — Ever   since 

Hutton  published  his  observations  and  reflections  on 

*  Pres.  Address  Victoria  Institute  for    1897.    Phil.   Mag., 

January,  1899. 

f  Rep.  Brit.  Ass.,  1896,  p.  518. 


GROWTH  OF  GEOLOGY.  043 

the  decay  of  continents,  it  has  been  a  recognised 
fact  that  there  is  a  universal  degradation  of  the 
dry  land.  The  span  of  the  longest  human  life  is  but 
a  tick  of  the  geological  clock,  and  so  we  speak  of  the 
eternal  hills.  But  there  is  no  doubt  in  the  mind  of 
any  observer  that  even  the  hills  are  slowly  melting 
and  crumbling  away.  "  The  hills  are  shadows,  and 
they  flow  from  form  to  form,  and  nothing  stands." 
Rain  and  frost,  lichens  and  burrowing  animals,  run- 
ning water  and  whistling  wind,  and  other  agencies 
contribute  to  the  unceasing  weathering  and  denuda- 
tion. There  are,  indeed,  conservative  agencies,  but  the 
wasting  goes  on  steadily.  The  present  land  surface 
is  being  reduced  in  height,  on  an  average  of  ^iVs 
to  33*00  foot  per  annum.  But  what  is  lost  here  is 
gained  somewhere  else,  denudation  and  deposition 
must  be  almost  equivalent  in  amount  (though  not  in 
area,  the  latter  being  usually  much  smaller),  and 
thus  we  can  arrive  at  some  estimate  of  the  amount 
of  wasting  by  measuring  the  amount  of  sediment 
deposited.  "  Actual  measurement  of  the  proportion 
of  sediment  in  river  water  shows  that  while  in  some 
cases  the  lowering  of  the  surface  may  be  as  much  as 
Ts-jj-  of  a  foot  in  a  year,  in  others  it  falls  as  low  as 
rejrff.  In  other  words,  the  rate  of  deposition  of  new 
sedimentary  formations,  over  an  area  of  sea-floor 
equivalent  to  that  which  has  yielded  the  sediment, 
may  vary  from  one  foot  in  730  years  to  one  foot  in 
6,800  years."  * 

Now,  a  considerable  part  of  the  outer  crust  of  the 
earth  is  made  up  of  sedimentary  rocks ;  among  these 
it  is  possible  with  considerable  accuracy  to  distin- 
guish the  deposits  which  were  laid  down  at  different 

*  Sir  Archibald  Geikie,  Pres.  Address,  Report  Brit.  As*, 
for  1892,  p.  21. 


2M    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

and  successive  times  (as  proved  in  some  cases  de- 
cisively by  their  fossils  and  in  other  cases  by  other 
facts) ;  and  "  on  a  reasonable  computation,  these 
stratified  masses,  where  most  fully  developed,  attain 
a  thickness  of  not  less  than  100,000  feet."  *  There- 
fore, if  we  assume  that  the  present  rate  of  change  is 
at  all  comparable  to  the  past  rate  of  change,  we  can 
form  geologically  some  estimate  of  the  antiquity  of 
our  earth.  "  If  they  were  all  laid  down  at  the  most 
rapid  recorded  rate  of  denudation,  they  would  re- 
quire a  period  of  seventy-three  millions  of  years  for 
their  completion.  If  they  were  laid  down  at  the 
slowest  rate  they  would  demand  a  period  of  not  less 
than  six  hundred  and  eighty  millions."  f 

But  how  much  experts  may  differ  is  here  again 
illustrated,  for  Prof.  Sollas  says : — "  The  total  maxi- 
mum thickness  of  the  stratified  rocks  is  265,000  feet, 
and  consequently  if  they  accumulated  at  the  rate  of 
one  foot  in  a  century,  as  evidence  seems  to  suggest, 
more  than  twenty-six  millions  of  years  must  have 
elapsed  during  their  formation."  $ 

Against  this  line  of  argument  various  objections 
may  be  raised.  It  may  be  said  that  the  rate  of 
denudation  and  therefore  of  deposition  may  have 
been  much  more  rapid  a  few  million  years  ago  than 
it  now  is,  and  the  possibility  cannot  be  denied.  But 
some  evidence  should  be  forthcoming;  and  there  is 
not  much.  In  ancient  sedimentary  rocks  we  see 
ripple  marks  and  sun-cracks  and  worm  or  mollusc 
tracks  and  it  may  even  be  the  markings  of  desiccated 
jellyfishes,  just  as  we  see  them  on  the  beach  to-day, 
and  this  certainly  does  not  point  to  rapid  deposition. 

*  A.  Geikie,  op.  cit.,  p.  21. 
t  A.  Geikie,  op.  cit.,  p.  21. 

JW.  J.  Sollas,  Address  Section  C,  Rep.  Brit.  Ass.,  1900. 
Nature,  Sept.  13,  1900,  p  485. 


GROWTH  OF  GEOLOGY.  245 

Moreover,  we  must  recall  the  fact  that  the  sedi- 
mentary rocks  are  in  scores  of  cases  interrupted  in 
a  manner  which  forces  us  to  infer  periods  of  up- 
heaval or  subsidence  or  volcanic  intrusion, — still 
further  extending  the  demand  for  millions  of  years. 

In  an  exceedingly  interesting  paper,  Goodchild  * 
has  tried  to  estimate  the  time  required  for  the  vari- 
ous sedimentary  formations  considered  seriatim, 
and  the  time  represented  by  great  unconformities, 
and  computes  the  total  time  since  the  commencement 
of  the  Cambrian  period  at  over  700,000,000  years. 
But  life  was  already  ancient  in  the  Cambrian  times, 
and  this  leads,  as  Goodchild  indicates,  to  an  enor- 
mous increase  of  the  seven  hundred  millions. 

Argument  from  the  Saltness  of  the  Sea. — Another 
interesting  line  of  argument  is  that  which  has  led 
Prof.  Joly  to  conclude  that  eighty  to  ninety  millions 
of  years  represent  the  maximum  period  of  time  since 
the  oceans  were  formed.  His  argument  is  that  since 
the  salt  sea  was  once  fresh,  and  since  the  saltness  is 
due  to  dissolved  salts  carried  into  the  sea  by  rivers, 
an  estimate  of  the  annual  amount  brought  down  by 
the  rivers  will  show  how  long  it  must  have  taken  to 
give  the  sea  its  present  salinity.  Taking  sodium 
alone,  it  is  computed  that  the  amount  in  the  sea  is  at 
least  ninety  millions  of  times  greater  than  the  quan- 
tity which  rivers  pour  in  annually  (about  160,000,- 
000  tons).  Joly's  argument  is  clear  and  simple; 
everything  depends,  however,  on  the  reliability  of 
the  data. 

(c)  Biological  Arguments. — 'Apart  from  domesti- 
cation and  cultivation  we  know  almost  nothing  in  re- 
gard to  the  present  rate  of  variation  of  living  crea- 
tures, though  researches  like  those  of  Prof.  Weldon 

*  Proc.  Roy.  Phys.  Soc.,  Edinburgh,  xiii.,  1897,  pp.  259-308. 


246    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

on  the  crabs  of  Plymouth  Harbour  are  beginning  to 
remedy  this  discreditable  ignorance.  Until  we  have 
much  information  of  this  sort  it  is  quite  idle  for  one 
biologist  to  say  that  he  thinks  one  hundred  millions  of 
years  enough  for  the  evolution  of  living  creatures, 
and  for  another  to  declare  himself  contented  with  a 
grant  of  a  quarter  of  that  amount. 

We  are  certain  that  the  evolution  of  backboned  ani- 
mals, from  Silurian  Fishes  to  Man,  has  occupied  "  a 
period  represented  by  a  thickness  of  34  miles  of  sedi- 
ment " ;  and  although  we  are  familiar  with  long-lived 
types,  like  the  tongue-shell,  Lingula,  which  has  per- 
sisted with  "  next  to  no  perceptible  change  "  from  the 
Cambrian  till  to-day,  we  are  also  aware  of  races,  like 
some  of  the  extinct  Reptiles,  which  have  appeared, 
grown  great,  and  disappeared  within  a  relatively 
short  time,  as  time  goes.  "  To  select  Lingula,  or 
other  species  equally  sluggish,  as  the  sole  measure  of 
the  rate  of  biologic  change  would  seem  as  strange  a 
proceeding  as  to  confound  the  swiftness  of  a  river 
with  the  stagnation  of  the  pools  that  lie  beside  its 
banks"  (Sollas). 

The  biological  argument  has  been  particularly  dis- 
cussed by  Professor  Poulton,*  with  the  general  result 
that  he  feels  it  necessary  to  demand  much  more  than 
even  the  geologist  demands.  The  general  fact  of  im- 
portance is  that  in  the  oldest  fossil-containing  rocks 
we  find  highly  specialised  animals  which  must  have 
had  a  long  history  behind  them;  that  in  the  Cam- 
brian, Ordovician,  and  Silurian  almost  all  the  great 
phyla  or  stocks  of  animals  are  already  represented, 
and  in  many  cases  by  forms  which  are  anything  but 
primitive.  To  the  geologist's  computation  of  the 
period  required  to  account  for  the  strata  between  the 

*  Address  Section  D,  Rep.  Brit.  Ass.,  1896,  pp.  808-828. 


GROWTH  OF  GEOLOGY.  247 

Cambrian  and  those  now  forming,  we  are  forced  to 
make  a  large  addition  in  order  to  account  for  the 
evolution  of  the  rich  Cambrian  fauna. 

Under  the  Cambrian  beds  there  is  evidence  of  some 
80,000  feet  of  stratified  rock,  in  which  there  are  no 
remains  of  organisms,  but  during  which  it  seems  al- 
most necessary  to  assume  that  the  chief  types  of  back- 
boneless  animals  and  simple  plants  had  their  origin. 
The  absence  of  fossils  is  most  plausibly  interpreted 
as  mainly  due  to  the  absence  of  hard  or  preservable 
parts  in  the  primitive  forms ;  and  even  the  modest  es- 
timate of  twenty-six  millions  of  years  as  the  period, 
since  the  earth  became  fit  to  be  a  home  of  life,  leaves 
a  considerable  number  of  millions  for  this  pre- 
Cambrian  period  during  which  the  unicellular  crea- 
tures may  have  given  origin  to  multicellular  bodies, 
taking  the  form  of  polyps  and  worms,  even  of  trilo- 
bites  and  molluscs.  The  suggestion  has  often  been 
made  that  in  early  times,  among  simple  creatures, 
the  rate  of  progress  may  have  been  much  more  rapid 
than  among  the  higher  forms  whose  stages  of  evolu- 
tion are  recorded  in  the  rocks.  But  this  is  mere 
opinion. 

At  the  beginning  of  the  nineteenth  century  there 
was  an  irrelevant  belief  that  the  habitable  earth  was 
some  6,000  years  old.  But  the  work  of  James  Hut- 
ton  alone  was  enough  to  convince  the  unprejudiced 
that  the  antiquity  of  the  earth  must  be  inconceivably 
great.  The  tendency  of  progressive  geologists  to 
draw  without  stint  upon  the  bank  of  time,  had  to  face 
a  wholesome  reminder  from  the  physicists  that  their 
credit  was  not  unlimited.  The  limitations  imposed 
by  the  physicists  have  been  vigorously  rebelled 
against,  and  criticism  has  tended  to  show  that  they 
were  too  narrow  and  not  altogether  warrantable.  The 

Q 


248    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

data  as  to  the  rate  of  cooling  of  earth  and  sun,  as  to 
tidal  retardation,  as  to  the  rate  of  sedimentation,  as  to 
the  rate  of  evolutionary  change  in  organisms,  are  in 
varying  degrees  only  approximate,  and  the  age  of  the 
earth  remains  a  problem  for  the  twentieth  century. 

BEADING  THE  BOCK-EECOBD. 

We  have  now  grown  accustomed  to  the  idea  that 
the  strata  of  the  earth's  crust  form  a  great  library  of 
historical  documents  relating  to  the  history  of  our 
world  and  its  inhabitants, — a  library  never  very  com- 
plete, but,  worse  than  that,  disordered,  half-burnt, 
flooded,  and  buried. 

There  are  two  ways  of  reading  history  in  this 
underground  library.  The  nature  of  the  rock,  sand- 
stone or  shale,  limestone  or  chert,  or  otherwise — tells 
the  experienced  observer  something  about  the  physi- 
cal conditions  of  the  time  when  the  rock  was  formed ; 
and  the  relation  of  one  stratum  or  set  of  strata  to 
another  makes  it  possible  to  determine  the  order  of 
succession  in  time.  Yet,  on  the  whole,  the  decisive 
evidence  as  to  the  physical  conditions  of  the  distant 
age  and  as  to  the  order  of  succession  in  time  is 
afforded  by  the  remains  of  plants  and  animals  which 
the  rocks  contain. 

That  fossils  furnish  the  clue  which  makes  it  pos- 
sible to  determine  the  historical  order  of  sequence  in 
the  various  strata  that  compose  the  earth's  crust  is  a 
familiar  fact  now;  but  the  realisation  of  it  was  a 
momentous  event  in  the  history  of  geology.  And 
it  may  be  noted  that  although  the  study  of  fossils 
had  begun  in  the  seventeenth  century  in  the  in- 
quiries of  Stenson,  Hooke,  Woodward,  and  others,  al- 
most no  progress  was  made  till  the  end  of  the  eight- 


GROWTH  OF  GEOLOGY.  249 

eenth  when  in  1795  Cuvier  and  Brongniart  began 
their  immortal  researches  on  the  remains  of  animals 
and  plants  in  the  Paris  basin,  and  William  Smith 
(1799)  published  his  table  of  strata  and  their  charac- 
teristic fossils.  It  mav  thus  be  said  that  the  utili- 
sation of  fossils  as  aids  in  stratigraphical  geology  is 
only  about  a  century  old.  But  the  whole  progress 
of  the  century  may  be  illustrated  by  the  difference 
between  Smith's  general  use  of  fossils  and — say 
Lapworth's  specific  use  of  Graptolites  in  deter- 
mining the  succession  of  closely  approximated 
zones. 

Gradually  the  key  which  Smith  has  used  to  so 
much  purpose  came  to  be  generally  appreciated. 
Zittel  notes  the  historical  importance  of  the  Out- 
lines of  the  Geology  of  England  and  Wales,  bv 
W.  D.  Conybeare  and  W.  Philips  (1822)  in  whict 
the  indispensable  value  of  fossils  was  clearly  recog- 
nised. Lyell,  Deshayes,  d'Omallius  d'Halloy  and 
Bronn  are  probably  the  most  outstanding  of  the 
early  geologists  who  vindicated  the  union  of  palaeon- 
tology and  geology  which  has  proved  so  profitable 
to  both  sciences. 

To  follow  the  development  of  stratigraphical 
g<H)logy  from  Sir  Roderick  Murchison  (1792-1871) 
and  Professor  Adam  Sedgwick  (1785-1873)  on- 
wards through  the  century  is  far  beyond  the  scope 
of  this  sketch.  As  with  comparative  anatomy,  the 
results  of  stratigraphical  geology  are  necessarily  for 
the  most  part  quantitative  and  appeal  more  to  the 
expert  than  to  the  general  reader.  It  may  be  said, 
however,  that 

"  While  the  whole  science  of  geology  has  made  gigan- 
tic advances  during  the  nineteenth  century,  by  far  the 
most  astonishing  progress  has  sprung  from  the  recogni- 


250    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

tion  of  the  value  of  fossils.  To  that  source  may  be 
traced  the  prodigious  development  of  stratigraphy  over 
the  whole  world,  the  power  of  working  out  the  geologi- 
cal history  of  a  country,  and  of  comparing  it  with  the 
history  of  other  countries,  the  possibility  of  tracing  the 
synchronism  and  the  sequence  of  the  earth's  surface 
since  life  first  appeared  upon  the  planet."  * 

PROBLEMS  OP  EARTH-SCULPTURE. 

What  is  often  called  "  Dynamical  Geology " 
is  concerned  with  the  factors  which  have  wrought 
out  the  present  state  of  the  various  land-forms.  It 
has  to  do  with  the  evolution  of  scenery,  or  with 
earth-sculpture, — one  of  the  most  fascinating  prob- 
lems of  geology. 

Air,  water,  ice,  volcanoes,  earthquakes,  changes 
in  coast-level,  thrust-movements,  living  creatures, 
are  the  most  important  factors  in  the  process  by 
which  the  face  of  the  earth  has  been  and  is  being 
slowly  changed.  To  some  of  these  we  wish  to  refer 
in  this  section,  while  others  have  found  notice  else- 
where. 

Hutton's  Recognition  of  Factors  in  Earth-Sculp- 
ture.— In  his  Theory  of  the  Earth  (1788),  Hutton 
recognised  the  following  factors  as  operative  in 
changing  the  earth's  surface: — degradation  of  land 
by  atmospheric  and  aqueous  agencies,  deposition  of 
the  debris  as  sediment  in  the  ocean,  consolidation  and 
metamorphosis  of  sedimentary  deposits  by  the  in- 
ternal heat  and  by  injection  of  molten  rock,  disturb- 
ance and  upheaval  of  oceanic  deposits,  and  forma- 
tion of  rocks  by  the  consolidation  of  molten  material 
both  at  the  surface  and  in  the  interior  of  the  earth. 

*  Sir  A.  Geikie.    Founders  of  Geology,  1897,  p.  241. 


GROWTH  OF  GEOLOGY.  251 

When  this  is  compared  with  a  recent  book  on  Physical 
Geology,  such  as  Prof.  James  Geikie's  Earth  Sculp- 
ture, we  are  at  once  impressed  by  the  fact  that  only  a 
few  additional  modes  of  operation  have  been  discov- 
ered in  the  course  of  the  century.  The  progress  has 
been  in  measuring  the  efficacy  of  the  factors  which 
Hutton  recognised,  rather  than  in  discovering  new 
ones. 

A  Case  of  Probable  Uniformity. — It  is  a  fa- 
miliar fact  that  water  and  air  in  various  ways  de- 
nude the  solid  land,  sometimes  acting  chemically, 
as  in  the  breaking  up  of  silicates  into  insoluble  and 
soluble  constituents,  sometimes  acting  more  me- 
chanically in  disintegrating  without  decomposing. 
The  insoluble  results  of  denudation  are  deposited  as 
gravel,  sand,  and  mud;  the  soluble  constituents  may 
also  be  deposited  (by  evaporation,  chemical  action, 
or  through  the  agency  of  living  creatures)  to  form 
carbonates,  sulphates,  chlorides,  or  less  frequently 
oxides.  This  is  a  world-wide  process,  which  prob- 
ably went  on  in  pre-Cambrian  times  very  much 
as  it  does  to-day.  "  There  is  no  evidence,"  says 
Prof.  J.  J.  H.  Teall  (now  Director-General  of  the 
Geological  Survey  of  Britain),  "  that  any  of  our  sedi- 
mentary rocks  carry  us  back  to  a  time  when  the  physi- 
cal conditions  of  the  planet  were  materially  different 
from  those  which  now  exist."  * 

Study  of  Volcanoes. — The  acrimonious  contro- 
versy between  "  Vulcanists "  and  "  Neptunists," 
which  has  been  already  referred  to,  dragged  its 
weary  length  into  the  first  quarter  of  the  nineteenth 
century.  The  "  Vulcanists,"  championed  by  Hut- 
ton,  upheld  the  igneous  origin  of  such  rocks  as  basalt ; 
the  "  Neptunists,"  led  by  Werner,  declared  igneous 

*  Address  Section  C,  Rep.  Brit.  Ass.  for  1893,  p.  737. 


252    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

rocks  to  be  chemical  precipitates  in  water;  and 
Werner  went  the  length  of  maintaining  that  volcanic 
action  was  altogether  a  modern  phenomenon. 

There  was  more  progress  in  the  work  of  Alexander 
von  Humboldt  (published  1808-1823)  who  took  a 
world-wide  survey  of  volcanoes,  and  concluded  from 
their  distribution  that  they  could  not  be  due  to 
merely  local  causes  (like  coal-pits  on  fire),  but  must 
be  interpreted  in  reference  to  the  state  of  the  earth's 
interior  and  clefts  in  the  overlying  crust.  Hum- 
boldt's  position  was  strengthened  by  the  work  of  his 
friend  Leopold  von  Buch,  who  began  as  a  ISTeptun- 
ist,  but  was  soon  led  by  observation  in  many  coun- 
tries to  sounder  views.  Relying,  like  Hutton,  on 
the  expansive  power  of  the  internal  heat  of  the  earth, 
he  made  a  point  of  distinguishing  from  true  vol- 
canoes what  he  called  "  craters  of  elevation." 
These  he  supposed  to  be  due  to  huge  blister-like  ele- 
vations of  the  strata  of  the  crust,  which  eventu- 
ally collapsed,  though  without  actual  volcanic  erup- 
tion. 

In  1825,  George  Poulett-Scrope  published  the 
first  edition  of  his  classic  book  on  volcanoes,  in  which 
he  gave  a  careful  description  of  the  physical  facts, 
and  sought  to  explain  volcanic  action  both  past  and 
present  on  a  simple  hypothesis.  Supposing  that 
subterranean  rock-masses  were  saturated  with  water, 
and  that  this  became  heated  from  the  interior,  the 
expansive  force  of  the  steam  would  account  for  erup- 
tions. Like  Lyell  (1830),  he  entirely  opposed  von 
Buch's  theory  of  "  craters  of  elevation "  as  con- 
trasted with  eruptive  volcanoes. 

For  many  years  a  healthy  conflict  of  opinions  con- 
tinued between  supporters  of  von  Buch,  such  as 
Daubeny,  Elie  de  Beaumont,  and  Dufrenoy,  and 


GROWTH  OF  GEOLOGY.  253 

supporters  of  Poulett-Scrope,  such  as  Prevost,  Hoff- 
mann, and  Montlosier. 

Facts  were  industriously  gathered  on  both  sides, 
splendid  work  was  done  by  both  schools,  but  after 
Lyell's  study  of  the  Canary  Islands  and  Madeira  in 
1854,  and  Poulett-Scrope's  papers  in  1856  and  1859, 
von  Buch's  theory  began  slowly  to  give  way.  Sir 
Archibald  Geikie's  work  on  The  Ancient  Volcanoes 
of  G-reat  Britain  (1897)  may  be  mentioned  as  a 
splendid  illustration  of  the  achievements  of  modern 
volcanology. 

Causes. — The  description  of  active  and  extinct 
volcanoes  has  reached  a  high  degree  of  perfection; 
much  has  been  done  in  interpreting  existing  features 
of  the  earth  in  terms  of  ancient  volcanic  activity; 
chemists  and  petrographers  have  contributed  greatly 
to  our  knowledge  of  volcanic  products ;  but  in  regard 
to  the  causes  of  volcanic  action  there  seems  still  con- 
siderable uncertainty. 

Standing  by  itself  is  the  theory  of  Mallet,  that 
thrusts  in  the  crust  (due  to  cooling  of  the  interior) 
may  have  locally  crushed  rocks  to  powder,  thus  de- 
veloping great  heat — sufficient  to  melt  the  rock. 
But  proof  of  the  crushing  to  powder  and  of  subse- 
quent melting  seems  absent.  "  This  hypothesis,  at- 
tractive as  it  may  be  at  first  sight,  appears  to  be  desti- 
tute of  any  real  foundation."  * 

A  survey  of  distribution  of  volcanoes  is  of  some 
assistance.  "  It  appears  to  lead  to  two  inferences — 
one  that  volcanoes  are  commonly  arranged  in  lines; 
the  other,  that  when  active  they  are  generally  in 
the  neighbourhood  of  large  sheets  of  water.  The 
former  fact  suggests  a  connection  between  volcanic 

*  Prof.  T.  G.  Bonney.  The  Story  of  our  Planet,  London. 
1893,  p.  287. 


254:    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

vents  and  lines  of  weakness  or  fracture  in  the  earth's 
crust;  the  latter  that  their  paroxysmal  activity,  per- 
haps even  their  existence,  depends  upon  the  prox- 
imity of  water,  so  that  '  without  water  no  eruption ' 
might  almost  be  regarded  as  an  axiom."  * 

On  the  other  hand,  it  seems  unsafe  to  lay  too  heavy 
a  burden  on  the  expansive  force  of  steam,  for  though 
steam  is  invariably  present  in  volcanic  discharges,  its 
amount  often  appears  (as  in  Hawaii)  disproportion- 
ate to  the  work  done. 

"  The  most  probable  view  is  that  volcanoes  are  closely 
related  to  those  earth  movements  which  have  resulted 
in  the  flexing  and  fracturing  of  strata.  All  the  greater 
wrinkles  of  the  earth's  surface — its  ocean-basins,  con- 
tinental plateaus,  and  mountains  of  elevation — owe 
their  origin  to  the  sinking-in  of  the  crust  upon  the 
cooling  and  contracting  nucleus.  The  crust  yields  to 
the  enormous  tangential  pressure  by  cracking  across 
and  wrinkling  up,  in  various  linear  directions,  and  it  is 
along  these  lines  of  fracture  and  flexure  that  molten 
matter  and  heated  vapours  and  gases  are  enabled  to 
make  their  escape  to  the  surface.  So  far,  then,  geolo- 
gists are  agreed  as  to  the  close  relation  that  obtains  be- 
tween fracturing,  folding,  and  volcanic  action.  But 
beyond  this  agreement  ceases."  f 

Study  of  Earthquakes. — In  the  first  half  of  the 
nineteenth  century  most  geologists  seem  to  have  ac- 
cepted the  conclusion  of  Humboldt  (1815),  that 
earthquakes  were  closely  associated  with  volcanic 
action. 

A  long  observational  period  in  which  data  as  to 
earthquakes  were  accumulated  by  many  workers, 
such  as  Alexis  Perrey  in  Dijon,  de  Rossi  in  Italy, 

*  Bonney,  op.  tit.,  p.  283. 

t  Prof.  James  Geikie.  Article,  Volcanoes,  Chambers's 
Encyclopaedia. 


GROWTH  OF  GEOLOG\.  255 

and  R  and  J.  W.  Mallet  in  England,  was  not  marked 
by  any  general  conclusion  of  importance. 

In  1873  and  1874,  Suess  changed  the  current  of 
opinion  by  showing  that  earthquakes  recurred  in 
definite  lines  determined  by  the  structure  of  the 
crust,  and  quite  independently  of  volcanic  ac- 
tion. 

A  by-path  was  opened  up  by  Perrey's  theory, 
suggested  by  his  statistical  data,  that  the  attraction 
of  the  moon  caused  what  may  be  called  internal 
tides  of  the  glowing  internal  fluid  mass  of  the  earth's 
interior,  and  that  these,  rising  at  times  against 
weaker  parts  of  the  heterogeneous  unequal  crust, 
caused  earthquakes.  A  somewhat  similar  tidal 
theory  was  elaborated  by  Rudolf  Falb,  partly  on 
astronomical  grounds,  and  led  him  into  the  dan- 
gerous field  of  prophecy.  Against  both  theories  it 
seems  sufficient  to  urge  the  enormous  probability 
in  favour  of  the  view  that  the  nucleus  of  the  earth 
is  solid. 

The  general  inclination  at  present  seems  to  be 
towards  a  combination  of  the  conclusions  of  Hum- 
boldt  and  of  Suess.  On  the  one  hand,  earth- 
quakes may  be  associated  with  volcanic  activity, — 
subterranean  explosions  of  gases,  the  pressure  of 
subterranean  flows  of  lava,  the  collapse  of  unsup- 
ported strata,  may  set  up  undulations  in  the  crust. 
On  the  other  hand,  even  when  volcanoes  and  earth- 
quakes occur  together  in  the  same  country,  it  has  been 
shown  that  there  may  be  no  demonstrable  connec- 
tion between  them.  This  has  been  especially  well 
brought  out  by  Prof.  J.  Milne's  seismological  work 
in  Japan.  He  remarks  that  "  earthquakes  gener- 
ally occur  in  mountainous  countries  where  the  moun- 
tains are  geologically  young,  or  in  countries  where 


256    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

there  is  evidence  of  slow  secular  movements  like 
elevation.  These  latter  movements  are  usually 
well  marked  in  volcanic  countries,  and  it  is  not  un- 
likely that  the  majority  of  earthquakes,  even  in  vol- 
canic countries,  are  the  result  of  the  sudden  yielding 
of  rocky  masses  which  have  been  bent  till  they  have 
reached  a  limit  of  elasticity.  The  after-shocks  are 
suggestive  of  the  settling  of  disjointed  strata."  * 

It  is  probable,  then,  that  while  some  earth- 
quakes are  due  to  subterranean  explosions  of  steam 
or  other  volcanic  disturbances,  the  majority  are  due 
to  slips  or  fractures  of  the  earth's  crust  in  areas  of 
great  strain. 

The  improvement  in  the  delicacy  of  earthquake- 
measuring  instruments  (seismometers)  has  led  to 
a  great  extension  of  our  knowledge  in  regard  to  the 
diffusion  of  the  undulations,  and  to  a  recognition  of 
the  frequent  minor  tremors  which  would  otherwise 
have  remained  undetected. 

Crust-Movements. — It  was  in  Scandinavia  that 
careful  attention  was  first  paid  to  those  secular 
changes  of  upheaval  and  depression,  which,  notwith- 
standing their  slowness,  are  more  important  geolog- 
ically than  either  earthquakes  or  volcanoes.  The 
facts  are  particularly  clear  along  the  Scandinavian 
coast,  and  even  the  fisher  folk  could  not  but  be  im- 
pressed when  they  saw  that  the  lines  once  cut  to 
mark  sea-level  became  gradually  more  and  more 
inaccurate.  Indeed  the  rise  of  land  in  Northern 
Sweden  has  been  estimated  at  as  much  as  2£  feet  in 
a  century. 

From  Scandinavia  the  study  of  raised  beaches 
and  uplifted  shell-beds  spread  to  Britain,  and  all 
over  the  world.  Evidences  of  depression  were  also 
*  Rep.  Brit.  Ass.  for  1892,  p.  128. 


GROWTH  OF  GEOLOGY.  257 

found  in  submerged  forests  and  even  villages. 
Proofs  of  the  gradualness  of  these  changes  prevailed 
against  theories  of  sudden  oscillations.  Almost  all 
the  eminent  geologists  of  the  century  have  contrib- 
uted to  the  subject. 

While  the  prevailing  interpretation  has  always 
been  that  the  local  level  of  the  land  changed  while 
that  of  the  sea  remained  constant,  there  have  been 
many  who  have  insisted  that  the  sea-level  may  also 
change, — in  consequence  of  great  subsidences,  accum- 
ulations of  sediment,  formation  of  polar  ice-caps, 
and  so  on. 

The  complications  of  the  problem  and  the  difficul- 
ties in  the  face  of  any  general  theory  are  recognised 
in  the  splendid  work  of  Suess  (Antlitz  der  Erde) 
which  touches  the  high-water  mark  in  this  depart- 
ment of  geology. 

Mountain-Making. — Far  ahead  of  his  time,  Steno, 
in  1669,  tried  to  interpret  the  hills  and  valleys  of 
Tuscany  in  terms  of  the  collapse  of  the  earth's 
crust,  the  uplift  of  stratified  rocks,  and  the  accum- 
ulation of  volcanic  material.  Long  afterwards, 
Hutton  found  satisfaction  in  referring  elevations 
of  the  crust  to  the  expansive  power  of  the  subterra- 
nean heat,  to  which  volcanoes  acted  as  safety  valves. 
Leopold  von  Buch  and  Poulett-Scrope  were  among 
those  who  upheld  Hutton's  theory,  and  sought  to 
improve  upon  it.  From  1829  to  1852  Elie  de  Beau- 
mont illustrated  the  important  idea  that  the  gradual 
cooling  of  the  earth  led  to  the  crumbling  of  the  crust. 
James  Hall  in  1859  pointed  out  that  the  gradual 
accumulation  of  sedimentary  masses  in  areas  of 
depression  may  be  associated  with  a  corresponding 
elevation  of  mountain  chains  elsewhere.  Dana 
returned  to  the  consideration  of  the  effects  produced 


258    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

on  the  crust  by  the  contraction  of  the  nucleus,  and 
studied  these  with  deeper  analysis  than  heretofore, 
laying  special  emphasis  on  the  horizontal  lateral 
pressures  involved  in  the  shrinkage.  N.  S.  Shaler 
in  1866  had  used  the  contraction  theory  to  explain 
the  origin  of  continents  as  well  as  mountain  chains, 
and  Le  Conte  was  also  closely  associated  with 
Dana's  work. 

A  new  chapter  begins  with  the  work  of  Edouard 
Suess.  "  A  small  book,  published  in  1875  under 
the  title,  The  Origin  of  the  Alps,  contained  in 
clear-cut  outlines  a  wealth  of  new  ideas ;  it  came 
like  vivifying  rain  on  the  dry  ground."  *  This  was  a 
preliminary  suggestion  of  the  author's  famous 
Antlitz  der  Erde  (1897).  In  the  preface  to  the 
French  translation  of  this  geological  masterpiece, 
Marcel  Bertrand  says : — "  The  creation  of  a  science, 
like  that  of  a  world,  demands  more  than  a  day;  but 
when  our  successors  come  to  write  the  history  of 
our  science,  they  will  say,  I  am  persuaded,  that  the 
work  of  Suess  marks  the  end  of  the  first  day,  when 
light  first  shone." 

No  one  could  give  a  summary  of  Gegenbaur's 
Comparative  Anatomy,  and  yet  it  is  one  of  the  zoolog- 
ical milestones.  The  same  must  be  said  in  regard 
to  the  work  of  Suess.  It  is  a  comparative  anatomy 
and  comparative  embryology  of  land-forms,  unified 
by  an  evolutionary  idea;  but  how  can  it  be  sum- 
marised ? 

The  theory  that  continents  or  mountains  are  due 
simply  to  a  force  working  from  below  upwards  is  an 
unworkable  crudity,  though  it  must  be  allowed  that 
the  shrinkage  of  the  crust  from  contraction  of  the 
nucleus  caused  vertical  as  well  as  horizontal  dislo- 
*  Zittel,  p.  462. 


GROWTH  OF  GEOLOGY.  259 

cations,  since  it  induces  radial  and  tangential 
strains.  The  theory  that  volcanic  eruptions  count 
for  much  in  mountain-making  is  a  superficial  ex- 
aggeration. The  architecture  (Tektonik)  of  moun- 
tains must  be  studied  in  detail.  They  have  a  one- 
sided structure — in  the  Alps,  the  Balkan,  the  Cau- 
casus, and  Ararat — all  expressions  of  a  tangential 
force  from  south  to  north  in  Europe,  and  towards 
the  south  in  Asia.  But  besides  the  dislocations  of 
the  lithosphere  there  have  been  great  transgressions 
and  regressions  of  the  hydrosphere,  not  less  momen- 
tous than  the  rise  of  mountain  chains.  The  conti- 
nents, as  Shaler  said,  are  due  to  contractions  of  the 
•whole  crust,  while  mountains  are  due  to  foldings  of 
the  outer  layers  in  consequence  of  contractions  in 
the  deeper.  But,  just  as  in  pack  ice,  there  may  be 
unyielding  masses,  which  have  to  be  piled  one  upon 
the  other,  or  may  be  simply  undisturbed  and  over- 
lapped. 

EECOGXITION  OF  ICE  AGES. 

Evidences  of  Glaciation. — In  a  suitable  area,  such 
as  Scotland,  every  beginner  in  geological  study  is 
familiar  with  the  smoothed  contours  of  rocks,  the 
striated  surfaces,  the  "  crags  and  tails,"  the  boulder- 
clay  and  so  on,  which  prove  the  former  presence  of 
enormous  glaciers,  and  that  at  no  very  distant  date. 
Many  of  the  phenomena  are  obvious  and  they  were 
of  course  familiar  to  Hutton  and  his  friends.  But 
they  received  other  interpretations  than  that  which 
seems  to  us  almost  self-evident — now  that  the  riddle 
has  been  read.  They  were  explained  as  due  to 
floods  of  water  and  strong  tides,  and  these  were 
again  explained  by  supposing  elevations  or  depres- 
sions wherever  they  were  required. 


260    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

Study  of  Glaciers. — The  study  of  glacial  action 
may  fairly  date  from  H.  B.  Saussure's  famous 
Travels  in  the  Alps,  in  which  glaciers  and  moraines 
were  described  with  detailed  accuracy.  Saussure  was 
followed  by  Hugi,  an  enthusiastic  mountaineer,  who 
explored  the  upper  reaches  and  was  the  first  liter- 
ally to  sojourn  on  the  slowly  moving  ice-sheets.  An 
important  step  was  taken  by  Venetz,  an  engineer, 
who,  from  1821  onwards,  sought  to  prove  from  the 
distribution  of  moraines  the  enormous  prehistoric 
development  of  glaciers,  not  only  in  Switzerland,  but 
in  North  Europe.  Venetz  converted  J.  v.  Charpen- 
tier,  who,  in  turn,  strengthened  his  friend's  argument 
with  evidence  drawn  from  the  wide  occurrence 
of  erratic  blocks  which  only  ice  could  have  car- 
ried. 

Agassiz. — Louis  Agassiz  soon  caught  the  enthu- 
siasm, and  began  along  with  Charpentier  and  the 
botanist  Schimper  a  prolonged  series  of  excursions 
and  observations  which  led  him  to  the  conception 
of  a  Great  Ice  Age,  which  was  developed  in  a  book 
published  in  1840.  From  his  study  of  past  floras 
and  faunas  Schimper  had  been  led  to  the  idea  of 
alternating  periods  of  desolation  and  rejuvenation 
as  a  Great  Ice  Age. 

Agassiz  was  stronger  in  his  description  of  glacial 
phenomena  and  in  his  recognition  of  the  previously 
wide  extension  of  glaciers  (as  proved  by  erratic 
blocks,  striated  surfaces,  etc.)  than  in  his  Ice  Age 
theory.  But  let  us  try  to  summarise  his  conclu- 
sions. Before  the  elevation  of  the  Alps,  an  immense 
ice-sheet  covered  most  of  the  northern  hemisphere; 
the  Alps  arose,  and  the  debris  of  broken  ice-sheet 
and  shattered  strata  fell  on  the  adjacent  glaciers,  which 
bore  off  their  heavy  burden,  grinding  the  movable 


GROWTH  OF  GEOLOGY.  261 

rocks  beneath  them  to  powder,  striating  and  polish- 
ing the  immovable ;  but  when  the  Alps  had  been  up- 
heaved, the  surface  of  the  earth  was  warmed  anew, 
the  ice  melted,  erosion  valleys  were  formed,  erratic 
blocks  were  left  stranded,  and  so  on. 

Along  with  much  truth,  there  was  also  much 
fancy  and  exaggeration  in  this  theory,  and  the  un- 
wholesome taint  of  catastrophism  was  especially  dis- 
tinct in  his  assumption  of  successive  ages  of  low  tem- 
perature at  the  close  of  the  various  geological  periods. 

Charpentier's  Essai  sur  les  Glaciers  (1841)  was 
more  thoroughly  scientific  than  the  work  of  Agassiz. 
Von  Zittel  speaks  of  its  precision — recalling  that 
of  de  Saussure,  of  its  thoroughness,  of  its  basis  in 
original  observations.  He  questioned  Agassiz's 
theory  of  one  great  northern  ice-sheet,  older  than  the 
Alps,  but  pictured  rather  a  great  extension  of  pres- 
ently existing  glaciers, — thus  reacting  to  an  opposite 
extreme.  In  subsequent  works,  Agassiz  modified 
some  of  his  views  in  deference  to  Charpentier,  and 
as  the  result  of  his  own  extended  experience  in 
Scotland  and  in  America. 

According  to  Agassiz  the  Swiss  glaciers  must  once 
have  been  large  enough  to  reach  to  the  Jura, — a  con- 
clusion that  seemed  to  many  of  his  contemporaries  an 
incredible  extravagance.  As  Sir  Archibald  Geikie 
notes,  "  even  a  cautious  thinker  like  Lyell  saw  less 
difficulty  in  sinking  the  whole  of  Central  Europe 
under  the  sea,  and  covering  the  waters  with  floating 
icebergs."  ..."  Men  shut  their  eyes  to  the  mean- 
ing of  the  unquestionable  fact  that,  while  there  was 
absolutely  no  evidence  for  a  marine  submergence, 
the  former  track  of  the  glaciers  could  be  followed 
mile  after  mile,  by  the  rocks  they  had  scored  and 
the  blocks  they  had  dropped,  all  the  way  from  their 


262    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

present  ends  to  the  far-distant  crests  of  the 
Jura."  *  In  fact  the  proof  might  be  taken  as  a 
model  of  scientific  inference. 

The  Drift  Theory. — In  spite  of  the  conclusive 
researches  of  Agassiz  and  Charpentier,  equally  able 
men  refused  to  be  convinced.  Thus  Leopold  von 
Buch  and  many  adherents  delayed  the  recognition 
of  the  ancient  glaciers  by  a  theory  of  great  floods, 
supposed  to  have  borne  Northern  blocks  even  to  the 
foot  of  the  Alps.  On  the  other  hand,  the  polar 
experiences  of  Parry,  Scoresbv,  and  Ross  led  some 
British  geologists — Lyell,  De  fa  Beche,  Charles  Dar- 
win, and  Roderick  Murchison — to  a  "drift-theory," 
which  supposed  the  transport  of  erratic  material  by 
icebergs,  and  in  this  they  were  supported  by  Both- 
lingk,  Bronn,  Forchhammer,  Frapolli,  and  others.f 
The  influence  of  this  "  drift-theory  " — which  seems 
a  big  error  enclosing  a  fragment  of  truth — was  con- 
siderable, and  lasted  till  1879  when  Penck  had  the 
satisfaction  of  giving  a  merciful  death-blow  to  a 
theory  which  was  slowly  dying  of  inanition. 

It  would  require  a  great  expert  to  select  wisely 
from  the  succession  of  events,  but  perhaps  we  may 
associate  the  next  great  step  with  Andrew  Crombie 
Ramsay  who  made  a  profound  study  of  the  glacia- 
tion  of  Scotland  and  Wales  (1854),  detected  traces 
of  at  least  two  ice  ages,  and  inferred  the  existence 
of  glaciers  in  the  Permian.  This  revived  the  idea 
of  recurrent  ice  ages.  Very  important,  also,  were 
the  observations  on  the  existing  glaciers  of  Green- 
land from  those  of  Rink  (1857)  to  those  of  Torell 
(1872),  and  onwards  to  those  of  Nansen. 

That  evidences  of  glaciation  were  obvious  in 
countries  now  free  from  glaciers,  that  there  had  been 
*  Founders  of  Geology,  p.  273.  f  Zittel,  op.  cit.,  p.  342. 


GROWTH  OF  GEOLOGY.  263 

a  relatively  recent  Great  Ice  Age,  probably  inter- 
rupted by  mild  periods,  and  that  there  had  been 
glacial  action  even  in  geological  antiquity,  were 
gradually  accepted  as  well-established  conclusions. 
There  sprang  up,  however,  a  memorable  controversy 
as  to  the  part  glaciers  had  played  in  gouging  out 
Alpine  lakes,  valleys,  and  fiords.  To  some  it 
seemed  that  this  erosive  action  -which  Gabriel  de 
Mortillet  (1858)  was  one  of  the  first  to  expound 
was  a  certainty;  to  others,  such  as  Heim,  glaciers 
were  regarded  rather  as  conservative  than  as  de- 
structive agents.  Modern  opinion  has  inclined 
strongly,  though  not  unanimously,  in  favour  of  the 
theory  that  glacial  erosion  has  been  a  very  important 
sculpturing  factor. 

Professor  James  Geikie's  Great  Ice  rAge  may  be 
mentioned  as  a  crowning  work  of  the  nineteenth 
century  study  of  glaciation,  as  a  modern  critical  de- 
velopment of  the  work  of  Agassiz  and  Charpentier, 
and  as  a  fascinating  contribution  towards  the  solu- 
tion of  earth-sculpture.  Geikie  argues  in  favour 
of  the  conclusion  that  there  must  have  been  six 
post-Tertiary  glacial  periods  with  intervening 
times  of  mildness,  but  as  to  this,  and  as  to  the  extent 
to  which  glacial  periods  may  be  recognised  in  ear- 
lier ages,  there  remains  much  difference  of  opin- 
ion. 

The  "  drift  "  which  spreads  over  Northern  Eu- 
rope, with  its  boulder-clays,  erratic  blocks,  moraines, 
and  the  like,  admits  of  only  one  interpretation, — 
that  it  is  the  residue  of  glacial  action.  The  polished 
and  striated  or  often  much  broken  rocky  floor  on 
which  the  deposits  rest ;  the  rounded  and  abraded 
roches  moutonnees;  the  arctic  marine  shells  found 
in  the  drift  of  Britain,  etc.,  up  to  heights  of 

B 


264:    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

over  a  thousand  feet  above  sea-level;  the  remains  of 
boreal  animals  in  North  Temperate  countries,  and 
so  on,  corroborate  the  main  conclusion. 

In  what  are  called  Pleistocene  times  enormous 
continental  mers  de  glace  covered  immense  areas  in 
Europe  and  North  America.  Great  snow-fields  and 
local  glaciers  accumulated  especially  in  those  areas 
where  the  precipitation  of  snow  and  rain  is  now 
most  abundant,  and  where  in  some  cases,  as  in 
Norway  and  the  Alps,  there  are  still  relics  of  the 
olden  times.  North  of  Central  Germany  and  Central 
Russia  all  Europe  was  buried  in  ice;  the  whole  of 
North  America  north  of  a  line  between  New  York 
and  the  Rockies  was  glaciated.  The  mean  annual 
temperature  of  Central  Europe  must  have  been  low- 
ered many  degrees  (perhaps  10°  or  11°  F.  according 
to  Penck,  5i°-7°  F.  according  to  Bruckner).  The 
climate  of  Southern  Germany  then  would  be  like 
that  of  Northern  Norway  now,  and  so  on;  in  short, 
"in  glacial  times  a  wholesale  displacement  of  cli- 
matic zones  took  place."  * 

It  is  some  progress,  then,  towards  a  clearer  inter- 
pretation of  the  earth,  that  what  were  by  older 
geologists  regarded  as  the  results  of  Noah's  flood 
are  now  known  to  be  the  marks  of  a  Great  Ice  Age — 
which,  though  very  gradual  in  its  coming  and  going, 
wrought  great  changes  upon  the  face  of  nature  and 
on  the  distribution  of  plants  and  animals. 

But  as  the  study  of  glacial  phenomena  has  be- 
come more  extensive  and  more  careful,  the  inter- 
pretation has  become  more  complex.  Thus,  the 
discovery  of  "  interglacial  deposits,"  whose  fossils 
indicate  conditions  of  warmth — often  greater  than 

*  Prof.   James  Geikie.     Trans.  Victoria  Inst.,  xxvi.,  1892- 
93,  p.  222,. 


GROWTH  OF  GEOLOGY.  265 

now  exist  in  the  same  localities — has  forced  geologists 
to  admit  the  intervention  of  temperate  stages,  inter- 
rupting the  monotonous  tyranny  of  the  cold.  Most 
geologists  now  recognise  at  least  two  glacial  epochs, 
and  many  find  strong  evidence  of  three  or  even 
more.* 

Causes. — There  has  been  no  lack  of  theories  as 
to  the  causes  of  the  Ice  Age  or  of  the  Ice  Ages. 
Some  of  these  theories  seem  too  laborious  and  others 
too  ingenious,  but  it  seems  doubtful  if  all  are  not 
premature.  That  is  to  say,  we  have  to  discover 
whether  the  post-Tertiary  Ice  Age,  so  obvious  in 
Europe,  was  universal  or  not;  and  we  have  also  to 
decide  as  to  the  periodicity  of  the  recurrence  of 
glacial  conditions  in  older  geological  periods,  which 
is  almost  too  difficult  a  problem. 

Since  the  days  of  Agassiz  and  Charpentier,  the 
causes  of  the  Ice  Age  have  been  sought  in  two  direc- 
tions which  were  to  some  extent  hinted  at  by  the 
pioneers.  Some  have  appealed  to  cosmical  or  astro- 
nomical changes,  while  others  have  been  satisfied 
with  geographical  factors. 

Adhemar  in  1842  seems  to  have  suggested  a 
theory,  which  was  rehabilitated  by  James  Croll 
(1875),  that  a  slight  alteration  in  the  eccentricity 
of  the  earth's  orbit  might  be  the  essential  cause  of 
glacial  conditions. 

Lyell  may  be  taken  as  a  representative  of  the 
view  that  geographical  changes  may  have  brought 
about  glacial  conditions.  Depressions  allowing  the 
Arctic  currents  to  overflow  parts  of  the  continents, 
elevation  of  large  areas  above  the  snow-line,  de- 
flections of  ocean  currents,  and  so  on,  have  been  as- 
sumed as  possible  causes. 

*  See  Prof.  James  Geikie's  Great  Ice  Age  and  Prehistoric 
Europe. 


266    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

There  are  others,  like  Oswald  Heer,  who  have 
found  satisfaction  in  combining  the  cosmical  and 
the  geographical  theories. 

The  last,  or,  since  the  stock  is  prolific,  perhaps 
the  latest  hypothesis  as  to  cause  of  glacial  periods, 
is  that  of  Professor  Chamberlin  who  maintains 
that  the  climatic  conditions  which  brought  about 
ice  ages  arose  from  an  impoverishment  of  the  quan- 
tity of  carbonic  acid  in  the  atmosphere. 

The  aim  of  this  section  has  been  to  indicate  (1) 
the  great  change  that  has  occurred  in  geology  since 
the  uniformitarians  attempted  to  interpret  glacia- 
tion  apart  from  glaciers,  (2)  the  gradual  develop- 
ment of  glacial  geology,  from  a  careful  study  of 
existing  glaciers  and  their  work  to  a  detection  of  the 
range  and  routes  of  ancient  glaciers  of  much  greater 
size,  (3)  the  importance  of  the  idea  of  a  relatively 
recent  (post-Tertiary}  Great  Ice  Age  interrupted 
by  intervening  periods  of  mildness,  and  (4)  the  un- 
certainty that  still  obtains  as  to  the  cause  or  causes 
of  this  and  previous  glacial  periods. 

THE  HAND  OF  LIFE  UPON  THE  EARTH. 

One  of  the  distinctive  results  of  nineteenth-cen- 
tury science  is  the  recognition  of  the  important  part 
which  living  creatures  have  played  in  fashioning  the 
features  of  the  earth.  Each  year's  work  has  of  late 
brought  to  light  some  fresh  instance  of  the  domi- 
nance of  the  hand  of  life,  and  we  have  devoted 
this  section  to  its  illustration.  The  central  names 
are  those  of  Charles  Darwin  and  Louis  Pasteur. 

Plants. — From  1810  when  Kennie  outlined  the 
history  of  Scottish  peat-bogs  to  the  latest  paper  on 
nitrifying  Bacteria,  the  importance  of  plants  in 


GROWTH  OF  GEOLOGY.  267 

relation    to    the    earth    has    been    more    and    more 
thoroughly  appreciated. 

"  The  sea-weeds  cling  around  the  shore  and  lessen 
the  shock  of  the  breakers.  The  lichens  eat  slowly  into 
the  stones,  sending  their  fine  threads  beneath  the  sur- 
face as  thickly  sometimes  '  as  grass-roots  in  a  meadow- 
land/  so  that  the  skin  of  the  rock  is  gradually  weath- 
ered away.  On  the  moor  the  mosses  form  huge  sponges, 
which  mitigate  floods  and  keep  the  streams  flowing  in 
days  of  drought.  Many  little  plants  smooth  away  the 
wrinkles  on  the  earth's  face,  and  adorn  her  with  jewels ; 
others  have  caught  and  stored  the  sunshine,  hidden  its 
power  in  strange  guise  in  the  earth,  and  our  hearths 
with  their  smouldering  peat  or  glowing  coal  are  warmed 
by  the  sunlight  of  ancient  summers.  The  grass  which 
began  to  grow  in  comparatively  modern  (i.  e.,  Tertiary) 
times  has  made  the  earth  a  fit  home  for  flocks  and  herds, 
and  protects  it  like  a  garment;  the  forests  affect  the 
rainfall  and  temper  the  climate  besides  sheltering  mul- 
titudes of  living  things,  to  some  of  whom  every  blow  of 
the  axe  is  a  death-knell.  Indeed,  no  plant  from  Bacte- 
rium to  oak-tree  either  lives  or  dies  to  itself,  or  is  with- 
out its  influence  on  earth  and  beast  and  man."  * 

From  the  vegetable  drift  borne  down  often  in 
immense  quantity  by  rivers  to  the  diatom  ooze  which 
accumulates  in  some  parts  of  the  deep-sea,  there  are 
many  modern  examples  of  additions  made  to  the 
earth  by  plants;  from  the  protective  action  of  sand- 
binding  grasses  and  sedges,  or  of  mangrove  belts 
along  the  coasts,  to  the  action  of  many  Algae  in 
forming  deposits  of  carbonate  of  lime,  there  are  many 
illustrations  of  processes  at  present  going  on  in 
which  plants  play  a  part  of  much  geological  in- 
terest. 

*  J.  Arthur  Thomson.  The  Study  of  Animal  Life,  fourth 
edition,  London,  1901,  p.  25. 


268    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

Almost  throughout  the  century  there  has  been 
continuous  inquiry  into  the  nature  and  origin  of 
coal;  much  has  been  done  in  the  recognition  of  the 
flowerless  plants  (especially  club-mosses)  which 
gave  rise  to  it;  experimental  work  has  shown  the 
probability  of  its  formation  under  water,  under 
great  pressure,  and  in  warm  conditions ;  but  there  is 
still  no  unanimity  in  answering  the  question  whether 
coal  was  formed  in  the  site  where  the  plants  that 
formed  it  grew,  or  whether  the  material  was  flooded 
off  from  the  old  forests  and  deposited  elsewhere. 

Animals, — The  influence  of  animal  life  upon  the 
earth  is  also  manifold.  On  the  one  hand,  we  see 
destructive  agencies, — the  boring  sponge  Cliona 
tunnelling  through  and  through  the  oyster  shell  and 
tending  to  reduce  it  to  sand,  the  Pholads  and  many 
other  borers  helping  to  break  down  the  most  solid 
sea-shore  rocks,  the  crayfish  and  their  enemies  the 
watervoles  uniting  to  make  the  river-banks  collapse, 
the  beavers  cutting  down  trees,  building  dams,  dig- 
ging canals,  and  changing  the  aspect  of  even  large 
tracts  of  country,  and  so  on  through  a  long  list. 

On  the  other  hand,  we  see  conservative  agen- 
cies,— the  formation  of  great  shell-beds,  the  accumu- 
lation of  calcareous  and  siliceous  ooze  in  the  great 
abysses  of  the  oceans,  and  most  strikingly  the  rise 
of  coral-reefs,  such  as  the  great  barrier  reef  of  Aus- 
tralia which  is  over  1000  miles  in  length. 

That  there  are  great  limestone  beds  which  have 
been  formed  by  the  remains  of  marine  animals  is 
an  obvious  fact.  They  are  often  so  thoroughly 
penetrated  by  recognisable  shells  of  nummulites, 
coral,  sea-lilies  and  molluscs,  that  he  who  runs 
may  read  their  origin.  In  other  cases,  however,  there 
are  no  big  remains  which  the  eye  recognises  at 


GROWTH  OF  GEOLOGY.  269 

once,  and  it  was  an  important  step  which  Ehrenberg 
made  in  1839,  when,  by  applying  the  microscope,  he 
proved  that  chalk  rocks  were  built  up  of  the  minute 
shells  of  Foraminifera.  The  full  importance  of 
this  became  plain  when  the  Challenger  explor- 
ers mapped  out  the  extent  of  Foraminiferal  ooze 
on  the  ocean  floor.  What  is  now  accumulating  in 
the  abysses  was  seen  to  be  the  modern  analogue  of 
ancient  chalk-cliffs,  and  the  present-day  represen- 
tation of  other  than  Foraminiferal  limestone  rocks 
has  also  been  disclosed.  The  Challenger  Report 
on  Deep-Sea  Deposits  by  Sir  John  Murray  and  the 
Abbe  Eenard  (1891)  may  be  cited  as  the  most  im- 
portant outcome  of  this  line  of  investigation. 

The  history  of  the  study  of  coral-reefs,  which  we 
have  been  forced  to  omit,  is  a  very  instructive  in- 
stance of  gradually  increasing  thoroughness  in  the 
investigation  of  a  particular  problem. 

The  Living  Earth. — Until  Charles  Darwin  fol- 
lowed up  Gilbert  White's  luminous  suggestions  and 
made  a  careful  estimate  of  the  work  of  earthworms 
as  soil-makers,  few  naturalists — even — had  any  ade- 
quate conception  of  the  busy  world  beneath  their 
feet  Fifty-three  thousand  earthworms  per  acre, 
bringing  ten  tons  of  soil  per  annum  to  the  surface, 
burying  thousands  of  leaves  and  thus  forming  vege- 
table mould,  bruising  the  particles  into  fineness,  and 
by  their  burrows  acting  as  ploughers  before  the 
plough, — facts  like  these,  which  Darwin  substan- 
tiated with  his  consummate  patience,  made  it  plain 
that  these  humble  creatures  must  be  regarded  as 
among  the  most  useful  and  important  animals. 

But  we  must  add  details  to  our  picture  of  the 
earthworms  in  their  burrows;  there  are  the  moles 
and  the  sharp-toothed  centipedes  both  persecuting 


270    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

the  worms,  there  are  burial  beetles  excavating 
beneath  the  corpse  of  bird  or  mouse,  weevils  and 
wireworms  destroying  the  roots  of  plants — and  scores 
of  other  more  or  less  subterranean  animals.  Then 
the  impression  of  the  living  earth  begins  to  grow 
upon  us.  Moreover  to  the  business  of  animals  we 
have  to  add  that  of  plants, — the  curving  movements 
of  rootlets,  the  spreading  growth  of  underground 
stems,  and  the  sprouting  of  seeds. 

Real,  however,  as  all  this  visible  activity  is,  it  is 
not  that  on  account  of  which  we  have  ventured  to 
speak  of  the  living  earth.  The  phrase  is  even  more 
thoroughly  justified  by  work  which  is  done  by  the 
Bacteria  of  the  soil,  and  the  recognition  of  this — 
dating  from  Pasteur — may  be  fairly  called  one  of 
the  characteristic  achievements  of  the  nineteenth 
century.  It  has  led  to  a  vivid  realisation  of  the  great 
fact  of  the  circulation  of  matter. 

THE    PROBLEM    OF    PETROGRAPHY. 

Microscopic  Analysis. — Just  as  the  biologist  an- 
alyses the  body  of  an  animal  into  organs,  tissues, 
and  cells,  and  ends  with  a  study  of  the  complex 
organic  substances  therein  contained,  so  the  geologist 
distinguishes  different  kinds  of  rocks — limestone, 
basalt,  granite,  and  so  on,  proceeds  to  describe  the 
fine  structure  of  each,  and  ends  with  a  determination 
of  the  chemical  composition  of  the  several  constitu- 
ents. In  a  general  way,  petrology  is  to  geology 
what  histology  is  to  anatomy, — an  analysis  of  micro- 
scopic structure;  and  just  as  the  study  of  histology 
inevitably  leads  to  the  study  of  histogenesis — that 
is,  how  the  different  tissues  are  developed — so  petrol- 
ogy will  only  be  completed  when  the  origin  as  well 


GROWTH  OF  GEOLOGY.  271 

as  the  nature  of  rock-structure  is  known.  In  a  few 
cases  the  problem  is  easy  of  solution,  as  when  it  is 
seen  that  some  kinds  of  limestone  are  almost  entirely 
composed  of  the  shells  of  Foraminif era ;  in  most 
cases  the  problem  is  all  unsolved. 

All  that  we  can  do  in  this  section  is  to  indicate 
some  of  the  important  steps  which  have  led  to  the 
present  vigorously  progressive  science  of  petrology 
or  petrography. 

Early  Methods. — In  1800  Fleurian  d.e  Bellevue 
recommended  the  microscopic  study  of  powdered 
fragments  of  rock,  and  Cordier,  in  1815,  resorted  to 
this  primitive  device,  and  succeeded  after  much  la- 
bour in  proving  that  basalt  was  made  up  of  several 
minerals.  In  the  fourth  decade  of  the  century 
Ehrenberg  began  to  apply  the  microscope  to  minute 
splinters  and  powdered  fragments  of  various  non- 
crystalline  rocks,  and  showed  that  some  of  these 
were  almost  entirely  composed  of  shells  of  minute 
animals  or  plants,  e.g.,  Foraminifera  and  Diatoms. 
The  step  was  important  in  itself  and  not  less  in  its 
suggestive  value. 

About  the  middle  of  the  century  G.  Bischof  pub- 
lished his  text-book  of  chemical  and  physical  geology 
(1848-55),  in  which  he  compared  the  earth  to  "  a 
great  chemical  laboratory."  Although  he  pushed 
chemical  interpretations  to  an  extreme,  he  suggested 
a  point  of  view  which  in  later  days  has  seemed  to 
many  like  a  Pisgah.  From  Bischof  and  Bunsen  to 
the  scientists  of  to-day  there  is  a  long  list. 

The  Section  Method. — It  is  said  that  the  first  to 
suggest  and  arrange  the  method  of  preparing  thin 
sections  of  rocks  was  William  Nicol,  the  inventor 
(1829)  of  the  most  useful  prism  of  Iceland  spar 
that  bears  his  name.  A  description  of  his  method 


272    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

of  making  sections  was  published  in  1831.*  But 
these  early  hints  had  little  result,  and  it  seems  fairly 
certain  that  the  first  to  use  and  appreciate  the  method 
of  studying  thin  rock-sections  in  transmitted  line 
under  the  microscope  was  Dr.  H.  Clifton  Sorby  of 
Sheffield  (1850),  who  had  been  stimulated  by  the 
sight  of  a  collection  of  !N"icol's  preparations  which 
had  been  preserved  and  added  to  by  Alexander  Bry- 
eon,  an  optician  in  Edinburgh. 

Professor  Zittel  notes  that,  in  1852,  Oschatz  ex- 
hibited in  Berlin  a  series  of  microscopic  sections  of 
rocks  which  he  had  made,  but  his  results  seem  to 
have  been  regarded  as  little  more  than  curiosities. 
A  proof  of  the  value  of  the  method  was  needed,  and 
that  was  furnished  in  1858  by  Sorby  in  a  classic 
memoir  "  On  the  microscopic  study  of  crystals,  indi- 
cating the  origin  of  minerals  and  rocks."  f  The 
next  steps,  and  for  many  years  almost  all  the  im- 
portant steps,  were  taken  by  continental  geologists. 
"  Even  Sorby's  papers,  which  continued  to  be  most 
suggestive  in  this  line  of  work,  had  reference  only 
to  very  special  points ;  and  it  may  be  doubted  if  his 
greatest  service  was  not  the  transplanting  of  his  ideas 
and  methods  to  Germany,  where  they  were  destined 
to  rapidly  take  root,  and  bear  a  fruitful  harvest.":}: 

It  was  a  most  fortunate  thing  for  science  that 
Zirkel,  as  a  young  student,  made  Sorby's  acquaint- 
ance in  Bonn  in  1862,  and  after  many  walks  and 
talks  became  an  enthusiastic  disciple,  soon  far  to 

*  Henry  Witham.  Observations  on  Fossil  Vegetables, 
Edinburgh,  1831.  See  The  Microscope,  by  Carpenter  and 
Dallinger,  London  (1891),  p.  990. 

f  Quart.  Journ.  Geol.  Soc.  XIV.  (1858),  pp.  453-500. 

$  G.  H.  "Williams.  Modern  Petrography,  an  account  of  the 
application  of  the  microscope  to  the  study  of  geology. 
Boston,  1886. 


GROWTH  OF  GEOLOGY.  273 

outstrip  his  master.*  Undertaking,  for  the  first 
time,  "  a  systematic  study  of  rock-sections  as  an  end 
in  itself,"  as  Williams  says,  Zirkel  began  rapidly  to 
lay  the  foundations  of  modern  petrography.  But 
with  his  name  that  of  Rosenbusch  must  be  immedi- 
ately coupled ;  both  as  investigators  and  as  teachers, 
they  stand  as  the  leaders  of  petrographical  enquiry. 

Among  the  earlier  petrologists  one  of  the  most 
original  and  suggestive  was  Hermann  Vogelsang, 
whose  Philosophy  of  Geology  (1867)  is  still  looked 
upon  with  great  admiration,  who  is  also  memorable 
for  his  persistent  and  successful  attempts  to  get 
nearer  the  secret  of  petrogenesis  by  reproducing  ex- 
perimentally results  similar  to  those  which  have  oc- 
curred in  nature.  We  cannot,  however,  pursue  the 
history,  and  to  mention  even  the  names  of  those  who 
have  done  great  service  in  petrography  since  Zirkel 
and  Eosenbusch  became  recognised  leaders,  would 
serve  no  useful  purpose  in  a  sketch  like  this.  One 
classification  has  succeeded  another,  and  no  petrolo- 
gist  seems  satisfied  either  with  his  own  or  his  neigh- 
bour's ;  the  question  of  "  species  "  seems  as  puzzling 
as  in  biology ;  and  there  can  be  no  solution  until  the 
static  results  of  description  are  illumined  by  a  theory 
of  rock-genesis.  To  this,  through  keen  struggle  for 
existence  among  conflicting  opinions,  every  year 
brings  us  nearer. 

Mineralogy. — Turning  to  the  department  of  petrog- 
raphy which  restricts  itself  to  minerals,  we  may  note 
that  in  the  early  days  of  mineralogy  the  physical  as- 
pect, the  study  of  crystalline  form,  specific  gravity, 
hardness,  etc.,  received  most  attention.  Of  especial 
importance  was  the  work  of  Haiiy  who,  without  de- 

*  See  F.  Zirkel.  Die  Einfuhrung  des  Mikroskops  in  das 
mineralogischgeologische  Studium,  Leipzig,  1881. 


274    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

predating  the  study  of  the  chemical  properties,  em- 
phasised the  value  of  crystallography,  and  referred 
the  numerous  crystalline  forms  to  a  few  primary 
types. 

There  was  for  a  time  a  tendency  among  mineral- 
ogists, as  among  physiologists,  to  refuse  the  chemists' 
offer  of  a  helping  hand,  but  sounder  views  gradually 
prevailed.  Berzelius  (quoted  by  E.  von  Meyer)  com- 
pares the  mineralogist  who  refuses  the  aid  of  chem- 
istry to  a  man  who  objects  to  use  a  light  in  the 
dark,  on  the  ground  that  he  would  thereby  see  more 
than  he  requires  to.  The  introduction  of  the  blow- 
pipe by  Cronstedt  was  an  event  of  much  importance, 
and  led  on  to  the  early  chemical  systems  of  Bergmann 
and  others.  But  the  modern  study  of  mineralogical 
chemistry  must  date  from  the  work  of  Berzelius, 
who  in  his  Chemical  System  brought  minerals  into 
line  with  other  inorganic  compounds.  The  general 
tendency  of  subsequent  systems  of  classification 
seems  to  have  been  to  emphasise  chemical  composi- 
tion, and  it  is  interesting  to  notice  the  suggestions  of 
Wurtz  and  others  as  to  the  collation  of  various  min- 
erals with  organic  compounds,  e.g.,  poly-silicic  acids 
with  poly-ethylene  alcohols. 

Isomorphism. — Another  great  event  in  the  history 
of  mineralogy  was  Mitscherlich's  discovery  of  isomor- 
phism. $".  Fuchs  had  previously  observed  that  cer- 
tain substances  can  replace  each  other  in  minerals; 
Mitscherlich  showed  that  the  same  material  might 
have  two,  three,  or  more  crystalline  forms.  This  set 
aside  the  exaggerated  conclusion  of  Haiiy  that 
difference  in  crystalline  form  necessarily  implies 
difference  in  chemical  composition. 

While  Mitscherlich  may  be  said  to  have  proved 
irrefutably  the  connection  between  chemical  com- 


GROWTH  OF  GEOLOGY.  275 

position  and  crystalline  form,  both  he  and  Berzelius 
went  too  far  in  declaring  similarity  of  crystalline 
form  to  be  "  a  mechanical  consequence  of  similarity 
in  atomic  constitution,"  or  in  other  words  that  the 
atomic  constitution  of  a  substance  could  be  inferred 
if  that  of  one  of  its  isomorphs  was  known.  For 
Mitscherlich  afterwards  showed  that  dissimilarly 
constituted  bodies  might  be  isomorphous  and  simi- 
larly constituted  ones  heteromorphous,  and  that  the 
same  substance  might  crystallise  in  different  forms. 
To  this  Scherer  added  "  cases  of  the  so-called  poly- 
meric isomorphism,  which  proved  that  elementary 
atoms  might  be  replaced  by  atomic  groups  without 
change  of  crystalline  form."  * 

Experimental. — We  have  already  referred  to  Sir 
James  Hall  as  the  founder  of  experimental  geology, 
and  may  here  recall  that  in  1801  he  showed  the  possi- 
ble transformation  of  chalk  into  marble.  For  this 
was  as  it  were  the  first  sentence  in  an  exceedingly 
interesting  chapter  in  the  history  of  research — the 
development  of  experimental  mineralogy.  Numer- 
ous experimenters — particularly  well  represented  in 
France — e.g.,  in  modern  times,  Fouque  and  Michel- 
Levy,  Friedel  and  Sarasin — have  worked  at  the  arti- 
ficial production  of  minerals,  and  have  thrown  much 
light  upon  the  possible  ways  in  which  minerals  may 
have  been  formed  in  nature. 

NOTE  OX  THE  SCIENTIFIC  DEVELOPMENT  OF 
GEOGRAPHY. 

One  of  the  great  intellectual  advances  of  the  nine- 
teenth century  has  been  the  scientific  development 
of  geography.  Whether  we  recognize  one  science  or 

*E.  von  Meyer.  History  of  Chemistry,  Trans.  1891,  p. 
454. 


276    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

twenty  is  merely  a  question  of  convenience;  the 
boundaries  of  the  sciences  whose  right  to  the  name 
is  seldom  questioned, — physics  and  chemistry,  as- 
tronomy and  geology,  biology  and  psychology, 
and  so  on, — are  flexible;  two  or  more  sciences  often 
seem  confluent ;  and  therefore  it  matters  little  wheth- 
er we  regard  geography  as  a  unified  and  well-defined 
department  of  science,  or  as  a  combination  of  sciences 
in  relation  to  a  particular  problem. 

According  to  a  definition  (by  Dr.  H.  E.  Mill), 
on  which  evident  care  has  been  expended,  "  Geog- 
raphy is  the  exact  and  organised  knowledge  of  the 
distribution  of  phenomena  on  the  surface  of  the 
Earth,  culminating  in  the  explanation  of  the  inter- 
action of  Man  with  his  terrestrial  environment."  * 
Dr.  Mill  goes  on  to  say,  "  As  the  meeting-place  of 
the  physical  and  the  human  sciences,  it  is  the  focus 
at  which  the  rays  of  natural  science,  history,  and 
economics  converge  to  illuminate  the  Earth  in  its 
relation  to  man.  .  .  .  The  unity  of  geography  re- 
sults from  viewing  nature  in  the  limited  but  still 
general  aspect  of  the  phenomena  which  affect  the 
surface  of  the  Earth." 

The  geographer  is  concerned  with  the  atmosphere, 
the  hydrosphere  (the  water-envelope),  and  the  litho- 
sphere  (the  rocky  crust  whether  of  the  continents  or 
the  ocean-floors).  "His  first  business  is  to  define 
the  form,  or  relief,  of  the  surface  of  the  solid  sphere, 
and  the  movements,  or  circulation,  within  the  two 
•fluid  spheres.  The  land-relief  conditions  the  circu- 
lation, and  this  in  turn  gradually  changes  the  land- 
relief.  The  circulation  modifies  climates,  and  these, 
together  with  the  relief,  constitute  the  environments 
of  plants,  animals,  and  men.  Short  of  complexities, 
*  The  International  Geography.  London,  1899.  p.  2, 


GROWTH  OF  GEOLOGY.  277 

this  is  the  main  line  of  the  geographical  argument. 
In  the  language  of  Eichthofen  the  earth's  surface 
and  man  are  the  terminal  links."  * 

It  might  seem  as  if  geography  had  become  a 
compendium  of  the  sciences  and  took  all  nature  for 
its  province,  but  that  is  a  misinterpretation  of  the 
modern  extension.  The  fact  is  that  geography 
is  a  synthesis  of  the  results  of  many  sciences  in 
relation  to  a  special  problem ;  or  it  may  be  compared 
to  a  central  circle  intersecting  a  cluster  of  other  cir- 
cles which  represent  physics,  chemistry,  astronomy, 
geology,  biology,  anthropology,  and  so  on. 

Alexander  von  Humboldt  is  ranked  as  one  of  the 
founders  of  scientific  geography,  not  merely  because 
of  his  explorations,  or  his  method  of  representing 
the  relief  of  a  country  (e.g.,  Mexico)  by  cross  sec- 
tion, or  his  invention  of  isotherms,  but  because  he 
had  the  distinctively  scientific  virtue  of  seeing 
things  in  their  inter-relations.  "  Humboldt's  Essai 
politique  sur  la  Nouvelle-Espagne,  published  in 
1809,  must  take  high  rank  among  the  efforts  of  the 
new  geography  as  the  first  complete  description  of 
a  land  with  the  aid  of  the  modern  methods.  Here, 
for  the  first  time,  we  have  an  exhaustive  attempt  to 
relate  causally  relief,  climate,  vegetation,  fauna,  and 
the  various  human  activities."  f  For  that  is  geo- 
graphy. 

But  along  with  Humboldt  there  are  others  who 
should  be  named, — Karl  Hitter  of  Berlin  (1779- 
1859),  "the  greatest  modern  professor  of  geogra- 
phy," author  of  the  famous  Erdkunde  and  founder 
of  a  great  school;  the  cartographer  Berghaus, 

*  H.  J.  Mackinder.  Address  Section  E,  Rep.  Brit.  Ass,, 
1895,  p.  739. 

t  H.  J.  Mackinder.    Loc.  tit.  p.  741. 


278    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

whose  great  Physical  atlas  is  an  immortal  monument ; 
Perthes,  "  the  capitalist  employer  of  cartographers  "  ; 
and  the  critical  Oscar  Peschel.  From  these  we  pass 
to  living  workers,  such  as  von  Kichthofen  and  Penck. 
One  of  the  great  results  of  the  nineteenth  century 
has  been  the  development  of  geography  as  a  synthetic 
science. 

AN   ILLUSTRATION    OF   OCEANOGRAPHY. 

The  whole  history  of  Oceanography,  in  its  various 
branches,  has  been  related  in  great  fulness  by  Sir 
John  Murray  in  his  Summary  of  the  Scientific  Re- 
sults of  the  Voyage  of  H.M.S.  Challenger;  we  can- 
not in  a  section  do  more  than  illustrate  the  fact  of 
its  rapid  development  in  the  second  half,  and  espe- 
cially in  the  last  quarter  of  the  nineteenth  century. 
The  illustration  we  take  is  the  familiar  but  striking 
one  that  within  a  few  years  we  have  gained  a  wealth 
of  information  in  regard  to  the  Deep  Sea,  which  was 
about  the  middle  of  the  century  an  almost  unexplored 
area.  In  spite  of  isolated  hints  which  might  have 
been  followed  up  earlier,  it  was  generally  believed 
until  1860  or  so,  that  the  great  depths  of  the  ocean 
were  uninhabitable,  and  there  was  almost  no  knowl- 
edge of  the  deposits  covering  the  floor.  A  notable  step 
was  taken  when  Surgeon-Major  G.  G.  Wallich, 
naturalist  with  Sir  Leopold  M'Clintock's  North 
Atlantic  Expedition  of  1860,  showed  that  animals 
lived  in  the  abysses  even  below  1,000  fathoms.  It 
is  interesting  also  to  notice  that  one  of  the  impulses 
which  gave  Deep-Sea  exploration  a  start  was  the 
purely  -practical  desire  to  establish  telegraphic  com- 
munication between  the  Old  and  New  Worlds.  In 
binding  these  together,  another  new  world  was  dis- 
covered. 


GROWTH  OF  GEOLOGY.  279 

The  recognition  of  oceanography  as  a  distinct 
branch  of  science  may  be  said  to  date  from  the 
commencement  of  the  Challenger  investigations, 
and  although  the  study  is  still  in  a  sense  in  its 
youth,  "  so  much  has  already  been  acquired  that  the 
historian  will,  in  all  probability,  point  to  the  ocean- 
ographical  discoveries  during  the  past  forty  years 
as  the  most  important  addition  to  the  natural  knowl- 
edge of  our  planet  since  the  great  geographical 
voyages  associated  with  the  names  of  Columbus,  Da 
Gama,  and  Magellan,  at  the  end  of  the  fifteenth  and 
the  beginning  of  the  sixteenth  centuries."  * 

Our  picture  of  the  Deep  Sea  is  necessarily  darkly- 
shaded  and  in  many  respects  dim  and  vague,  but 
it  is  not  wanting  in  precise  detail.  Some  indication 
of  this  may  be  given.  At  great  depths  there  is 
necessarily  enormous  pressure  (at  2,500  fathoms 
about  2£  tons  upon  the  square  inch)  ;  it  is  quite 
calm,  untouched  by  the  severest  storms ;  the  tempera- 
ture is  low  and  uniform,  often  just  a  little  above  the 
freezing-point  all  the  year  round;  the  water  is  rel- 
atively rich  in  oxygen;  there  is  practically  no  light, 
apart  from  phosphorescence;  there  are  therefore  no 
green  plants  and  there  is  no  secure  evidence  even 
of  Bacteria;  there  is  no  depth  limit  to  the  distri- 
bution of  animal  life  and  the  population  includes 
representatives  of  most  of  the  great  types  of  animals 
from  Protozoa  up  to  fishes;  the  animals  necessarily 
feed  to  a  large  extent  upon  one  another,  but  funda- 
mentally upon  the  organic  debris  which  sinks  from 
above,  and  not  least  upon  the  ceaseless  rain  of  pelagic 
Protozoa  which  sink  down  from  the  surface  as  they 
die.  A  strange,  silent,  cold,  dark,  plantless  world ! 

*  Sir  John  Murray.    Address  Section  E,  Hep.  Brit.  Asa., 
1899,  p.  790. 

8 


280    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

While  the  shallow-water  areas  down  to  the  100- 
fathom  line  are  now  known  with  much  exactness  in 
many  parts  of  the  glohe,  there  is  naturally  much  less 
certainty  in  regard  to  the  deeper  parts,  though,  as 
Sir  John  Murray  remarks,  some  10,000  deep  sound- 
ings were  taken  in  the  last  decade  of  the  nineteenth 
century.  He  estimates  that  considerably  more  than 
half  of  the  sea-floor  (103,000,000  square  geo- 
graphical miles  in  all)  lies  at  a  depth  exceeding 
2,000  fathoms,  or  over  two  geographical  miles. 
There  is  a  relatively  rapid  descent  along  the  conti- 
nental slopes  between  100  and  1,000  fathoms,  and 
there  are  over  forty  known  depressions  of  more  than 
3,000  fathoms.  The  greatest  known  depth  is  in  the 
S.  Pacific,  to  the  east  of  the  Kermadecs  and  Friendly 
Islands,  530  feet  more  than  five  geographical  miles, 
or  2,000  feet  more  below  the  level  of  the  sea  than  the 
top  of  Mount  Everest  is  above  it. 

Direct  observations  with  deep-sea  thermometers, 
and  indirect  inferences  from  the  electric  resistance 
of  the  telegraph  cables  lying  on  the  floor  of  the 
oceans,  show  that  about  92  per  cent,  of  the  entire 
sea-floor  has  a  temperature  less  than  40°  Fahr.  The 
surface-water  cooled  at  the  poles,  spreads  over  the 
floor  towards  the  equator,  carrying  with  it  the  oxygen 
which  makes  abyssal  life  possible.  Since  the  light 
as  well  as  the  warmth  of  the  sun  does  not  penetrate 
below  the  superficial  layers  of  water,  the  deep-sea 
area  is  dark  as  well  as  cold.  Therefore  there  are 
no  plants  (apart  from  some  doubtful  forms  and  the 
resting  stages  of  two  or  three  AlgaB),  and  this  implies 
that  the  abundant  deep-sea  animals  depend  in  the 
long  run  on  supplies  which  sink  downwards  from 
the  populous  surface  or  the  crowded  shore-areas. 

Especially  by  Sir  John  Murray  and  the  Abbe 


GROWTH  OF  GEOLOGY.  281 

Renard  a  most  careful  study  has  been  made  of  the 
marine  deposits  on  the  ocean-floor.  These  are  con- 
veniently divided  into  two  sets — (1)  the  terrigenous 
deposits,  for  the  most  part  consisting  of  the  dis- 
integrated particles  of  the  adjacent  emerged  land, 
and  of  great  interest  as  illustrating  accumulations 
analogous  to  those  which  formed  many  of  the  strati- 
fied rocks;  and  (2)  pelagic  deposits,  which  begin  at 
an  average  of  about  200  miles  from  the  continental 
coast-lines,  and  are  mainly  composed  of  the  shells 
of  pelagic  organisms  (Molluscs,  Foraminifera,  Ra- 
diolaria,  Diatoms,  etc.),  besides  inorganic  particles 
of  volcanic  or  cosmic  origin.  The  "  Red  Clay," 
which  covers  nearly  half  of  the  sea-floor,  and  all  the 
deeper  parts,  is  probably  due  to  the  chemical  altera- 
tion of  organic  and  inorganic  remains  during  a  pro- 
longed period  of  slow  accumulation.  Sir  John 
Murray  argues  that  the  number  of  sharks'  teeth,  of 
earbones  and  other  bones  of  whales,  and  of  cosmic 
spherules  in  a  deposit  may  be  taken  as  a  measure 
of  the  rate  of  deposition.  These  bodies  are  most 
abundant  in  the  Red  Clay,  probably  because  few 
other  substances  reach  the  great  depths  to  cover 
them  up.  "  One  haul  of  a  small  trawl  in  the  Central 
Pacific  brought  to  the  surface  on  one  occasion,  from 
a  depth  of  about  2^  miles,  many  hundreds  of  man- 
ganese nodules,  along  with  1500  sharks'  teeth,  over 
50  fragments  of  earbones  and  other  bones  of 
whales." 

It  may  seem  to  the  careless  both  dull  and  unprofit- 
able to  map  out  with  care  the  sediments  which  are 
now  forming  on  the  floor  of  the  ocean,  but  the  im- 
portance of  these  maps  to  the  geologist  is  immense. 
For  it  is  from  them  that  we  can  argue  back  to  the 
history  of  the  sedimentary  part  of  the  earth's  crust, 


282    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

and  show  how  in  the  Triassic,  for  instance,  there 
was  sea  where  there  is  now  the  great  mountain  belt 
of  the  Euro-Asiatic  continent,  or  how  the  great  chalk 
deposits  of  the  Cretaceous  are  the  analogues  of  the 
deep  sea  Globigerina  ooze  of  to-day. 

SUMMARY. — One  of  the  great  discoveries  of  the 
nineteenth  century  was  that  of  the  Deep  Sea — almost 
a  new  world.  The  vast  depths,  the  low  temperature, 
the  abundant  animal  population  and  the  deposits 
which  accumulate  on  the  -floor  have  been  the  subject 
of  careful  and  fruitful  study,  but  the  vastness  of  the 
area  makes  it  certain  that  much  that  is  new  still 
awaits  the  explorer  of  the  abysses. 


BOOK  THREE. 

SCIENCE  OF  ORGANISMS— LIFE-LORE. 


CHAPTER  VIII. 

THE  DEEPENING  OF  PHYSIOLOGY. 

HISTORICAL,  OUTLINE. 

Aspects  of  the  Organism. — The  living  body  as  a 
subject  of  scientific  enquiry  may  be  approached  from 
many  different  sides.  A  dim  personality  it  often 
seems,  intelligent  or  instinctive  in  its  actions;  or  it 
may  live  its  life  on  a  lower  plane  where  neither  of 
these  terms  is  applicable.  It  is  a  unit  in  a  family  or 
flock,  in  a  fauna  or  flora,  an  item  in  the  midst  of  an 
environment,  and  must  be  studied  in  its  inter-rela- 
tions of  dependence  or  antagonism,  of  co-operation 
or  competition,  of  successful  adaptation  or  failure  to 
survive.  It  is  a  member  of  a  race,  starting  in  life 
with  a  multiple  inheritance  from  many  ancestors ;  its 
individual  becoming  must  be  studied  in  the  light  of 
its  past  history,  its  development  in  the  light  of  its 
evolution.  It  is  an  engine,  transforming  matter 
and  energy,  and  must  be  studied  as  a  problem  in 
dynamics.  It  is  a  chemical  laboratory,  in  which 
reductions,  oxidations,  disruptions,  constructions, 
explosions,  and  fermentations  go  on  in  manifold 
complexity. 


284    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

In  these  various  ways  the  living  body  may  be 
studied,  and  no  one  of  them  has  been  disregarded  by 
the  physiologists.  It  is  plain,  however,  that  along 
some  of  these  lines  at  least  no  secure  progress  could 
be  made  until  the  sciences  on  which  physiological 
investigations  depend  had  begun  to  gain  clearness 
and  stability.  There  could  be  no  chemical  physiol- 
ogy when  combustion  was  not  understood,  and  little 
physical  physiology  when  heat  was  regarded  as  an 
element  or  as  an  entity.  It  follows  that  almost  all 
analytic  physiology  involving  chemistry  and  physics 
must  be  comparatively  modern,  and  that  we  are  not 
likely  to  find  much  value  in  the  physiology  of  the 
eighteenth  century  or  earlier  except  in  so  far  as  that 
was  concerned  with  descriptions  of  the  habits  of  the 
intact  creature,  with  observations  on  the  gross  func- 
tions of  organs,  or  with  merely  mechanical  analysis. 

Sketch  of  Physiological  Progress. — In  what  are 
called  the  Middle  Ages  (to  which,  as  regards  biology 
and  psychology,  many  people  still  belong)  the  an- 
alysis of  the  organism  was  only  incipient.  Compara- 
tive anatomy  and  comparative  physiology  were  still 
embryonic.  Chemistry  and  Physics  were  not  yet  suf- 
ficiently stable  themselves  to  be  able  to  help  another 
science  to  a  firm  foothold.  Yet  then,  as  ever,  men 
looked  out  upon  nature  with  inquisitive  eyes,  accum- 
ulated a  wealth  of  sense-impressions,  and  recorded 
their  perceptions  in  more  or  less  orderly  form. 
Many  interesting  phenomena  of  plant  and  animal  life 
were  observed,  and  sometimes  accurately  described. 
But  when  the  medieval  observers  went  beyond 
this,  and  took  the  more  characteristically  scientific 
step  of  devising  general  formula?  for  the  sequences 
and  likenesses  which  they  perceived,  they  were  al- 
most forced  to  do  so  in  metaphysical  terms.  Their 


THE  DEEPENING  OF  PHYSIOLOGY.  285 

shorthand  was  frankly  anthropomorphic  or  spiritual- 
istic ;  they  invoked  "  animal  spirits "  and  "  vital 
spirits,"  "  principles  of  life "  and  "  vires  form- 
ative" "humours"1  and  "temperaments."  It  is 
difficult  to  see  how  it  could  have  been  otherwise. 

But  as  inquisitiveness  became  gradually  more  pen- 
etrating, as  the  organs  of  the  body  were  disclosed  in 
many  other  creatures  besides  man,  as  the  uses  of 
many  of  them  were  in  part  discovered,  the  spirit- 
ualistic formula?  began  to  appear  somewhat  gratui- 
tous. Thus  it  is  interesting  to  note  that  Mariotte 
(d.  1684),  who  compared  the  entrance  of  water  into 
the  roots  of  plants  to  its  rise  in  capillary  tubes  — a 
shrewd  suggestion — was  one  of  the  first  to  discard  the 
hypothesis  of  "  a  vegetable  soul  " — as  a  factor  in  the 
plant's  every-day  functions.  Harvey's  demonstra- 
tion of  some  of  the  factors  in  the  circulation  of  the 
blood  may  be  taken  as  one  of  the  first  of  the  long 
series  of  attempts  to  express  vital  phenomena  in  terms 
of  mechanism — attempts  which  put  an  end  to  the 
reign  of  spirits,  though  not  to  the  intrusion  of  meta- 
physics. The  great  work  of  Haller  (1708-1777) — 
Elementa  Pliysiologice  Corporis  Humani — represents 
the  position  of  the  study  of  the  functions  of  the 
organs  of  the  body  at  the  beginning  of  the  nineteenth 
century,  and  it  is  marked  by  its  endeavour  to  reject 
all  that  could  not  be  verified  by  observation  and  ex- 
periment. 

When  we  pass  from  the  work  of  Haller  to  that  of 
Johannes  Mliller  (1801-1858)  we  feel  at  once  in  a 
new  century.  Chemistry  and  physics  had  made 
great  strides,  and  he  calls  them  to  his  aid  in  his  phys- 
iological work.  Man  was  no  longer  studied  alone, 
for  Miiller's  physiology  was  essentially  comparative. 
The  facts  of  mental  life  were  no  longer  kept  wholly 


286    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

apart  from  corporeal  affairs,  for,  as  Verworn  notes, 
Miiller  defended  even  in  his  examination  for  the  doc- 
torate the  thesis :  Psychologus  nemo  nisi  physiologus. 
But  it  is  interesting  to  find  that  this  genius  who  did 
so  much  to  give  physiology  its  modern  aspect  was  like 
most  of  his  contemporaries,  a  vitalist.  He  main- 
tained that  the  functions  of  the  body  exhibited  se- 
quences comparable  to  those  observed  by  the  chemist 
and  physicist  in  not-living  bodies,  yet  he  believed  that 
there  was  in  the  organism  a  "  vital  force  "  which  had 
to  be  taken  account  of  in  physiology. 

Meanwhile  pursuing  the  general  trend  of  biologi- 
cal research,  we  may  note  that  just  as  the  study  of 
the  intact  organism  as  a  bundle  of  habits  and  tem- 
peraments more  or  less  kept  in  order  by  a  "  spiritus 
rector  "  gave  place  to  a  study  of  the  activities  of  par- 
ticular organs — the  brain,  the  heart,  the  lungs,  the 
liver,  and  so  on,  so  the  resulting  conception  of  the 
living  creature  as  an  engine  of  many  parts  had  to 
be  supplemented  by  the  study  of  the  properties  of 
tissues  (muscular,  nervous,  glandular,  and  so  on), 
— a  step  which  we  particularly  associate  with  the  pub- 
lication of  Bichat's  Anatomie  Generale  in  1801. 
Gradually,  however,  as  the  microscope  was  im- 
proved, the  existence  and  importance  of  the  little 
areas  of  living  matter  which  we  (unfortunately) 
call  cells  was  recognised,  and  in  1838-39  Schwann 
and  Schleiden  formulated  their  "  Cell-Theory "  or 
Cell-Doctrine, — (a)  that  all  plants  and  animals  have 
a  cellular  structure,  (&)  that  the  life  of  all  multi- 
cellular  organisms  (reproduced  in  the  ordinary  way) 
begins  in  a  single  cell — the  fertilised  ovum — which 
proceeds  to  build  up  the  body  by  a  process  of  cell- 
division,  and  (c}  that  the  life  of  the  whole  is  ex- 
pressible in  terms  of  the  activities  of  its  component 


THE  DEEPENING  OF  PHYSIOLOGY.  287 

cells.  One  step  further  in  analysis  brings  us  to 
the  characteristically  modern  study  of  the  chemical 
and  physical  changes  which  go  on  in  the  contents  of 
the  cells,  that  is  to  say  in  "  the  physical  basis  of  life," 
as  Huxley  phrased  it,  or  protoplasm. 

PHYSIOLOGY  OF  THE  LIVING   ORGANISM  AS  A  WHOLE. 

The  Life  of  Living  Creatures. — In  the  childhood 
— a  prolonged  period — of  Life-Lore,  attention  was  in 
great  part  directed  to  the  study  of  the  activity  of  the 
living  creature  as  an  intact  whole.  It  is  or  should 
be  so  in  the  childhood  of  the  individual.  Life  as  it 
is  lived  in  nature,  the  behaviour  of  the  animal,  its 
relations  to  other  living  things,  the  "  habit "  of  the 
plant,  its  friends  and  foes, — these  form  part  of  the 
oldest  physiology  and  they  should  still  command  our 
attention  to-day. 

The  term  physiology  is  too  much  restricted  to  a 
study  of  the  internal  economy  of  the  organism.  Just 
as  anatomical  analysis  may  be  compared  to  picking 
a  watch  to  pieces — an  operation  which  dimly  suggests 
the  delights  of  dissection — so  physiological  analysis 
may  be  compared  to  a  study  of  the  kinetic  aspect  of 
the  watch,  and  even  when  physiology  becomes  com- 
parative it  is  still  like  comparing  one  kind  of  watch 
with  another.  To  save  the  results  from  inexcusable 
partiality  and  incompleteness  it  is  necessary  to 
sound  the  natural  history  note,  the  recognition  of  or- 
ganisms in  the  plural,  as  members  of  a  pair,  a  fam- 
ily, a  flock,  an  association,  a  fauna,  as  threads  in  a 
web  of  life,  as  agents  in  a  complex  environment. 
In  short,  it  must  be  recognized  that  physiological 
analysis  has  seriously  to  deal  with  the  intact  living 
creature  in  its  natural  surroundings,  with  its 


288    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

domestic  and  social  relations,  with  its  habits  and 
adaptations,  with  its  struggle  for  existence  and  en- 
deavour after  well-being.  Physiological  analysis 
thus  completes  and  corrects  itself  in  "  Natural  His- 
tory." 

Two  Lessons  from  the  Old  Natural  History. — 
The  two  chief  lessons  now  to  be  learned  from  the  old 
books  on  natural  history  are  lessons  of  warning.  (1) 
On  the  one  hand  we  are  warned  against  the  extreme- 
ly analytic  method  of  modern  biology,  against  the 
necrology  which  is  always  destroying  in  the  effort 
to  understand.  Since  our  methods  force  us  to  ab- 
stract certain  aspects  of  the  organism,  there  is  an 
undoubted  risk  lest  we  forget  the  unity  of  the  organ- 
ism which  we  take  so  carefully  to  bits;  there  is  an 
undoubted  risk  lest  we  forget  that  what  we  measure 
and  weigh  and  analyse  belonged  to  a  creature  which 
had  something  analogous  to  our  personality.  We 
cannot  dispense  with  our  analysis,  however,  and  the 
corrective  for  its  partiality  is  simply  more  study  of 
the  real  life  of  the  creature  in  its  natural  environ- 
ment, in  other  words  more  "  Natural  History,"  what 
some  indeed  have  called  "  the  higher  physiology." 

(2)  On  the  other  hand,  the  comparative  failure 
of  much  of  the  old  natural  history — so  often  vague, 
inaccurate,  and  fallacious — warns  us  of  the  futility 
of  trying  to  dispense  with  the  analytic  methods  and 
their  results.  In  proportion  as  our  analysis  is 
thorough  so  will  our  realisation  of  the  life  around  us 
be  vivid.  To  say  that  no  one  really  knows  a  bird 
who  has  not  watched  it  build  its  nest  may  be  true; 
but  it  may  be  justly  retorted  that  no  one  really 
knows  a  bird  who  does  not  understand  the  peculiari- 
ties of  its  respiration. 

Historical  Note. — The   "  higher  physiology  "   or 


THE  DEEPENING  OF  PHYSIOLOGY.  289 

"(Ecology"  (as  Haeckel  calls  it)  of  living  crea- 
tures is  the  oldest  department  of  the  science.  It  had 
its  basis  in  the  lore  of  the  hunter  and  fisher,  the 
shepherd  and  farmer,  or  further  back  still  in  that  of 
Mowgli  in  the  jungle. 

But  the  old  lore  was  much  mixed  with  superstition, 
it  was  often  inexact,  and  on  the  whole  uncritical. 
Exact  natural  history  is  essentially  modern,  and, 
apart  from  a  few  pioneers,  may  be  said  to  date  from 
the  enthusiastic  observations  of  men  like  Swammer- 
dam  (1637-1680),  Leeuwenhoek  (1632-1723), 
Keaumur  (1683-1757),  Koesel  von  Kosenhof 
(1705-1759),  Trembley  (1700-1784),  Schaeffer 
(1718-1790),  Gilbert  White  (1720-1793),  and  Buf- 
fon  (1707-1788). 

We  have  placed  Buffon's  name  last  because  he  rep- 
resents a  transition  between  the  old  naturalists  and 
the  new,  for  while  he  may  not  have  had  the  exactness 
of  some  of  his  predecessors  he  had  a  clearer  vision  of 
the  wide  import  of  his  studies.  As  a  philosophic 
naturalist,  he  deliberately  set  himself  to  a  study  of 
the  habits  of  animals  and  their  adaptations  to  their 
surroundings,  and  unified  his  results  in  the  light  of 
the  evolution-idea. 

It  is  especially  the  recognition  of  the  evolution- 
idea  that  makes  the  difference  in  mood  between  the 
old  and  new  naturalists.  "  Before  Darwin's  day  the 
student  of  habits,  inter-relations,  and  adaptations 
had  been  looked  upon  by  his  sterner  brethren  (anato- 
mists, classifiers,  etc.)  with  more  or  less  contemp- 
tuous indulgence.  Since  Darwin's  day,  however, 
the  study  of  bionomics  has  risen  to  worth  and  dig- 
nity." * 

The  study  of  the  life  of  plants  and  animals  as  it 

*  See  the  author's  Science  of  Life,  1899,  Chapter  XIV. 


290    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

is  lived  in  nature  is  an  essential  part  of  a  general 
system  of  Biology.  It  began  in  practical  lore,  at- 
tained a  high  degree  of  excellence  in  the  seventeenth 
and  eighteenth  centuries,  but  acquired  in  the  nine- 
teenth century  greater  dignity  and  definiteness  espe- 
cially through  the  influence  of  evolution-doctrine. 

STUDY  OF  THE  FUNCTIONS  OF  ORGANS. 

Sir  John  Burdon-Sanderson  dates  modern  physiol- 
ogy from  the  work  of  Johannes  Miiller  (1801-1858). 
"  Just  as  there  was  no  true  philosophy  of  living  na- 
ture until  Darwin,  we  may  with  almost  equal  truth 
say  that  physiology  did  not  exist  as  a  science  before 
Johannes  Miiller.  For  although  the  sum  of  his 
numerous  achievements  in  comparative  anatomy  and 
physiology,  notwithstanding  their  extraordinary 
numher  and  importance,  could  not  be  compared  for 
merit  and  f ruitfulness  with  the  one  discovery  which 
furnished  the  key  to  so  many  riddles,  he,  no  less 
than  Darwin,  by  his  influence  on  his  successors  was 
the  beginner  of  a  new  era."  ^ 

Steps  of  Progress  since  Johannes  Miiller. — What 
then  has  been  the  nature  of  the  steps  of  progress  in 
regard  to  the  physiology  of  organs  during  this 
period  which  dates  from  Miiller  ?  As  it  seems  to  us, 
the  steps  may  be  grouped  under  four  heads: — (1) 
the  partial  elucidation  of  the  function  of  organs  pre- 
viously enigmatical,  (2)  the  recognition  that  the 
functions  of  organs,  whose  uses  were  partially  known, 
are  much  more  complex  than  was  previously  sup- 
posed, (3)  a  fuller  understanding  of  the  correlation 
and  co-operation  of  the  various  organs  in  the  life  of 
the  whole,  and  (4)  the  progress  made  in  comparing 
analogous  organs  in  different  kinds  of  organisms. 
*Pres.  Address.  Rep.  Brit.  Ass.  for  1893,  p.  9. 


THE  DEEPENING  OF  PHYSIOLOGY.  291 

Of  each  of  these  steps  we  propose  to  give  some  brief 
illustration. 

(1)  Elucidation  of  Enigmatical  Organs. — In  the 
body  of  a  higher  animal  there  are  numerous  organs 
which  take  materials  from  the  blood  and  get  rid  of 
these,  usually  in  modified  form,  as  a  secretion  which 
exudes  through  a  duct  or  ducts  on  some  internal  or 
external  surface.  We  call  these  "  glands " ;  the 
liver,  the  pancreas,  the  sweat-glands,  the  milk-glands 
are  familiar  examples. 

But  there  are  other  organs,  somewhat  analogous  in 
structure,  which  though  they  take  materials  from 
the  blood,  and  form  a  secretion,  have  no  ducts.  If 
these  "  ductless  glands "  get  rid  of  their  secretion 
it  must  be  by  returning  it  to  the  blood.  Some  of 
them  have  directly  to  do  with  the  cells  of  the  blood ; 
thus  the  spleen  is  in  mammals  a  grave  for  worn-out 
red  blood  corpuscles,  while  in  some  lower  verte- 
brates it  seems  to  be  one  of  their  birthplaces.  But 
in  many  other  cases  the  ductless  glands  do  not  return 
any  cellular  material  to  the  blood,  i.e.,  they  do  not 
form  corpuscles,  and  what  fluid  material  they  return 
to  the  blood  can  only  be  discovered  indirectly.  A 
good  example  of  this  is  furnished  by  the  thyroid 
gland. 

The  thyroid  gland  is  a  small  reddish  organ,  richly 
supplied  by  blood-vessels,  weighing  from  one  to  two 
ounces  in  man,  situated  in  the  front  of  the  throat  on 
each  side  of  the  windpipe.  What  its  precise  function 
is  we  do  not  yet  know,  but  very  suggestive  hints  have 
been  gradually  accumulating  of  recent  years,  and 
we  are  certain  that  in  spite  of  its  minuteness  it  is 
extremely  important.  When  it  atrophies  or  is  ex- 
cised, the  disease  myxcedema  ensues,  in  which  the 
connective  tissue  becomes  overloaded  with  mucinous 


£92     PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

substance;  when  it  is  hypertrophied  the  resulting 
state  is  known  as  goitre.  Associated  with  the  enlarge- 
ment there  are  often  disturbances  of  the  nervous 
and  circulatory  system,  leading  to  what  is  known  as 
cretinism,  a  state  of  semi-idiocy.  "  It  is  found  that 
even  if  a  minute  part  of  the  thyroid  gland  be  left 
whilst  the  greater  part  is  removed,  the  symptoms 
(which  follow  complete  excision)  do  not  supervene. 
Indeed,  certain  contradictory  results  which  have  been 
got  by  some  observers  after  removal  of  the  thyroid 
are  explained  by  the  fact  that  in  some  individuals 
there  are  minute  detached  particles  of  thyroid  gland 
lying  apart  from  the  main  organ;  and  that  after  the 
latter  has  been  removed  these  detached  particles  may 
sufficiently  carry  on  the  function  of  the  organ  in 
relation  to  the  blood  and  the  nervous  system  to  pre- 
vent the  supervention  of  the  deleterious  symptoms 
which  usually  occur  after  its  removal.  Here  is,  then, 
a  notable  instance  of  the  enormous  influence  exerted 
by  a  '  next  to  nothing '  upon  the  general  organism." 

The  story  does  not,  however,  end  here,  though  there 
is  the  usual  need  for  caution  in  speaking  of  what 
is  still,  so  to  speak,  in  the  melting  pot.  It  has  been 
shown  in  many  cases  that  patients  whose  thyroid  has 
been  excised,  atrophied,  or  functionally  disordered, 
can  be  greatly  benefited,  or  temporarily  cured,  by 
utilising  the  thyroid  glands  of  sheep,  etc.,  either 
along  with  the  food,  or  by  sub-cutaneous  injection  of 
the  extract.  This  goes  to  show  that  the  thyroid  in  its 
normal  state  forms  a  potent  internal  secretion,  even 
small  quantities  of  which  are  sufficient  to  keep  the 
blood  and  the  nervous  system  up  to  a  certain  standard 
of  efficiency. 

*  Prof.  E.  A.  Schafer.  Address  Section  I,  Report  Brit. 
Ass.  for  1894,  p.  801. 


THE  DEEPENING  OF  PHYSIOLOGY.  293 

(2)  Recognition  of  Greater  Complexity  of  Func- 
tion.— In  the  early  years  of  the  nineteenth  century 
physicians  were  wont  to  say  that  the  liver  was  an 
organ  whose  function  consisted  in  secreting  bile. 
In  other  words,  a  very  obvious  function  of  a  big  organ 
had  been  seized  upon,  and  the  demonstrable  certainty 
of  it  served  rather  to  hinder  than  to  promote  further 
research.  That  the  liver  does  secrete  bile  is  plain 
enough,  but  the  detection  of  this  function  did  not 
even  hint  at  the  real  importance  of  the  organ  in  ques- 
tion. 

The  transition  towards  a  recognition  of  the  more 
complex  and  manifold  functions  of  this — the  largest 
— gland  in  the  body  may  be  associated  with  the  work 
of  Claude  Bernard  (1813-1878)  who  demonstrated 
its  "glycogenic  function."  He  showed  (1857)  that 
after  a  meal  the  liver  acts  upon  the  food-laden  blood, 
and  forms  glycogen  or  animal  starch,  C12,  H20,  O10, 
H2O,  and  thereafter  allows  this  store  to  pass  away 
gradually,  probably  in  the  form  of  a  soluble  sugar,  in 
the  blood,  to  serve  as  a  food  for  the  tissues,  the 
muscles  in  particular.  The  carbohydrates  digested 
in  the  food-canal  enter  the  blood  as  sugars,  assuming 
the  form  of  dextrose,  and  while  the  amount  of  this  in 
the  general  blood  is  about  0.1  per  cent.,  it  reaches 
0.2—0.3  per  cent,  in  the  (hepatic-portal)  veins  leading 
from  the  gut  to  the  liver  after  a  meal  rich  in  starch. 
'After  abundant  carbohydrate  food  the  glycogen-store 
in  the  liver  may  become  enormous,  amounting  to 
even  12  per  cent,  in  the  fowl. 

But  the  glycogenic  function  which  Claude  Bernard 
disclosed  is  only  a  second  out  of  the  many  functions 
of  the  liver.  Interposed  as  it  is,  a  great  living 
sponge,  in  the  current  of  blood  that  bears  soluble 
material  from  the  food-canal  to  the  heart,  it  has  the 


294    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

especial  function  of  maintaining  the  approximately 
uniform  composition  of  the  blood,  arresting  super- 
fluities and  poisons,  and  converting  harmful  into 
harmless  compounds.  Any  good  text-book  *  will  fur- 
nish the  details. 

An  equally  good  illustration  of  the  increasing  rec- 
ognition of  complexity  and  multiplicity  of  function 
is  afforded  by  the  pancreas  (the  sweetbread  of  rum- 
inants). This  organ,  which  lies  in  the  (duodenal) 
fold  of  the  gut  succeeding  the  stomach  and  pours  its 
secretion  into  the  duodenum,  has  been  recognised — 
almost  since  digestion  was  understood  at  all — as  a 
very  important  digestive  organ.  Its  secretion  acts 
powerfully  on  all  the  three  main  kinds  of  food, — 
starch,  proteids,  and  fats, — converting  starch  into 
sugar,  proteids  into  peptones,  and  fats  into  fatty  acids 
and  glycerine.  But  in  spite  of  its  importance  its 
digestive  secretion  can  be  dispensed  with,  as  has 
been  proved  experimentally. 

:  On  the  other  hand,  as  Minkowski  and  von  Mering 
showed,  a  removal  of  the  pancreas  deranges  the  whole 
metabolism  of  the  body,  and  the  result  is  chronic  dia- 
betes or  permanent  glycosuria,  marked  by  the  abun- 
dance of  sugar  in  the  urine.  As  the  amount  of  sugar 
can  be  readily  measured,  Minkowski  was  able  (1889) 
to  show  with  some  precision  the  relation  between 
cause  and  effect,  between  tampering  with  the  pan- 
creas and  the  degree  of  glycosuria.  An  additional 
function  of  the  pancreas  wa&  thus  discovered,  or  at 
all  events  rendered  very  probable,  f 

These  two  examples  illustrate  that  line  of  progress 
which  has  revealed  an  unsuspected  complexity  and 

1    *  Bunge.      Physiological     and     Pathological     Chemistry, 
Trans.  1890.     Lecture  XVII.     Metabolism  in  the  Liver. 
f  See  Bunge.    Op.  cit.,    Lecture  XXI.,  Diabetes  Mellitus. 


THE  DEEPENING  OF  PHYSIOLOGY.  295 

multiplicity  of  function,  even  in  organs  so  familiar 
as  the  liver  and  the  pancreas. 

(3)  Fuller  Recognition  of  Correlation. — For  ages 
men  have  been  familiar  with  the  general  idea  of  the 
unity  of  the  organism.  There  are  many  members, 
but  there  is  one  body ;  if  one  member  suffer,  the  others 
suffer  with  it.  At  the  beginning  of  the  century 
(1805),  Xavier  Bichat  recognised  that  "  each  func- 
tion is  linked  to  all  the  rest,"  and  the  same  fact  was 
behind  the  "  balance  of  organs  "  of  which  Etienne 
Geoffrey  St.  Hilaire  often  spoke,  and  the  "  division 
of  labour  "  on  which  Henri  Milne-Edwards  insisted. 

As  long  as  we  keep  to  a  general  view,  the  facts 
seem  clear  enough.  That  certain  organs  should  be 
mutually  dependent  follows  from  their  nature; 
muscles  are  dependent  on  the  nerves  which  stimulate 
them  and  the  blood  vessels  which  bring  them  food; 
the  health  of  the  brain  or  of  any  other  part  is  affected 
by  that  of  the  liver  whose  fundamental  function  it 
is  to  be  a  food-filter  and  to  keep  the  composition  of 
the  blood  approximately  constant.  Facts  like  these 
are  necessary  consequences  of  the  way  in  which  the 
organism  is  made. 

We  get  nearer  a  realisation  of  what  correlation 
means,  perhaps,  when  we  notice  the  facts  of  func- 
tional compensation.  If  one  lung  or  one  kidney  go 
out  of  gear  the  other  may  do  double  duty ;  if  a  thyroid 
gland  be  extirpated  an  accessory  thyroid  body  may 
begin  to  take  its  place,  and  grow  large  in  so  doing; 
if  a  lobe  of  a  kidney  or  liver  has  to  be  removed  there 
may  be  a  compensatory  increase  of  function  in  the 
remainder. 

•  But  let  us  briefly  refer  to  some  less  familiar  facts 
which  bring  out  more  clearly  the  intimate  correlation 
which  makes  the  whole  body  one. 


296    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

As  has  been  noticed  in  the  preceding  section,  the 
discovery  of  internal  secretions,  like  those  of  the 
thyroid  and  the  pancreas,  shows  that  various  organs 
of  the  body  act  on  the  blood  passing  through  them  in 
some  specific  way  which  is  essential  to  the  health  of 
the  whole.  Even  at  the  beginning  of  the  century 
(1801)  Legallois  had  a  prevision  of  this;  in  1857  it 
was  brought  into  prominence  by  Claude  Bernard's 
discovery  of  the  glycogenic  function  of  the  liver;  in 
1889  it  was  re-emphasised  when  von  Mering  and 
Minkowski  showed  that  the  pancreas,  besides  being 
a  digestive  gland,  acted  as  a  regulator  of  the  quan- 
tity of  sugar  produced  or  destroyed  in  the  organism. 

When  the  reproductive  organs  come  to  maturity, 
changes  ensue  in  many  parts  of  the  body  which  bear 
witness  to  an  intimate  correlation,  though  we  are 
unable  to  follow  the  physiological  links.  The  larnyx, 
the  hair,  the  milk-glands,  and  many  other  structures 
feel  the  influence.  Conversely,  the  removal  of  the 
reproductive  organs  is  followed  by  changes  wide- 
spread throughout  the  body — penetrating  even  into 
the  bones.  Observations  on  the  correlation  between 
the  reproductive  organs  and  the  antlers  of  stags 
(Rorig)  are  now  so  well-established,  that  one  who 
has  given  attention  to  the  matter  could  predict  from 
a  peculiarity  of  the  antlers  the  state  of  the  male 
organs,  or  could  argue  from  the  appearance  of  ant- 
lers in  a  female  as  to  the  abnormality  of  the  ovaries. 

To  sum  up,  there  appears  to  be  a  noteworthy  step 
of  progress  in  the  discovery  of  intimate  correlations 
previously  unsuspected.,  and  in  the  (incipient}  inves- 
tigation of  the  manner  in  which  these  are  brought 
about.  It  implies  a  deeper  realisation  of  the  unity 
of  the  organism. 

(4)  Progress    of    Comparative    Physiology. — As 


THE  DEEPENING  OF  PHYSIOLOGY.  297 

far  back  as  the  second  century  we  find  Galen  dis- 
secting and  experimenting  on  pigs  and  monkeys,  and 
arguing  thence  to  man,  then  a  forbidden  subject  to 
biological  analysis.  But  apart  from  such  premoni- 
tions there  was  practically  no  comparative  physiol- 
ogy until  Johannes  Miiller  showed  that  organisms  of 
high  and  low  degree  threw  light  on  one  another. 
Prompted  by  this  great  master  there  have  been  many 
students  of  comparative  physiology,  though  few  have 
given  themselves  wholly  to  it.  Thus  comparative 
physiology  lags  far  behind  comparative  anatomy ;  and 
no  one  has  done  for  the  former  what  Gegenbaur,  for 
instance,  has  done  for  the  latter.  This  is  partly  due 
to  the  intrinsic  difficulties  of  dealing  with  the  phys- 
iology of  the  lower  animals  (not  to  speak  of  plants) 
where  division  of  labour  is  less  marked.  And  an- 
other reason,  as  we  have  pointed  out  elsewhere,*  is 
that  the  zoologist  rarely  knows  enough  chemistry, 
or  the  chemist  enough  zoology,  to  enable  either  to 
contribute  much  to  comparative  physiology. 

"  One  zealous  worker  in  the  latter  part  of  the  Vic- 
torian era  deserves  to  be  commemorated,  C.  F.  W. 
Krukenberg.  He  realised  the  dignity  of  the  problem 
to  which  he  set  himself,  and  the  results  recorded  in 
his  Studien  and  Vortrdge  remain  a  monument  to  the 
industry  of  an  unfortunately  short  life."  f  But  the 
example  he  set  is  being  enthusiastically  followed  by 
men  like  Cuenot,  Verworn,  and  Loeb,  and  the  contri- 
butions of  older  workers  like  Kowalewsky  and  Met- 
chnikoff  help  to  sustain  the  Miillerian  tradition. 

As  an  illustration  of  the  value  of  comparative 
work  we  may  refer  to  another  of  the  enigmatical 
organs  of  the  human  body — the  thymus  gland.  In 

*  Science  of  Life,  1899,  p.  57. 
t  Thomson,  loc.  cit.,  p.  57. 


298    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

embryonic  life  it  arises  in  the  neck  and  grows  down 
into  the  chest;  it  continues  to  grow  after  birth,  but 
in  adult  life  it  gradually  shrivels  till  its  size  is  in- 
considerable. It  is  one  of  the  ductless  glands,  and 
is  vaguely  supposed  to  have  some  specific  influence 
on  the  blood. 

Since  Kolliker  discovered  its  endodermic  origin 
in  mammals  from  the  epithelium  of  a  gill-pouch,  and 
stated  that  the  original  epithelial  cells  give  rise  to 
lymph  cells  or  leucocytes,  two  views  have  been  held 
regarding  this  puzzling  organ.  "  On  the  one  hand, 
Stieda  and  His  have  maintained  that  the  leucocytes 
which  always  form  integral  parts  of  the  thymus  soon 
after  its  first  origin  have  migrated  thither  from  the 
exterior,  possibly  from  the  mesoblast.  In  this  con- 
clusion they  have  been  supported  by  the  researches 
of  Dohrn,  Gulland,  and  Maurer,  and  by  almost  every 
text-book  of  embryology  and  comparative  anatomy 
published  since  1879.  On  the  other  hand,  Kolliker 
has  stoutly  maintained  his  original  position,  and  the 
results  of  his  investigations  have  been  emphatically 
confirmed  by  Prenant,  Oscar  Schultze,  and  Beard."  * 

In  short,  it  has  been  known  for  a  long  time  that 
the  thymus  arises  in  the  neck  region  of  vertebrates  in 
connection  with  a  pair  or  more  of  gill-clefts,  and  that, 
at  an  early  date  in  life,  it  is  rich  in  leucocytes  or 
white  blood  corpuscles,  which  some  believed  to  have 
been  born  there,  while  others  regarded  them  as 
migrants  from  elsewhere.  It  was  also  known  that 
in  many  mammals,  it  degenerates  after  youth  is  over, 
being  for  instance  large  in  the  calf,  but  small  in  the 
cow.  Generally  speaking  we  may  also  say  that  the 
thymus  was  known  to  be  more  abundantly  represented 
in  lower  than  in  higher  vertebrates. 

*  J.  Beard,  Lancet,  January  21,  1899. 


THE  DEEPENING  OF  PHYSIOLOGY.  299 

The  last  impression  has  been  made  more  exact  by 
the  zoological  embryologists  who  have  shown  that 
there  are  28  thymus  rudiments  in  the  lamprey,  14  in 
the  shark,  10  in  the  skate,  6  in  the  lizard,  2  in  birds 
and  mammals.  This  diminished  representation  in 
the  higher  vertebrates  suggested  the  idea  that  the 
thymus  might  be  an  organ  specially  adapted  for  the 
phagocytic  protection  of  the  gills  from  the  invad- 
ing bacteria,  or  from  the  effects  of  other  parasites 
or  of  injuries.  If  this  be  so,  we  can  understand 
why  the  thymus  should  be  less  represented  in  the 
higher  vertebrates — Reptiles,  Birds,  and  Mammals 
— in  which  there  is  no  trace  of  gills,  in  which,  more- 
over, other  structures,  such  as  the  palatal  and  pharyn- 
geal  tonsils  have,  according  to  some  authorities 
(Stohr,  Killian,  Gulland)  become  garrisons  of  pro- 
tective phagocytes,  most  strategically  disposed. 

At  the  beginning  of  1899,  however,  Dr.  John 
Beard  published  a  short  paper,  announcing  his  dis- 
covery that  leucocytes  appear  in  the  thymus  rudi- 
ments of  the  skate  (Raia  batis)  at  a  time  when  the 
spleen  has  no  existence,  when  there  are,  apart  from 
the  thymus,  no  lymphoid  structures  of  any  sort. 
Cradled  in  the  thymus,  the  leucocytes  soon  begin  to 
emerge  and  migrate  elsewhere. 

The  conclusion  that  ilie  thymus  is  the  original 
cradle  of  the  white  blood  corpuscles  of  the  body  re- 
quires to  be  confirmed  and  extended,  but  it  is  at  least 
a  good  illustration  of  the  way  in  which  comparative 
study  may  throw  welcome  light  on  the  physiological 
puzzles  of  the  human  body. 

Experimental. — More  generally  it  should  be  noted 
as  characteristic  of  the  second  half  of  the  nineteenth 
century  that  physiological  investigation  became  more 
and  more  experimental  in  its  method.  We  allude 


300    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

especially  to  the  precise  application  of  chemical  and 
physical  methods  to  physiological  problems.  On  the 
chemical  line,  the  researches  of  Wohler,  Liebig, 
Claude  Bernard,  Pettenkofer  and  Voit,  Ludwig, 
Pfliiger,  Kiihne,  Hoppe-Seyler,  Bunge,  Halliburton, 
Kossel,  Heidenhain,  and  many  more  have  been  mo- 
mentous; on  the  physical  line  we  have  especially  to 
remember  the  achievements  of  Weber,  Volkmann, 
Helmholtz,  du  Bois-Reymond,  Marey,  Fechner,  Lud- 
wig, Briicke,  Pfliiger,  Foster,  and  Burdon-Sander- 
son.  But  both  lines  of  work  have  been  prosecuted 
by  so  many  that  it  is  almost  invidious  to  mention 
names  at  all. 

PHYSIOLOGY  OF  TISSUES. 

The  Beginnings  of  Tissue. — The  simplest  living 
creatures  are  single  corpuscles  of  living  matter, 
structurally  comparable  to  the  individual  unit-areas 
or  cells  which  build  up  the  body  of  a  higher  plant  or 
animal,  but  functionally  different  since  each  one  is 
necessarily  "  physiologically  complete  in  itself," 
while  the  cell  of  a  more  complex  creature  shows  more 
or  less  restriction  of  function  as  the  result  of  the 
division  of  labour  in  the  body. 

Even  when  we  pass  a  step  upwards  to  the  simplest 
multicellular  organisms,  such  as  the  beautiful  spher- 
ical colony  or  community  of  cells  called  Volvox,  we 
do  not  yet  find  tissues.  The  members  of  the  com- 
munity, though  numerous,  are  almost  quite  like  one 
another;  there  is  little  or  no  division  of  labour. 

A  step  higher,  however,  in  the  more  complex  Algse 
and  Fungi  among  plants,  and  in  sponges  among  ani- 
mals, we  find  tissues,  as  it  were,  a -making.  In  a 
sponge,  for  instance,  we  may  see  a  number  of  elon- 


THE  DEEPENING  OF  PHYSIOLOGY.  301 

gated,  spindle-shaped,  contractile  cells  arranged  in  a 
ring  around  one  of  the  openings, — clearly  represent- 
ing the  beginning  of  a  sphincter  muscle.  Tissues  are 
aggregates  of  more  or  less  similar  cells  with  at  least 
one  predominant  function  in  common. 

Bichat. — It  was  in  1801,  at  the  threshold  of  our 
period,  that  Xavier  Bichat  published  his  Anatomic 
Generate  which  included  an  analysis  of  the  body  into 
its  component  tissues — muscular,  nervous,  glandu- 
lar, connective,  and  so  on, — and  furthermore  a  de- 
velopment of  the  idea  that  the  functions  of  organs 
might  be  expressed  in  simpler  terms,  namely,  in 
terms  of  the  properties  of  the  tissues.  We  may  take 
this  great  work  as  the  foundation-stone  of  the  physiol- 
ogy of  tissues,  the  study  of  which  has  occupied  no 
small  part  of  the  energy  of  physiologists  throughout 
the  century.  The  literature  of  research  on  muscular 
or  contractile  tissue  alone  would  fill  a  library. 
Since  it  is  necessary  to  restrict  ourselves  to  one  illus- 
tration, we  have  chosen  that  which  is  perhaps  most 
generally  interesting, — the  physiology  of  nervous 
tissue. 

Nervous  Tissue. — Aristotle  does  not  seem  to  have 
had  any  idea  of  the  physical  basis  of  his  own  genius ; 
he  did  not  know  the  function  of  the  brain,  nor  was 
he  clear  as  to  difference  between  nerves  and  sinews. 
The  contrast  between  this  primitive  ignorance — on 
the  part  of  one  of  the  greatest  minds  the  world  has 
known — and  the  knowledge  of  the  nervous  system 
possessed  by  physiologists  to-day  is  remarkable,  but 
even  more  remarkable  is  the  relative  recentness  of 
that  knowledge.  Guesses  and  hints  there  may  have 
been,  but  the  elementary  distinction  between  sensory 
and  motor  nerves  was  unknown  a  hundred  years  ago. 

At  the  beginning  of  the  nineteenth  century  it  was 


302    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

well  known  that  nerves  stimulated  and  controlled 
muscular  activity,  that  the  nervous  system  was  the 
seat  of  feeling  and  thought,  that  different  parts  of 
the  brain  had  different  functions,  and  so  on,  but  the 
mechanism  of  nerve  ganglia  and  nerve  fibres  was 
almost  unknown,  though  some  physiologists  were 
pondering  over  it.  Indeed  the  history  of  the  subject 
may  be  said  to  begin  with  1811,  when  an  English 
surgeon,  Charles  Bell,  privately  published  a  pam- 
phlet setting  forth  a  "  ISTew  Idea,"  that  "  the  nerves 
are  not  single  nerves  possessing  various  powers,  but 
bundles  of  different  nerves,  whose  filaments  are  united 
for  the  convenience  of  distribution,  but  which  are 
distinct  in  office  as  they  are  in  origin  from  the  brain." 
As  Sir  Michael  Foster  has  said,  "  our  present  knowl- 
edge of  the  nervous  system  is  to  a  large  extent  only 
an  exemplification  and  expansion  of  Charles  Bell's 
*  New  Idea,'  and  has  its  origin  in  that."  * 

"  During  the  latter  part  of  the  present  century,  and 
especially  during  its  last  quarter,  the  analysis  of  the 
mysterious  processes  in  the  nervous  system,  which  issue 
as  feeling,  thought,  and  power  to  move,  has  been  pushed 
forward  with  a  success  conspicuous  in  its  practical,  and 
full  of  promise  in  its  theoretical,  gains.  That  analysis 
may  be  briefly  described  as  a  following  up  of  threads. 
We  now  know  that  what  takes  place  along  a  tiny  thread 
which  we  call  a  nerve-fibre  differs  from  that  which 
takes  place  along  its  fellow-threads,  that  differing 
nervous  impulses  travel  along  different  nerve-fibres,  and 
that  nervous  and  physical  events  are  the  outcome  of 
the  clashing  of  nervous  impulses  as  they  sweep  along 
the  closely-woven  web  of  living  threads  of  which  the 
brain  is  made.  We  have  learnt  by  experiment  and  by 
observation  that  the  pattern  of  the  web  determines  the 
play  of  the  impulses,  and  we  can  already  explain  many 
*  Pres.  Address.  Rep.  Brit.  Ass.  for  1899,  p.  11. 


THE  DEEPENING  OF  PHYSIOLOGY.  303 

of  the  obscure  problems  not  only  of  nervous  disease, 
but  of  nervous  life,  by  an  analysis  which  is  a  tracking 
out  the  devious  and  linked  paths  of  nervous  threads. 
The  very  beginning  of  this  analysis  was  unknown  in 
1799." 

We  have  noticed  that  in  1811,  Charles  Bell  (1774- 
1842)  announced  his  "  new  idea  "  that  the  posterior 
or  dorsal  roots  of  the  spinal  nerves  are  sensory  in 
function  (conducting  impulses  centripetally ) ,  while 
the  anterior  or  ventral  roots  are  motor  in  function 
(conducting  impulses  centrifugally), — a  conclusion 
afterwards  proved  experimentally  by  Johannes 
Miiller. 

The  next  great  step  was  due  to  Johannes  Miiller 
(1801-1858),  and  was  expressed  in  his  doctrine  of 
the  specific  energies  of  the  nerves  and  sense-organs 
(1826).  Different  kinds  of  stimuli  applied  to  the 
same  sense-organ  always  evoke  the  same  kind  of 
sensation ;  or,  conversely,  one  and  the  same  stimulus 
or  the  same  external  phenomenon,  evokes  different 
sensations  by  acting  on  different  organs.  As  Bunge 
says :  *  "  The  phenomena  of  the  outer  world, 
therefore,  have  nothing  in  common  with  the  sensa- 
tions and  ideas  they  call  forth  in  us,  and  the  states 
and  processes  of  our  own  consciousness  are  alone  im- 
mediately subject  to  our  observation  and  recogni- 
tion." 

Miiller  was  right  in  his  conclusion  that,  however 
a  particular  nerve  is  stimulated,  the  message  is 
always  of  the  same  kind  as  that  which  is  normally 
delivered  by  the  nerve;  an  unusual  stimulus  to  the 
optic  nerve  will  result  in  visual  sensation.  But  he 
was  wrong  in  ascribing  the  specific  effects  to  the 

*  Physiological  and  Pathological  Cliemistry.  Trans.  1890, 
p.  12. 


304    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

nerves  instead  of  to  the  nerve-centres  with  which  they 
are  associated. 

It  was  recognised  by  Vulpian  (1866)  that  "all 
nerves — sensory,  motor,  vaso-motor,  and  others — 
have  the  same  properties,  and  are  only  distinct  in 
their  effects.  This  question  is  of  the  highest  impor- 
tance for  general  physiology.  It  dominates  the  whole 
physiology  of  nerve-fibres."  *  "  Many  observations 
made  since  Vulpian  wrote  have  shown  that  a  nerve 
has  no  functions  more  specific  than  those  of  a  tele- 
graph wire.  It  conducts  impulses  and  is  incapable 
of  tampering  with  the  messages  which  it  trans- 
mits." f 

Since  the  days  of  Miiller  the  progress  of  this  de- 
partment of  physiology  has  depended  on  work  along 
several  distinct  lines.  There  is,  on  the  one  hand, 
the  more  experimental  method  which  aims  mainly  at 
localising  certain  functions  in  certain  parts  of  the 
system;  from  Willis  and  Flourens  (1794-1864) 
among  the  early  workers,  to  Ferrier,  Eritsch,  Hitzig, 
Munk,  Goltz,  and  Horsley,  there  has  been  a  remark- 
able record  of  achievement.  This  has  depended 
partly  on  experimentation  with  living  creatures,  and 
partly  on  the  observation  of  pathological  conditions, 
i.e.,  on  the  correlation  of  abnormal  functions  studied 
during  life  with  the  abnormal  structure  revealed  on 
post-mortem  examination. 

There  is,  on  the  other  hand,  the  histological  path — 
"  the  attempt  by  microscopic  analysis  to  find  a  way 
through  the  extraordinary  maze  of  cells  and  fibres 
which  form  the  brain  and  spinal  cord.  Albert  von 

*  Quoted  by  Dr.  Alex.  Hill.  Introduction  to  Science,  1900, 
p.  118. 

id.,  p.  118. 


THE  DEEPENING  OF  PHYSIOLOGY.  305 

Kolliker  was  one  of  the  most  illustrious  pioneers,  and 
even  as  veteran  he  has  not  ceased  to  lead.  No  small 
part  of  the  progress,  however,  has  been  due  to  the 
discovery  of  new  methods,  which  we  especially  associ- 
ate with  the  names  of  the  Italians,  Golgi  and  Marchi, 
and  the  Spaniard,  Ramon  y  Cajal."  *  This  method 
of  investigation  has  been  aided  by  embryologieal 
studies  in  which  the  development  of  the  various  parts 
and  elements  has  been  worked  out,  and  by  compar- 
ative anatomical  studies  which  show  the  increasing 
complexity  of  nervous  structure  as  we  ascend  the 
series. 

From  very  early  stages  it  is  evident  that  the  central 
nervous  system  consists  of  two  classes  of  elements — 
(1)  very  numerous  cells  (spongioblasts)  which  serve 
for  the  support  (neuroglia)  of  the  essential  nervous 
tissue,  and  (2)  less  numerous  mother-cells  of  nerve- 
cells  or  neuroblasts. 

Each  neuroblast  gives  origin  (in  higher  animals) 
to  an  "  axis-cylinder  process  "  or  nerve-fibre,  and  a 
number  of  dendritic  "  protoplasmic  processes."  The 
nerve-fibre  passes  from  the  cell  in  the  central  system 
to  its  distribution,  which  may  be  in  the  nerve-cord 
itself,  or  on  muscle,  or  in  peripheral  sense-organs. 

Within  what  is  called  "  the  grey  matter  "  of  the 
brain  and  spinal  cord,  these  nerve-cells  lie  in  a  net- 
work or  feltwork  of  extraordinary  complexity  formed 
by  the  branching  of  the  processes  of  the  cells  and 
fibres.  Whether  the  fine  twigs  of  the  branches  of 
adjacent  cells  end  freely,  or  are  in  contact  or  conti- 
nuity with  one  another,  or  are  in  some  cases  inde- 
pendent and  in  other  cases  inter-united,  remains  a 
subject  of  discussion.  But  the  majority  of  histolo- 
gists  have  accepted  the  "  Neuron-Theory "  which 
*  Thomson,  Science  of  Life,  1899,  p.  62. 


306    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

Waldeyer  stated  in  1891: — "A  nerve  fibre  is  an  es- 
sential part  of  the  cell  with  which  it  is  continuous 
and  the  cell,  its  processes,  the  nerve  fibre  and  the 
collaterals  which  arise  from  the  nerve  fibre  collect- 
ively form  a  neuron  or  structural  nerve-unit."  * 

The  kernel  of  the  neuron-theory  is  in  the  con- 
clusion that  nerve-cell  and  nerve-fibre  represent  a 
single  cell,  that  the  axis-cylinder  of  the  nerve-fibre, 
with  its  collateral  branches  and  terminal  ramifica- 
tions, is,  like  a  dendritic  process,  an  outgrowth  from 
the  nerve-cell.  Verworn  speaks  of  the  triple  founda- 
tion of  this  doctrine, — (1)  anatomical,  (2)  em- 
bryological,  and  (3)  experimental. 

(1)  Eemak  in  1838  and  Helmholtz  in  1842  had 
shown  the  continuity  of  nerve-cell  and  nerve-fibre; 
Deiters  distinguished  the  axis-cylinder  process  from 
the  protoplasmic  processes ;  the  methods  of  Golgi  and 
Ramon  y  Cajal,  of  Ehrlich  and  Nissl,  helped  the  his- 
tologist  to  find  his  way  in  the  maze ;  the  work  of  K61- 
liker,  Waldeyer,  Retzius,  Lenhossek,  Van  Gehuchten, 
Biedermann  and  many  more  gradually  led  the  ma- 
jority to  the  idea  of  the  unity  of  the  neuron. 

(2)  To  Prof.  Wilhelm  His  in  particular  we  owe 
our  knowledge  of  the  development  of  a  mother-nerve- 
cell  into  a  neuroblast  and  of  this  into  a  nerve-cell, 
with  a  nerve-fibre,  and  dendrites.    There  is  an  unfor- 
getable  figure  by  Ramon  y  Cajal,  which  shows  on  the 
upper  line  the  increasing  complexity  of  a  certain  kind 
of  nerve-cells  in  the  series — frog,  lizard,  rat,  man; 
while  the  lower  line  shows  five  stages  in  the  individ- 
ual development  of  a  neuroblast;  the  result  showing 
the  general  parallelism  between  individual  growth 
and  racial  progress. 

*  Sir  William  Turner,  Pres.  Address,  Rep.  Brit.  Ass.  for 
1900. 


THE  DEEPENING  OF  PHYSIOLOGY.  307 

(3)  A  third  foundation  for  the  neuron-theory 
has  been  afforded,  as  Verworn  points  out,  by  experi- 
mental work.  As  early  as  1852  Waller  showed  that 
a  nerve-fibre  degenerates  when  its  connection  with  the 
associated  nerve-cell  is  severed;  Von  Gudden,  Von 
Monakow,  Ranvier,  Forel,  and  many  others  have  con- 
tinued the  enquiry,  and  have  demonstrated  that  the 
cell  as  well  as  the  fibre  suffers  when  their  connection 
is  broken.  This  points  again  to  the  unity  of  the 
neuron. 

The  last  decennium  of  the  nineteenth  century  has 
been  rich  in  investigations  prompted  by  the  neuron 
theory.  (a)  The  internal  complexity  of  the  nerve- 
cell  and  its  processes  has  been  disclosed  by  many 
different  methods ;  it  is  enough  to  say  that  the  nerve- 
cell  is  a  microcosm  in  itself.  (&)  The  difficult 
question  of  the  inter-relations  of  adjacent  neurons  has 
been  much  discussed,  and  although  it  is  certain  that 
the  neurons  of  adult  animals  have  intimate  functional 
inter-relations,  it  is  difficult  to  make  any  general  state- 
ment in  regard  to  the  exact  nature  of  the  contact  or 
continuity,  (c)  It  is  necessary  to  have  some  hypoth- 
esis in  order  to  interpret  the  making  and  breaking 
of  the  conducting  paths  through  the  jungle-like  com- 
plexity of  the  grey  matter  and  many  suggestions  have 
been  made,  discarded,  rehabilitated,  and  again  re- 
jected. In  no  other  way,  until  an  epoch-making  dis- 
covery is  made,  can  there  be  progress.  Thus,  Prof. 
Mathias  Duval  in  his  "  histological  theory  of  sleep  " 
suggested  that  the  dendrites  of  the  cerebral  cortex 
contract,  like  the  pseudopodia  of  an  Amoeba,  when 
the  cell  is  fatigued,  that  sleep  (with  its  dislocated 
consciousness)  ensues,  and  that  during  the  period  of 
rest  the  dendritic  processes  stretch  out  again  into 
contact  with  their  neighbours.  The  idea  that  the  cells 


308    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

of  the  cortex  are  "  like  a  group  of  Amoebae  having  n 
talk  together,"  as  it  has  been  romantically  expressed, 
may  be  a  fascinating  one,  but  there  is  very  little 
scientific  evidence  in  its  favour. 

(d)  Not  less  difficult  to  answer  is  the  question 
"  What  part  do  the  nerve-cells  play  in  relation  to  the 
conducting  or  impulse-transmitting  function  of  the 
nerve-fibres  ?  "     One  extreme  is  expressed  in  the  an- 
swer— for  which  the  explorer  Nansen  was  first  re- 
sponsible— that  the  substance  of  the  nerve-cell  or 
ganglion-cell  has  merely  a  nutritional  value,  but  thia 
is  almost  contradicted  by  the  facts  known  in  regard 
to  nerve-fatigue.     The  other  extreme  is  expressed  in 
the  answer,  for  which  there  is  much  more  to  be  said, 
that  the  specific-nervous  functions  have  their  seat  in 
the  substance  of  the  ganglion-cell.      Between  these 
may  be  placed  the  view  that  the  nervous  processes 
have  their  physical  basis  in  a  functionally  homoge- 
neous   fibrillar    substance    continuous    through    the 
whole  of  the  neuron.      This   again   is  one   of  the 
problems    handed    on    unsolved    to    the    twentieth 
century. 

(e)  But  we  must  not  pass  over  the  line  of  in- 
vestigation which  first  became  prominent  in  a  re- 
search by  Prof.  Hodge — "  A  microscopical  study  of 
changes  due  to  functional  activity  in  nerve  cells  "  * 
and  has  since  been  pursued  by  many, — Mann,  Lu- 
garo,  Nissl,  Goldschneider  and  Flatau,  Marinesco, 
Fick,  Guerrini,  and  others.      Not  many  years  ago 
the  possibility  of  demonstrating  the  structural  effects 
of  nerve-fatigue  would  have  seemed  an  impossibility ; 
it  may  now  be  called  an  achievement.     Whether  we 
follow  Hodge  in  showing  the  difference  between  the 

*  Journal  of  Morphology,  VII.,  1892. 


THE  DEEPENING  OF  PHYSIOLOGY.  309 

fresh  bee's  brain  in  the  morning  and  the  fatigued 
bee's  brain  in  the  evening,  or  the  results  of  others 
who  have  investigated  the  fatigue-conditions  in  vari- 
ous nerve-centres,  we  find  an  impressive  set  of  facts, 
showing  how  fatigued  nerve-cells  pass  into  a  state  of 
collapse  from  which  recovery  may  be  rapid,  long- 
delayed,  or  impossible.  That  the  enquiry  has  its 
bearings  on  mis-education,  over-pressure,  strain,  and 
worry,  and  the  like  is  obvious  enough.  But  as  to 
the  particular  components  of  the  neuron  on  which 
the  fatigue-state  most  essentially  depends  we  are 
still  in  doubt. 

We  have  been  particularly  indebted  in  this  sec- 
tion to  a  lecture  by  Prof.  Max  Verworn  *  who  sup- 
ports the  neuron-theory  enthusiastically,  and  we 
should  also  refer  to  another  by  Hoche,t  who  main- 
tains that  the  functional  unity  of  the  neuron  must 
be  recognised,  though  its  histological  unity  is  in  adult 
animals  undemonstrable. 

"  The  kernel  of  the  neuron-theory  is  that  the  body 
of  the  ganglion-cell  with  its  nerve-fibre  and  its  den- 
drites  is  a  cellular  unity.  .  .  .  The  anatomical  and 
physiological  investigations  of  the  last  decennium  have 
not  been  able  to  shake  this.  .  .  .  Whether  the  individ- 
ual neurons  are  merely  connected  by  contact,  or  in 
many  cases  are  continuous  by  the  anastomoses  of  fibrils 
or  protoplasmic  concrescence,  is  a  minor  question,  affect- 
ing the  neuron-theory  not  more  than  the  fact  of  inter- 
cellular bridges  affects  the  cell-theory.  .  .  .  The  con- 
ception of  the  neuron  stands,  unless  it  can  be  shown 
that  what  is  regarded  as  a  cellular  unity  is  really  com- 
posed of  several  cells.  .  .  .  The  neuron  is  varied  in  its 

*  Max  Verveoin,  Das  Neuron  in  Anatomic  und  Physioloqie: 
Jena,  1900,  p.  54. 

f  A.  Hoche,  Die  Neuronen-lehre  und  ihre  Gegner  :  Berlin, 
1899. 


310    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

form  and  function,  but  it  remains  an  uncontroverter! 
fact."* 

Tens  of  thousands  of  neurons  go  to  form  the  brain 
and  spinal  cord  of  higher  animals,  and  it  is  certain 
that  they  are  not  homogeneous  in  structure  or  uni- 
form in  function  throughout.  To  some  degree,  at 
least,  there  is  a  localisation  of  psychical  functions. 

"  The  foundation  of  a  scientific  basis  for  localisa- 
tion dates  from  1870,  when  Fritsch  and  Hitzig  an- 
nounced that  definite  movements  followed  the  appli- 
cation of  electrical  stimulation  to  definite  areas  of 
the  cortex  in  dogs.  The  indication  thus  given  was 
at  once  seized  upon  by  David  Ferrier,  who  explored 
not  only  the  hemispheres  of  dogs,  but  those  of 
monkeys  and  other  vertebrates."  f  Motor  and  sen- 
sory areas  were  distinguished,  and  the  researches  of 
Munk,  Beevor,  Horsley,  Goltz,  Schafer,  Flechsig, 
and  many  others  have  contributed  to  the  preliminary 
mapping  out  of  the  brain. 

Apart  from  centres  of  special  sense  and  motor 
centres,  Prof.  Flechsig  has  distinguished  (1896) 
"  association-centres,"  which  he  speculatively  regards 
as  engaged  in  the  higher  intellectual  operations. 
While  this  interpretation  remains  quite  uncertain, 
we  owe  much  to  the  observations  by  which  Flechsig 
has  shown  that  different  centres  in  the  human  brain 
attain  their  perfect  structural  development  at  dif- 
ferent periods.  "  When  a  child  is  born,  very  few  of 
the  fibres  of  the  cerebrum  are  myelinated  (let  us  say, 
structurally  completed),  and  we  have  thus  an  anatom- 
ical explanation  of  the  reason  why  an  infant  has 
so  inactive  a  brain  and  is  so  helpless  a  creature.  It 

*  Freelv  translated  from  Verworn,  op.  cit. 
t  Sir  William  Turner,  Address  Section  H,  Rep.  Brit.  Ass., 
1897,  p.  785. 


THE  DEEPENING  OF  PHYSIOLOGY.  3H 

will  be  of  special  interest  to  determine  whether  in 
those  animals  which  are  active  as  soon  as  they  are 
born,  and  which  can  at  once  assume  the  characteristic 
attitude  of  the  species,  the  fibres  of  the  cerebrum 
are  completely  developed  at  the  time  of  birth."  * 

THE  LIFE  OF  CELLS. 

The  Cell-Doctrine. — A  recognition  of  the  impor- 
tance of  cells  as  structural  and  functional  units  was 
one  of  the  distinctive  biological  steps  of  the  nine- 
teenth century. 

"  Without  hesitation  I  should  say  that  one  of  the 
greatest  achievements  of  biology  in  the  nineteenth  cen- 
tury was  the  recognition  that  plants  and  animals  are 
composed  of  cells,  or,  more  generally  expressed,  of 
numberless  very  minute,  elementary  organisms.  By 
the  co-operation  of  famous  biologists — I  mention  only 
Pnrkinje,  Schleiden  and  Schwann,  Hugo  von  Mohl, 
JSfiigeli,  Kemak,  Kolliker  and  Virchow,  Briicke,  Cohn 
and  Max  Schultze — our  knowledge  of  the  organisation 
of  living  substance  has  been  greatly  extended  and  deep- 
ened. In  the  theory  of  cells  and  protoplasm,  anatomy 
and  physiology  secured  a  firm  foundation  similar  to  the 
theory  of  atoms  and  molecules  in  chemistry."! 

Speaking  of  the  cell-theory,  Prof.  E.  B.  Wilson 
gives  a  similar  verdict,  "  No  other  biological  general- 
isation, save  only  the  theory  of  organic  evolution,  has 
brought  so  many  apparently  diverse  phenomena  un- 
der a  common  point  of  view,  or  has  accomplished 
more  for  the  unification  of  knowledge."  ^ 

The  cell-doctrine  includes  three  propositions: — 
(1)  Morphological,  that  all  living  creatures  have  a 

*Sir  William  Turner,  loc.  cit.,  p.  785. 

f  Prof.  O.  Hertwig,  Die  Entwicklung  der  Biologie  im  19 
Jahrhundert :  Jena,  1900,  p.  5. 

*  The  Cell  in  Development  and  in  Inheritance,  2nd  ed., 
1900. 


312    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

cellular  .structure,  i.e.,  are  either  single  corpuscles 
of  living  matter  (the  unicellular  Protozoa  and  Proto- 
phytes),  or  are  built  up  of  a  large  number  of  such 
corpuscles  and  modifications  of  these;  (2)  Embryo- 
logical,  that  every  organism,  reproduced  in  the  ordi- 
nary sexual  way,  starts  in  life  as  a  fertilised  ovum, 
which  divides  and  re-divides  into  a  coherent  em- 
bryonic mass  of  cells, — the  beginning  of  a  body; 
and  (3)  Physiological,  that  the  functions  of  a  multi- 
cellular  organism  are  to  some  extent  expressible  in 
terms  of  the  activities  of  its  component  cells.  * 

The  history  of  microscopic  analysis  will  be 
alluded  to  in  the  next  chapter,  but  it  may  be  noted 
here  that  the  cell-doctrine  is  a  fine  example  of  a 
generalisation  reached  gradually  by  work  done  along 
many  different  lines  and  by  many  investigators.  We 
may  particularly  associate  its  formulation  with  the 
work  of  Schleiden  (1838)  and  Schwann  (1839), 
Goodsir  (1845)  and  Virchow  (1858),  but  there  were 
many  others  who  contributed  to  the  result.  As  to 
the  different  paths  pursued,  we  should  notice  (a) 
the  analysis  of  the  body  into  tissues  (Bichat),  (&) 
the  discovery  and  study  of  unicellular  organisms 
(e.g.,  the  investigation  of  Bacteria  and  Infuso- 
rians  by  Leeuwenhoek,  of  the  Amreba  by  Roesel  von 
Eosenhof,  of  Foraminifera  by  Dujardin),  (c)  the 
recognition  of  the  unicellular  nature  of  ovum  and 
spermatozoon  and  of  the  cleavage  that  follows  fertil- 
isation, and  (d}  the  gradual  disclosure  of  the  cel- 
lular structure  of  organisms, — first  in  plants,  and 
then  in  animals. 

'Cellular  Physiology. — This  is  a  distinctively 
modern  study  and  is  still  embryonic.  Its  central 
idea  is  that  of  expressing  vital  processes  in  terms  of 

*  See  The  Science  of  Life,  p.  103. 


THE  DEEPENING  OF  PHYSIOLOGY.  313 

the  activities  of  the  cells.  "  Consideration  of  the 
individual  functions  of  the  body  urges  us  constantly 
toward  the  cell.  The  problem  of  the  motion  of  the 
heart  and  of  muscle-contraction  resides  in  the  muscle- 
cell  ;  that  of  secretion  in  the  gland-cell ;  that  of  food- 
reception  and  resorption  in  the  epithelium-cell  and 
the  white  blood-cell;  that  of  the  regulation  of  all 
bodily  activities  in  the  ganglion-cell.  If  physiol- 
ogy considers  its  task  to  be  the  investigation  of  vital 
phenomena,  it  must  investigate  them  in  the  place 
where  they  have  their  seat,  i.e.,  in  the  cell."  * 

The  central  idea  of  cellular  physiology  was  clear 
long  before  its  realisation  began  to  be  effected.  In 
1838,  Schleiden  said :  "  Each  cell  leads  a  double  life : 
an  independent  one,  pertaining  to  its  own  develop- 
ment alone;  and  another  incidental,  in  so  far  as  it 
has  become  an  integral  part  of  a  plant."  In  1839, 
Schwann  said :  "  The  whole  organism  subsists  only 
by  means  of  the  reciprocal  action  of  the  single  ele- 
mentary parts."  In  1858,  Virchow  said:  "Every 
animal  appears  as  a  sum  of  vital  units,  each  one  of 
which  bears  with  it  the  characteristics  of  life."  But, 
although  the  general  idea  was  thus  more  or  less  clear 
at  the  dates  cited,  the  special  study  of  the  physiology 
of  the  cell  is  much  more  modern. 

One  of  the  shrewdest  and  keenest  of  the  pioneers 
of  cellular  physiology  was  Prof.  John  Goodsir,  who 
in  1842  communicated  to  the  Royal  Society  of  Edin- 
burgh a  memoir  on  secreting  structures,  "  in  which 
he  established  the  principle  that  cells  are  the  ultimate 
secreting  agents;  he  recognised  in  the  cells  of  the 
liver,  kidney,  and  other  organs  the  characteristic 
secretion  of  each  gland.  The  secretion  was,  he  said, 
situated  between  the  nucleus  and  the  cell  wall.  At 

Max  Verworn,  General  Physiology,  trans.  1889,  p.  48. 


314    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

first  he  thought  that,  as  the  nucleus  was  the  repro- 
ductive organ  of  the  cell,  the  secretion  was  formed  in 
the  interior  by  the  agency  of  the  cell  wall ;  but  three 
years  later  he  regarded  it  as  a  product  of  the  nucleus. 
The  study  of  the  process  of  spermatogenesis  by  his 
brother,  Harry  Goodsir,  in  which  the  head  of  the 
spermatozoon  was  found  to  correspond  with  the  nu- 
cleus of  the  cell  in  which  the  spermatozoon  arose, 
gave  support  to  the  view  that  the  nucleus  played  an 
important  part  in  the  genesis  of  the  characteristic 
product  of  the  gland  cell."  *  This  is  in  general 
agreement  with  the  modern  conclusion  that  the  nu- 
cleus is  the  trophic  centre  of  the  cell. 

Following  Verworn,  one  of  the  most  enthusiastic 
advocates  and  students  of  cell-physiology,  we  may 
briefly  indicate  some  of  the  paths  of  investigation 
that  have  been  pursued  with  success. 

(a)  Unicellular  organisms  offer,  as  it  were,  a 
natural  analysis  of  the  higher  creatures.  Types  of 
cell  which  occur  in  complex  combinations  in  multi- 
cellular  organisms  may  be  studied  in  isolation  in 
the  unicellular  forms.  The  study  of  their  normal 
behaviour  has  led  to  many  interesting  results,  e.g., 
as  regards  amreboid  movement  and  ciliary  action. 

(6)  Much  has  been  done  in  the  way  of  studying 
the  reactions  of  unicellular  organisms  to  diverse  arti- 
ficial stimuli  of  heat,  light,  and  chemical  re-agents, 
as  may  be  seen  by  a  reference  to  the  first  two  volumes 
of  Prof.  Davenport's  Physiological  Morphology. 

(c)  Microscopic  vivisection-operations — to  which 
the  most  pronounced  humanitarian  can  offer  no  ob- 
jections, since  there  can  be  no  question  of  pain  nor 
even  of  the  destruction  of  life — have  disclosed  some 

*  Sir  William  Turner,  Pres.  Address,  Rep.  Brit.  Ass., 
1900,  p.  15. 


THE  DEEPENING  OF  PHYSIOLOGY.  315 

interesting  facts,  e.g.,  that  a  fragment  of  a  Protozoon, 
if  bereft  of  any  representative  of  the  nucleus,  will 
show  contractility  and  irritability  for  a  short  time, 
but  has  no  power  of  nutrition,  growth,  or  recupera- 
tion. The  work  of  Gruber,  Balbiani,  Hofer,  and 
Verworn  on  this  by-path  is  of  especial  importance; 
and  with  it  we  may  associate  the  "  tricks  with  eggs  " 
which  are  played  by  the  now  numerous  experimental 
embryologists,  such  as  Eoux  and  O.  Hertwig,  Herbst 
and  Driesch. 

(d)  Such  organisms  as  Flowers  of  Tan  (^Efha- 
lium  [Fuligo]  septicum)  afford  large  masses  of 
relatively  undifferentiated  living  substance  which 
have  been  studied  by  the  physiological  chemist.  And 
similarly,  it  is  possible  to  obtain  quantities  of  Pro- 
tozoa, Protophytes,  leucocytes,  spermatozoa,  ova,  etc., 
in  which  structural  differentiation  is  only  im- 
plicit. "  A  great  variety  of  favourable  research-ob- 
jects are  also  found  for  microchemical  investigation, 
although  thus  far,  since  the  methods  are  still  little 
developed,  only  the  first  beginning  in  this  direction 
has  been  made.  The  labours  of  Miescher,  Kossel, 
Lilienfeld,  Loew,  and  Bokorny,  Zacharias,  Schwartz, 
Lowit,  and  others,  have  already  proved  that  the  mi- 
crochemical investigation  of  the  cell  has  before  it  a 
rich  future."  * 

AS  KEGAEDS  PBOTOPLASM. 

The  earlier  observers,  from  Dujardin  and  Von 
Mohl  to  Max  Schultze,  were  well  aware  that  the  cell 
contained  or  was  a  minute  mass  of  substance,  often 
viscid,  often  vacuolar,  often  apparently  homogeneous, 

*  Verworn,  op.  tit.  p.  54. 


316    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

often  full  of  granules.  But  they  had  little  idea  of 
the  intricate  complexity  of  the  cell-substance,  which 
Virchow  has  lived  to  realise  and  in  part  to  eluci- 
date. Perhaps  it  is  to  Briicke  (1861)  that  we  should 
trace  back  the  beginning  of  the  recognition  that  the 
cell-substance  is  anything  but  homogeneous,  any- 
thing but  like  white  of  egg.  We  have  elsewhere  * 
sketched  some  of  the  steps  which  led  to  our  present 
realisation  of  the  complexity  of  the  cell-substance, 
which  some  compare  to  a  network,  others  to  a 
tangled  coil  of  fibrils,  others  to  a  gelatinous  matrix 
with  embedded  granules,  and  others  to  a  foam  or 
emulsion.  It  seems  probable  enough  that  one  and 
the  same  cell-substance  may  at  different  times  ex- 
hibit different  complexities  of  structure.  But  the 
important  fact  is  the  one,  to  which  more  perfect 
lenses,  more  rapidly  acting  fixatives  and  subtler  stain- 
ing re-agents  have  led  modern  workers,  that  the  cell 
has  a  complex  structural  organisation. 

What  is  meant  by  Protoplasm. — The  term  proto- 
plasm, which  Huxley  defined  as  "  the  physical  basis 
of  life,"  is  often  used  topographically  to  include  the 
whole  of  the  physically  complex  cell-substance.  It 
is  also  employed  as  the  equivalent  of  cytoplasm; 
i.e.,  for  the  complex  cell-substance  minus  the  nucleus. 
In  another  usage  it  means  the  whole  cell-substance  in 
so  far  as  that  is  actively  concerned  in  vital  processes, 
that  is  to  say,  the  cell-substance  minus  obviously  life- 
less inclusions  (metaplasm).  There  are  some  again 
who  try  to  confine  the  term  to  designate  the  genu- 
inely living  stuff,  and  this  would  be  most  convenient 
were  it  not  for  the  unhappy  fact  that  we  are  at 
present  unable  to  isolate  that  genuinely  living  stuff, 
or  even  to  be  sure  that  there  is  any  one  stuff  that 
*  The  Science  of  Life,  1899,  Chap.  IX. 


THE  DEEPENING  OF  PHYSIOLOGY.  317 

could  be  isolated.  Therefore,  it  seems  advisable  to 
keep  to  the  cautious  vagueness  of  Huxley's  phrase, 
protoplasm  is  the  physical  basis  of  life. 

There  are  three  slightly  different  physiological 
conceptions  of  protoplasm  at  present  in  the  field, 
(a)  Some  regard  protoplasm  as  a  substance  analogous 
to  a  ferment,  capable  of  acting  on  less  complex  ma- 
terial which  is  brought  within  its  sphere  of  influ- 
ence. It  is  the  strange  characteristic  of  a  ferment, 
like  diastase  or  pepsin,  that  it  can  act  on  other  sub- 
stances without  being  itself  essentially  affected  by 
the  changes  it  induces,  and  that  a  minute  quantity 
can  continue  its  work  with  a  power  which  seems  to 
have  little  direct  relation  to  its  amount.*  (6) 
Others  have  suggested  that  protoplasm  is,  as  it  were, 
the  central  term  in  a  complex  series  of  chemical 
changes,  itself  the  seat  of  continual  change,  ever  be- 
ing unmade  and  remade. f  (c)  Others  again  have 
suggested  that  there  is  probably  no  one  thing  that  can 
be  called  protoplasm,  for  vital  function  may  depend 
upon  the  interactions  or  inter-relations  of  several 
complex  substances,  none  of  which  could  by  .itself  be 
called  alive.  Just  as  the  secret  of  a  firm's  success 
may  depend  upon  a  particularly  fortunate  associa- 
tion of  partners,  so  it  may  be  with  vitality.^ 

As  to  the  chemical  composition  of  the  physical 
basis  of  life,  physiologists  are  not  at  present  in  a 
position  to  make  many  general  statements. 

"Just  as  very  different  structural  constituents  may 
be  distinguished  in  living  substance,  so  very  different 

*  See  Sir  J.  S.  Burden-Sanderson,  Pres.  Address,  Section 
D,  Rep.  Brit.  Ass.  for  1889,  pp.  604-614. 

t  See  Sir  Michael  Foster,  Article,  Physiology.  Encycl. 
Brit. 

t  See  E.  B.  Wilson.  The  Cell  in  Development  and  Inherit- 
ance, 1896,  new  ed.,  1900. 


318    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

chemical  bodies  are  present.  The  elements  of  which 
they  consist  are  only  such  as  exist  in  the  inanimate 
world  also,  but  their  number  is  small,  and  it  is  chiefly 
the  elements  having  the  lowest  atomic  weights  that 
compose  living  substance.  A  special  vital  element 
does  not  exist,  but  the  compounds  in  which  these 
elements  occur  are  characteristic  of  living  substance, 
and  in  great  part  are  absent  from  the  inorganic  world. 
They  are,  first  of  all,  proteids,  the  most  complex  of  all 
organic  compounds,  which  consist  of  the  elements  car- 
bon, hydrogen,  oxygen,  nitrogen,  and  sulphur,  and  are 
never  wanting  in  living  substance.  Further,  there 
occur  other  complex  organic  compounds,  such  as  carbo- 
hydrates, fats,  and  simpler  substances,  all  of  which 
either  are  derived  from  the  decomposition  of  proteids  or 
are  necessary  to  their  construction;  and  inorganic  sub- 
stances, such  as  salts  and  water ;  the  latter  gives  to  living 
substance  its  requisite  liquid  consistency."  * 

It  has  to  be  remembered  that  living  substance  must 
be  killed  before  it  is  chemically  studied,  and  that 
we  have  no  means  of  knowing  now  rapidly  changes 
of  molecular  arrangement  may  occur  after  death. 
But,  as  Verworn  says,  "  the  biting  sarcasm  that 
Mephistopheles  pours  out  before  the  scholar  upon 
this  practice  of  physiological  chemistry  must  be  quiet- 
ly endured." 

Although  we  do  not  know  the  nature  of  living 
matter — either  in  its  simplest  expression  in  the 
Protist  gliding  in  the  pond,  or  in  its  highest  ex- 
pression when  its  activity  in  our  brains  is  associated 
with  thought — we  are  not  without  data  in  regard  to 
the  sequence  of  vital  processes.  We  can  trace,  by 
chemical  analysis,  at  least  some  of  the  steps  by  which 
food  is  transformed  until  it  becomes  a  usable  part 

*  Prof.  F.  S.  Lee's  translation  of  Prof.  Max  Verworn's 
General  Physiology,  1SS9,  p.  117. 


THE  DEEPENING  OF  PHYSIOLOGY.  319 

of  the  living  body,  and  we  can  also  trace  some  of  the 
steps  by  which  the  waste  products  of  activity  are 
got  rid  of.  Our  position  may  be  compared  to  that 
of  visitors  to  the  manufactory  of  some  complex  prod- 
uct: they  see  the  raw  materials  coming  in,  they  are 
allowed  to  follow  the  preliminary  steps  in  their 
transformation;  they  see  the  final  products  passing 
out,  and  they  are  allowed  to  witness  the  process  of 
"  finishing  "  them ;  they  see  the  rubbish  that  is  cast 
away  and  are  shown  how  some  of  the  waste-products 
are  re-utilised;  but  what  they  do  not  see  is  the  gist 
of  the  whole  business — the  affairs  of  "  the  secret 
room  " — where  the  essential  transformations  are  kept 
secret. 

Metabolism. — All  theory  apart,  it  is  a  fact  of  ob- 
servation that  there  is  in  the  living  body  a  twofold 
process — of  waste  and  of  repair,  of  disruption  and 
construction,  of  disassimilation  and  assimilation. 

"  One  of  the  first  to  make  this  general  idea  more 
precise  was  De  Blainville.,  who  described  vitality  '  as  a 
twofold  internal  movement  of  composition  and  decom- 
position.' At  a  later  date,  Claude  Bernard,  who  may 
be  called  the  pioneer  of  the  '  protoplasmic  movement,' 
distinguished  *  disassimilating  combustion  and  assimi- 
lating synthesis/  Of  recent  years  various  researches 
and  speculations,  especially  those  of  Hering  and  of 
Gaskell,  have  led  to  yet  more  precise  statements  in  re- 
gard to  metabolism."  * 

Prof.  Hering  says :  "  Assimilation  and  disassimi- 
lation must  be  conceived  as  two  closely  interwoven 
processes,  which  constitute  the  metabolism  (unknown 
to  us  in  its  intrinsic  nature)  of  the  living  subtance, 
and  are  active  in  its  smallest  particles, — since  living 
*  Thomson,  Science  of  Life,  p.  114. 


320    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

matter  is  neither  permanent  nor  quiescent,  but  is  in 
more  or  less  constant  internal  motion."  In  some- 
what similar  terms,  Prof.  Gaskell  expounds  the  idea 
that  life  implies  an  alternation  of  two  processes — one 
of  them  a  running  down  or  disruption  (katabolism), 
the  other  a  winding  up  or  construction  (anabolism). 

THE  UNSOLVED  SECRET  OF  THE  ORGANISM. 

In  the  preceding  portion  of  this  chapter  we  have 
suggested  the  nature  of  the  analysis  by  which  the  in- 
tact living  creature  has  been,  so  to  speak,  taken  to 
pieces,  as  one  might  do  with  a  watch,  and  then  theo- 
retically reconstructed.  Organism,  organs,  tissues, 
cells,  protoplasm — these  words  express  the  various 
levels  of  analysis,  and  one  result  at  least  has  been 
a  greater  precision  of  description,  a  more  detailed 
and  vivid  picture  of  the  facts  of  the  case. 

As  the  analysis  has  proceeded  throughout  the  cen- 
tury, the  enthusiasm  of  discovery  has  led  again  and 
again  to  a  short-lived  belief  that  a  solution  of  the 
secret  of  the  organism  had  been  reached, — now  as  a 
system  of  correlated  organs,  or  again  as  a  city  of 
co-operating  cells.  The  discovery  of  the  mainspring 
may  be  said  to  disclose  the  secret  of  the  watch,  and 
the  discovery  of  the  cylinder  and  piston  may  be  said 
to  disclose  the  secret  of  the  steam-engine;  and  so  it 
has  seemed  to  some  that  the  secret  of  the  organism 
has  been  discovered  in  the  combined  functioning 
of  the  organs,  in  the  combined  properties  of  the 
tissues,  in  the  combined  changes  of  the  cells,  or 
in  the  metabolism  of  the  protoplasm.  But  just  as 
the  mainspring's  elasticity  demands  further  analysis, 
and  just  as  the  change  of  water  into  expansive 
steam  does  not  quite  explain  itself,  so  the  biologists 
have  sooner  or  later  come  to  see  that  their  presumed 


THE  DEEPENING  OF  PHYSIOLOGY.  321 

explanations  were  in  terms  of  things  that  required 
themselves  to  be  explained. 

For  this  reason,  epoch  after  epoch,  one  "  explana- 
tion "  after  another  has  been,  so  to  speak,  "  found 
out,"  and  there  has  been  a  recoil  of  caution  or  of 
disgust  to  the  postulate  of  a  specific  "  vital  force," 
or  to  some  other  verbalism  cloaking  intellectual  de- 
feat. 

To  express  the  life  of  the  organism  in  terms  of  its 
organs  is  no  doubt  a  useful  endeavour,  so  long  as 
it  is  not  forgotten  that  the  functions  of  the  organs — 
and,  what  is  more,  their  correlated  adaptations — re- 
main a  problem.  To  express  the  activity  of  the 
organs  in  terms  of  the  activities  of  their  component 
cells  is  an  even  more  interesting  task — useful  and 
necessary  like  the  previous  step — yet  surely  in  no 
sense  an  "  explanation  "  as  long  as  the  life  of  the 
cell  remains  an  unread  riddle. 

To  some  it  has  seemed  for  a  brief  moment  that 
they  saw  the  whole  life  of  the  organism  clearly  as 
comparable  to  an  automatic,  self-stoking,  self-repair- 
ing heat-engine,  or  thermo-electric  engine,  or  some 
unique  combination  of  engines,  but  the  vision  has 
soon  been  obscured  by  the  shadow  of  the  thought  that 
this  marvellous  engine  grew  into  obvious  complexity 
in  a  few  days  or  months  from  a  state  of  apparent 
simplicity,  that  it  had  the  power  of  adjusting  itself 
to  more  or  less  new  conditions,  and  that  it  actually 
gave  rise  to  other  engines  like  itself,  or  that  even  a 
fragment  of  it  reproduced  the  wonderful  whole,  and 
then  has  come  the  recoil  to  some  subtle  or  crude 
theory  of  vitalism. 

When  the  physiologist  tries  to  express  the  func- 
tion of  an  organ  in  terms  of  the  activities  of  its  cells 
he  is  really  seeking  a  more  thorough  description, 


322    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

and  the  search  has  been  a  fruitful  one  for  physi- 
ology. The  analysis  is  entirely  consistent  with  sci- 
entific method  and  has  been  justified  in  its  results. 
But  the  history  of  the  enquiry  reveals  a  twofold 
danger,  (a)  that  the  careless  mistake  a  deeper  de- 
scription for  an  explanation,  as  if  the  cell  and  its 
protoplasm  did  not  imply  a  mysterious  microcosm, 
and  (&)  that  in  the  analysis  the  unity  of  the  organ- 
ism be  overlooked  or  slurred  over  as  an  unimportant 
fact. 

But,  it  may  be  remarked,  the  physiologist  has 
surely  done  more  than  analyse  the  organism  into  its 
component  parts.  Has  he  not  summoned  chemistry 
and  physics  to  his  aid,  and  shown  that  many  phe- 
nomena which  we  call  vital,  which  our  predecessors 
attributed  to  the  action  of  a  special  vital  force,  may 
be  expressed  in  chemical  and  physical  terms?  Has 
he  not  interpreted  by  diffusion  and  osmosis  the  ab- 
sorption of  food  from  the  alimentary  canal  and  the 
interchange  of  gases  which  takes  place  in  the  lungs  ? 
Has  he  not  given  a  physical  account  of  the  circula- 
tion of  the  blood  and  the  ascent  of  sap  ?  Has  he  not 
found  the  source  of  animal  heat  in  the  chemical 
changes  which  occur  in  the  body-tissues,  has  he  not 
artificially  manufactured  from  simple  substances 
various  carbohydrates  and  the  like,  whose  formation 
was  previously  believed  to  be  inseparably  associated 
with  the  controlling  action  of  vital  force  ?  And  thus 
we  reach  the  position  of  those  who  say  "  that  the 
further  physiology  advances,  the  more  does  it  become 
possible  to  explain,  on  physical  and  chemical 
grounds,  phenomena  which  have  hitherto  been  re- 
garded as  associated  with  a  special  vital  force;  that 
it  is  only  a  question  of  time;  that  it  will  finally  be 
shown  that  the  whole  process  of  life  is  only  a  more 


THE  DEEPENING  OF  PHYSIOLOGY.  323 

complicated  form  of  motion  regulated  solely  by  the 
laws  which  govern  inorganic  nature."  * 

What  has  been  achieved  is  a  detection  of  chemical 
and  physical  sequences  in  vital  phenomena,  what  has 
not  been  achieved  as  yet  is  a  redescription  of  a 
vital  phenomenon  in  terms  of  chemistry  and  phys- 
ics. Prof.  J.  T.  Wilson  states  the  case  in  an  able 
address :  f — "  I  shall  not  dispute  the  proposition 
that,  in  the  progress  of  the  science  of  physiology, 
physico-chemical  theories  of  living  processes  have 
broken  down  all  along  the  line.  I  readily  admit  that 
such  theories  have  in  every  direction  failed  to  accom- 
plish that  mechanical  analysis  of  function  which 
seemed  to  the  physiologists  of  the  later  decades  of 
the  century  to  be  so  nearly  within  their  grasp.  Yet 
it  would  be  grossly  inaccurate  to  assert  that  the  at- 
tempt to  explain  life  as  mechanism  has  resulted  in 
nothing  but  failure.  The  fact  is  that  mechanism, 
after  mechanism  has  been  displayed,  through  the 
operation  of  whose  chemical  and  physical  properties 
the  functional  activity  of  the  organism  is  subserved. 
On  the  other  hand,  it  is  true  that  the  residual  phe- 
nomena unexplained  by  these  mechanisms  may  in  a 
sense  be  held  to  embody  the  very  essence  of  the 
mystery  of  organisation.  It  is  not  difficult  to  see 
that  in  the  nature  of  the  case  this  must  be  so.  It  is 
the  penalty  of  the  abstract  character  of  the  causal 
principle  employed  as  the  instrument  of  research. 
The  forging  of  links  in  an  endless  chain  of  mechan- 
ical causation  is  a  never-ending  process, — the  mys- 

*  G.  Bunge,  Text-book  of  Physiological  and  Pathological 
Chemistry,  trans,  by  L.  C.  Wooldridge;  London,  1890,  p.  3. 
The  quotation  expresses  the  reverse  of  Bunge's  own  posi- 
tion. 

t  President's  Address,  Proc.  Linn&an  Soc.  N.  8.  Wales 
XXIV.,  1899,  pp.  1-29. 


324:    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

tery  ever  recedes  as  we  pursue  it  further  into  the  re- 
cesses of  organisation." 

It  may  seem  strange  to  ask  whether  the  progress  of 
nineteenth  century  physiology  has  been  signalised  by 
the  achievement  of  re-expressing  any  vital  pheno- 
menon in  terms  of  physics  and  chemistry.  But  it  is, 
to  say  the  least,  very  doubtful  if  there  has  been  any 
such  success.  Leaving  out  of  sight  all  phenomena, 
like  the  bursting  of  a  dry  pea-pod,  or  the  projection 
of  an  image  by  the  lens  of  the  eye,  which  cannot  be 
called  vital,  we  press  the  question  whether  the  con- 
traction of  a  muscle  or  the  movement  of  a  sensitive 
plant,  the  flow  of  the  blood  or  the  ascent  of  sap,  the 
respiratory  changes  in  a  lung  or  in  a  leaf,  the  ab- 
sorption of  food  from  the  intestine  or  the  formation 
of  starch  in  a  plant, — or  any  vital  process  can  be 
completely  described  in  chemical  or  physical  terms. 
No  doubt,  chemical  and  physical  processes  have  been 
detected,  and  have  been  followed  out  in  some  cases 
with  great  success,  but  has  a  complete  redescription 
in  chemical  or  physical  terms  ever  been  attained? 
"  To  me,"  Bunge  says,*  "  the  history  of  physiology 
teaches  the  exact  opposite.  I  think  the  more  thor- 
oughly and  conscientiously  we  endeavour  to  study 
biological  problems,  the  more  are  we  convinced  that 
even  those  processes  which  we  have  already  regarded 
as  explicable  by  chemical  and  physical  laws,  are  in 
reality  infinitely  more  complex,  and  at  present  defy 
any  attempt  at  a  mechanical  explanation." 

Dr.  J.  S.  Haldane  goes  even  further : — "  If  we 
look  at  the  phenomena  which  are  capable  of  being 
stated,  or  explained  in  physico-chemical  terms,  we 
see  at  once  that  there  is  nothing  in  them  character- 
istic of  life.  .  .  .  We  are  now  far  more  definitely 
*  Op.  cit.,  p.  3. 


THE  DEEPENING  OF  PHYSIOLOGY.  325 

aware  of  the  obstacles  to  any  advance  in  this  (phys- 
ico-chemical) direction,  and  there  is  not  the  slightest 
indication  that  they  will  be  removed,  but  rather  that, 
with  further  increase  of  knowledge,  and  more  re- 
fined methods  of  physical  and  chemical  investiga- 
tion, they  will  only  appear  more  and  more  difficult 
to  surmount.  .  .  .  All  that  is  really  shown  by 
the  partial  success  which  has  attended  the  applica- 
tion of  physical  and  chemical  principles  of  explana- 
tion in  physiology  is  that  in  the  course  of  investi- 
gation it  is  often  possible  to  ignore  for  the  time  the 
distinctive  features  of  life.  For  certain  scientific 
purposes  we  may  treat  some  part  of  the  body  as 
a  mechanism,  without  taking  into  consideration 
the  manner  in  which  it  is  controlled  and  maintained ; 
and  in  this  way  results  of  great  value  have  been 
attained.  But  in  doing  all  this  we  are  deliberately 
ignoring  or  abstracting  from  all  that  is  character- 
istic of  life  in  the  phenomena  dealt  with.  The  action 
of  each  bodily  mechanism,  the  composition  and  struc- 
ture of  each  organ,  the  intake  and  output  of  energy 
from  the  body,  are  all  mutually  determined  and  con- 
nected with  one  another  in  such  a  way  as  at  once  to 
distinguish  a  living  organism  from  anything  else. 
As  this  mutual  determination  is  the  characteristic 
mark  of  what  is  living,  it  cannot  be  ignored  in  the 
framing  of  fundamental  working  hypotheses." 

We  are  lingering  over  this  discussion  because  of 
its  great  historical  interest.  Again  and  again  some 
success  in  discovering  physico-chemical  sequences  in 
the  living  organism  has  awakened  the  expectation 
that  the  dawn  of  a  mechanical  theory  (interpretation 
or  re-description)  of  life  was  drawing  nigh.  Again 
and  again  the  expectation  has  been  disappointed, 
and  the  investigators  have  returned  to  rest  in  a 


32 G    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

postulate  of  "  vital  force."  This  postulate  is  a 
vague  one  and  its  content  has  altered  greatly  even 
during  the  nineteenth  century.  For  a  time  "  vital 
force "  was  spoken  of  as  a  "  hyper-mechanical " 
factor,  a  mystical  power,  a  non-material  agent,  pre- 
siding over  the  activities  of  the  body.  But  reason 
could  not  "  repose  on  this  pillow  of  obscure  quali- 
ties," and  the  content  of  the  postulate  changed,  for 
it  is  difficult  to  believe  that  Johannes  Miiller  meant 
more  by  his  vitalism  than  to  express  the  fact  that 
the  physical  and  chemical  processes  in  the  living 
body  are  correlated  in  a  manner  which  defies  re- 
statement in  simpler  terms.  Many  nowadays  would 
agree  with  this  or  would  advance  to  the  more  posi- 
tive idealist  position  occupied  by  Bunge.  This 
physiologist  declares  that  "  it  would  indeed  be  a  lack 
of  intelligence  to  expect  with  the  senses  to  make 
discoveries  in  living  nature  of  a  different  order  to 
those  revealed  to  us  in  inorganic  nature,"  and  yet  he 
maintains  "  that  all  the  processes  of  our  organism 
capable  of  explanation  on  mechanical  principles  are 
as  little  to  be  regarded  as  vital  phenomena  as  the 
rustling  of  leaves  on  a  tree,  or  as  the  movement  of 
the  pollen  when  blown  from  stamen  to  pistil."  In 
other  words,  he  holds  that  the  distinctively  vital  does 
not  admit  of  mechanical  restatement,  and  that  light 
must  come  from  above,  not  from  below,  i.e.,  from 
psychological  rather  than  physical  concepts. 

Many  other  opinions  of  authoritative  experts 
might  be  cited,  varying  greatly  in  their  form,  but 
with  this  common  basis  of  agreement  that  the  phe- 
nomena of  life  cannot  be  restated  in  the  language  of 
chemistry  and  physics.  And  yet,  the  reader  may 
well  ask,  "  Is  this  more  than  a  pious  opinion,  an  argu- 
mentum  ad  ignorantiam?  Is  not  biological  anal- 


THE  DEEPENING  OF  PHYSIOLOGY.  327 

ysis  still  in  its  youth?  Have  not  partial  restate- 
ments been  given  of  numerous  functions  ?  May  one 
not  look  forward  to  the  time  when  these  may  be 
completed  ?" 

This  leads  us,  in  concluding  this  discussion,  to 
follow  Prof.  Karl  Pearson  in  pointing  out  again  the 
radical  misunderstanding  which  exists  in  many 
minds  in  regard  to  scientific  method.  The  material 
of  science  is  "  the  routine  of  our  perceptual  ex- 
perience "  ;  we  think  over  this,  though  we  never 
understand  it;  we  make  sure  by  experiment  that 
the  sequence  of  sense-impressions  which  constitutes 
the  routine  is  not  illusory;  we  make  sure  that  the 
routine  is  perceived  by  others  also  (for  science  is 
social),  lest  we  should  be  the  victims  of  an  idio- 
syncrasy; and  by  and  by,  if  we  are  clever  enough, 
we  give  "  a  description  in  conceptual  shorthand 
(never  the  explanation)  of  the  routine  of  our  per- 
ceptual experience."  "  The  problem  of  whether 
life  is  or  is  not  a  mechanism  is  thus  not  a  question 
of  whether  the  same  things,  •  matter '  and  l  force/ 
are  or  are  not  at  the  back  of  organic  and  inorganic 
phenomena — of  what  is  at  the  back  of  either  class 
of  sense-impressions  we  know  absolutely  nothing — 
but  of  whether  the  conceptual  shorthand  of  the 
physicist,  his  ideal  world  of  ether,  atom,  and  mole- 
cule, will  or  will  not  also  suffice  to  describe  the  biol- 
ogists' perceptions."  That  it  does  not  at  present 
seems  the  opinion  of  the  more  philosophical  physi- 
ologists ;  if  it  ever  should  it  would  be  "  purely  an 
economy  of  thought;  it  would  provide  the  great  ad- 
vantages which  flow  from  the  use  of  one  instead  of 
two  conceptual  shorthands,  but  it  would  not  '  ex- 
plain '  life  any  more  than  the  law  of  gravitation 
explains  the  elliptic  path  of  a  planet." 


328      PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

"  Atom  "  and  "  molecule  "  and  the  rest  are  con- 
cepts, not  phenomenal  existences,  therefore  even 
if  the  physicists'  formulae  should  fit  vital  phenomena 
— which  they  do  not  seem  to  do — there  would  be 
no  "  explanation  "  forthcoming,  for  "  mechanism 
does  not  explain  anything." 


CHAPTER  IX. 
THE  STUDY  OF  STBUCTURE. 

THE  MOEPHOLOGICAL  QUESTION  AXD  ITS  PEO- 
GBESSIVE  ANSWERS. 


of  the  naturalist's  first  questions  —  however 
learnedly  he  may  phrase  it  —  is  just  one  of  the  child's 
first  questions,  asked  long  before  it  can  speak  — 
"  What  is  this  ?  "  In  how  many  different  tones  —  of 
fear,  of  awe,  of  wonder,  of  inquisitiveness  —  has  this 
question  been  asked  since  man  and  science  began! 
Was  it  not  Aristotle's  question  when  a  new  specimen 
was  brought  to  him  ?  was  it  not  the  question  on  the 
Challenger  when  the  dredge  came  up  ?  is  it  not  the 
question  on  the  lips  of  every  teacher  and  student  of 
natural  history  to-day?  —  What  is  this?  It  is  a 
"  simple  question,"  but  how  hard  to  answer,  as  we 
press  it  further  and  further  home,  from  external 
features  to  internal  structure,  from  organs  to  tissues, 
from  tissues  to  cells,  as  we  put  one  lens  after  another 
in  front  of  our  own,  as  we  call  to  our  aid  all  sorts  of 
devices  —  scalpel  and  forceps,  razor  and  microtome, 
fixative  and  stain.  "  What  is  this,"  we  say,  "  in 
itself  and  in  all  its  parts  ?  what  is  this  by  itself  and 
when  compared  with  its  fellows  and  kindred  ?  "  and 
our  answer  broadens  and  deepens  till  it  furnishes  the 
raw  materials  of  the  science  of  Morphology. 

The  answer  to  the  question:    What  is  this?  asked 


330      PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

again  and  again  at  different  planes  of  analysis 
forms  the  raw  material  of  morphology.  This  is  the 
science  of  form  and  structure,  just  as  physiology  is 
the  study  of  habit  and  function;  the  one  has  to  do 
with  the  static,  the  other  with  the  dynamic  aspect  of 
the  organism.  But  the  descriptive  facts — the  raw  ma- 
terials— do  not  constitute  the  science;  the  morphol- 
ogist  has  to  find  unity  amid  manifoldness,  to  dis- 
close the  styles  and  principles  of  organic  architecture, 
and  to  recreate  the  Systema  Naturae,  not  as  a  mere 
classification,  but  as  the  chart  of  history. 

The  history  of  morphology  is,  as  Prof.  Patrick 
Geddes  points  out,  parallel  to  that  of  physiology.  It 
is  the  history  of  a  gradually  deepening  analysis. 

(1)  The  Organism. — In  early  times,  the  answer 
to  the  question:   What  is  this?  was  chiefly  concerned 
with  the  external  appearance  of  the  intact  creature, 
— its  symmetry,  shape,  architectural  plan,  and  the 
like,  as  is  expressed  in  the  work  of  men  like  Ray 
and  Linnaeus.     Even  at  this  level  the  morphologists' 
labours    are    not   nearly    completed.      "  Each    new 
species  described  means  a    leaf    added    to    Linne's 
Systema  Naturae"  * 

(2)  The   Organs. — The   description   of   external 
characters  is,  however,  only  the  beginning  of  mor- 
phology;   an  analysis   of  organs   is  the  next  step, 
which  may  be  especially  associated  with  the  work 
of  Cuvier  as  zoologist,  of  Jussieu  as  botanist,  and  of 
Goethe  as  both.     This  task  is  also  an  unending  one, 
"  to  which  every  new  descriptive  anatomical  research 
belongs  as  clearly  as  if  it  were  published  as  an  ap- 
pendix to  Cuvier's  Regne  Animal."  * 

(3)  The    Tissues. — The   next   logical    step    was 

*  P.  Geddes,  A  synthetic  outline  of  the  history  of  biology, 
Proc.  Boy.  Soc.  Edin.,  1885-1886,  pp.  905-911. 


THE  STUDY  OF  STRUCTURE.  331 

taken  just  at  the  dawn  of  the  nineteenth  century, 
when  Bichat,  in  his  Anatomic  Generale  (1801)  ana- 
lysed the  body  into  its  component  tissues, — muscular 
nervous,  glandular,  connective,  and  so  on.  This  may 
be  called  the  beginning  of  histology,  which  has  now 
so  many  devotees.  From  Bichat's  classic  we  pass 
to  Leydig's  foundation  of  comparative  histology 
(Lehrbuch  der  Histologie  des  Menschen  und  der 
Thiere,  Frankfurt,  1857) — a  most  remarkable  work 
for  its  date,  and  it  brings  us  to  the  modern  study  of 
tissues,  which  has  been  so  much  stimulated  by  im- 
provements in  microscopic  apparatus  and  technique. 
As  the  researches  of  Professor  Albert  von  KolHker 
of  Wiirzburg  extend  over  a  period  of  sixty  years,  and 
over  the  entire  field  of  animal  histology,  we  could 
not  choose  a  more  fitting  or  more  illustrious  repre- 
sentative of  nineteenth-century  histological  research. 

(4)  The  Cells. — To   the   scalpel    the   lens    was 
added ;  and  then  the  scalpel  was  supplemented  by  the 
razor  (first  used  by  hand  and  now  in  a  microtome)  ; 
and  lens  was  added  to  lens  to  form  a  compound 
microscope.    Thus  minute  analysis  could  not  remain 
long  at  the  level  of  tissues ;  these  were  soon  analysed 
into  their  component  or  originative  cells, — the  nucle- 
ated corpuscles  of  living  matter  which   form  the 
basis  of  all  organic  structure.     This  step  must  be 
especially  associated  with  the  work  of  Schleiden  and 
Schwann,   who   formulated   the   "  Cell-Theory "    in 
1838-39.    With  the  study  of  cell-structure  hundreds 
of  modern  workers  are  more  or  less  exclusively  occu- 
pied. 

(5)  Protoplasm. — The  fifth  and  last  step  in  mor- 
phological analysis,  within  the  limits  of  biology,  is 
that  which  passes  from  the  cell  as  such  to  a  study  of 
the  living  matter  and  other  substances  which  com- 


332      PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 


pose  it.  With  this,  though  it  is  difficult  to  select 
names,  the  work  of  Dujardin,  Von  Mohl,  and  Max 
Schultze  may  be  associated. 

This  outline  is  based  on  the  luminous  but  exceed- 
ingly short  paper  by  Professor  Patrick  Geddes 
already  referred  to,  and  a  fuller  exposition  will  be 
found  in  the  writer's  Science  of  Life  (1899).  A 
diagrammatic  summary  may  be  useful. 


Activi- 

Form 

» 

ties  of 

of 

<J*             intact 

Organ- 
ism 

\ 

.gP               Organ- 
^                    ism 

Struc- 

6 /si                           Func- 

ture  of 

\\  ^^                       Jt 

r/s*                             tiona 

Organs 

/  /vj)                            of  Or- 

Str 

UC-                XtVX                     &/ 

/^r              Prop-      gans 

ture 

of           ^uN>j          ^/ 

/XF"                  erties 

Tissues                 ~fo  \~            A-  / 

^V                    of  Tis- 

Forms                                ' 

Phases  sues 

of 

^  of  Oil. 

Cells 

Life 

PROTOPLASM 

It  should  be  carefully  noted  that  each  step  in 
analysis  makes  a  corresponding  step  of  synthetic  re- 
interpretation  possible.  But  the  reconstructive  proc- 
ess always  lags  far  behind  that  of  analysis. 

In  studying  structure  (morphology)  the  methods 
are — observation,  analysis,  and  comparison.  We 
begin  with  external  form  and  symmetry,  always  har- 
monious and  beautiful  in  a  natural  wild  animal. 
We  work  with  the  scalpel  till  we  see  the  creature 
through  and  through  as  if  it  were  transparent;  we 
persevere  till  we  see  it  as  a  great  city — usually  far 
excelling  any  city  of  ours — with  regions  which  we 
call  organs,  streets  which  we  call  tissues,  houses 


THE  STUDY  OF  STRUCTURE.  333 

which  we  call  cells.  We  get  the  help  of  microtome 
and  microscope,  of  fixing  and  staining  re-agents,  and 
work  on  until  we  see  the  intricate  structure  of  each 
house, — the  furnishings  and  inhabitants  of  each  cell. 
We  try  to  work  back  again  to  the  unity  which  we 
have  taken  to  pieces;  we  compare  organism  with 
organism  and  detect  their  relationships ;  we  compile 
a  census  and  construct  a  genealogical  tree.* 

FOUNDATIONS  OF  MOEPHOLOQY. 

Although  there  were  untiring  and  keen-sighted 
comparative  anatomists  in  the  eighteenth  century — 
such  as  John  Hunter  and  Vicq  d'Azyr — the  modern 
period  may  be  fairly  dated  from  the  work  of  Cuvier 
and  Goethe,  who,  though  almost  antithetic  in  their 
outlook  on  nature,  may  be  called  the  joint-founders 
of  comparative  morphology. 

To  Georges  Cuvier  (1769-1832)  the  science  owes 
much,  not  only  for  his  rich  accumulation  of  anatom- 
ical description,  but  for  his  attempt  to  give  an 
anatomical  basis  to  classification,  for  his  appreci- 
ation of  the  value  of  fossils,  and  for  his  insistence 
on  the  correlation  of  parts.  The  idea  expressed  in 
the  phrase  "  the  correlation  of  parts "  is  now  fa- 
miliar:— the  organism  is  no  haphazard  aggregate  of 
characters,  but  a  unified  integrate.  Part  is  bound 
to  part,  so  that  if  the  one  varies  the  other  varies  with 
it.  In  short,  "there  are  many  members  which  are 
members  one  of  another,  in  one  body."  It  must  be 
confessed,  however,  that  Cuvier  tended  to  exaggerate 
the  value  of  his  guiding  principle,  and  that  he  did 
not  appreciate  its  full  significance  as  that  has  ap- 

*  See  J.  Arthur  Thomson,  The  Humane  Study  of  Natural 
History,  Humane  Science  Lectures,  Bell,  London,  1897. 


334:    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

peared  in  post-Darwinian  days.  To  Cuvier,  who  was 
an  anti-evolutionist,  the  "  correlation  of  parts  "  was 
simply  a  morphological  fact. 

We  would  place  next  the  name  of  Goethe,  not  be- 
cause of  his  anatomical  discoveries,  which  were  few 
in  number,  but  because  of  the  clearness  with  which 
his  genius  discerned  and  proclaimed  "  the  funda- 
mental idea  of  all  morphology — the  unity  which 
underlies  the  multifarious  varieties  of  organic 
form."  * 

The  idea  which  was  more  or  less  clearly  in  the 
mind  of  Joachim  Jung  (1678)  and  of  Linnaeus 
(1760,  1763)  that  the  appendicular  organs  (leaves, 
bracts,  sepals,  petals,  etc.)  arising  from  the  stem  of 
a  flowering  plant  are  all  fundamentally  the  same 
leaf-organ  in  various  forms,  was  rehabilitated  and 
in  part  demonstrated  by  the  embryologist  Casper 
Friedrich  Wolff  (1767),  who  said  "all  parts  of 
the  plant,  except  the  stem,  are  modified  leaves,"  and 
by  Goethe  in  his  famous  essay  Versuch  die  Meta- 
morphose der  Pflanzen  zu  erkl'dren  (1790).  It 
may  be  that  the  evidence  Goethe  gave  of  the  funda- 
mental unity  of  foliar  and  floral  organs  would  not 
be  considered  conclusive  nowadays,  but  his  essay — 
published  with  some  difficulty  and  for  many  years 
little  noticed — is  a  famous  document  in  the  archives 
of  botany,  an  early  expression  of  an  idea  which  has 
now  saturated  the  whole  science.  The  morphological 
equivalence  of  the  appendicular  organs  is  now  uni- 
versally admitted,  though  the  direction  in  which  the 
evolution  has  taken  place — whether  from  foliage-leaf 
to  reproductive-leaf  (sporophyll)  or  vice  versa — re- 
mains a  subject  of  discussion. 

Some    years    previously    Goethe    had    made    an- 

*  Geddes,  Article  Morphology,  Encyclopedia  Britannica. 


THE  STUDY  OF  STRUCTURE.  335 

other  discovery,  regarding  which  he  wrote  to  Herder : 
— "  I  must  hasten  to  tell  you  of  a  piece  of  good 
fortune  that  has  happened  to  me.  I  have  found 
— neither  gold  nor  silver,  but  what  gives  me  inex- 
pressible delight — the  intermaxillary  bone  in  man." 
"  I  have  such  delight,"  he  wrote  to  another,  "  doss 
sicli  mir  alle  Eingeweide  bewegen."  The  reason 
for  his  exuberant  delight  in  proving  the  presence  of 
this  little  bone  in  front  of  the  upper  jaw  was  due 
to  his  conviction  of  the  unity  of  plan  in  vertebrate 
skeletons.  That  man  had  no  intermaxillary  had 
been  regarded  as  a  distinctive  peculiarity ;  but  Goethe 
was  right  in  his  conviction  of  the  all-pervading  simil- 
itude of  structure  between  man  and  beast.  While 
Goethe  was  quite  independent  in  his  discovery,  it 
should  be  noted  that  the  name  of  Vicq  d'Azyr  must 
also  be  associated  with  the  bone  in  question. 

The  two  discoveries  which  we  have  noticed  remain 
as  part  of  the  framework  of  science,  but  the  same 
cannot  be  said  of  Goethe's  vertebral  theory  of  the 
skull  (which  Oken  also  suggested).  According  to 
this  theory,  which  Goethe  arrived  at  partly  from  a 
study  of  the  insect's  body,  evidently  built  up  of  a 
series  of  rings  or  segments,  and  partly  from  the  sight 
of  a  crumbling  sheep's  skull  which  fell  to  pieces  as 
he  disinterred  it,  the  skull  is  formed  of  six  modified 
vertebrae.*  The  death-blow  to  this  view,  which  pre- 
vailed for  a  long  time,  was  given  by  Reichert  and 
Ratke,  Gegenbaur  and  Huxley,  who  showed  that,  al- 
though the  head  is  built  up  of  a  series  of  segments, 
originally  comparable  to  those  of  the  trunk,  this  can- 

*  It  is  a  strange  historical  fact  that  a  sheep's  skull  on 
the  Hartz  Mountains  led  Oken  to  the  same  theory  as  the 
sheep's  skull  in  the  Jewish  cemetery  in  Venice  had  sug- 
gested to  Goethe. 


336    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

not  be  said  of  the  skull  as  such.  At  'the  same  time, 
Goethe's  theory  was  a  keen-sighted  morphological 
hypothesis,  well  worthy  of  being  carefully  tested. 

We  might  also  refer  to  Goethe's  views  on  indi- 
viduality, division  of  labour,  correlation,  adaptation, 
and  the  general  doctrine  of  evolution ;  *  but  we  have 
probably  said  enough  to  show  why  the  poet-naturalist 
may  be  ranked  among  those  who  laid  the  foundations 
of  morphology. 

Lamarck  was  rather  an  evolutionist  than  a  mor- 
phologist,  but  it  must  be  remembered  that  in  1794 
he  drew  with  a  firm  hand  the  distinction,  which 
Aristotle  had  hinted  at,  between  vertebrate  or  back- 
boned and  invertebrate  or  backboneless  animals. 
Although  our  knowledge  of  transitional  forms,  like 
Balanoglossus,  not  to  speak  of  the  Tunicates,  has 
lessened  the  rigidity  of  Lamarck's  line,  the  distinc- 
tion is  universally  recognised  as  one  of  great  practi- 
cal convenience.  Lamarck  also  defined  a  number  of 
groups — Crustacea,  Arachnida,  and  Annelida — 
which  are  still  regarded  as  natural  divisions,  and  he 
may  be  fairly  called  one  of  the  founders  of  the  com- 
parative anatomy  of  invertebrates.  The  very  antith- 
esis of  Cuvier,  he  allowed  his  evolutionary  theory  to 
colour  his  whole  work. 

fitienne  Geoffroy  Saint-Hilaire,  author  of  the  re- 
markable Philosophic  'Anatomique  (1818-1823)  in 
which  he  exaggerated  the  idea  of  "  unity  in  organic 
structure,"  was  another  expert  comparative  anato- 
mist who  was  profoundly  influenced  by  the  evolution- 
idea.  Meckel,  on  the  other  hand,  even  more  illus- 
trious as  an  anatomist,  was  distinctly  Cuvierian. 

*  See  Prof.  H.  Reichenbach,  Goetlie  und  die  Biologie.  Bericht 
Senckenberg  Nat.  Gesellschaft,  Frankfurt  a.  M.,  1899,  pp.  124- 
155. 


THE  STUDY  OF  STRUCTURE.  337 

Although  Johannes  Miiller  was  probably  greatest 
as  a  physiologist,  he  touched  and  influenced  every 
department  of  biology,  and  his  touch  was  that  of 
genius.  Even  if  he  had  left  no  record  behind  him 
but  his  work  in  comparative  anatomy,  his  place  on 
the  roll  of  honour  would  be  high.  And  apart  from 
actual  work,  it  should  be  recalled  that  Virchow, 
Kolliker,  Gegenbaur,  Haeckel,  Briicke,  Giinther,  and 
Helmholtz  were  among  his  pupils. 

Sir  Eichard  Owen  (1804-1892)  links  Cuvier,  at 
whose  feet  he  sat  for  a  short  time,  to  Gegenbaur  and 
Huxley,  excelling  Cuvier  in  the  accuracy  of  his  work 
and  in  the  generalising  spirit  which  he  brought  to 
bear  upon  his  problems,  but  occupying  a  strange 
midway  position, — on  the  one  hand,  extremely  con- 
servative and  unappreciative  of  Darwinism;  on  the 
other  hand,  really  believing  in  the  derivation  of 
species  from  one  another. 

Of  the  work  of  Owen  and  others  we  have  else- 
where given  a  brief  sketch,*  and  must  be  content 
here  to  emphasise  the  importance  of  the  service  which 
he  rendered  to  morphology  by  his  clear  distinction 
between  homologous  and  analogous  organs. 

Organs  which  resemble  one  another  in  essential 
structure  and  in  development  are  called  homologous; 
organs  which  resemble  one  another  in  the  function 
they  perform  are  called  analogous,  (a)  Thus  the 
wing  of  a  flying  bird  is  homologous  with  the  arm  of 
man ;  there  is  a  fundamental  similarity  in  the  bones, 
muscles,  nerves,  and  blood-vessels;  they  have  also 
the  same  mode  of  development;  both  are  true  fore- 
limbs,  but  they  are  not  analogous,  for  men  do  not 
fly,  nor  do  birds  grip  with  their  fingers,  (fc)  The 

*  Science  of  Life,  1899. 


338    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

wing  of  a  flying  bird  is  analogous  with  that  of  a 
butterfly,  for  both  are  organs  of  true  flight,  which 
strike  the  air ;  but  they  are  not  homologous,  for  there 
is  no  resemblance  in  their  structure  or  development, 
(c)  Thirdly,  the  wing  of  a  flying  bird  is  both  homolo- 
gous and  analogous  with  the  wing  of  a  bat. 

It  must  not  be  supposed  that  the  question  is  so 
easy  as  the  illustrations  given  may  suggest.  Indeed 
there  are  few  questions  more  difficult  than  the  cri- 
teria of  homology.  But  the  importance  of  the  dis- 
tinction which  Owen  drew  is  obvious,  for  a  true  or 
natural  classification  which  groups  related  forms  to- 
gether must  be  based  on  the  demonstration  of  homol- 
ogies.  Perhaps  the  most  important  addition  to 
what  Owen  said  is  due  to  Professor  Ray  Lankester 
who,  in  1870,  distinguished  homogeny  (correspond- 
ence due  to  common  descent)  from  homoplasty  (cor- 
respondence due  to  similar  adaptations  in  unrelated 
forms). 

Starting  again  from  Goethe,  we  might,  if  space 
permitted,  seek  to  show  how  the  morphology  of 
plants  developed  through  the  labours  of  Schleiden 
(1804-1881)  the  title  of  whose  text-book  (1842-43) 
Botany  as  an  Inductive  Science  struck  a  new  note,  of 
Von  Mohl,  of  Carl  von  Nageli,  of  Hofmeister,  who 
from  1849  onwards  did  for  the  pedigree  of  plants 
what  Gegenbaur,  Huxley,  and  others  did  for  animals, 
of  Robert  Brown,  Irmisch,  Hanstein,  Alex.  Braun, 
and  many  more.  From  these  through  De  Bary  and 
Sachs,  we  pass  naturally  to  the  active  botanical  mor- 
phologists  of  to-day. 

It  may  be  more  useful  to  try  to  illustrate  some  of 
the  more  general  steps  in  the  progress  of  morphology. 

The  first  edition  of  Herbert  Spencer's  Principles 
of  Biology  and  Ernst  Haeckel's  Generelle  Morpho- 


THE  STUDY  OF  STRUCTURE.  339 

logic  are  classics  of  which  the  nineteenth  century 
might  have  been  prouder  than  it  was.  They  are 
monumental  attempts  to  systematise  and  clarify  the 
general  conceptions  which  underlie  all  biological 
thinking  and  research. 

Let  us  take  a  simple  illustration.  We  say  that 
one  animal  is  "  higher  "  than  another,  what  do  we 
mean  ?  Merely,  that  it  is  liker  ourselves  ?  Or  is  there 
more  precision  in  our  standard  ?  The  answer  is  to  be 
found  in  the  words  "  differentiation  "  and  "  integra- 
tion " ;  the  higher  animal  is  more  differentiated  and 
more  integrated  than  the  lower.  And  what  the  two 
big  words  mean  is  made  plain  in  the  classics  referred 
to. 

The  progress  of  the  individual,  and  of  the  race, 
is  from  simplicity  to  complexity.  When  we  think 
over  the  animal  series  we  also  notice  that  before  defi- 
nite nervous  organs  appear  there  is  diffuse  irritabil- 
ity, before  definite  muscular  organs  appear  there  is 
diffuse  contractility,  and  so  on.  In  other  words, 
functions  come  before  organs.  The  attainment  of 
organs  implies  specialisation  of  parts,  or  concentra- 
tion of  functions  in  particular  areas  of  the  body. 

Contrast  a  frog  with  Hydra,  and  one  of  the  great 
facts  about  the  evolution  of  organs  is  illustrated. 
Among  the  living  units  which  make  up  a  frog,  there 
is  much  more  division  of  labour  than  there  is  among 
those  of  Hydra.  An  excised  representative  sample 
of  Hydra  will  reproduce  the  whole,  but  you  cannot 
perform  this  experiment  with  the  frog.  Now,  the 
structural  result  of  this  physiological  division  of 
labour  is  differentiation.  The  animal,  or  part  of 
it,  becomes  more  complex,  more  heterogeneous. 

Contrast  a  bird  and  a  sponge,  and  another  great 
fact  about  the  evolution  of  organs  is  illustrated. 


340    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

The  bird  is  more  of  a  unity  than  a  sponge ;  its  parts 
are  more  closely  knit  together  and  more  adequately 
subordinated  to  the  life  of  the  whole.  We  call  this 
kind  of  progress  integration.  Differentiation  in- 
volves the  acquisition  of  new  parts  and  powers,  these 
are  consolidated  and  harmonised  as  the  animal  be- 
comes more  integrated.* 

Stephenson's  "  Puffing  Billy  "  was  a  lower  organ- 
ism than  a  locomotive  of  1901 ;  it  showed  less  com- 
plexity of  usefully  functional  parts,  and  it  was  less 
under  unified  control. 

Our  point  is  that  we  are  continually  using  words 
like  "  organism,"  "  development,"  "  differentiation," 
"  integration,"  "individuality,"  "character,"  "  adap- 
tation," and  so  on, — using  them  lightly  as  if  there 
were  no  difficulties  hidden  in  them — and  that  there- 
fore such  general  philosophic  works  as  the  two  we 
have  named  are  of  great  value  in  expressing  at  least 
an  attempt  to  criticise  and  clarify  the  categories 
which  even  the  purest  of  "  pure  anatomists  "  must 
use  in  spite  of  himself.  Neither  Spencer  nor 
Haeckel  would  regard  his  masterpiece  of  1866  as 
final ;  indeed  Spencer  in  his  last  years  began  to 
re-edit  The  Principles  of  Biology;  and  it  is  plain 
that  the  criticism  of  categories  must  develop  as  the 
science  does,  but  the  fact  remains  that  there  are  few 
biological  books  of  more  recent  date  which  come  near 
those  of  Spencer  and  Haeckel  in  extent  or  lucidity 
of  outlook. 

Change  of  Function. — Division  of  labour  involves 
restriction  of  functions  in  the  several  parts  of  an 
animal,  and  no  higher  animals  could  have  arisen  if 
all  the  cells  had  remained  with  the  many-sided 
qualities  of  Amoebae.  Yet  we  must  avoid  thinking 
*  See  the  writer's  Oixtlines  of  Zoology,  3rd  edition,  1899, 


THE  STUDY  OF  STRUCTURE.  34-1 

about  organs  as  if  they  were  necessarily  active  in 
one  way  only.  For  many  organs,  e.g.,  the  liver, 
have  several  very  distinct  functions,  and  we  know 
how  wondrously  diverse  are  the  activities  in  our 
brains.  In  addition  to  the  main  function  of  an  organ 
there  are  often  secondary  functions ;  thus,  the  wings 
of  an  insect  may  be  respiratory  as  well  as  locomotor, 
and  part  of  the  food  canal  of  ascidians  and  lanceleta 
is  almost  wholly  subservient  to  respiration.  More- 
over, in  organs  which  are  not  very  highly  specialised, 
it  seems  as  if  the  component  elements  retained  a  con- 
siderable degree  of  individuality,  so  that  in  course  of 
time  what  was  a  secondary  function  may  become  the 
primary  one.  Thus  Dohrn,  who  has  especially  em- 
phasised the  idea  of  function  change,  says :  Si  Every 
function  is  the  resultant  of  several  components,  of 
which  one  is  the  chief  or  primary  function,  while 
the  others  are  subsidiary  or  secondary.  The  diminu- 
tion of  the  chief  function  and  the  accession  of  a 
secondary  function  changes  the  total  function;  the 
secondary  function  becomes  gradually  the  chief  one ; 
the  result  is  the  modification  of  the  organ."  We 
may  notice,  in  illustration,  how  the  structure  known 
as  the  allantois  is  an  unimportant  bladder  in  the 
frog,  while  in  Birds  and  Eeptiles  it  forms  a  foetal 
membrane  (chiefly  respiratory)  around  the  embryo, 
and  in  most  Mammals  forms  part  of  the  placenta 
which  effects  nutritive  connection  between  offspring 
and  mother. 

Substitution  of  Organs. — The  idea  of  several 
changes  of  function  in  the  evolution  of  an  organ, 
suggests  another  of  not  less  importance  which  has 
been  emphasised  by  Eleinenberg.  An  illustration 
will  explain  it.  In  the  early  stages  of  all  vertebrate 
embryos,  the  supporting  axial  skeleton  is  the  noto- 


342    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

chord, — a  rod  developed  along  the  dorsal  wall  of  the 
gut.  From  Fishes  onwards,  this  embryonic  axis  is 
gradually  replaced  in  development  by  the  vertebral 
column  or  backbone;  the  notochord  does  not  become 
the  backbone,  but  is  replaced  by  it.  It  is  a  tem- 
porary structure,  around  which  the  vertebral  column 
is  constructed,  as  a  tall  chimney  may  be  built  around 
an  internal  scaffolding  of  wood.  Yet,  it  remains 
as  the  sole  axial  skeleton  in  Amphioxus,  likewise-  in 
great  part  in  hag  and  lamprey,  but  becomes  less  and 
less  persistent  in  Fishes  and  higher  vertebrates,  as 
its  substitute,  the  backbone,  develops  more  perfectly. 
Now,  what  is  the  relation  between  the  notochord  and 
its  substitute,  the  backbone,  seeing  that  the  former 
does  not  become  the  latter  ?  Kleinenberg's  suggestion 
is  that  the  notochord  supplies  the  stimulus,  the  neces- 
sary condition,  for  the  formation  of  the  backbone. 
Of  course,  we  require  to  know  more  about  the  way 
in  which  an  old-fashioned  structure  may  stimulate 
the  growth  of  its  future  substitute,  but  the  general 
idea  of  one  organ  leading  on  to  another  is  suggestive. 
It  is  consistent  with  our  general  conception  of  de- 
velopment— that  each  stage  supplies  the  necessary 
stimulus  for  the  next  step ;  it  also  helps  us  to  under- 
stand more  clearly  how  new  structures,  too  incipient 
to  be  of  use,  may  persist. 

Rudimentary  Organs. — In  many  animals  there 
are  structures  which  attain  no  complete  development, 
which  are  rudimentary  in  comparison  with  those  of 
related  forms,  and  seem  retrogressive  when  compared 
with  their  promise  in  embryonic  life.  But  it  is  neces- 
sary to  distinguish  various  kinds  of  rudimentary 
structures,  (a)  As  a  pathological  variation,  probably 
due  to  some  germinal  defect,  or  to  the  insufficient 
nutrition  of  the  embryo,  the  heart  of  a  mammal  ia 


THE  STUDY  OF  STRUCTURE.  343 

sometimes  incompletely  formed.  Other  organs  may 
be  similarly  spoilt  in  the  making.  They  illustrate 
arrested  development.  (&)  Some  animals  lose,  in 
the  course  of  their  life,  some  of  the  promiseful 
characteristics  of  their  larval  life;  thus  parasitic 
crustaceans  at  first  free-living,  and  sessile  sea-squirts 
at  first  free-swimming,  always  undergo  degenera- 
tion. The  retrogression  can  be  seen  in  each  life- 
time. But  the  little  Kiwi  of  New  Zealand,  with 
mere  apologies  for  wings,  and  many  cave  fishes  and 
cave  crustaceans  with  slight  hints  of  eyes,  illustrate 
degeneration  which  has  taken  such  a  hold  of  the 
animals  that  the  young  stages  also  are  degenerate. 
The  retrogression  cannot  be  seen  in  each  lifetime, 
evident  as  it  is  when  we  compare  these  degenerate 
forms  with  their  ancestral  ideal.  (c)  But  among 
"  rudimentary  organs "  we  also  include  structures 
somewhat  different,  e.g.,  the  gill  clefts  which  persist 
in  embryonic  reptiles,  birds,  and  mammals,  though 
they  serve  no  obvious  purpose,  or  the  embryonic 
teeth  of  whalebone  whales.  These  are  "  vestigial 
structures,"  traces  of  ancestral  history  and  intel- 
ligible on  no  other  theory.  The  gill  clefts  are  used 
for  respiration  in  all  vertebrates  below  reptiles;  the 
ancestors  of  whalebone  whales  doubtless  had  func- 
tional teeth.  In  regard  to  these  persistent  vestigial 
structures,  it  must  also  be  recognised  that  we  are  not 
warranted  in  calling  them  useless.  Though  they 
themselves  are  not  functional,  they  may  sometimes 
be,  as  Kleinenberg  suggests,  necessary  for  the  growth 
of  other  structures  which  are  useful. 

The  foundations  of  comparative  anatomy  were 
laid  by  Cuvier.  But  the  historical  lineage  shows  the 
influence  of  another  strain,  that  of  the  evolutionary 
anatomists,  like  Goethe  and  Etienne  Geoffroy  St.- 

w 


344:    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

•Eilaire.  From  these,  as  well  as  from  Cuvier,  there 
is,  through  Owen  as  a  transition-type,  an  affiliation 
with  more  modern  morphologists  like  Gegenbaur  and 
Huxley,  Lankester  and  Cope.  Starting  again  from 
Goethe  there  has  been  an  evolution  of  botanical  mor- 
phologists, through  Schleiden  to  Hofmeister,  thence 
to  De  Bary  and  Sachs,  and  onwards  to  Goebel,  Bow- 
er, Campbell,  and  others.  'But  the  development  of 
general  ideas  of  homology,  differentiation,  integra- 
tion, substitution  of  organs,  and  the  like  has  not  been 
less  important. 

THE  APPRECIATION  OF  FOSSILS. 

When  natural  science  was  young,  fossils  had  been 
regarded  as  "  sports  of  nature  "  of  a  mineral  sort, 
as  still-born  expressions  of  the  earth's  maternal  vir- 
tue, as  victims  of  the  Noachian  flood,  and  so  on. 
The  artist  and  thinker  Leonardo  da  Vinci  (born 
1452)  did  indeed  maintain  that  fossils  were  what 
they  seemed  to  be — remains  of  animals  that  had  once 
lived;  Bernard  Palissy  (1580)  a  century  later,  was 
of  the  same  opinion;  and  Steno,  a  Danish  professor 
in  Padua,  was  equally  shrewd.  Thus,  through  Mar- 
tin Lister,  contemporary  with  Ray,  we  reach  the 
beginning  of  the  nineteenth  century  when  the  foun- 
dations of  paleontology  were  laid  by  Smith,  Cuvier, 
Lamarck,  and  Brongniart.  The  word  palaeontology, 
like  the  idea  which  it  expresses,  is  quite  modern. 
Ducrotay  de  Blainville  and  Fischer  von  Waldheim 
seem  to  have  been  responsible  for  the  term  (about 
1830),  and  it  soon  afterwards  became  a  household 
word  in  science. 

But  although  Smith,  Cuvier,  Lamarck,  and  Alex. 
Brongniart  laid  the  foundations  and  made  it  impos- 


THE  STUDY  OF  STRUCTURE.  345 

sible  to  ignore  the  value  of  fossils  as  indices  of  the 
geological  age  and  succession  of  strata,  it  was  not  till 
long  afterwards  that  it  became  a  general  common- 
place that  palaeontology  was  part  of  zoology  and  bot- 
any. To  Huxley  in  particular  we  are  indebted  for 
the  conviction  that  the  study  of  an  animal  living  to- 
day and  of  one  living  a  million  years  ago,  differ  only 
as  regards  the  method  of  preservation  and  exami- 
nation. 

As  one  of  the  most  illustrious  of  British  palaeonto- 
logists— Dr.  E.  H.  Traquair — has  said :  *  "  PalaBon- 
tology,  however  valuable,  nay,  indispensable,  its  bear- 
ings on  Geology  may  be,  is  in  its  own  essence  a  part 
of  Biology,  and  its  facts  and  its  teachings  must  not 
be  overlooked  by  those  who  would  pursue  the  study 
of  Organic  Morphology  on  a  truly  comprehensive 
and  scientific  basis.  .  .  .  Does  an  animal  cease  to  be 
an  animal  because  it  is  preserved  in  stone  instead  of 
spirits  ?  Is  a  skeleton  any  the  less  a  skeleton  because 
it  has  been  excavated  from  the  rock,  instead  of  pre- 
pared in  a  macerating  trough  ?  .  .  .  Do  animals,  be- 
cause they  have  been  extinct  for  it  may  be  millions 
of  years,  thereby  give  up  their  place  in  the  great 
chain  of  organic  being,  or  do  they  cease  to  be  of  any 
importance  to  the  evolutionist  because  their  soft  tis- 
sues, now  no  longer  existing,  cannot  be  imbedded  in 
paraffine  and  cut  with  a  Cambridge  microtome  ?  " 

That  Palaeontology  is  Biology  and  that  Biology 
includes  Palaeontology  is  now  admitted  by  all  (as  a 
theoretical  proposition  at  least),  but  the  recognition 
has  been  an  important  result  of  nineteenth-century 
work.  The  only  hindrance  to  the  practical  recogni- 
tion of  the  unity  is  that  the  correct  interpretation 

*  Address  Zoological  Section,  Rep.  Brit.  Ass.,  Bradford, 
1900. 


346    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

of  fossil  remains  often  demands,  e.g.,  in  the  case  of 
fishes,  a  prolonged  special  training.  "  The  nature 
of  the  remains  with  which  the  palaeontologist  has 
to  deal  renders  their  interpretation  a  task  of  so 
different  a  character  from  that  allotted  to  the  in- 
vestigation of  the  structure  and  development  of 
recent  forms  "  *  that  the  necessary  division  of  labour 
tends  to  be  exaggerated.  Of  the  founders  of  pale- 
ontology three  were  on  the  whole  biological, — Cuvier 
(Tertiary  mammals),  Lamarck  (Molluscs),  and 
Brongniart  (Plants),  while  William  Smith  was 
mainly  interested  in  the  relation  of  the  fossils  to 
stratigraphical  problems. 

The  palseontological  work  of  the  nineteenth  century 
has  been  marked  by  several  different  kinds  of  achieve- 
ments:— the  compilation  of  a  descriptive  census  of 
the  extinct,  the  anatomical  study  of  lost  races, 
i.e.,  of  those  with  no  living  representatives,  nor,  so 
far  as  we  know,  direct  descendants,  the  discovery  of 
missing  links,  and  the  working  out  of  pedigree-lines 
in  particular  groups. 

Study  of  Lost  Races. — In  studying  fossils  a  dis- 
tinction must  be  drawn  between  (a)  those  which 
are  in  no  sense  extinct,  being  represented  to-day  by 
living  forms,  e.g.,  Lingula,  EstJieria,  Ceratodus,  (&) 
those  which,  though  forming  extinct  species,  are 
represented  to-day  by  living  descendants,  as  is  true 
of  a  very  large  number,  and  (c)  those  which  are 
without  known  living  descendants,  which  we  must 
therefore  call  extinct  types  or  lost  races,  e.g.,  Grap- 
tolites  and  Trilobites,  Eurypterids  and  Pterodactyls. 
It  is  indeed  a  distinction  of  degrees,  and  more  de- 
grees might  be  recognised,  but  it  is  plain  that  the 

*Traquair,  loc.  cit. 


THE  STUDY  OF  STRUCTURE.  34:7 

student  of  the  wholly  extinct  Graptolites  has  no  clue 
such  as  he  has  who  studies  fossil  corals.  Yet  the 
study  of  these  lost  races  is  of  profound  interest,  since 
they  must  be  fitted  into  their  appropriate  place  in 
the  general  scheme  of  zoological  or  botanical  classi- 
fication. 

The  famous  French  palaeontologist,  Albert  Gaudry, 
has  spoken  thus  of  the  extinction  of  races :  "  A  host 
of  creatures  have  vanished;  the  most  powerful,  the 
most  fertile  have  not  been  spared.  There  is  a  sad- 
ness in  the  spectacle  of  so  many  inexplicable  losses." 
Let  us  linger  for  a  little  over  the  fact — the  details 
of  which  have  been  accumulated  with  consummate 
patience  through  the  past  century. 

It  seems  clear  from  the  rock-record  that  sudden 
disappearance  has  been  very  rare.  The  American 
bison's  practical  extermination  in  a  few  years  is 
without  parallel  in  pre-human  days.  Races  waned 
and  died  out,  but  were  not  suddenly  extinguished. 
They  did  not  come  to  a  catastrophic  end.  Another 
striking  fact  is  that  while  evidences  of  senility  have 
been  detected  in  some  of  the  last  representatives  of 
dwindling  races,  there  are  many  cases  where  a  full 
stop  seems  to  have  been  put  to  the  history  of  a  stock 
while  it  was  still  in  its  prime.  !N"or  is  there  any 
reason  to  speak  of  an  elimination  of  weaklings;  as 
Gaudry  says :  "  While  insignificant  creatures  per- 
sist, the  princes  of  the  animal  world  vanish — with- 
out return." 

The  problem  of  the  causes  which  led  to  the  extinc- 
tion of  races  has  been  left  by  the  nineteenth  century 
unsolved.  It  is  easy  enough  to  refer  to  changes  of 
environment  for  which  the  plasticity  of  the  organism 
was  insufficient,  or  to  the  struggle  for  existence  be- 
tween cuttlefishes  and  trilobites,  between  ichthyo- 


348    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

saurians  and  cuttlefishes,  or  to  constitutional  defects, 
such  as  Lucretius  thought  of  when  he  pictured  races 
going  down  to  destruction  "  hampered  all  in  their 
own  death-bringing  shackles,"  or  to  other  more  or 
less  plausible  reasons,  but  the  suggestions  remain  very 
vague  and  unsatisfactory. 

Against  the  puzzling  facts  of  extinction,  we  have 
to  place  the  grander  fact  that,  in  spite  of  all,  life 
has  been  slowly  creeping  upwards.  We  may  quote 
a  paragraph — freely  translated  from  Gaudry's  En- 
cJiainements  du  Monde  animal  dans  les  temps  geo- 
logiques  (1878-1896). 


"The  organic  world  taken  as  a  whole  has  made 
progress.  Suppose  a  voyager  on  the  oceans  of  ages;  in 
the  Cambrian  times  his  barque  meets  trilobites,  but  no 
fishes;  he  nears  the  shore  and  there  is  the  silence  of 
death.  After  long  voyaging  he  finds  himself  at  the  end 
of  the  primary  era,  fishes  have  replaced  trilobites,  and 
on  land  there  is  no  longer  silence:  there  is  the  tramp 
and  cry  of  reptiles  who  prophesy  the  advent  of  warm- 
blooded vertebrates.  The  traveller  sails  from  age  to 
age  and  reaches  the  middle  of  the  secondary  era. 
Charmingly  beautiful  ammonites  play  around  his 
vessel,  legions  of  belemnites  mingle  with  them;  ichthy- 
osaurs,  plesiosaurs,  and  teleosaurs  follow  his  track.  He 
goes  ashore,  and  the  giant  dinosaurs  resting  on  their 
tails  open  their  huge  arms;  pterodactyls  and  other 
dragons  swoop  aloft;  the  first  bird  tries  its  wings,  and 
some  small  mammals  show  face  timidly.  Nature,  mar- 
vellous in  the  primary  ages,  has  become  yet  more  mar- 
vellous; it  has  made  progress.  If  our  traveller  be  not 
fatigued  with  his  long  wanderings,  he  will  find  in  the 
Tertiary  ages  the  first  monkeys,  and  horses,  and  a  thou- 
sand other  mammals.  Later  on  he  will  find  himself — 
the  man — artist  and  poet — minister  and  interpreter  of 


THE  STUDY  OF  STRUCTURE.  349 

nature — the  man  who  thinks  and  prays.  Truly  the 
history  of  the  world  as  a  whole  is  the  history  of  a 
progressive  development.  Where  will  this  development 
lead  us?" 


Discovery  of  Missing  Links. — In  trying  to  re- 
construct the  pedigree  of  a  race  reliance  is  placed 
on  three  sets  of  facts, — (a)  the  grades  of  structure 
exhibited  among  the  living  representatives,  (6)  the 
steps  in  individual  development,  and  (c)  the  evidence 
of  the  race's  history  as  found  in  the  fossils  of  succes- 
sive ages.  The  third  method  is  the  most  direct,  and 
if  the  rock-record  were  complete,  the  facts  of  the  his- 
tory of  life  would  be  clear. 

The  fossil-containing  rocks  have  often  been  com- 
pared to  a  library,  with  the  oldest  books  on  the  lowest 
shelves,  but  what  a  library !  Spoilt  by  fire,  by  water, 
by  earthquake,  by  decay ;  here  half  a  shelf  a-wanting 
and  there  a  series  of  volumes  with  most  disappointing 
gaps ;  pages  out  of  books,  words  missing  in  sentences, 
and  the  vowels  a-wanting  like  the  points  in  Hebrew. 
One  is  troubled  also  by  palimpsests,  one  record  on 
the  top  of  another. 

It  is  important  to  realise  this  from  the  study  of 
strata,  since  there  are  still  ill-natured  people  who 
suggest  that  evolutionists  simply  take  refuge  in  "  the 
imperfection  of  the  geological  record,"  when  they 
are  getting  the  worst  of  an  argument.  The  im- 
perfection is  a  lamentable  fact,  and  we  cannot  won- 
der at  it  when  we  remember  how  young  man  is — his 
whole  history  but  a  tick  of  the  geological  clock; 
when  we  notice  that  many  areas  are  still  unexplored, 
and  that  much  ground — being  covered  by  sea — must 
remain  unknown ;  when  we  understand  that  only  hard 
organisms  or  hard  parts  are  likely  to  be  preserved, 


350    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

that  only  certain  rocks  are  suitable  for  preserving 
their  enclosures,  and  that  many  rocks  have  been  un- 
made and  remade  in  the  course  of  ages.  As  we  walk 
along  the  shore  and  study  the  jetsam,  we  see  how 
quickly  many  of  the  sea's  memoranda  are  lost. 

On  the  other  hand,  we  must  not  exaggerate  the 
imperfection;  indeed,  the  biologist  has  often  much 
reason  to  be  gratefully  surprised  at  the  reverse. 
Many  fossil  jelly-fishes — most  unlikely  subjects  of 
preservation — are  known,  and  have  been  carefully 
studied,  e.g.,  by  Haeckel  and  by  Walcott.  Some- 
times a  whole  series  can  be  followed,  and  the  transi- 
tions from  species  to  species  studied,  as  in  the  case 
of  fresh-water  beds  containing  shells  of  Paludina  and 
Planorbis.  On  a  larger  scale,  Hyatt's  tracking  of 
the  evolutionary  paths  of  the  Ammonites  is  a  monu- 
mental piece  of  work.  In  some  cases,  even  in  Grap- 
tolites,  a  little  palseontological  embryology,  or  study 
of  young  forms  at  least,  is  possible.  Half  a  dozen 
unborn  young  may  be  seen  inside  an  ichthyosaurus 
in  the  museum  at  Stuttgart  and  the  remains  of 
belemnites  may  be  counted  in  the  stomach.  Some- 
times in  a  fossil  fish  there  is  not  a  bone  a-missing  or 
out  of  place,  though  very  much  the  reverse  is  the 
rule. 

It  is  difficult  to  have  much  satisfaction  in  the 
fragmentary  remains  (skull-cap,  femur,  and  two 
teeth)  of  Pithecanthropus  erectus  found  by  Dubois 
(1894)  in  what  were  regarded  as  Upper  Pliocene  de- 
posits in  Java.  The  remains  may  be  those  of  a 
transitional  form  between  man  and  his  unknown 
simian  ancestors,  but  the  evidence  is  by  no  means 
sufficient.  But,  in  other  cases,  the  preservation  is 
so  perfect  that  certain  conclusions  may  be  arrived 
at.  The  skeleton  of  Phenacodus,  carefully  studied 


THE  STUDY  OF  STRUCTURE.  351 

by  Cope  and  Osborn,  is  certainly  that  of  an  old- 
fashioned  Ungulate,  with  some  affinities  to  other 
stocks,  and  perhaps  one  of  the  earliest  ancestors  of 
the  horse.  The  skeleton  of  Archceopteryx,  in  the 
lithographic  slates  of  Solenhofen,  carefully  studied 
by  Dames  and  others,  is  certainly  that  of  a  bird  with 
more  distinctly  reptilian  affinities  than  any  living 
form  shows.  The  skeleton  of  Palceospondylus,  from 
the  Devonian  of  Caithness,  discovered  and  described 
by  Traquair,  is  certainly  that  of  a  tiny  primitive 
vertebrate,  whose  real  reconstruction  from  many  spec- 
imens has  been  a  triumph  of  palaeontological  skill. 
And  thus  we  might  continue,  for  nineteenth-century 
palaeontology  has  made  it  abundantly  clear  that  links 
are  not  always  missing.  It  would  be  absurdly  pessi- 
mistic to  suppose  that  there  are  not  many  still  await- 
ing discovery. 

Evolutionary  Palaeontology. — The  doctrines  of 
the  Cuvierian  school  dominated  most  of  the  palae- 
ontological  work  of  the  first  half  of  the  nineteenth 
century.  The  work  of  Owen,  Louis  Agassiz,  and 
Bronn  was  in  some  respects  transitional,  for  though 
none  was  a  thorough-going  evolutionist,  they  all  had 
an  idea  of  progressive  development.  The  dawn  of 
evolutionary  palaeontology  practically  dates  from 
Darwin's  Origin  of  Species  (1859),  and  now  it  may 
be  said  that  almost  all  palaeontologists  are  keen  evo- 
lutionists. 

Von  Zittel  says : — "  To  determine  the  genetic  re- 
lationships, the  ancestry,  the  modification,  and  the 
further  development,  in  short  the  race-history  or 
phylogeny,  of  the  organisms  under  consideration  is 
now  regarded  as  the  essential,  by  many,  indeed,  as 
the  chief  aim  of  palaeontology." 

Traquair  says : — "  From  the  nature  of  things  it 


352    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

is  clear  that  the  voice  of  the  palaeontologist  can  only 
be  heard  on  the  morphological  aspect  of  the  question 
(factors  of  evolution),  but  to  many  of  us,  including 
myself,  the  morphological  argument  is  so  convincing 
that  we  believe  that  even  if  the  Darwinian  theory 
were  proved  to-morrow  to  be  utterly  baseless,  the 
Doctrine  of  Descent  would  not  be  in  the  slightest 
degree  affected,  but  would  continue  to  have  as  firm 
a  hold  on  our  minds  as  before."  Thus  he  took  for 
the  theme  of  his  Presidential  Address  to  the  zoo- 
logical section  of  the  British  Association  in  1900, 
the  palseontological  evidence  of  Descent  in  the  case 
of  fishes. 

Marsh  said : — "  This  revolution  has  influenced 
pala3ontology  as  extensively  as  any  other  department 
of  science,  and  hence  the  new  period.  .  .  .  To- 
day, the  animals  and  plants  now  living  are  believed 
to  be  genetically  connected  with  those  of  the  distant 
past ;  and  the  palaeontologist  no  longer  deems  species 
of  the  first  importance,  but  seeks  for  relationships 
and  genealogies  connecting  the  past  with  the  pres- 
ent." 

The  appreciation  of  the  true  nature  of  fossils,  the 
recognition  of  palceontology  as  biological,  the  com- 
pilation of  great  censuses  of  the  extinct,  the  study  of 
lost  races,  the  discovery  of  missing  links,  and  the 
adoption  of  the  evolutionary  outlook  in  palceontology, 
are  among  the  great  steps  in  the  morphological  prog- 
ress of  the  nineteenth  century. 

MINUTE  ANALYSIS. 

One  of  the  clearest  illustrations  of  tKe  influence 
of  improvements  in  instruments  on  the  progress  of 


THE  STUDY  OF  STRUCTURE.  353 

theoretical  science  is  that  afforded  by  the  results 
which  have  come  to  biology  through  the  perfection  of 
the  microscope.  In  no  case  has  an  instrument  con- 
tributed more  to  the  deepening  of  a  science. 

It  is  hardly  necessary  to  point  out  that  the  magni- 
fication of  an  object  does  not  necessarily  mean  a 
better  understanding  of  it,  and  it  must  be  admitted 
that  there  are  many  results  of  microscopic  analysis 
which  have  complexified  problems  without  helping 
towards  their  solution;  but  the  historical  fact  is 
certain  that  microscopic  analysis  has  made  many 
biological  problems  clearer,  and  has  saved  us  from 
supposing  that  the  apparent  simplicity  of  others  is 
real. 

Invention  of  the  Compound  Microscope. — As  dis- 
tinguished from  a  mere  magnifying  lens,  the  mi- 
croscope is  about  three  centuries  old.  There  is  strong 
evidence  that  the  compound  microscope  was  invented 
by  Galilei  about  1610,  but  there  is  also  evidence  in 
favour  of  giving  credit  to  Hans  and  Zacharias  Jans- 
sen,  spectacle-makers  of  Middelburg  in  Holland,  who 
are  said  to  have  made  a  compound  microscope  some- 
time between  1590  and  1609.  Huyghens  and  others 
have  claimed  the  discovery  for  Cornelius  Drebbel,  a 
Dutchman,  about  the  year  1621,  and  Fontana,  a  Nea- 
politan, claimed  that  he  had  made  a  compound  micro- 
scope in  1618.  The  case  for  Galilei  seems,  on  the 
whole,  strongest;  but  it  is  probably  impossible  now 
to  decide  with  certainty.* 

Early  Microscopists. — Although  many  of  those 
who  first  used  the  microscope  did  little  more  than 
accumulate  magnifications,  we  must  look  back  grate- 

*  See  May  all,   Lectures  on  the  Microscope,    London,   1886. 
The  Microscope,  Carpenter  and  Dallinger,  London,  1891. 


354    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

fully  to  the  pioneers  who  began  the  minute  analysis 
so  characteristic  of  the  nineteenth  century.  Keen 
sighted  observers  like  Leeuwenhoek,  Malpighi, 
Hooke,  and  Grew,  in  the  second  half  of  the  seven- 
teenth century  were  the  forerunners  of  modern  his- 
tology. When  Leeuwenhoek  demonstrated  unicel- 
lular organisms  to  the  then  young  Eoyal  Society  of 
London,  whose  members  (present  at  the  meeting) 
signed  an  affidavit  that  they  had  really  seen  the 
minute  creatures  in  question,  a  vista  was  opened 
which  is  still  widening  before  us  after  the  lapse  of 
more  than  two  centuries. 

Steps  towards  the  Cell-Doctrine. — The  word 
"cell"  (an  unfortunate  one  at  the  best)  was  first 
used  in  histological  description  by  Hooke  (1665) 
and  Grew  (1671-75),  but  not  in  a  very  accurate  or 
definite  way.  Malpighi  (1675)  also  described  mi- 
nute "  utricles,"  some  of  which  we  should  now  call 
cells. 

Leeuwenhoek  (Phil.  Trans.  1674)  seems,  as  we 
have  noted  above,  to  have  been  the  first  to  describe 
single-celled  organisms.  But  the  hint  was  not 
quickly  followed,  for  it  was  not  till  1755  that  Rosel 
von  Rosenhof  described  the  Amoeba  or  "  Proteus 
animalcule." 

In  his  Theoria  Generationis  (1759)  Caspar 
Friedrich  Wolff  recognised  the  "  spheres "  and 
"  vesicles "  composing  the  embryos  of  plants  and 
animals.  But  he  did  not  discern  their  nature  or 
their  importance. 

In  1784,  Fontana  discovered  the  kernel  or  nucleus 
of  the  cell  which  we  now  know  to  be  essential  to 
the  vitality  of  any  ordinary  protoplasmic  unit. 
But  he  did  not  know  the  importance  of  his  discovery, 


THE  STUDY  OF  STRUCTURE.  355 

and  had  not  the  least  idea  that  the  little  spot  he  ob- 
served was  a  most  intricate  structure. 

The  fact  that  Bichat,  in  his  Anatomie  Generale 
(1801),  speaks  only  of  tissues,  shows  that  the  import 
of  cells  was  not  realised  at  the  beginning  of  the 
nineteenth  century.  Little  importance  can  be  at- 
tached to  the  "  vesicles  "  and  "  TJrschleim  "  which 
Oken  discussed  in  1805,  for  this  illustrious  repre- 
sentative of  the  "  !N"aturphilosophie "  did  not  con- 
cern himself  much  with  concrete  details.  The  obser- 
vations of  Mirbel  on  the  structure  of  embryos  had 
more  objective  worth. 

"  A  still  closer  approximation  to  the  truth  is  found 
in  the  works  of  Turpin  (1826),  Meyen  (1830),  Eas- 
pail  (1831),  and  Dutrochet  (1837)  ;  but  these,  like 
others  of  the  same  period,  only  paved  the  way  for  the 
real  founders  of  the  cell-theory."  * 

In  the  first  volume  of  his  epoch-making  work  on 
the  development  of  animals  (1828),  Karl  Ernst  von 
Baer  "  made  the  following  prophetic  statement  " : — 
"  Perhaps  all  animals  are  alike,  and  nothing  but 
hollow  globes  at  their  earliest  developmental  begin- 
ning. The  farther  back  we  trace  their  development, 
the  more  resemblance  we  find  in  the  most  different 
creatures.  And  thus  to  the  question  whether  at  the 
beginning  of  their  development  all  animals  are  alike, 
and  referable  to  one  common  ancestral  form,  con- 
sidering that  the  germ  (which  at  a  certain  stage 
appears  in  the  shape  of  a  hollow  globe  or  bag)  is  the 
undeveloped  animal  itself,  we  are  not  without  reason 
for  assuming  that  the  common  fundamental  form  is 


*  Prof.  E.  B.  Wilson,  The  Cell  in  Development  and  Inher- 
itance, 2ded.,  1900,  p.  2. 


356    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

that  of  a  simple  vesicle,  from  which  every  animal  is 
evolved,  not  only  theoretically,  but  historically."  * 
Considering  the  date  we  cannot  regard  the  statement 
as  other  than  a  marvellous  premonition. 

In  1835,  Robert  Brown  showed  that  a  nucleus  was 
normally  present  in  all  vegetable  cells,  thus  raising 
Montana's  discovery  to  a  higher  level  of  importance. 
And,  in  the  same  year,  Johannes  Miiller  made  a 
definite  comparison  between  the  cells  of  plants  and 
those  of  the  notochord  in  animals, — the  beginning  of 
a  recognition  of  the  fundamental  unity  of  vegetable 
and  animal  structure.  The  observations  of  Du jar- 
din,  Purkinje,  Von  Mohl,  Valentin,  linger,  ISTageli, 
Hofmeister,  Henle,  and  many  others  might  also  be 
alluded  to. 

This  is  no  complete  history,  but  we  have  cited 
enough  to  show  how  very  gradually  the  way  was 
prepared  for  the  formulation  of  the  cell-doctrine 
by  Schwann  and  Schleiden  in  1838-39. f  "The 
"  significance  of  Schleiden's,  and  especially  of 
"  Schwann's,  work  lies  in  the  thorough  and  compre- 
"  hensive  way  in  which  the  problem  was  studied, 
"  the  philosophic  breadth  with  which  the  conclusions 
"  were  developed,  and  the  far-reaching  influence 
"  which  they  exercised  upon  subsequent  research." 
In  this  respect  it  is  hardly  too  much  to  compare  the 
Mikroskopische  Untersuchungen  with  the  Origin  of 
Species. 

*  Cited  from  Dr.  Hans  Gadow's  notes  to  Haeckel's  Last  LinJe, 
1898. 

f  Sir  William  Turner,  "  The  Cell  Theory,  Past  and 
Present,"  Inaug.  Address  Scottish  Microsc.  Soc.,  1890,  and 
in  Nature,  1890  ;  Prof.  J.  G.  McKendrick,  "  On  the  Modern 
Cell  Theory  "  (Proc.  Phil.  Soc.,  Glasgow,  1888),  and  in  his 
text-book  of  Physiology  ;  P.  Geddes,  articles  HorpJwlogy  and 
Protoplasm,  Encyclopaedia  Britannica. 


THE  STUDY  OF  STRUCTURE.  357 

The  cell-doctrine  has  been  already  stated;  in 
its  morphological  aspect  it  emphasises  the  funda- 
mental unity  of  minute  structure  in  all  living  crea- 
tures. The  simplest  organisms  are  single  cells.  All 
other  organisms  are  built  up  of  many  cells  or  modi- 
fications of  cells.  Among  themselves  they  show  di- 
vision of  labour  which  is  expressed  in  the  great  va- 
riety of  form  and  structural  detail.  From  the  fertil- 
ised ovum  onwards,  the  formation  and  growth  of  the 
body  is  due  to  cell-division.  This  occurs  in  various 
fashions,  but  especially  in  one  complex  (indirect  or 
karyokinetic)  fashion  which  shows  a  fundamental 
similarity  throughout  the  entire  series. 

Corroborations  of  the  analysis  into  cells  were 
rapidly  forthcoming.  As  early  as  1824,  Prevost  and 
Dumas  had  studied  the  cleavage  of  the  fertilised 
ovum,  and  it  may  be  noted  that  some  stages  of  this 
can  be  seen  with  the  naked  eye  in  the  relatively  large 
egg  of  the  frog,  which  measures  about  one-tenth  inch 
in  diameter.  Similarly,  Martin  Barry  (1838- 
41),  Reichert  (1840),  Henle  (1841),  Kolliker 
(1843^6),  and  Eemak  (1841-52)  showed  how  the 
cells  of  the  embryo  arise  from  the  division  of  the 
fertilised  egg  cell. 

Moreover,  Goodsir  in  1845,  Virchow  in  1858, 
proved  that  in  all  cases,  pathological  as  well  as  nor- 
mal, cells  arise  from  pre-existing  cells,  that  omnis 
cellula  e  cellula  is  a  general  fact  of  histology. 

There  was  a  strong  tendency,  however,  to  attach 
too  much  importance  to  the  cell  wall,  and  too  little 
to  the  contained  cell  substance.  The  all-important 
protoplasm  was  not  adequately  appreciated. 

In  1835,  Dujardin  described  the  "  sarcode "  of 
Protozoa,  and  other  animal  cells ;  in  1839,  Purkinje 
compared  the  substance  of  the  animal  embryo  (which 


358    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

he  was  the  first  to  call  "  protoplasm ")  with  the 
"  cambium  "  of  plant  cells ;  in  1846  Von  Mohl  em- 
phasised the  importance  of  the  "  protoplasm  "  in  veg- 
etable cells;  Ecker  (1849)  compared  the  contractile 
substances  of  muscles  with  the  living  matter  of 
Amoebae ;  Bonders  also  referred  the  contractility  from 
the  wall  to  the  contents;  Cohn  suspected  that  the 
"  sarcode "  of  animals  and  the  "  protoplasm "  of 
plants  must  be  "  in  the  highest  degree  analogous  sub- 
stances"; and  finally,  Max  Schultze  (1861)  ac- 
cepted the  growing  belief  that  plants  and  animals 
were  made  of  very  similar  living  matter,  and  defined 
the  cell  as  a  unit  mass  of  nucleated  protoplasm.* 

"The  full  physiological  significance  of  protoplasm, 
its  identity  with  the  '  sarcode '  of  the  unicellular  forms, 
and  its  essential  similarity  in  plants  and  animals,  was 
first  clearly  placed  in  evidence  through  the  classical 
works  of  Max  Schultze  and  De  Bary,  beside  which 
should  be  placed  the  earlier  works  of  Dujardin,  TJnger, 
Nageli,  and  Mohl,  and  that  of  Cohn,  Huxley,  Virchow, 
Leydig,  Briicke,  Kiihne,  and  Beale."  f 

Louis  Agassiz,  not  being  an  evolutionist,  spoke  of 
the  cell-doctrine  as  "  the  greatest  discovery  in  the 
natural  sciences  in  modern  times  " ;  and,  apart  from 
the  idea  of  evolution,  it  may  be  called  the  most  in- 
fluential. For  it  is  important  to  notice  that  it  has 
not  only  affected  the  analysis  of  the  anatomist  and 
the  physiologist,  and  the  whole  of  embryology,  but 
has  entirely  changed  our  position  in  regard  to  some 

*  See  the  writer's  Outlines  of  Zoology,  Introduction. 
t  E.  B.  Wilson,  The  Cell  in  Development  and  Inheritance,  p.  5. 


THE  STUDY  OF  STRUCTURE.  359 

of  the  general  problems  of  biology,  notably  in  regard 
to  heredity  and  inheritance. 

The  student  who  wishes  to  understand  the  position 
of  cellular  biology  at  the  beginning  of  the  twentieth 
century  should  read  a  luminous  book  by  Prof.  E. 
B.  Wilson  (The  Cell  in  Development  and  Inherit- 
ance, 2nd  ed.,  1900),  along  with  which  we  may  cite 
Delage's  La  structure  du  protoplasma  et  les  theories 
sur  I'heredite  et  les  grands  problemes  de  la  biologic 
generale  (1895).  From  Wilson's  work,  we  venture 
to  quote  the  first  paragraph : — 

"  During  the  half-century  that  has  elapsed  since  the 
enunciation  of  the  cell-theory  by  Schleiden  and 
Schwann,  in  1838-39,  it  has  become  ever  more  clearly 
apparent  that  the  key  to  all  ultimate  biological  prob- 
lems must,  in  the  last  analysis,  be  sought  in  the  cell. 
It  was  the  cell-theory  that  first  brought  the  structure 
of  plants  and  animals  under  one  point  of  view,  by  re- 
vealing their  common  plan  of  organisation.  It  was 
through  the  cell-theory  that  Kolliker,  Remak,  Nageli, 
and  Hofmeister  opened  the  way  to  an  understanding  of 
the  nature  of  embryological  development,  and  the  law 
of  genetic  continuity  lying  at  the  basis  of  inheritance. 
It  was  the  cell-theory  again  which,  in  the  hands  of 
Goodsir,  Virchow,  and  Max  Schultze,  inaugurated  a 
new  era  in  the  history  of  physiology  and  pathology,  by 
showing  that  all  the  various  functions  of  the  body,  in 
health  and  in  disease,  are  but  the  outward  expression 
of  cell-activities.  And  at  a  still  later  day  it  was 
through  the  cell-theory  that  Hertwig,  Fol,  Van  Bene- 
den,  and  Strasburger  solved  the  long-standing  riddle 
of  the  fertilisation  of  the  egg  and  the  mechanism  of 
hereditary  transmission.  No  other  biological  general- 
isation, save  only  the  theory  of  organic  evolution,  has 
brought  so  many  apparently  diverse  phenomena  under  a 
common  point  of  view  or  lias  accomplished  more  for  the 
unification  of  knowledge.  The  cell-theory  must  there- 


360    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

fore  be  placed  beside  the  evolution-theory  as  one  of  the 
foundation-stones  of  modern  biology." 


The  progress  of  cellular  biology  or  cytology  since 
the  formulation  of  the  cell-doctrine  has  been  along 
several  different  lines,  connected  of  course  by  side 
branches. 

(a)  The  complexity  of  cell-structure  has  become 
more  and  more  apparent.  It  includes  many  com- 
ponents,— the  general  cell-substance  or  cytoplasm, 
the  nucleus  with  its  readily  stainable  "  chromatin  " 
and  illusive  unstainable  "  achromatin,"  the  centro- 
somes  (present  in  the  majority  of  animal-cells) 
which  play  an  important  part  in  division,  the  cell- 
wall  or  the  cell-margin  which  shows  many  degrees 
of  differentiation,  the  intercellular  bridges  which  in 
many  cases  bind  one  cell  to  another,  and  so  on.  The 
cell  is  a  little  world  of  extraordinary  complexity,  as 
the  work  of  Auerbach,  Biitschli,  Carnoy,  Memming, 
Fol,  Guignard,  Hertwig,  Strasburger,  Van  Beneden, 
and  a  score  of  other  prominent  workers  has  shown. 

(&)  The  same  impression  of  a  progressive  reve- 
lation of  complexity  is  afforded  if  we  consider  any 
particular  component  of  the  cell,  such  as  the  nucleus, 
or  the  system  of  radiating  filaments  which  form  a 
halo  round  the  centrosome,  or  the  structure  of  a 
vibratile  lash  or  cilium,  or  the  general  cell-substance. 
In  regard  to  the  last,  some,  like  Frommann  and  Ar- 
nold, have  described  an  intricate  network;  others, 
like  Flemming,  a  tangled  coil  of  fibrils ;  others,  like 
Altmann,  a  crowd  of  granules  in  a  gelatinous  ma- 
trix; and  others,  like  Biitschli,  a  fine  alveolar  or 
vacuolar  appearance  like  that  of  an  emulsion.  It 
seems  probable  that  the  minute  structure  of  cell-sub- 


THE  STUDY  OF  STRUCTURE.  361 

stance  varies  in  different  cells  and  even  at  different 
times  within  the  same  cells.  The  investigations  of 
Biitschli,  who  has  studied  the  structure  of  fine  arti- 
ficial emulsions  and  compared  this  with  that  of  cells 
both  fixed  and  living,  who  has  also  investigated  the 
fine  structure  of  dead  organic  substances  like  cellu- 
lose, starch  grains,  chitinous  shells,  spicules,  etc., 
mark  at  present  the  extreme  of  microscopical  analy- 
sis. It  is  interesting  to  note  that  all  his  results 
favour  the  interpretation  that  the  complexity  is 
alveolar  or  vacuolar  like  that  of  a  very  delicate  emul- 
sion. Better  lenses,  thinner  sections,  differential 
staining,  and  other  improvements  in  technique  have 
led  to  the  disclosure  of  a  complexity  undreamt  of 
half  a  century  ago.  The  contrast  between  the  mod- 
ern analysis  of  a  spermatozoon  or  of  a  cilium  and 
that  of  even  a  quarter  of  a  century  ago  is  most 
vividly  illustrative  of  the  increased  precision.  If  any 
one  name  may  be  associated  with  the  recognition  of 
complex  cellular  organisation,  it  should  be  that  of 
Briicke,  whose  classic  work  entitled  Die  Elementar- 
organismen  was  published  in  1861.  But  even  if  we 
have  succeeded,  at  length,  in  getting  down  to  the 
ultimate  elements  of  living  matter,  or  "  idiosomes," 
in  which  some  believe  that  the  secret  of  organisation, 
growth,  and  development  lies  hidden,  we  have  to 
hand  on  the  problem  of  their  nature  to  the  twentieth 
century  still  unsolved.  "  What  these  idiosomes  are, 
and  how  they  determine  organisation,  form,  and  dif- 
ferentiation, is  the  problem  of  problems  on  which 
we  must  wait  for  more  light.  All  growth,  assimila- 
tion, reproduction,  and  regeneration  may  be  sup- 
posed to  have  their  seats  in  these  fundamental  ele- 
ments. They  make  up  all  living  matter,  are  the 


362    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

bearers  of  heredity,  and  the  real  builders  of  the  organ- 
ism." This  deliverance  is  quoted  from  an  essay  by 
Prof.  C.  O.  Whitman,  one  of  the  modern  leaders, 
but  it  will  be  observed  that  it  leaves  the  riddle  of 
organisation  unread. 

(c)  An  exceedingly  important  step  was  made 
when  it  was  made  clear  that  new  cells  arise  from  the 
division  of  pre-existing  cells, — a  step  which  may  be 
particularly  associated  with  the  names  of  Goodsir 
(1845)  and  Virchow  (1858).  Of  great  importance 
also  was  the  general  rationale  of  cell-division,  which 
seems  to  have  been  suggested  independently  by  R. 
Leuckart,  Herbert  Spencer,  and  Alexander  James; 
it  is  often  referred  to  as  the  Leuckart-Spencer  prin- 
ciple, and  is  based  on  the  fact  that  in  cell-growth  the 
increase  of  mass  or  volume  outruns  the  increase  of 
surface.  When  the  cell  has,  let  us  say,  quadrupled 
its  original  mass  by  growth,  it  has  by  no  means  quad- 
rupled its  surface  (the  former  increasing  in  spheri- 
cal cells  as  the  cube,  the  latter  as  the  square,  of  the 
radius)  ;  physiological  difficulties  set  in,  and  at  "  the 
limit  of  growth  "  the  cell  divides,  halving  its  mass, 
and  gaining  new  surface.*  But  attention  has  been 
mainly  concentrated  on  the  details  of  the  actual  proc- 
ess of  cell-division,  which  is  due,  as  Prof.  Wilson 
says,  to  "  the  co-ordinate  play  of  an  extremely  com- 
plex system  of  forces."  Its  necessity  is  clear  (on 
the  Leuckart-Spencer  principle)  as  the  only  feasible 
mode  of  growth;  its  end  is  clear — to  divide  the  es- 
sentials of  the  mother-cell  equally  between  the 
daughter-cells;  but,  in  spite  of  continuous  attempts, 
the  actual  mechanism  of  the  process  remains  obscure. 
Three  results  seem  clear: — (a)  the  fundamental 

*  See  the  writer's  The  Science  of  Life,  p.  108. 


THE  STUDY  OF  STRUCTURE.  333 

similarity  of  process  and  result  in  spite  of  many 
peculiarities  in  individual  cases,  (6)  the  occurrence 
of  complex  tensions,  strains,  and  stresses  in  the  proc- 
ess, and  (c)  the  impossibility  (at  present)  of  any 
mechanical  interpretation. 

(d)  Various  facts,  such  as  the  multiplication  of 
nuclei  in  embryos  without  corresponding  cell-delimi- 
tation, and  the  influence  that  the  growth  of  the  mass 

has  upon  the  forms  of  cell-division  which  follow, 
have  led  many  to  add  saving-clauses  to  the  cell- 
theory,  as  Sachs  did  when  he  said  "  cell-formation  is 
merely  one  of  the  numerous  expressions  of  the  for- 
mative forces  which  reside  in  all  matter,  in  the  high- 
est degree,  however,  in  organic  substance  "  ;  or  as  De 
Bary  did  when  he  said,  "  That  the  plant  forms  cella 
is  more  accurate  than  the  statement  that  cells  form 
plants."  "  Die  Pflanze  bildet  Zellen,  niclit  die  Zelle 
bildet  Pftanzen"  In  short,  the  conception  of  the  cell 
has  to  change  with  increasing  knowledge  of  its  na- 
ture and  origin;  though  it  may  be  still  defined  as  a 
protoplasmic  area  in  which  nucleoplasm  and  cyto- 
plasm are  combined  in  a  unified  life. 

(e)  Though  it  is  not  exactly  relevant  in  this  chap- 
ter, we  must  note  the  gradually  increasing  body  of 
facts  which  inform  us  as  to  the  physiological  rela- 
tions of  the  individual  cell  to  its  environment  (of 
physical  and  chemical  influences,  and  of  its  fellows). 
The   bulk   of   Davenport's   Physiological   Morphol- 
ogy is  occupied  with  a  discussion  of  this  problem. 

(f)  Finally,  the  progress  of  cytology  has  had  its 
influence  on  that  study  of  Bacteria  and  other  micro- 
organisms which  has  been  one  of  the  features  of  the 
latter  part  of  the  nineteenth  century.      The   door 
which  Leeuwenhoek  opened  in  the  seventeenth  cen- 


364    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

tury  remained  merely  ajar  till  after  the  cell-theory 
had  been  formulated.  Since  then  the  study  of  uni- 
cellular plants  and  animals  has  been  eagerly  pur- 
sued. From  Dujardin  and  Ehrenberg  to  Haeckel 
and  Biitschli  for  Protozoa, — from  Pringsheim  and 
Cohn  to  De  Bary  for  Protophytes,  there  was  a  con- 
tinuous study  of  the  simplest  forms  of  life,  and  there 
are  many  to-day  who  devote  themselves  to  this  study 
and  maintain  that  it  is  still  only  beginning.  In 
connection  with  bacteriology  the  names  of  Pasteur 
and  De  Bary,  Lister  and  Koch,  Duclaux  and  Koux, 
deserve  particular  mention. 


CHAPTEK  X. 

GENEOLOGICAI* 
GENEOLOGY. 

A  TEBM  is  needed  for  the  study  of  living  crea- 
tures in  their  time-relations,  for  the  enquiry  into 
their  individual  development,  racial  evolution,  and 
historical  aspects  generally;  and  we  have  suggested 
the  term  genealogy  (changing  a  letter  in  the  narrower 
word  genealogy).  This  "science  of  becoming" 
would  include  (a)  individual  development,  growth, 
and  life-history  (ontogeny)  ;  (6)  the  racial  history 
(phylogeny)  ;  (c)  the  relation  of  genetic  continuity 
between  successive  generations  (heredity). 

DEVELOPMENT  OF  THE  INDIVIDUAL. 

Beginnings  of  Embryology. — Embryology  is  en- 
tirely a  modern  science.  Though  Aristotle  watched 
the  heart-beats  of  the  unhatched  chick,  and  had  hold 
of  the  idea  that  development  is  a  progressive  differ- 
entiation and  not  an  unfolding  of  preformed  parts, 
he  had  practically  no  successors  before  Harvey 
(1578-1675). 

William    Harvey. — With  the  aid  of  magnifying 


366    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

glasses  (perspecillce)  Harvey  demonstrated  the 
connection  between  the  "  cicatricula "  of  the  yolk 
and  the  rudiments  of  the  chick,  and  he  also  observed 
some  of  the  stages  of  uterine  gestation  in  mammals. 
He  maintained  (1)  that  every  animal  is  produced 
from  an  ovum  (ovum  esse  primordium  commune 
omnibus  animalibus),  and  (2)  that  the  organs  arise 
by  new  formation  (epigenesis)  and  not  from  the 
mere  expansion  of  some  invisible  preformation,  or, 
in  other  words,  that  in  the  primordium  "  no  part  of 
future  organism  exists  de  facto,  but  all  parts  inhere 
in  potentia."  But  it  has  to  be  carefully  remembered 
that  he  had  no  way  of  accounting  for  the  primordium 
with  which  he  started ;  he  admitted  that  it  might  pro- 
ceed from  parents,  or  might  arise  spontaneously,  or 
out  of  putrefaction.  It  was  not  he  who  coined  the 
aphorism  "  omne  vivum  ex  ovo"  for  which  he  often 
gets  credit.  Even  if  he  had  said  it,  the  statement 
would  not  have  meant  to  him  what  it  means  to  us. 

Early  Observations. — Malpighi  (1672),  using  a 
microscope  with  remarkable  skill,  traced  back  the 
chick-embryo  into  the  recesses  of  the  cicatricula 
lying  on  the  top  of  the  yolk,  but  he  missed  a  magnifi- 
cent discovery  by  supposing  that  the  rudiments  of 
the  organs  pre-existed  in  the  egg.  Spermatozoa  were, 
it  is  generally  believed,  discovered  by  Leeuwenhoek's 
pupil,  Ludwig  Hamm,  in  1677,  though  Hartsoeker 
afterwards  claimed  priority  by  three  years : — a  ques- 
tion of  little  interest,  since  neither  understood  what 
he  saw.  In  1664,  Steno  had  given  the  ovary  its 
present  designation,  and  De  Graaf  had  interpreted 
the  vesicles  of  this  organ  ("  the  Graafian  follicles  ") 
as  for  the  most  part  equivalent  to  the  ova  which  he 
thought  he  had  discovered  in  the  oviduct. 

Theory  of  Preformation. — In  spite  of  the  begin- 


GENEOLOGICAL.  367 

nings  of  embryological  observation  in  the  seven- 
teenth century,  there  was  little  progress  for  another 
hundred  years.  For  the  eighteenth  century  embry- 
ologists,  if  so  they  may  be  called,  gave  more  atten- 
tion to  arguments  over  general  conceptions  than  to 
the  accumulation  of  facts. 

In  the  early  part  of  the  eighteenth  century,  the 
embryological  observations  of  investigators,  like 
Boerhaave  and  Malpighi,  were  summed  up  in  the 
conception  that  development  was  merely  an  expan- 
sion or  unfolding  of  a  pre-existent  or  preformed 
rudiment  within  the  egg. 

This  preformation  theory,  which  found  more  and 
more  definite  expression  in  the  works  of  Bonnet, 
Buffon,  and  others,  may  be  thus  summed  up : — * 

The  germ,  whether  egg-cell  or  seed,  was  believed 
to  be  a  miniature  model  of  the  adult.  "  Pre- 
formed "  in  all  transparency  the  organism  lay 
within  the  egg,  only  requiring  to  be  unfolded.  In 
contrast  to  Harvey's  conclusion :  "  the  first  concre- 
ment  of  the  future  body  grows,  gradually  divides, 
and  is  distinguished  into  parts;  not  all  at  once,  but 
some  produced  after  the  others,  each  emerging  in  its 
order,"  was  Haller's  first  and  last  utterance,  "  There 
is  no  becoming;  no  part  of  the  body  is  made  from 
another,  all  are  created  at  once,"  or  Bonnet's  "  fun- 
damental principle,  that  nothing  is  generated,  and 
that  what  we  call  generation  is  but  the  simple  de- 
velopment of  wEat  pre-existed  under  an  invisible 
form,  and  more  or  less  different  from  that  which 
becomes  manifest  to  our  senses." 

But  this  was  not  all.    The  germ  was  more  than  a 

*  See  Geddes  and  Thomson,   The  Evolution  of  Sex,    4th 
ed.,  1901,  p.  90. 


368    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

marvellous  bud-like  miniature  of  the  adult,  it  neces- 
sarily included  in  its  turn  the  next  generation,  and 
this  the  next — in  short  all  future  generations. 
Germ  within  germ,  in  ever  smaller  miniature,  after 
the  fashion  of  an  infinite  juggler's  box,  was  the  cor- 
ollary of  "  emboitement" — logically  appended  to  this 
theory  of  preformation  and  unfolding, — of  evolu- 
tion, as  it  was  then  called,  in  a  very  different  but 
more  literal  sense  from  that  in  which  we  now  use 
the  word. 

"  The  whole  chapter  is  a  somewhat  lamentable  one 
in  the  history  of  embryology,  and  yet  it  must  be  noted 
in  fairness  that  the  pref  ormationist  doctrine  had  a  well- 
concealed  kernel  of  truth  within  its  thick  husk  of 
error.  There  is  a  certain  sense  in  which  the  whole 
future  organism  is  potentially  and  materially  implicit 
in  the  fertilised  egg-cell ;  there  is  a  sense  in  which  the 
germ  contains  not  only  the  rudiment  of  the  adult 
organism,  but  of  successive  generations  as  well.  But 
in  neither  of  these  senses  was  preformationism  under- 
stood by  any  of  its  upholders."  * 

In  1759  Caspar  Eriedrich  Wolff  (1733-1794:) 
raised  a  strong  protest  against  the  doctrines  and 
methods  of  the  prefonnationists.  He  showed  that 
the  egg  does  not  contain  a  preformed  embryo,  but 
that  the  organs  were  to  be  seen  being  formed.  But 
his  vindication  of  "epigeneais"  against  "evolution" 
did  not  win  conviction  as  it  ought  to  have  done ; 
indeed  it  remained  for  about  sixty  years  without  ef- 
fect. 

In  1817  Christian  Pander  took  up  embryological 
research  where  Wolff  had  left  it,  and  worked  out  the 

*See  the  writer's  Science  of  Life,  1899,  p.  121. 


GENEOLOGICAL.  369 

history  of  the  chick  in  more  exact  detail.  In  1824, 
Prevost  and  Dumas  observed  the  division  of  the 
frog's  ovum  into  masses.  In  1827,  Von  Baer  ful- 
filled, after  a  century  and  a  half,  what  De  Graaf  had 
attempted,  he  discovered  the  mammalian  ovum 
and  traced  it  from  uterus  to  oviduct,  and  thence  to 
its  position  in  the  ovary  itself.  Soon  afterwards, 
Wagner,  Von  Siebold,  and  others  elucidated  what 
was  still  hidden  from  Von  Baer — the  real  nature  of 
the  spermatozoon.  Kolliker  began  to  trace  the  cells 
into  which  the  ovum  divides  to  their  results  in  the 
tissues  of  the  developing  organism.  In  short,  em- 
bryology began  to  get  a  firm  basis. 

Von  'Baer. — The  foundation  of  modern  embry- 
ology may  be  dated  from  the  work  of  Karl  Ernst  von 
Baer  ( 1792-18 76).  He  broadened  embryology  as 
Cuvier  has  broadened  anatomy,  as  Johannes  Miiller 
afterwards  broadened  physiology, — by  making  it 
comparative.  He  showed  how  the  development  of 
an  embryo  proceeded  from  the  general  to  the  spe- 
cial. He  was  the  first  to  show,  though  his  own 
illustrations  have  not  survived,  how  embryological 
facts  may  be  of  service  in  classification. 

Von  Baer  is  linked  to  Francis  Balfour  by  many 
illustrious  workers  in  embryology: — Alex.  Agassiz, 
Claus,  Gegenbaur,  Goethe,  Haeckel,  His,  Kolliker, 
Kowalevsky,  Leuckart,  Loven,  Metschnikoff,  Jo- 
hannes Miiller,  Ratke,  Remak,  Sars,  Semper,  Van 
Beneden,  and  many  others.  A  strong  stimulus  was 
given  by  Balfour's  monumental  text-book  (1880- 
1881),  and  in  the  last  twenty  years  embryology  has 
been  the  most  progressive  department  of  biology. 

The     Germ-Cells. — The    cell-theory     (1838-39) 
enunciated  the  important  fnot  that  every  mnlticellu- 
lar  organism,  if  reproduced  in  the  ordinary  way,  be- 


370    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

gins  its  life  as  a  cell ;  in  short,  that  the  egg  is  a  cell. 
Somewhat  later  (1841)  Kolliker  traced  the  spermat- 
ozoa to  their  origin  in  the  essential  male  organs  or 
testes,  and  it  was  soon  recognised  that  the  spermato- 
zoon also  is  a  cell.  We  now  know  that  both  ovum 
and  spermatozoon  may  show  a  complexity  of  minute 
organisation  which  was  not  suspected  in  the  first  half 
of  the  century,  but  this  after  all  is  a  matter  of  detail. 
The  fundamentally  important  fact,  which  differ- 
entiates modern  embryological  conceptions  from 
those  of  the  first  half  of  the  nineteenth  century  is 
the  idea  of  genetic  continuity.  This  may  be  espe- 
cially traced  to  the  work  of  Virchow  (1858),  though 
several  others  were  approaching  it  about  the  same 
time. 

"  To  the  modern  student  the  germ  is,  in  Huxley's 
words,  simply  a  detached  living  portion  of  the  sub- 
stance of  a  pre-existing  living  body  carrying  with  it  a 
definite  structural  organisation  characteristic  of  the 
species."  *  In  other  words,  an  egg  or  a  sperm  liberated 
from  or  set  apart  in  any  organism  is  connected  by  a 
lineage  of  cell-divisions  with  the  fertilised  ovum  which 
gave  rise  to  that  organism,  and  so  on  backwards.  It 
was  an  epoch-making  step  when  embryologists  arrived  at 
"the  conception  so  vividly  set  forth  by  Virchow  of  an 
uninterrupted  series  of  cell-divisions  extending  back- 
ward from  existing  plants  and  animals  to  that  remote 
and  unknown  period  when  vital  organisation  assumed 
its  present  form.  Life  is  a  continuous  stream.  The 
death  of  the  individual  involves  no  breach  of  continuity 
in  the  series  of  cell-divisions  by  which  the  life  of  the 
race  flows  onwards.  The  individual  body  dies,  it  is 
true,  but  the  germ-cells  live  on,  carrying  with  them,  as 

*  E.  B.  Wilson,  The  Cell  in  Development  and  Inheritance,  2nd 
ed.,  1900,  p.  7. 


GENEOLOGICAL.  371 

it  were,  the  traditions  of  the  race  from  which  they  have 
sprung,  and  handing  them  on  to  their  descendants."  * 

Fertilisation. — In  his  49th  Exercitation  on  "  the 
efficient  cause  of  the  chicken,"  Harvey  thus  quaintly 
expressed  what  was  to  him,  as  it  is  to  us,  a  baffling 
problem : — "Although  it  be  a  known  thing  subscribed 
by  all,  that  the  fretus  assumes  its  original  and  birth 
from  the  male  and  female,  and  consequently  that  the 
egge  is  produced  by  the  cock  and  henne,  and  the 
chicken  out  of  the  egge,  yet  neither  the  schools  of 
physicians  nor  Aristotle's  discerning  brain  have  dis- 
closed the  manner  how  the  cock  and  its  seed  doth 
mint  and  coine  the  chicken  out  of  the  egge." 

Even  after  Spallanzani  had  shown  experimentally 
(1786)  that  the  fertilising  power  must  be  in  the 
minute  spermatozoa,  since  filtered  spermatic  fluid 
of  frogs  was  inoperative,  vague  and  even  absurd  views 
continued  to  abound. 

"  Even  von  Baer  (1835)  was  inclined  to  interpret 
the  spermatozoa  as  minute  parasites  peculiar  to  the 
male  fluid ;  Johannes  Miiller  seems  also  to  have  been 
in  doubt;  and  Richard  Owen  included  them  in  his 
article  on  *  Entozoa '  (internal  parasites)  in  Todd's 
Cyclopaedia  of  Anatomy  and  Physiology"  f  In  1843 
Martin  Barry  saw  the  union  of  sperm  and  ovum  in 
the  rabbit,  but  it  was  not  till  1854  that  Bischoff 
abandoned  the  theory  that  a  mere  touch  of  sperm  and 
ovum  was  sufficient  to  ensure  fertilisation. 

In  fact,  the  distinctively  modern  period  in  the 
study  of  fertilisation  only  began  about  a  quarter  of 
a  century  ago,  when  the  researches  of  Auerbach,  E. 
van  Beneden,  Biitschli,  Fol,  De  Bary,  Strasburger, 

*  E.  B.  Wilson,  op.  cit.,  p.  10. 
f  Thomson,  Science  of  Life,  p.  125. 


372    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

Oscar  Hertwig,  and  others  made  it  clear  that  fertil- 
isation in  plants  and  animals  alike  is  an  intimate 
and  orderly  union  of  a  spermatozoon  and  an  ovum, 
— a  union  in  which  the  two  nuclei  play  a  very  im- 
portant part. 

It  is  generally  believed  that  the  paternal  and 
maternal  hereditary  qualities  which  are  united  in 
fertilisation  have  their  seat  in  the  sperm-nucleus  and 
the  ovum-nucleus,  especially  or  exclusively  in  the 
readily  stainable  or  chromatin  substance  of  these ;  as 
the  ovum  is  very  much  larger  than  the  spermatozoon, 
it  evidently  supplies  most  of  the  initial  capital  of 
cell-substance;  the  spermatozoon,  however,  contrib- 
utes, apart  from  its  nucleus,  a  little  body  called  the 
centrosome  which  is  now  well  known  in  many  cases 
of  animal  fertilisation,  and  seems  to  play  an  impor- 
tant part  in  the  process  of  egg-cleavage;  the  result 
of  the  cleavage  is  that  each  daughter-cell  gets  an 
equal  share  of  the  heritage  of  chromatin. 

We  have  alluded  to  the  importance  of  the  idea  of 
genetic  continuity — that  the  germ-cell  is  a  link  in  a 
continuous  chain  of  germ-cells;  but  we  must  place 
close  beside  it  the  striking  fact,  which  is  for  some 
stages  visibly  demonstrable,  that  the  maternal  and 
paternal  chromatin-contributions  which  come  together 
in  fertilisation  are  distributed  equally  in  the  cells  of 
the  offspring. 

During  the  last  quarter  of  the  nineteenth  century 
there  were  many  hundreds  of  researches  on  ferti- 
lisation, and  there  is  perhaps  a  larger  amount  of 
observational  material  on  this  subject  than  on  any 
other  except  cell-division,  but  it  must  not  be  sup- 
posed for  a  moment  that  the  process  is  understood. 
The  general  tendency,  following  Hertwig  and  Stras- 
burger,  is  to  credit  the  nuclei  with  being  alone  im- 


GENEOLOGICAL.  373 

portant  in  the  process,  but  against  this  we  have  the 
facts — as  yet  uncontroverted — that  a  non-nucleated 
ovum  or  even  fragment  of  an  ovum  may  be  fertilised 
and  may  develop  to  the  larval  stage  (Boveri  and  De- 
lage),  and  that  artificial  conditions  may  induce  an 
ovum  to  develop  without  a  spermatozoon.  Thus, 
Loeb  induced  artificial  parthenogenesis  in  sea-urchin 
ova  by  placing  them  for  a  couple  of  hours  in  sea- 
water,  to  which  some  magnesium  chloride  had  been 
added,  disturbing  the  normal  proportions  of  the 
ions.  There  are  also  incipient  experiments  (Fieri, 
Winkler,  and  others)  on  the  effect  of  an  extract  of 
sperm  in  stimulating  the  cleavage  of  the  ovum. 
Everything  points  to  the  desirability  of  extreme  cau- 
tion, but  it  seems  likely  that  we  have  to  distinguish 
in  fertilisation  two  distinct  results — (a)  a  mingling 
of  heritable  qualities,  and  (6)  a  physiological  stimu- 
lus to  division.* 

Since  the  formulation  of  the  Cell-Theory,  the  de- 
velopment of  Embryology  has  been  rapid,  and  this 
may  in  part  account  for  the  insecurity  of  its  general- 
isations. We  propose  to  refer  to  a  few  of  these. 

Germ-Layers. — The  fertilised  animal  ovum  di- 
vides into  a  mass  of  cells — a  solid  ball,  or  morula; 
a  hollow  ball,  or  blastula;  a  convex  disc  on  the  top 
of  the  yolk,  and  so  on.  The  next  great  step  is  the 
differentiation  of  two  germinal  layers — the  diplo- 
blastic  state.  Of  these  the  outer  layer  is  called  the 
ectoderm  or  epiblast,  and  the  inner  the  endoderm  or 
hypoblast  When  the  egg  is  not  encumbered  with 
much  yolk  this  two-layered  stage  most  frequently 
assumes  the  form  of  a  thimble-shaped  or  barrel- 
shaped  embryo,  whose  cavity  is  the  primitive  gut  or 

*  See  Geddes  and  Thomson,  The  Evolution  of  Sex,  revised 
(4th)  edition,  1901. 


374    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

archenteron.  The  ectoderm  gives  rise  to  epidermis, 
nervous  system,  foundations  of  the  sense-organs  and 
so  on ;  the  endoderm  forms  the  lining  of  the  future 
mid-gut  and  of  the  various  organs  (such  as  lungs, 
liver,  and  pancreas)  which  grow  out  as  diverticula 
from  it,  and  likewise,  in  vertebrates,  to  the  primi- 
tive dorsal  axis  or  notochord;  while  a  third  median 
stratum  of  cells — the  mesoderm — of  considerable 
definiteness  above  the  level  of  the  unsegmented 
worms,  gives  origin  chiefly  to  muscular  and  skeletal 
tissue. 

From  the  work  of  Von  Baer  onwards  much  atten- 
tion has  been  paid  to  these  germinal  layers ;  in  1849 
Huxley  collated  the  epiblast  and  hypoblast  of  the  em- 
bryo with  the  two  layers  of  cells  which  form  the  body 
of  adult  polyps,  like  the  common  Hydra ;  and  it  was 
regarded  as  one  of  the  criteria  of  complete  homology 
that  organs  similar  in  structure  should  also  be  homo- 
dermic,  i.e.,  traceable  to  a  similar  origin  from  the 
germinal  layers.  The  work  of  the  brothers  Hert- 
wig  in  connection  with  this  germ-layer-theory 
(Keimblattertheorie)  was  of  particular  importance. 

"  Gradually,  however,  the  confidence  of  embryol- 
ogists  in  this  germ-layer-theory  has  been  shaken — 
by  the  following,  among  other,  considerations,  (a) 
What  one  may  call  the  stratification  of  the  embryo 
is  established  in  very  different  ways  in  different 
types;  (&)  there  are  some  cases,  notably  sponges, 
where  the  history  of  the  outer  and  inner  layers  can- 
not be  readily  brought  into  line  with  the  state  of 
affairs  in  the  majority;  (c)  the  mesoderm  is  so 
varied  in  its  origin  (from  ectoderm,  from  endoderm, 
or  from  both)  and  in  its  expression,  that  the  concep- 
tion lacks  even  a  pretence  at  unity;  and  (d)  in  many 
cases  the  facts  of  development  show  that  certain 


GENEOLOGICAL.  375 

orgnns  can  be  traced  back  to  a  few  cells  specifically 
predestined  from  their  first  appearance,  rather  than 
to  a  homogeneous  germinal  layer."  *  In  fact,  the 
germ-layer-theory  is  now  regarded  by  many  experts 
as  "  inadequate  and  misleading,"  and  it  is  being  re- 
placed by  a  more  detailed  study  of  cell-lineage  in 
which  segmentation-cells  or  blastomeres  are  traced 
from  their  origin  to  their  final  result. 

Gastrcea-Tlieory. — The  same  kind  of  remark  must 
be  made  in  regard  to  Haeckel's  famous  Gastrcea- 
TJieory  (1874:).  In  this  there  are  two  propositions, 
— (1)  that  the  gastrula-embryo  (the  two-layered  sac) 
is  of  general  occurrence,  though  often  disguised,  in 
the  development  of  animals;  and  (2)  that  the  hypo- 
thetical ancestral  form  of  multicellular  animal  (the 
Gastraea)  was  a  two-layered  sac  like  a  gastrula. 
But  it  requires  extraordinary  ingenuity  to  find  the 
gastrula-stage  in,  let  us  say,  the  development  of  a 
hedgehog,  or  even  in  that  of  the  chick.  And 
even  when  the  gastrula  is  plain,  as  in  starfishes,  it 
is  not  always  clear  that  its  layers  are  homologous 
with  those  of  other  gastrulae,  e.g.,  in  Sponges.  As 
to  the  other  part  of  the  Gastraea-Theory,  there  are 
three  or  four  plausible  hypotheses  in  the  field  as  to 
the  possible  form  of  the  ancestral  multicellular 
animal.  It  is  likely  enough  that  there  were  several 
forms. 

Recapitulation-Doctrine. — Once  more,  to  take  the 
largest  generalisation  of  nineteenth-century  embryol- 
ogy,— the  Recapitulation-Doctrine  or  biogenetie 
law, — which  suggests  that  the  individual  develop- 
ment is  in  some  measure  a  recapitulation  of  the 
racial  history,  there  are  few  modern  embryologists 
who  regard  it  without  hesitation  and  suspicion. 
*  Science  of  Life,  p.  131. 


376    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

Meckel  in  1821  wa8  one  of  the  first  to  speak  of  the 
"correspondence  between  the  development  of  the 
embryo  and  that  of  the  entire  animal  series."  Kiel- 
meyer  seems  to  have  something  to  do  with  the  origi- 
nation of  the  idea ;  Oken  and  Goethe  both  express  it. 
Yon  Baer,  to  whom  the  recapitulation-idea  is  often 
carelessly  ascribed,  was  very  cautious  on  the  subject; 
Louis  Agassiz  (though  a  non-evolutionist)  gave  it 
clear  expression  in  his  famous  Essay  on  Classifica- 
tion (1859)  ;  his  son  Alexander  was  also  an  adher- 
ent, though  more  guardedly;  Fritz  Miiller  was  an 
enthusiastic  exponent  in  his  Facts  for  Darwin, 
Haeckel  formulated  it  in  his  "  Biogenetisches  Grund- 
gesetz  "  (fundamental  biogenetic  law)  that  "  Ontog- 
eny tends  to  recapitulate  Phylogeny " ;  and  Her- 
bert Spencer  also  made  it  part  of  his  biological 
system.* 

There  is  no  doubt  that  we  have  here  a  big  idea 
and  a  clear  one,  that  of  individual  development  in 
some  measure  recapitulating  racial  history,  and  it 
must  not  be  hastily  condemned  because  of  popular 
exaggerations  on  the  one  hand  (no  idea  has  suffered 
more  from  its  friends),  or  because  critics  have  sought 
rather  to  controvert  than  to  correct  it.  Let  us  admit 
the  grotesqueness  of  popular  exposition,  e.g.,  that 
the  mammal  is  at  one  time  a  little  fish ;  let  us  allow 
that  Milnes  Marshall  did  not  mean  to  be  taken  too 
literally  when  he  spoke  of  "  every  animal  climbing 
up  its  own  genealogical  tree  " ;  let  us  grant  that  evi- 
dence from  the  child's  acquirement  of  language  and 
ideas  is  not  very  cogent  evidence  of  parallelism  to 
a  past  whicK  is  more  than  half-concealed;  let  us 
remember  Haeckel's  explicit  declaration  that  the 

*  For  some  details,  see  the  writer's  Science  of  Life,  pp.  133- 
138. 


GENEOLOGICAL.  377 

recapitulation  is  general,  not  exact,  that  there  is 
often  a  tendency  to  abbreviation,  and  that  relatively 
recent  adaptations  (kainogenetic  characters)  may 
disguise  the  ancient  ancestral  features  (palingenetic 
characters) ;  let  us  emphasise  that  the  recapitu- 
lation-idea was  not  intended  as  a  contribution  to  the 
physiology  of  development,  but  was  merely  suggested 
as  a  historical  interpretation — a  light  from  a  dis- 
tance; and  let  us  even  acknowledge  that  more  exact 
knowledge  sees  differences  where  more  hasty  earlier 
observations  saw  only  resemblances.  Yet,  after  all, 
there  is  a  good  word  to  be  said  for  the  recapitulation 
idea. 

If  we  take  an  individual  animal,  like  the  frog, 
and  study  its  life-history,  we  cannot  but  conclude 
that  in  a  general  way  and  in  respect  to  certain 
changes  in  organs,  its  ontogeny  does  recapitulate  its 
phylogeny. 

But  let  us  notice  two  possible  fallacies.  In  sum- 
ming up  the  so-called,  we  think  miscalled,  "  evidences 
of  evolution,"  it  is  customary  to  cite  a  case  like 
that  of  the  frog's  life-history — with  its  fish-like  and 
dipnoan-like  stages — as  part  of  the  "  evidence." 
The  frog,  in  its  tadpole  and  other  stages,  is  sup- 
posed to  oblige  the  naturalist — the  evolutionist — by 
climbing  up  its  own  genealogical  tree;  and  that  it 
does  so  is  cited  as  a  corroboration  of  the  evolution- 
idea.  But  when  we  come  to  study  the  frog's  de- 
velopment in  itself,  as  part  of  the  practical  course  of 
embryology,  and  are  puzzled  by  its  circuitousness, 
we  explain  (or  are  tempted  to  explain)  the  turns  and 
twists  of  the  ontogeny  by  saying,  that  in  so  doing 
the  larval  frog  is  recapitulating  the  historical 
evolution  of  its  race. 

The  second  fallacy  is  this,  that  when  we  examine 


378    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

the  facts  carefully  it  is  at  once  evident  that  the 
larval  frog  (or  tadpole  in  the  wide  sense)  is  never 
a  little  fish,  though  it  has  undoubtedly  a  fish-like 
heart,  a  fish-like  circulation,  and  fish-like  gills.  It 
is,  none  the  less,  from  the  very  outset  an  amphibian, 
and  even  more  than  that  a  frog ;  whether  we  consider 
its  scaleless  skin  with  multicellular  skin-glands,  or 
its  muscular  tongue,  or  its  rayless  dorsal  fin,  or  its 
posterior  nares,  or  a  dozen  other  features,  it  is  an 
amphibian  from  beginning  to  end.  The  parallelism 
is  rather  between  the  development  and  the  phylogeny 
of  organs,  than  between  the  life-history  and  the  evo- 
lution of  organisms.  And  even  in  regard  to  organs, 
the  recapitulation-doctrine  in  its  cruder  forms  breaks 
down,  for  in  RabPs  recent  monograph  on  the  lenses 
of  vertebrates,  it  is  clearly  shown  that  although  in 
the  development  of  the  higher  lenses  (of  mammals, 
for  instance)  there  is  some  recapitulation  of  the  evo- 
lutionary stages,  yet  the  earliest  rudiment  of  the  lens 
(of  a  cat  or  of  a  bat)  is  specifically  peculiar  in  every 
case. 

Probably  as  the  result  of  rapid  development,  the 
generalisations  of  embryology — such  as  the  germ- 
layer-theory,  the  gastrcea-theory,  the  recapitulation 
doctrine, — are  no  longer  tenable  without  many 
saving-clauses.  But,  since  each,  undoubtedly,  ex- 
presses some  truth,  our  endeavour  should  be  not  that 
of  destructive  criticism,  but  rather  that  of  adapting 
them  to  the  new  data. 

Physiological  Embryology. — What  Pander  and 
Lotze  suggested, — that  there  should  be  an  enquiry 
into  the  immediate  conditions  which  are  operative  in 
development,  was  recognised  by  His  in  the  famous 
work  Unsere  Korperform  und  das  Problem  ihrer 
Entstehung  (1875),  and  by  Rauber  in  his  Formbil- 


GENEOLOGICAL.  379 

dung  und  Formstorung  (1880).  "To  think  that 
heredity  will  build  up  organic  beings  without  me- 
chanical means  "  is,  according  to  His,  "  a  piece  of 
unscientific  mysticism " ;  and  from  many  different 
sides  there  has  been  an  attempt  to  analyse  the  proc- 
esses of  organic  growth  and  embryonic  architecture. 
The  task,  which  is  involved  in  stupendous  difficulties, 
has  been  touched  by  the  work  of  O.  Hertwig,  Pfliiger, 
Fol,  Born,  O.  Schultze,  Berthold,  Gerlach,  Van  Ben- 
eden,  Boveri,  Heidenhain,  Loeb,  Davenport,  and 
many  others,  but  the  name  of  Roux  should  be  par- 
ticularly associated  with  the  attempt  to  get  nearer 
some  concrete  conception  of  developmental  mechan- 
ism. 

"  Developmental  mechanics/'  he  says,  "  or  the  causal 
morphology  of  organisms,  is  the  doctrine  of  the  causes 
of  organic  forms — the  doctrine  of  the  causes  of  the 
origin,  maintenance,  and  involution  (degeneration)  of 
these  forms.  ...  In  any  given  case,  we  must  trace 
back  each  individual  formative  process  to  the  special 
combination  of  energies  by  which  it  is  conditioned,  or, 
in  other  words,  to  its  modi  operandi,  and  each  of  these 
modi  operandi  must  be  ascertained  with  respect  to 
place,  time,  direction,  magnitude,  and  quality.  Or,  in- 
versely we  may  endeavour  to  determine  in  the  individual 
structure  the  special  part  which  is  performed  by  every 
modus  operandi  known  to  participate  in  the  develop- 
ment of  the  organism." 

To  mention  those  who  have  helped  Roux  towards 
the  realisation  of  this  ambitious  aim  would  be  to 
give  a  list  of  the  contributors  to  the  ArcJiiv  fur  Ent- 
wickelungs-Mechanik.  But  this  could  serve  no  use- 
ful purpose. 

The  problem  of  development  has  been  passed  on 
to  the  twentieth  century  quite  unsolved,  and  we  can- 


380    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

not  here  discuss  the  various  theories.  It  may  be  said, 
however,  that  each  step  in  development  is  a  function 
of  three  factors:  (a)  the  organisation  of  the  germ- 
cells,  objectively  expressed  in  a  visible  complexity  of 
structure,  and  in  an  inconceivable  molecular  com- 
plexity beneath  this:  (&)  the  vital  relation  of  the 
various  blastomeres  or  segmentation-cells  to  one  an- 
other; and  (c)  the  environmental  influences  (pres- 
sure, osmosis,  chemical  composition  of  the  medium, 
temperature,  light,  etc.)  which  play  upon  the  whole. 

EXPERIMENTAL  EMBRYOLOGY. 

Although  the  idea  of  artificially  influencing  the 
germ  is  very  old,  although  even  Swammerdam  is  said 
to  have  succeeded  in  producing  monstrosities,  ex- 
perimental embryology  is  practically  a  new  depar- 
ture in  biology.  Almost  all  the  experiments  of  mo- 
ment have  been  made  in  the  last  twenty  years,  and 
since  1890  it  has  been  a  prominent  line  of  research. 
There  is  a  Journal — Archiv  fur  Eniwickelungs- 
Mechanik,  edited  by  Roux — which  is  in  great  part 
devoted  to  the  subject,  and  there  are  already  at  least 
two  text-books  mainly  devoted  to  its  exposition.* 

(a)  One  of  the  first  modes  of  experiment  in  this 
direction  was  in  the  artificial  production  of  monstros- 
ities. Just  as  pathology  sheds  light  on  physiology — 
in  the  case  of  the  thyroid  gland  for  instance — so 
teratology  and  teratogenesis  (the  study  and  produc- 
tion of  monstrosities)  may  help  us  to  understand 
normal  development.  The  most  successful  worker 
along  this  line  has  been  Camille  Dareste,f  the 

*  W.  Haacke,  EntwicTcelungs-MecJianik.  C.  Labbe,  Cytol- 
ogie  Exptrimentale. 

t  Recherches  sur  la  production  artificielle  des  monstruos- 
iUs;  ou  Essais  de  Ttratog&nie  Expcrimentdle,  Paris,  1877; 
2nd  ed.,  1891. 


GENEOLOGICAL.  381 

acknowledged  chief  of  monster-makers.  He  has  ex- 
perimented for  instance,  with  the  egg  of  the  fowl, — 
a  corpus  vile  for  many  purposes — placing  it  verti- 
cally instead  of  horizontally,  keeping  it  slightly 
above  or  slightly  below  the  normal  temperature  of 
incubation,  heating  different  parts  of  the  egg  un- 
equally, hermetically  varnishing  part  of  the  shell, 
and  so  on.  He  has  not  only  shown  that  the  germ 
is  plastic  in  the  grip  of  its  environment,  but  he  has 
been  able  to  induce  a  number  of  particular  malfor- 
mations which  are  of  interest  to  the  student  of 
normal  structure. 

Of  great  importance,  perhaps  inadequately  recog- 
nised, is  the  work  of  Prof.  A.  Rauber,  Formbildung 
und  Formstorung*  (1880),  which  showed  the  sig- 
nificance of  relating  the  results  of  abnormal  disturb- 
ance to  the  normal  sequence  of  events,  and  described 
a  number  of  interesting  experiments.  To  it  we  may 
refer  the  serious  student  for  a  historical  sketch  of  the 
results  achieved  before  1880. 

There  are  many  other  workers,  such  as  O.  Hert- 
wig,  B.  C.  A.  Windle,  and  Ch.  Fere,  whose  investi- 
gations are  in  part  on  the  same  lines  as  those  of 
Dareste  and  Rauber. 

(6)  Puncturing  Experiments. — The  egg  of  the 
frog,  about  one-tenth  of  an  inch  in  diameter,  is  a  very 
convenient  subject  for  embryological  experiment. 
The  first  three  cleavages,  visible  even  with  the  naked 
eye,  lie  along  three  planes,  which,  in  order  of  se- 
quence, correspond  to  those  which  divide  the  tadpole 
into  right  and  left  sides,  head  and  tail  regions,  dorsal 
and  ventral  areas.  Of  the  first  two  cells  into  which 
the  egg  of  a  frog  divides  one  has  in  it  the  material 
for  forming  the  right  half  of  the  body,  the  other  has 
*  I.e.,  Forming  and  deforming. 


382    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

in  it  the  material  for  forming  the  left  half  of  tho 
body. 

When  Roux  punctured  one  of  the  first  two  segmen- 
tation-cells (or  blastomeres)  with  a  hot  needle  or 
otherwise,  he  found  that  the  intact  other  cell  devel- 
oped into  a  typical  7mZ/-morula,  or  /&aZ/-gastrula,  or 
7iaZ/-embryo,  according  to  the  success  in  survival. 
Thus,  there  might  be  in  the  embryo,  half  of  the 
normal  cerebrum,  one  ear-sac,  a  one-sided  gut,  a 
single  row  of  protovertebrae,  and  so  on.  Thus  it  was 
proved  that  one  of  the  first  two  segmentation  cells  (or 
blastomeres)  may  form  half  an  embryo;  it  has  the 
requisite  material  and  the  requisite  power  of  inde- 
pendent development.  This,  and  many  similar  ex- 
periments, led  Eoux  to  his  theory  that  the  early  de- 
velopment of  the  frog-ovum  is  like  a  kind  of  mosaic 
work  pieced  together  in  independent  parts.  He  sug- 
gested that  there  were  at  least  four  independently-de- 
veloping pieces.  It  should  be  noted,  however,  that 
the  half -embryo  may  eventually  form  a  whole,  either 
with  the  aid  of  a  re-vitalisation  of  the  injured  half- 
egg  which  has  been  lying  passive  while  the  uninjured 
half  was  developing,  or  even  without  any  co-opera- 
tion on  the  part  of  the  injured  half  of  the  first 
cleavage.* 

So  far,  there  seemed  to  be  a  definite  conclusion 
reached  by  an  investigator  of  the  first  rank,  that  the 
puncturing  of  one  of  the  first  two  cells  into  which 
a  frog's  egg  divides,  has  for  its  result  that  the  intact 
other  cell  forms  a  half -embryo, — a  one-sided  em- 
bryo, which  by  "  post-regeneration "  may  become 
eventually  a  whole. 

But  in  1893,  Professor  Oscar  Hertwig,  whose  con- 

*  Virchow's  Archiv  f.  Pathologic,  CXIV.  (1888). 


GENEOLOGICAL.  383 

tributions  to  biology  have  been  momentous,  pub- 
lished the  results  of  an  extensive  series  of  experi- 
ments *  on  the  same  subject,  and  these  were  far 
from  harmonising  with  the  conclusion  reached  by 
Roux. 

According  to  Hertwig,  if  one  of  the  first  two  seg- 
mentation-cells (or  blastomeres)  be  completely  des- 
troyed, the  surviving  half  forms  a  fairly  normal 
embryo,  with  structural  defects  of  slight  importance. 
If  the  destruction  be  partial,  division  may  occur  in 
the  injured  half,  either  in  its  own  strength  or  with 
help  from  the  intact  half.  But  a  destroyed  half 
cannot  be  revitalised,  nor  does  Koux's  post-genera- 
tion occur.  The  development  of  the  uninjured  half 
is  quite  normal.  No  half-gastrula  or  half-embryo 
is  ever  formed,  when  one  of  the  first  two  blastomeres 
is  destroyed.  Therefore,  as  Hertwig  concluded,  the 
mosaic  theory  of  development  is  contradicted  by  fact 

We  wish  to  dwell  upon  this  particular  case  be- 
cause it  is  so  vividly  illustrative  of  scientific  method. 
Here  we  have  observers  of  equal  competence  reach- 
ing discrepant  conclusions  from  similar  experiments 
on  the  same  material ! 

The  puzzle  was  solved  (in  great  part  at  least) by 
the  very  careful  research  of  Prof.  T.  H.  Morgan,  | 
who  showed  that  either  a  half -embryo  or  a  whole  half- 
sized  dwarf  may  result  from  the  experiment,  accord- 
ing to  the  position  of  the  blastomere.  If,  after  one 
of  the  first  two  cells  has  been  destroyed,  the  other 
be  left  in  its  normal  position,  then  a  half-embryo 
results  (11  cases)  as  Roux  described.  But  if  the 

*  Archiv  fur  mikroskopische  Anatomic,  XLII.  (1893), 
pp.  662-807,  6  plates  (with  bibliography  of  52  papers). 

t  Half-embryos  or  whole-embryos  from  one  of  the  first 
two  blastomeres  of  the  frog's  egg.  Anat  Anzeig.,  1895. 


384    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

intact  blastomere  be  inverted,  then  it  may  develop 
into  a  half -embryo  (3  cases)  or  into  an  entire  dwari 
(9  cases). 

"  Morgan  therefore  concluded  that  the  production 
of  whole  embryos  by  the  inverted  blastomeres  was, 
in  part  at  least,  due  to  a  rearrangement  or  rotation 
of  the  egg-materials  under  the  influence  of  gravity, 
the  blastomeres  thus  returning  as  it  were,  to  a  state  of 
equilibrium  like  that  of  an  entire  ovum."  * 

(c)  Isolation-Experiments. — Professor  C.  Chun 
observed  in  1877  that  when  the  two  first  segmenta- 
tion-cells of  a  ctenophore  ovum  were  shaken  apart, 
each  formed  a  half-larva,  with  four  instead  of  eight 
ciliated  ridges  and  meridional  vessels,  with  one  ten- 
tacle instead  of  two.  The  half-larva3  actually  be- 
came sexual,  and  by  a  process  of  budding,  the  missing 
half  was  eventually  formed.  The  observer  also 
added  the  interesting  note  that  united  twin  cteno- 
phore-larvse  were  most  abundant  after  stormy  days, 
probably  resulting  from  the  incomplete  separation 
of  the  first  two  blastomeres  and  their  independent 
development. 

The  importance  of  Chun's  hint  was  recognised 
by  Driesch  who  was  the  first  to  develop  the  method 
of  isolating  segmentation-cells  by  shaking.  The 
device  has  been  resorted  to  in  many  cases, — with 
ascidians  and  sea-urchins  in  particular.  As  a  par- 
ticularly fine  piece  of  work,  we  may  refer  to  Prof. 
E.  B.  Wilson's  experiments  on  the  eggs  of  the  lance- 
let  (Amphioxus)  .f 

By  shaking  the  water  in  which  the  two-celled 
stages  floated,  Wilson  separated  the  two  cells,  and 

*  B.  B.  Wilson,  The  Cell  in  Development  and  Inheritance, 
2nd  ed.,  1900,  p.  422. 
t  Journal  of  Morphology,  VIII.    (1893),  pp.  579-638,  10 

pis. 


GENEOLOGICAL.  385 

the  result  was  two  quite  separate  and  independent 
twins  of  half  the  normal  size.  Each  of  the  isolated 
cells  segments  like  a  normal  ovum,  and  gives  origin, 
through  blastula  and  gastrula  stages,  to  a  half-sized 
metameric  larva. 

If  the  shaking  has  separated  the  two  first  segmen- 
tation cells  incompletely,  double  embryos — like  Si- 
amese twins — result,  and  also  form  short-lived 
(twenty-four  hours)  segmented  larvae. 

Similar  experiments  with  the  four-celled  stages 
succeeded,  though  development  never  continued  long 
after  the  first  appearance  of  metamerism.  Com- 
plete isolation  of  the  four  cells  resulted  in  four 
dwarf  blastulae,  gastrulae,  and  even  larvae.  Separa- 
tion into  two  parts  of  cells  resulted  in  two  half-sized 
embryos.  Incomplete  separation  resulted  in  one  of 
three  types — (a)  double  embryos,  (6)  triple  em- 
bryos— one  twice  the  size  of  the  other  two — and  (c) 
quadruple  embryos,  each  a  quarter  size. 

The  eager  observer  proceeded  to  shake  up  the 
eight-celled  stages,  but  in  no  case  did  he  succeed  in 
rearing  a  gastrula  from  an  isolated  unit  of  the  eight- 
celled  stages.  Flat  plates,  curved  plates,  even  one- 
eighth  size  blastulae  were  formed,  but  none  seemed 
capable  of  full  development. 

Thus,  a  unit  from  the  four  cell  stage  may  form  an 
embryo,  but  a  unit  from  the  eight  cell  stage  does  not. 
For  various  reasons  it  seems  likely  that  this  is  due 
to  qualitative  limitations,  not  merely  to  the  fact 
that  the  units  of  the  eight  cell  stage  are  smaller.  For 
although  the  separated  cells  of  the  eight  cell  stage 
have  considerable  vitality,  and  swim  about  actively, 
the  difference  between  macromeres  and  micromeres 
has  by  this  time  been  established;  in  fact  the  cells 
have  begun  to  be  specialised,  and  have  no  longer  the 


386    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

primitive  indifference,  the  absence  of  differentia- 
tion, which  explains  the  developmental  potentiality 
of  the  separated  units  of  the  two-celled  or  four- 
celled  stages. 

Somewhat  similar  experiments  have  been  made  by 
other  investigators  on  the  developing  ova  of  ascidians, 
sea-urchins,  etc.  Specialisation  of  segmentation- 
cells  appears  to  occur  at  different  times  in  different 
animals,  but  it  is  illogical  to  infer  the  absence  of 
specialisation  from  the  fact  that  any  of  the  first  four 
blastomeres,  let  us  say,  can  produce  an  entire  embryo. 
For  specialised  cells  may  retain  a  power  of  regener- 
ation. 

(d)  Pressure-Experiments. — Many  investigators, 
e.g.,  Driesch,  O.  Hertwig,  Born — have  studied  the 
behaviour  of  an  ovum  subjected  to  the  constraint  of 
slight  pressure  between  glass  plates.  Prof.  Hertwig 
shows  that  various  compressions  profoundly  modify 
the  course  of  segmentation,  the  direction  and  suc- 
cession of  the  cleavage  planes,  and  the  size  of  the 
blastomeres.  The  nuclei  may  be  most  variably  dis- 
posed, they  may  lie  in  disorder,  "  like  a  heap  of  balls 
thrown  together,"  and  yet  normal  embryos  result. 
This  is  regarded  by  many  as  a  strong  argument 
against  the  theory  that  qualitatively  different  por- 
tions of  the  nucleus  are  separated  from  one  another 
by  the  early  cleavages. 

Here  we  may  also  refer  to  the  interesting  results 
of  rotating  the  eggs  so  that  the  distribution  of  their 
substance  is  affected  by  "centrifugal  force."  This 
may  also  have  a  profound  effect  on  the  segmenta- 
tion ;  thus  O.  Hertwig  has  shown  in  the  ease  of  the 
frog's  egg  that  the  normal  segmentation  (total  and 
unequal)  may  be  replaced  by  a  process  closely  akin 
to  the  type  known  as  partial  and  discoidal. 


GENEOLOGICAL.  387 

(e)  Influence  of  Temperature. — In  his  account  of 
the  development  of  one  of  the  earthworms  (Allolobo- 
phora  trapezoides) ,  whose  eggs  very  frequently  form 
twins,  Vejdovsky  suggested  that  the  "  twinning  "  was 
perhaps  influenced  by  warmth,  for  it  was  most  fre- 
quent in  warm  weather.  This  suggestion  prompted 
Driesch  to  try  the  effect  of  increased  warmth  on  the 
developing  eggs  of  the  sea-urchin  (Sphosrechinus) . 
The  usual  result  was  very  striking,  though  it  was 
not  quite  constant,  nor  verifiable  in  related  forms, 
e.g.,  Echinus.  What  often  happened  in  the  case  of 
S pliasrechinus  was  the  formation  of  distinct  twin- 
embryos  and  even  twin-larva?  (Plutei)  from  each 

egg- 

In  a  later  series  of  experiments,  Driesch  showed 
that  when  the  blastula-embryos  (hollow  balls  of 
cells)  of  Splioerechinus  granularis  are  kept  in  sea- 
water  on  a  stove  heated  to  about  30°C.,  the  great 
majority  show  in  about  18  hours  a  remarkable  state 
of  affairs  (exogastrula-state)  in  which  the  area  of 
cells  which  is  normally  invaginated  to  form  the 
primitive  gut,  bulges  outwards  instead  of  inwards. 
The  final  result,  which  may  survive  for  a  week,  is  a 
gut-less  larva — an  "  Anenteria." 

Many  other  experiments,  both  as  to  heat  and  cold, 
have  been  made,  and  they  are  probably  of  great  im- 
portance since  vicissitudes  of  temperature  are  of 
frequent  occurrence  in  natural  conditions.  It  may 
be  conjectured  that  the  temperature  influences  the 
metabolism  of  the  cells,  e.g.,  the  rate  of  formation 
of  nuclein-compounds,  and  thus  affects  the  manner 
of  growth. 

(/)  Influence  of  Chemical  Re-agents. — In  1887, 
O.  and  R.  Hertwig  published  a  pioneer-research  on 
the  influence  of  chemical  and  other  stimuli  on  fertil- 


388    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

isation  and  cleavage.*  This  was  the  beginning  of 
a  long  series  of  researches,  of  which  the  most  remark- 
able are  probably  those  of  Curt  Herbst.  t 

Herbst  placed  fertilised  ova  of  various  sea-urchins 
in  sea-water  whose  normal  composition  had  been  dis- 
turbed by  the  addition  of  solutions  of  potassium 
chloride,  lithium  chloride,  and  so  on,  usually  in  the 
proportions  of  3.8  grms.  to  100  centimetres  of  sea- 
water.  Nothing  could  be  quainter  than  some  of  the 
resulting  abnormal  forms  which  nevertheless  tended 
to  reach  the  normal  (Pluteus)  type  by  entirely 
abnormal  paths.  It  remains  uncertain  how  far  the 
chemical  re-agents  act  directly,  or  only  by  disturb- 
ing the  osmotic  pressure,  but  Herbst  favours  the 
second  interpretation. 

(#)  Loeb's  Experiments. — Profs.  O.  and  R.  Hert- 
wig,  Prof.  T.  H.  Morgan,  and  others  have  shown  that 
if  unfertilised  eggs  (especially  of  sea-urchins)  be  sub- 
jected to  the  influence  of  weak  solutions  of  various 
salts  (sodium-chloride,  magnesium-chloride,  etc.) 
or  of  other  substances  (such  as  strychnine),  they 
may  exhibit  changes  comparable  to  those  of  cleavage 
or  of  preparation  for  cleavage. 

In  1899,  Professor  Jacques  Loeb  of  Chicago  suc- 
ceeded in  rearing  perfect  larvas  of  sea-urchins  from 
unfertilised  eggs  which  had  been  left  for  a  couple 
of  hours  in  sea-water  disturbed  by  the  addition  of 
some  magnesium  chloride.  It  seems  to  us  im- 
possible to  find  any  reason  for  doubting  the  ac- 
curacy of  the  carefully  controlled  experiments.^:  It 
may  be,  however,  that  sea-urchin  ova  are  sometimes 

*  Jenaische  Zeitschrift  f.  Naturwissenschaften,  XX.,  1887. 

t  Zeitschr.  wiss.,  Zool.,  LV.,  1892,  pp.  446-518,  2  pis.  Mt. 
Zool.  Stat.  Neapel,  XI.  1893,  Archivf.  Entwickelungs-Mechanik, 
II.,  1896,  etc. 

J  American  Journal  of  Physiology,  1889  and  1900. 


GENEOLOGICAL.  389 

parthenogenetic  in  natural  conditions,  but  this  is 
only  a  supposition  and  will  not,  even  if  verified,  af- 
fect the  interest  of  Loeb's  experiments. 

(h)  Boveri's  Experiment. — The  brothers  Hert- 
wig  showed  that  non-nucleated  fragments  of  a  sea- 
urchin's  egg  might  be  "  fertilised  "  by  a  spermato- 
zoon, and  might  segment.  In  1889,  Boveri  proved 
that  they  might  form  dwarf  larvae,  and  Morgan  in 
1895  demonstrated  that  the  nuclei  of  such  larvae  con- 
tained only  half  the  normal  number  of  nuclear  ele- 
ments or  chromosomes, — an  indication  of  the  fact 
that  the  nuclear  material  was  wholly  paternal,  i.e., 
derived  from  the  sperm-nucleus. 

"Now,  by  fertilising  enucleated  egg-fragments  of 
one  species  (Splicer echinus  granularis)  with  the  sper- 
matozoa of  another  (Echinus  tuberculatus) ,  Boveri 
obtained  in  a  few  instances  dwarf  Plutei  (larvae) 
showing  except  in  size  the  pure  paternal  characteristics, 
i.  e.,  those  of  the  Echinus.  From  this  he  concluded 
that  the  maternal  cytoplasm  has  no  determining  effect 
on  the  offspring,  but  supplies  only  the  material  in 
which  the  sperm-nucleus  operates.  Inheritance  is, 
therefore,  effected  by  the  nucleus  alone. 

"The  later  studies  of  Seeliger  (1894),  Morgan 
(1895),  and  Driesch  (1898)  showed  that  this  result  is 
not  entirely  conclusive,  since  hybrid  larvae  arising  by  the 
fertilisation  of  an  entire  ovum  of  one  species  by  a  sper- 
matozoon of  the  other  show  a  very  considerable  range 
of  variation;  and  while  most  such  hybrids  are  inter- 
mediate in  character  between  the  two  species,  some  in- 
dividuals may  nearly  approximate  to  the  characters  of 
the  father  or  the  mother.  Despite  this  fact,  Boveri 
(1895)  has  strongly  defended  his  conclusion,  though 
admitting  that  only  further  research  can  definitely  de- 
cide the  question."  * 

*  E.  B.  Wilson,  The  Cell  in  Development  and  Inheritance, 
2nd  ed.,  1900,  p.  353. 


390    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

(i)  Delage's  Experiments. — In  a  short  paper 
entitled  "  Embryos  without  Maternal  Nucleus/' 
Professor  Yves  Delage  described  in  1898  *  a  remark- 
able experiment,  implying  a  very  delicate  operation. 
He  divided  the  egg  of  a  sea-urchin  under  the  micro- 
scope into  two  parts,  one  containing  the  nucleus  and 
the  centrosome,  the  other  simply  cytoplasmic.  Be- 
side them  he  placed  an  intact  ovum,  and  then  let 
spermatozoa  in.  All  the  three  objects  showed  equal 
"  sexual  attraction,"  all  were  "  fertilised,"  and  all 
segmented,  the  intact  ovum  most  rapidly,  the  nucle- 
ated fragment  more  slowly,  the  non-nucleated  frag- 
ment more  slowly  still.  In  one  case,  the  develop- 
ment proceeded  for  three  days ;  the  intact  ovum  had 
become  a  typical  gastrula  (two-layered  embryo), 
the  nucleated  fragment  a  smaller  gastrula,  and  the 
non-nucleated  fragment  also  a  gastrula,  but  with  a 
very  much  reduced  cavity.  The  experimenter  there- 
fore concluded  that  fertilisation  and  some  measure 
of  development  may  occur  in  a  fragment  of  ovum 
without  a  maternal  nucleus;  and  he  was  led  to  dis- 
tinguish between  (a)  the  stimulus  given  to  the  ovum 
by  something  which  the  spermatozoon  brought  to 
it,  and  (&)  the  mingling  of  heritable  characteris- 
tics— as  two  distinct  processes  in  fertilisation. 

In  the  following  year,  Delage  extended  his  experi- 
ments,f  and  showed  that  a  non-nucleated  fragment 
of  the  ovum  of  a  sea-urchin  (Echinus),  of  a  mol- 
lusc (Dentalium),  and  of  a  worm  (Lanice)  may  be 
effectively  fertilised  and  give  rise  to  a  Pluteus,  a 
Veliger,  or  a  Trochophore  larva  respectively.  He 

*  Oomptes  Renclus  Acad.  Sci.,  Paris,  CXXVII.,  1898.  pp. 
528-531. 

t  Archives  Zoologie  Exptrimentale,  VII.  (1899),  pp.  383- 
417,  11  figs. 


GENEOLOGICAL.  391 

showed  that  three  larvae  may  be  reared  from  a  single 
sea-urchin  ovum  divided  into  three  pieces,  and  that 
a  normal  blastula  might  develop  from  -g\  of  an 
ovum.  To  this  development  of  fragments  he  ap- 
plied the  term  merogony. 

It  will  be  observed  that  while  Loeb  showed  that 
normal  development  was  possible  without  the  pa- 
ternal nucleus,  Delage  showed  that  this  was  possible 
without  the  maternal  nucleus.  If  both  sets  of  ex- 
periments are  duly  confirmed,  there  will  be  need  for 
some  reconstruction  in  the  current  views  as  to  fer- 
tilisation. 

(;')  Determination  of  Sex. — A.  reference  should 
be  made  here  to  the  numerous  experiments  on  the 
factors  which  determine  whether  a  germ  is  to  be- 
come a  male  or  a  female  organism.  The  investi- 
gations of  Born,  Pfliiger,  Yung,  Maupas,  Xussbaum, 
and  Diising  are  of  especial  importance ;  but  we  may 
refer  for  detailed  discussion  to  The  Evolution  of 
Sex  (4th  edition,  revision)  by  Prof.  Patrick  Geddes 
and  the  writer,  and  to  the  dispassionate  review  by 
Henneberg  (Anatomiscne  Ergebnisse,  Merkel  and 
Bonnet,  VIL,  189?;  pp.  697-721).  We  must  be 
content  with  a  general  summary : — 

The  epoch  at  which  the  sex  is  finally  determined 
is  variable  in  different  animals,  and  diverse  factors 
operative  at  successive  epochs.  Theological  and  meta- 
physical theories  of  sex  have  preceded  the  sci- 
entific ;  observation  and  statistics  have  been  resorted 
to  before  experiment;  and  over  500  theories  in  all 
have  been  set  forth.  That  there  are  two  kinds  of 
ova  is  still  for  the  most  part  an  assumption;  that 
the  entrance  of  more  than  one  spermatozoon  fre- 
quently occurs,  and  is  a  determining  factor,  is 
erroneous.  Thury's  emphasis  on  the  age  of  the  ovum 


392    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

when  fertilised  is  probably  justified;  while  Hensen 
extends  this  notion  to  the  male  element  as  well.  The 
age  of  the  parents  is  probably  only  of  secondary 
import,  and  the  law  of  Hofacker  and  Sadler  as  to 
the  importance  of  this  is  not  confirmed.  Theories 
of  "  comparative  vigour  "  and  the  like  must  be  dis- 
missed; while  Starkweather's  theory  of  the  relative 
superiority  of  either  sex,  and  of  the  influence  of  this 
on  the  sex  of  the  offspring,  requires  further  analysis. 
But  there  is  much  importance  in  Diising's  explana- 
tion of  the  self-regulating  numerical  proportion  of 
the  sexes. 

It  must  first  be  recognised  that  a  number  of  fac- 
tors co-operate  in  the  determination  of  sex;  but  the 
most  important  of  these  may  be  more  and  more 
resolved  into  plus  or  minus  nutrition,  operating  upon 
parent,  sex  elements,  embryo,  and  in  some  cases 
larvae,  (a)  Starting  with  the  parent  organisms 
themselves,  we  find  this  general  conclusion  most 
probable, — that  adverse  circumstances,  especially  of 
nutrition,  but  also  including  age  and  the  like,  tend 
to  the  production  of  males,  the  reverse  conditions 
favouring  females.  (6)  As  to  the  reproductive  ele- 
ments, a  highly  nourished  ovum,  compared  with  one 
less  favourably  conditioned,  in  every  probability  will 
tend  to  a  female  rather  than  to  a  male  development. 
Fertilisation,  when  the  ovum  is  fresh  and  vigorous, 
before  waste  has  begun  to  set  in,  will  corroborate 
the  same  tendency,  (c)  Then  if  we  accept  Sutton's 
opinion  as  to  a  transitory  hermaphrodite  period  in 
most  animals,  from  which  the  transition  to  uni- 
sexuality  is  effected  by  the  hypertrophy  of  the  female 
side  or  preponderance  of  the  male  in  respective  cases, 
the  vast  importance  of  early  environmental  influ- 
ences must  be  allowed.  The  longer  the  period  of 


GENEOLOGICAL.  393 

sexual  indifference  (though,  this  term  be  an  objec- 
tionable one)  continues,  the  more  important  must 
be  those  outside  factors,  whether  directly  operative 
or  indirectly  through  the  parent.  Here  again,  then, 
favourable  conditions  of  nutrition,  temperature,  and 
the  like,  tend  towards  the  production  of  females, 
the  reverse  increase  the  probability  of  male  prepon- 
derance. 

The  general  conclusion,  then,  more  or  less  clearly 
grasped  by  numerous  investigators,  is  that  favour- 
able nutritive  conditions  tend  to  produce  females, 
and  unfavourable  conditions  males. 

"Let  us  express  this,  however,  in  more  precise  lan- 
guage. Such  conditions  as  deficient  or  abnormal  food, 
high  temperature,  deficient  light,  moisture,  and  the 
like,  are  such  as  tend  to  induce  a  preponderance  of 
waste  over  repair — a  relatively  katabatic  habit  of  body, 
— and  these  conditions  tend  to  result  in  the  production 
of  males.  Similarly,  the  opposed  set  of  factors,  such 
as  abundant  and  rich  nutrition,  abundant  light  and 
moisture,  favour  constructive  processes,  i.  e.,  make  for 
a  relatively  anabolic  habit,  and  these  conditions  tend 
to  result  in  the  production  of  females.  With  some  ele- 
ment of  uncertainty,  we  may  also  include  the  influence 
of  the  age  and  physiological  prime  of  either  sex,  and  of 
the  period  of  fertilisation.  But  the  general  conclusion 
is  tolerably  secure, — that  in  the  determination  of  sex, 
influences  inducing  a  relative  predominance  of  kata- 
bolism  tend  to  result  in  production  of  males,  as  those 
favouring  a  relative  predominance  of  anabolism  simi- 
larly increase  the  probability  of  females."  * 

(&)  Other  Experiments. — (1)  The  importance 
of  the  age  or  staleness  of  the  germ-cells  in  affecting 
the  growth  of  the  embryo  has  been  carefully  studied 

*  Evolution  of  Bex,  4th  ed.,  1901,  p.  55. 


394:    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

by  Dr.  H.  M.  Vernon.*  (2)  Heape  is  responsible 
for  a  number  of  experiments  on  artificial  insemina- 
tion, and  for  such  daring  experiments  as  the  follow- 
ing, f  From  an  Angora  doe  rabbit  (fertilized  32 
hours  previously  by  an  Angora  buck)  he  transferred 
two  ova  into  the  upper  end  of  the  oviduct  of  a  Bel- 
gian doe  rabbit  (inseminated  three  hours  previously 
by  a  Belgian  buck),  with  the  result  that  when  the 
Belgian  doe  gave  birth,  four  of  the  young  were 
Belgian  and  two  Angoras.  (3)  Prof.  Cossar  Ewart's 
"  Penycuik  Experiments "  have  added  not  a  little 
to  our  knowledge  as  to  the  variable  results  of  hybri- 
disation and  as  to  the  occurrence  of  reversions.^: 
(4)  The  experiments  of  Eitzema-Bos  and  others 
as  to  in-breeding  (in  rats)  suggest  that  there  are 
limits  beyond  which  this  is  likely  to  prove  very  dis- 
advantageous. 

(5)  Of  the  utmost  importance,  as  indeed  a  be- 
ginning of  an  experimental  study  of  the  conditions 
of  reproduction  in  plants,  has  been  the  careful  work 
of  Klebs  (1896),  in  which  he  has  shown  how  changes 
in    the    environmental   conditions    may    induce,    in 
Algae  and  Fungi,  the  occurrence  of  sexual  or  asexual 
reproduction.     The  factors  investigated  were  nutri- 
tion, moisture,  light,  temperature,  and  chemical  re- 
agents ;  and  the  general  result  is  a  proof  that  certain 
external  conditions  determine  the  occurrence  of  asex- 
ual  reproduction    (by   zoospores),   while   others   as 
certainly  evoke  sexual  reproduction   (by  gametes). 

(6)  Maupas'  Experiments. — Though  the  work  of 
Maupas,  like  that  of  Klebs,  has  chiefly  to  do  with 

*Proc.  Roy.  Soc.  London,  LXV.  (1899),  pp.  350-360. 
fProc.  Roy.  Soc.,  London,  XLVIII.  (1891),  pp.  457-58. 
,t  The  Penycuik  Experiments,  1899. 


GENEOLOGICAL.  395 

unicellular  organisms  and  not  with  embryos,  this 
seems  the  fittest  place  to  take  note  of  both,  and  it 
must  be  remembered  that  the  Protozoa  and  Proto- 
phyta  stand  to  the  whole  race  of  animals  and  plants 
in  somewhat  the  same  relation  as  the  germ-cells  and 
embryos  do  to  individual  organisms. 

As  the  result  of  a  long  series  of  observations — 
models  of  patient  accuracy — Maupas  reached  the 
general  conclusion  that  sexual  union  in  ciliated  In- 
fusorians,  dangerous  perhaps  for  the  individual  life, 
— a  loss  of  time  so  far  as  immediate  multiplication  is 
concerned, — is  necessary  for  the  continued  vigour 
of  the  race.  The  life  runs  in  cycles  of  asexual 
division,  which  are  strictly  limited.  Conjugation 
with  unrelated  forms  must  occur,  else  the  whole 
life  ebbs.  Without  it,  the  Protozoa,  which  some 
have  called  "  immortal,"  die  a  natural  death.  Con- 
jugation is  the  necessary  condition  of  their  eternal 
youth  and  immortality.  Even  at  this  low  level, 
only  through  the  fire  of  love  can  the  phoenix  of  the 
species  renew  its  youth.* 

(1)  Regeneration  Experiments. — In  the  eight- 
eenth century,  the  attention  of  naturalists  was  for 
a  time  focussed  on  the  problem  of  the  regeneration  or 
regrowth  of  lost  parts.  Trembley  discovered  to  his 
great  delight  that  the  fresh-water  polyp  (Hydra) 
might  be  multiplied  by  being  cut  in  pieces;  Spal- 
lanzani  showed  that  the  earthworm  cut  by  the  spade 
might  regrow  a  new  tail  or  even  a  new  head;  Bon- 
net made  numerous  experiments  on  other  worms, 
and  thought  out  an  elaborate  theory;  Reaumur 
pointed  out  the  advantage  of  the  regenerative  capac- 
ity in  animals  which  were  in  their  natural  condi- 
tions exposed  to  frequent  risks  of  breakage  or 
*See  Evolution  of  Sex  (4th  e<L,  1901),  pp.  176-78. 


396    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

wounds.  Neither  facts  nor  interpretations  were 
a-wanting  a  hundred  years  ago. 

Towards  the  end  of  the  nineteenth  century  the 
problem  of  regeneration  came  again  to  the  forefront 
of  biological  enquiry.  The  basis  of  fact  was  broad- 
ened, and  the  interpretations  became  less  vague. 

The  regenerative  capacity  is  very  unequally  dis- 
tributed in  the  animal  kingdom ;  it  is  often  exhibited 
in  regard  to  external  parts,  but  rarely  in  regard  to 
internal  parts.  Its  mechanism  remains  very  ob- 
scure, but  there  seems  much  reason  to  accept  the 
interpretation,  which  has  occurred  to  many  natu- 
ralists from  Reaumur  to  Weismann,  but  was  summed 
up  in  Lessona's  law  (1868) — that  regeneration  tends 
to  be  well-marked  in  those  animals  and  in  those  parts 
of  animals  which  are  in  the  course  of  natural  life 
very  liable  to  injury.  To  this  we  may  add  two 
saving-clauses, — (a)  always  provided  that  the  lost 
part  is  of  some  vital  importance,  and  (6)  that  the 
wound  or  breakage  is  not  fatal.  The  theory,  the 
Darwinian  interpretation  as  we  may  call  it,  is,  in 
Weismann's  words,  that  "  the  power  of  regenera- 
tion possessed  by  an  animal  or  by  a  part  of  an  ani- 
mal is  regulated  by  adaptation  to  the  frequency  of 
loss  and  to  the  extent  of  the  damage  caused  by  the 
loss."  The  importance  of  comparing  regenerative 
processes  with  those  of  normal  development  is  ob- 
vious, even  though  both  remain  unread  riddles.  The 
researches  of  Weismann  and  Morgan,  Barfurth  and 
Bordage,  Werner  and  Wheeler,  Wolff  and  Miiller, 
Loeb  and  Michel,  are  of  special  importance. 

In  the  last  quarter  of  the  nineteenth  century  em- 
bryology, hitherto  observational,  became  more  defi- 
nitely experimental.  Dareste  and  Rauber  were 
pioneers  on  a  line  of  research  which  has  been  fol- 


GENEOLOGICAL.  397 

lowed  by  many  workers, — the  Hertwigs,  Roux, 
Driesch,  Herbst,  Wilson,  Morgan,  Loeb,  Delage,  and 
many  others.  The  results  have  contributed  (a)  to 
the  morphological  problem  of  cell-lineage,  (b)  to 
the  physiological  problem  of  growth-conditions  or 
body-physics,  (c)  to  the  general  theory  of  the  mean- 
ing of  fertilisation  and  development,  and  (d)  to  our 
knowledge  of  the  influence  of  the  environment  in 
inducing  modifications.  But  it  is  too  soon  to  appre- 
ciate the  results,  some  of  which  seem  mere  curiosities, 
while  others  suggest  a  revolutionary  change  of  out- 
look. 


HEREDITY  AND  INHERITANCE. 

Old  Problems,  but  a  Modern  Study. — Even  in 
ancient  times  men  pondered  over  the  resemblances 
and  differences  between  children  and  their  parents, 
and  wondered  as  to  the  nature  of  the  bond  which 
links  generation  to  generation.  But  although  the 
problems  are  old,  the  precise  study  of  them  is  alto- 
gether modern,  and  may  almost  be  called  Darwinian. 
For  it  was  largely  under  Darwin's  influence,  dating 
from  the  publication  of  the  Origin  of  Species  (1859), 
that  the  scientific  study  of  the  problems  of  heredity 
began.  The  other  chief  influence  was  the  cell- 
theory,  especially  that  development  of  it  which  Vir- 
chow  expounded — the  idea  of  genetic  continuity.  It 
should  also  be  remembered  that  the  first  adequate  pre- 
sentation of  the  facts  of  inheritance  was  published 
about  the  middle  of  the  century,  namely,  Traite 
de  I'heredite  naturelle  (1847-1850),  by  Prosper 
Lucas,  which  furnished  a  useful  basis  for  more  crit- 
ical enquiry. 


398    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

Let  us  briefly  notice  some  of  the  changes  since  the 
beginning  of  Darwin's  day. 

(1)  Before  the  middle  of  the  nineteenth  century 
much  attention  was  given  to  what  might  be  called  the 
demonstration  of  the  general  fact  of  inheritance. 
Hundreds  of  pages  in  the  treatise  of  Prosper  Lucas 
are  devoted  to  proving  that  the  present  is  the  child  of 
the  past,  that  our  start  in  life  is  no  haphazard  affair, 
but  is  rigorously  determined  by  our  parents  and 
grandparents,  and  that  all  sorts  of  innate  peculiar- 
ities— both  great  and  small — may  reappear  genera- 
tion after  generation.  Nowadays,  no  one  doubts  the 
general  fact;  almost  everyone  rather  will  agree  with 
Prof.  E.  B.  Wilson  that  "the  studies  of  Darwin, 
Galton,  and  others  have  shown  that  there  is  no  pecu- 
liarity of  structure  or  function  in  any  part  of  the 
body  too  slight  to  escape  the  influence  of  either  parent 
or  both  in  inheritance.  .  .  .  Both  parents  affect  the 
whole  development  of  the  child  and  may  exert  an 
influence  on  every  detail  of  its  organisation."  * 

It  is  hardly  too  much  to  say  that  in  the  develop- 
ment of  natural  knowledge,  science  begins  where 
measurement  begins.  And  this  is  the  case  in  regard 
to  inheritance.  Or,  perhaps,  instead  of  measure- 
ment, which  may  be  taken  in  too  narrow  a  sense,  we 
should  say  that  precision  of  observation  and  record 
which  admits  of  statistical,  mathematical,  or  some 
other  exact  formulation.  While  nothing  can  take 
the  place  of  experiment — which  is  urgently  needed 
for  the  further  development  of  our  knowledge  of 
heredity — much  has  been  gained  by  the  application 
of  statistical  and  mathematical  methods  to  biological 
results — a  new  contact  between  different  disciplines 

*  International  Monthly,  II.,  July,  1900,  p.  80. 


GENEOLOGICAL.  399 

— which  we  may  particularly  associate  with  the 
names  of  Mr.  Francis  Galton  and  Mr.  Karl  Pear- 
son. 

(2)  A  second  step  is  the  further  elucidation  and 
widespread  acceptance  of  the  idea  which  Virchow 
was  one  of  the  first  to  state, — the  somewhat  subtle, 
yet  essentially  simple  idea,   which  may  be  called 
"  the  continuity  of  generations" 

There  is  a  sense,  as  Mr.  Galton  says,  in  which  the 
child  is  as  old  as  the  parent,  for  when  the  parent's 
body  is  developing  from  the  fertilised  ovum,  a  resi- 
due of  unaltered  germinal  material  is  kept  apart  to 
form  the  reproductive  cells,  one  of  which  may  be- 
come the  starting-point  of  a  child.  Similarly,  Weis- 
mann,  generalising  from  cases  where  it  seems  to  be 
visibly  demonstrable,  maintains  that  the  germinal 
material  (germ-plasm}  which  starts  an  offspring 
owes  its  virtue  to  being  materially  continuous  with 
the  germinal  material  from  which  the  parent  or 
parents  arose. 

(3)  A  third  step  is  that  we  are  learning  not  to 
spell  heredity  with  a  capital.     "We  no  longer  think 
of  it  as  a  power  or  principle,  as  a  fate  or  as  one  of 
the  forces  of  nature;  we  study  it  as  a  relation  of 
genetic  continuity  between  successive  generations,  in 
a  sense  mysterious,  as  every  fact  of  life  is,  but  none 
the  less  a  relation  sustained  by  a  visible  material 
basis   (the  germ-cells)   and  expressing  itself  in  re- 
semblances and  differences  which  can  be  measured 
and  weighed. 

The  very  terms  "  heredity,"  "  heritage,"  "  inherit- 
ance," "  transmit,"  are  perhaps  apt  to  deceive  us  by 
their  suggestion  of  a  false  analogy.  In  regard  to 
property  there  is  a  clear  distinction  between  the  heir 
and  the  estate  which  he  inherits;  in  regard  to  life 


400    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

there  is  at  first  no  such  distinction.  We  inherit  our- 
selves; organism  and  inheritance  are,  to  begin  with, 
one  and  the  same.  For  by  inheritance  we  simply 
mean,  in  plain  English,  all  that  is  involved  in  the 
vital  material  which  is  set  apart  from  parents  to 
start  a  new  life.  The  inheritance  is  the  fertilised 
egg-cell,  and  heredity  is  no  entity,  but  merely  a 
convenient  term  for  the  relation  of  genetic  continu- 
ity between  successive  generations. 

But  our  particular  point  is  that  "  Heredity,"  like 
"  Horologity  in  clocks,"  like  "  Phlogiston "  and 
"  Caloric,"  and  how  many  more  "  entities,"  has 
yielded  before  the  sharpness  of  William  of  Occam's 
razor. 

(4)  Another  change  is  marked  by  the  more  criti- 
cal attitude  which  is  now  taken  up  in  regard  to 
various  sets  of  facts  or  alleged  facts  relating  to  in- 
heritance, which  were  once  accepted  without  ques- 
tion. We  allude  to  the  modern  criticism  of  alleged 
cases  of  maternal  impressions,  "  telegony,"  and  the 
transmission  of  acquired  characters.  Experience 
has  brought  home  the  lesson  that  easy-going  accept- 
ance of  the  first  solution  offered  is  not  the  scientific 
method.  The  most  important  line  of  criticism  is 
that  which  has  at  least  shaken  the  formerly  wide- 
spread belief  in  the  transmission  of  acquired  char- 
acters or  somatic  modifications.  The  scepticism 
which  Kant  and  Prichard  and  others  had  long  before 
expressed  was  re-asserted  more  convincingly  by 
Weismann  in  1883  in  his  thesis  that  the  child  in- 
herits from  the  parent  germ-cell,  rather  than  from 
the  parent  body. 

Methods. — The  problems  of  heredity  have  long 
since  ceased  to  be  studied  in  the  arm-chair.  They 
have  been  attacked  precisely  and  practically  by 
several  distinct  methods,  of  which  the  most  im- 


GENEOLOGICAL.  401 

portant  are  (a)  the  minute  study  of  the  history  of 
the  germ-cells  by  which  life  is  continued  from  gen- 
eration to  generation;  (&)  the  statistical  study  of 
the  measurable  characters  of  successive  generations; 
and  (c)  the  testing  of  various  conclusions  by  ex- 
perimental breeding.  The  first  may  be  illustrated 
by  reference  to  Weismann's  Germ-Plasm  (1893)  and 
Wilson's  The  Cell  in  Development  and  Inheritance 
(2nd  ed.,  1900)  ;  the  second  by  Galton's  Natural  In- 
heritance (1889)  and  Karl  Pearson's  memoirs;  and 
the  third  by  Professor  Cossar  Ewart's  Penycuik  Ex- 
periments (1899). 

Facts  of  Inheritance. — We  do  not  propose  to  ex- 
pound the  facts  of  inheritance,  but  merely  to  indi- 
cate the  present  position  of  biology  by  a  brief 
reference. 

(I.)  The  physical  basis  of  inheritance  is  in  the 
fertilised  ovum.  Since  the  egg-cell  is  often  micro- 
scopic and  the  sperm  cell  may  be  only  -nruvsw  of 
the  ovum's  size,  it  seems  to  many  difficult  to  conceive 
how  there  can  be  room  in  these  minute  elements  for 
the  complexity  of  organisation  supposed  to  be  requi- 
site; and  the  difficulty  will  be  increased  if  the  cur- 
rent opinion  be  accepted  that  only  the  nuclei  within 
the  germ-cells  are  the  true  bearers  of  the  hereditary 
qualities.  It  must  be  at  once  admitted  that  it  is 
quite  impossible  to  form  any  mental  picture  of  the 
fact  which  the  word  potentiality  implies. 

To  the  question:  What  accounts  for  the  poten- 
tiality of  the  germ-cell, — what  makes  it,  in  con- 
trast to  any  other  cell,  able  to  develop  into  an 
organism  ? — only  two  plausible  answers  have  been 
given.  To  the  preformationists,  no  objective  answer 
was  forthcoming,  and  the  majority  fell  back  upon 
a  hypothesis  of  hyperphysical  agencies. 


4:02    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

The  first  attempt  at  an  objective  answer  is  ex- 
pressed in  a  theory  which  seems  to  have  occurred  at 
intervals  throughout  the  centuries,  the  theory  of  pan- 
genesis.  It  was  hinted  at  by  Democritus,  Hippoc- 
rates, Paracelsus,  Maupertuis,  and  Buffon.  It  was 
suggested  as  a  provisional  hypothesis  by  Darwin  and 
also  by  Spencer  (1864).  According  to  the  theory  of 
pangenesis,  the  cells  of  the  body  are  supposed  to  give 
off  characteristic  and  representative  gemmules,  these 
are  supposed  to  find  their  way  to  the  reproductive 
elements,  which  thus  come  to  contain,  as  it  were, 
concentrated  samples  of  the  different  components  of 
the  body,  and  are  therefore  able  to  develop  into  an 
offspring  like  the  parent.  The  theory  involves  many 
hypotheses,  and  is  avowedly  unverifiable  in  direct 
sense-experience,  but  the  same  might  be  said  about 
many  other  theories.  It  is  perhaps  more  to  the 
point  to  notice  that  there  is  another  theory  of  heredity 
which  is,  on  the  whole,  simpler,  which  seems,  on 
the  whole,  to  fit  the  facts  better,  especially  the  fact 
that  our  experience  does  not  warrant  the  conclusion 
that  the  modifications  or  acquired  characters  of  the 
body  of  the  parent  affect  in  any  specific  and  repre- 
sentative way  the  inheritance  of  the  offspring. 

As  we  have  already  hinted,  the  view  which  many, 
if  not  most  biologists  now  take  of  the  uniqueness  of 
the  germ-cells  is  rather  different  from  that  of  pan- 
genesis.  It  is  expressed  in  the  phrase  "  germinal 
continuity,"  and  was  suggested  by  several  thinkers 
— Owen,  Haeckel,  Jaeger,  Brooks,  Galton,  and  Nuss- 
baum — before  Weismann  worked  it  out  into  a  con- 
sistent theory.  In  many  cases,  scattered  through 
the  animal  kingdom,  from  worms  to  fishes,  the  be- 
ginning of  the  lineage  of  germ-cells  is  demonstrable 
in  very  early  stages  before  the  differentiation  of  the 


GENEOLOGICAL.  403 

body-cells  has  more  than  begun.  In  the  development 
of  the  threadworm  of  the  horse,  according  to  Boveri, 
the  very  first  cleavage  divides  the  fertilised  ovum 
into  two  cells,  one  of  which  is  the  ancestor  of  all  the 
body-cells,  and  the  other  the  ancestor  of  all  the  germ- 
cells.  In  other  cases,  particularly  among  plants, 
the  segregation  of  germ-cells  is  not  demonstrable  un- 
til a  relatively  late  stage.  Weismann,  generalising 
from  cases  where  it  seems  to  be  visibly  demonstrable, 
maintains  that  in  all  cases  the  germinal  material 
which  starts  an  offspring,  owes  its  virtue  to  being 
materially  continuous  with  the  germinal  material 
from  which  the  parent  or  parents  arose.  But  it  is 
not  on  a  continuous  lineage  of  recognisable  germ- 
cells  that  Weismann  insists,  for  this  is  often  un- 
recognisable, but  on  the  continuity  of  the  germ- 
plasm — that  is  of  a  specific  substance  of  definite 
chemical  and  molecular  structure  which  is  the 
bearer  of  the  hereditary  qualities.  In  develop- 
ment a  part  of  the  germ-plasm  "  contained  in  the 
parent  egg-shell  is  not  used  up  in  the  construction  of 
the  body  of  the  offspring,  but  is  reserved  unchanged 
for  the  formation  of  the  germ-cells  of  the  following 
generation."  Thus  the  parent  is  rather  the  trustee 
of  the  germ-plasm  than  the  producer  of  the  child. 
In  a  new  sense  the  child  is  a  chip  of  the  old 
block. 

While  early  segregation  of  the  germ-cells  is  in 
many  cases  an  observable  fact — and  doubtless  the  list 
of  such  cases  will  be  added  to — the  conception  of  a 
germ-plasm  is  hypothetical,  just  as  the  conception 
of  a  specific  living  stuff  or  protoplasm  is  hypothetical. 
We  cannot  demonstrate  the  germ-plasm,  even  if  we 
may  assume  that  it  has  its  physical  basis  in  the  stain- 
able  nuclear  bodies  or  chromosomes.  The  theory  has 


4:04    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

to  be  judged,  like  all  such  formulae,  by  its  adequacy 
in  fitting  facts. 

Let  us  suppose  that  the  fertilised  ovum  has  cer- 
tain qualities,  a,  b,  c,  .  .  .  x,  yf  z;  it  divides  and 
re-divides,  and  a  body  is  built  up;  the  cells  of  this 
body  exhibit  division  of  labour  and  differentiation, 
losing  their  likeness  to  the  ovum  and  to  the  first  re- 
sults of  its  cleavage.  In  some  of  the  body-cells  the 
qualities  a,  b,  find  predominant  expression,  in  others 
the  qualities  y,  z,  and  so  on.  But  if,  meanwhile, 
there  be  certain  germ-cells  which  do  not  differentiate, 
which  retain  the  qualities  a,  b,  c,  .  .  .  x,  y,  z,  un- 
altered, which  keep  up,  as  one  may  say  figuratively, 
"  the  protoplasmic  tradition,"  these  will  be  in  a  posi- 
tion by  and  by  to  develop  into  an  organism  like  that 
which  bears  them.  Similar  material  to  start  with, 
similar  conditions  in  which  to  develop,  therefore, 
like  tends  to  beget  like.  Various  attempts  have  been 
made  to  elaborate  the  general  idea  of  genetic  con- 
tinuity, in  terms  for  instance  of  "  organic  memory  " 
(Haeckel,  Hering,  Samuel  Butler)  but  it  is  doubtful 
whether  they  have  been  of  real  service. 

It  may  be  mentioned  that  Jaeger,  Brooks,  De 
Vries,  and  others  have  tried  to  combine  the  modern 
view  with  a  modified  version  of  the  pangenetic  hy- 
pothesis. 

(II.)  The  dual  nature  of  inheritance  is  another 
great  fact,  though  it  may  seem  a  commonplace  to 
the  superficial.  Apart  from  exceptional  cases  (a- 
sexual  multiplication,  parthenogenesis,  and  autog- 
amy), the  inheritance  of  every  multicellular  plant  or 
animal  is  dual,  part  of  it  comes  from  the  mother  in 
the  ovum  or  ovum-nucleus,  part  of  it  comes  from 
the  father  in  the  spermatozoon  or  sperm-nucleus ;  the 
beginning  of  the  new  individuality  is  a  fertilised 


GENEOLOGICAL.  405 

egg-cell  in  which  two  organisations  are  subtly 
mingled.  We  have  already  referred  to  the  inter- 
esting fact  that  the  partition  of  paternal  and  mater- 
nal chromatin-contributions  between  the  daughter 
cells  of  the  segmenting  ovum  can  be  demonstrated  in 
early  stages  of  development. 

In  regard  to  this  fact  of  dual  inheritance,  three 
saving-clauses  are  suggested  by  recent  researches. 

(a)  Although  inheritance  is  dual,  it  is  in  quite  as 
real  a  sense  multiple,  from  ancestors  through-  parents, 
as  we  shall  afterwards  see.  (&)  If  Loeb  is  able  to 
induce  artificial  parthenogenesis  in  sea-urchins'  eggs 
exposed  for  a  couple  of  hours  to  sea-water  to  which 
some  magnesium  chloride  has  been  added ;  if  Delage 
is  able  to  fertilise  and  to  rear  normal  larvae  from 
non-nucleated  ovum-fragments  of  sea-urchin,  worm 
and  mollusc,  we  should  be  chary  of  committing  our- 
selves definitely  to  the  conclusion  that  the  nuclei  are 
the  exclusive  bearers  of  the  hereditary  qualities,  or 
that  both  must  be  present  in  all  cases.  Further- 
more, the  fact  that  an  ovum  without  any  sperm- 
nucleus,  or  an  ovum-fragment  without  any  but  a 
sperm-nucleus,  can  develop  into  a  normal  larva  points 
to  the  conclusion,  probable  also  on  other  grounds, 
that  each  germ-cell,  whether  ovum  or  spermatozoon, 
bears  a  complete  equipment  of  hereditary  qualities. 
(c)  It  must  be  carefully  observed  that  our  second 
fact  does  not  imply  that  the  dual  nature  of  inherit- 
ance must  be  patent  in  the  full-grown  offspring, 
for  hereditary  resemblance  is  often  strangely  uni- 
lateral, the  characters  of  one  parent  being  "  pre- 
potent "  as  we  say,  over  those  of  another. 

(III.)  Although  specific  inheritance  tends  to  be 
approximately  complete,  there  are  many  degrees  in 
the  completeness  with  which  an  inheritance  is  ex- 


406    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

pressed.  It  will  be  granted  by  all  that  the  complete- 
ness with  which  the  characters  of  race,  genus, 
species,  and  stock  are  reproduced  generation  after 
generation,  is  one  of  the  large  facts  of  inheritance. 
But  it  is  obvious  that  this  does  not  sum  up  our  ex- 
perience. The  familiar  saying,  "  like  begets  like," 
should  rather  read,  "  like  tends  to  beget  like,"  for 
variation  is  a  more  frequent  occurrence  than  complete 
hereditary  resemblance.  An  offspring  cannot  be  a 
facsimile  reproduction  of  both  its  parents.  If  it 
seem  to  show  no  characteristic  which  its  parents  did 
not  between  them  possess,  this  may  be  due  to  absence 
of  variation,  or,  what  comes  almost  to  the  same  thing, 
to  completeness  of  inheritance,  but  it  is  more  likely 
that  the  apparent  completeness  of  resemblance  is  a 
fallacious  inference  due  to  our  inability  to  detect  the 
idiosyncrasies. 

The  popular  platitude,  "  the  child  is  a  chip  of  the 
old  block,"  will  not  suffice ;  there  are  some  characters, 
e.g.,  tendencies  to  certain  diseased  conditions,  which 
are  more  frequently  transmitted  than  others,  and  the 
student  of  inheritance  must  work  towards  precise 
statistics  of  the  probabilities  of  transmission;  there 
are  some  subtle  qualities  whose  heritability  must  not 
be  assumed  without  evidence,  thus  it  is  of  great  im- 
portance to  students  of  organic  evolution  that  Prof. 
Karl  Pearson  has  recently  supplied,  for  certain  cases, 
definite  proof  of  the  inheritance  of  fecundity,  fer- 
tility, and  longevity. 

Before  we  notice  some  of  the  common  modes  of 
inheritance,  we  must  emphasize  a  preliminary  con- 
sideration. It  is  a  matter  of  observation  that  there 
are  great  differences  in  the  degree  in  which  offspring 
resemble  their  parents ;  but  it  is  a  matter  of  conjec- 
ture that  lack  of  resemblance  is  necessarily  due  to 


GENEOLOGICAL.  407 

incompleteness  in  the  inheritance.  Indeed,  the  fact 
that  resemblance  so  often  reappears  in  the  third 
generation,  makes  it  probable  that  the  incompleteness 
is  not  in  the  inheritance  but  simply  in  its  expression. 
The  characters  which  seem  to  be  absent,  to  "  skip  a 
generation,"  as  we  say,  are  probably  part  of  the  in- 
heritance, as  usual.  But  they  remain  latent,  neutral- 
ised, silenced  (we  can  only  use  metaphors)  by  other 
characters,  or  else  unexpressed  because  of  the  ab- 
sence of  the  appropriate  stimulus. 

The  three  most  frequent  modes  of  inheritance  are, 
for  convenience,  called — blended,  exclusive,  and  par- 
ticulaie. 

(a)  In  blended  inheritance,  the  characters  of  the 
two  parents,  e.g.,  in  regard  to  a  particular  structure, 
such  as  the  colour  of  the  hair,  are  intimately  com- 
bined in  the  offspring.  This  is  particularly  well 
seen  in  some  hybrids,  where  the  offspring  seems  like 
the  mean  of  the  two  parents ;  it  is  probably  the  most 
frequent  mode  of  inheritance. 

(6)  In  exclusive  inheritance,  the  expression  of 
maternal  or  of  paternal  characters  in  relation  to  a 
given  structure,  such  as  eye-colour,  is  suppressed. 
Sometimes  the  unilateral  resemblance  is  very  pro- 
nounced, and  we  say  that  the  boy  is  "  the  very  image 
of  his  father,"  or  the  daughter  "  her  mother  over 
again " ;  though  even  more  frequently  the  resem- 
blance seems  "  crossed,"  the  son  taking  after  the 
mother,  and  the  daughter  after  the  father. 

(c)  It  seems  convenient  to  have  a  third  category 
for  cases  where  there  is  neither  blending  nor  exclu- 
siveness,  but  where  in  the  expression  of  a  given 
character,  part  is  wholly  paternal  and  part  wholly 
maternal.  This  is  called  particulate  inheritance. 
Thus,  an  English  sheep-dog  may  have  a  paternal  eye 

2  A 


408    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

on  one  side,  and  a  maternal  eye  on  the  other.  Sup- 
pose the  parents  of  a  foal  to  be  markedly  light  and 
dark  in  colour;  if  the  foal  is  light  brown  the  in- 
heritance in  that  respect  is  blended,  if  light  or  dark 
it  is  exclusive,  if  piebald  it  is  particulate.  In  the 
last  case  there  is  in  the  same  character  an  exclusive 
inheritance  from  both  parents. 

(IV.)  Regression. — To  Mr.  Francis  Gait  on  espe- 
cially we  owe  an  analysis  of  the  fact  which  stares  us 
in  the  face  that  there  is  a  sensible  stability  of  type 
from  generation  to  generation.  "  The  large,"  he 
says,  "  do  not  always  beget  the  large,  nor  the  small 
the  small;  but  yet  the  observed  proportion  between 
the  large  and  the  small,  in  each  degree  of  size  and  in 
every  quality,  hardly  varies  from  one  generation  to 
another."  In  other  words,  there  is  a  tendency  to 
keep  up  a  specific  average.  This  may  be  partly  due 
to  the  action  of  natural  elimination,  weeding  out 
abnormalities,  often  before  they  are  born.  But  it 
is  to  be  primarily  accounted  for  by  what  Mr.  Galton 
calls  the  fact  of  "  filial  regression."  Let  us  take 
an  instance  from  Mr.  Pearson's  Grammar  of  Sci- 
ence. Take  fathers  of  stature  72  inches,  the  mean 
height  of  their  sons  is  70.8,  we  have  a  regression 
towards  the  mean  of  the  general  population.  On  the 
other  hand,  fathers  with  a  mean  height  of  66  inches 
give  a  group  of  sons  of  mean  height  68.3  inches, 
again  nearer  the  mean.  "  The  father  with  a  great 
excess  of  the  character  contributes  sons  with  an  ex- 
cess, but  a  less  excess  of  it;  the  father  with  a  great 
defect  of  the  character  contributes  sons  with  a  de- 
fect, but  less  of  it," 

As  Mr.  Galton  puts  it,  society  moves  as  a  vast 
fraternity.  The  sustaining  of  the  specific  average 
is  certainly  not  due  to  each  individual  leaving  his 


GEXEOLOGICAL.  409 

like  behind  him,  for  we  all  know  that  this  is  not  the 
case.  It  is  due  to  a  regression  which  tends  to  bring 
the  offspring  of  extraordinary  parents  nearer  the 
average  of  the  stock.  In  other  words,  children  tend 
to  differ  less  from  mediocrity  than  their  par- 
ents. 

This  big  average  fact  is  to  be  accounted  for  in  terms 
of  that  genetic  continuity  which  makes  an  inherit- 
ance not  dual,  but  multiple.  "  A  man,"  says  ]Mr. 
Pearson,  "  is  not  only  the  product  of  his  father,  but 
of  all  his  past  ancestry,  and  unless  very  careful  se- 
lection has  taken  place,  the  mean  of  that  ancestry  is 
probably  not  far  from  that  of  the  general  population. 
In  the  tenth  generation  a  man  has  (theoretically) 
102-i  tenth  great-grandparents.  He  is  eventually 
the  product  of  a  population  of  this  size,  and  their 
mean  can  hardly  differ  from  that  of  the  general 
population.  It  is  the  heavy  weight  of  this  mediocre 
ancestry  which  causes  the  son  of  an  exceptional 
father  to  regress  towards  the  general  population 
mean ;  it  is  the  balance  of  this  sturdy  commonplace- 
ness  which  enables  the  son  of  a  degenerate  father  to 
escape  the  whole  burden  of  the  parental  ill." 

At  this  point  one  should  discuss  reversion  or  ata- 
vism, but  it  is  exceedingly  difficult  to  get  a  firm  basis 
of  fact.  The  term  reversion  is  here  used  to  include 
cases  where  through  inheritance  there  reappears  in 
an  individual  some  character  which  was  not  ex- 
pressed in  his  parents,  but  which  did  occur  in  an 
ancestor.  It  includes  abnormal  as  well  as  normal 
characters,  and  even  the  reappearance  of  characters, 
the  normal  occurrence  of  which  is  outside  of  the 
limits  of  the  race  altogether,  i.e.,  in  some  phyleti- 
cally  older  race.  In  other  words,  the  character 
whose  reappearance  is  called  a  reversion  may  be 


410    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

found  within  the  verifiable  family,  within  the  breed, 
within  the  species,  or  even  in  a  presumed  ancestral 
species. 

The  best  illustrations  of  reversion  are  furnished 
by  hybrids.  Thus  in  one  of  Prof.  Cossar  Ewart's 
experiments  a  pure  white  f  antail  cock  pigeon,  of  old- 
established  breed,  which  in  colour  had  proved  itself 
prepotent  over  a  blue  pouter,  was  mated  with  a  cross 
previously  made  between  an  owl  and  an  archangel, 
which  was  far  more  of  an  owl  than  an  archangel. 
The  result  was  a  couple  of  fantail-owl-archangel 
crosses,  one  resembling  the  Shetland  rock-pigeon,  and 
the  other  the  blue  rock  of  India.  ~Not  only  in 
colour,  but  in  shape,  attitude,  and  movements  there 
was  an  almost  complete  reversion  to  the  form  which 
is  believed  to  be  ancestral  to  all  the  domestic  pigeons. 
The  only  marked  difference  was  a  slight  arching  of 
the  tail.  Similar  results  were  got  with  fowls  and 
rabbits. 

Such  facts  lead  us  to  the  theory  that  characters 
may  lie  latent  for  a  generation  or  for  generations, 
or  in  other  words  that  certain  potentialities  or 
initiatives  which  form  part  of  the  heritage  may  re- 
main unexpressed  for  lack  of  the  appropriate  liberat- 
ing stimulus,  or  for  other  reasons,  or  may  have  their 
normal  expressions  disguised.  But  it  does  not  follow 
that  the  reappearance  of  an  ancestral  character  not 
seen  in  the  parents  is  necessarily  due  to  the  reasser- 
tion  of  latent  elements  in  the  inheritance.  It  may  be 
a  case  of  ordinary  regression;  it  may  be  a  case  of 
arrested  development;  it  may  be  an  extreme  varia- 
tion whose  resemblance  to  an  ancestral  charac- 
teristic is  a  coincidence;  it  may  be  an  individually 
acquired  modification, reproduced  apart  from  inherit- 


GENEOLOGICAL.  411 

ance,  by  a  recurrence  of  suitable  external  conditions, 
and  so  on.  In  short,  what  are  called  reversions  are 
properly  in  many  cases  misinterpretations. 

(V.)  Galton's  Law. — The  most  important  general 
conclusion  which  has  yet  been  reached  in  regard  to 
inheritance  is  formulated  in  Galton's  Law.  Mr. 
Galton  was  led  to  it  by  his  studies  on  the  inheritance 
of  human  qualities,  and  more  particularly  by  a  series 
of  studies  on  Basset  hounds.  It  is  one  of  those  gen- 
eral conclusions  which  have  been  reached  statistic- 
ally, and  we  must  refer  for  the  evidence  and  also 
for  its  strictest  formulation  to  the  revised  edition  of 
Mr.  Pearson's  Grammar  of  Science. 

As  we  have  seen,  it  is  useful  to  speak  of  a  heritage 
as  dual,  half  derived  from  the  father  and  half  from 
the  mother.  But  the  heritable  material  handed  on 
from  each  parent  was  also  dual,  being  derived  from 
the  grandparents.  And  so  on,  backwards.  We  thus 
reach  the  idea  that  a  heritage  is  not  merely  dual, 
but  in  a  deeper  sense  multiple. 

According  to  Galton's  law,  "  the  two  parents  be- 
tween them  contribute  on  the  average  one-half  of 
each  inherited  faculty,  each  of  them  contributing 
one-quarter  of  it.  The  four  grandparents  contribute 
between  them  one-quarter,  or  each  of  them  one-six- 
teenth ;  and  so  on,  the  sum  of  the  series  £  +  %  +  -J-  + 
^  +  etc.,  being  equal  to  1,  as  it  should  be.  It  is  a 
property  of  this  infinite  series  that  each  term  is  equal 
to  the  sum  of  all  those  that  follow :  thus  \  =  ?  +  %  + 
fg-  +  etc. ,  i  =  i  +  yfr  +  etc-j  an(l  so  on-  The  prepo- 
tencies or  subpotencies  of  particular  ancestors,  in 
any  given  pedigree,  are  eliminated  by  a  law  that 
deals  only  with  average  contributions,  and  the  vary- 
ing prepotencies  of  sex  in  respect  to  different  quali- 
ties are  also  presumably  eliminated." 


412    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

Transmissibility  of  Acquired  Characters  or  Modi- 
fications.— Since  1883,  when  Weismann  expressed 
his  entire  scepticism  as  to  the  transmission  of  ac- 
quired characters,  the  question  has  been  almost  con- 
tinuously debated.  This  is  not  surprising,  for  it  is 
much  more  than  a  technical  problem  for  biologists. 
It  is  of  profound  interest  to  the  parent,  the  physi- 
cian, the  teacher,  the  moralist,  and  the  social  reform- 
er ;  and  it  really  concerns  us  all,  for  the  answer  to  it 
affects  every-day  conduct.  This  is  sufficient  reason 
for  devoting  some  attention  to  it  here,  and  this 
is  further  justified  by  the  fact  that  although  the 
negative  position  has  been  tentatively  assumed  at 
various  periods,  e.g.,  by  Kant  and  by  Prichard 
(b.  1786),  the  careful  discussion  of  the  question  is 
characteristic  of  the  last  quarter  of  the  nineteenth 
century,  and  dates  from  an  essay  by  Galton  in 
1875,*  and  from  one  by  Weismann  in  1883.f 

"  Modifications  "  or  "  Acquired  Characters  "  may 
be  defined  as  structural  changes  in  the  body  of  the 
organism  induced  by  changes  in  the  environment  or 
in  the  function,  and  such  that  they  transcend 
the  limit  of  organic  elasticity,  and  therefore  persist. 
Plants  of  the  plain  when  brought  into  Alpine  condi- 
tions may  develop  more  protective  tissue  and  exhibit 
many  other  modifications.  The  white  man  who 
works  for  many  years  under  a  tropical  sun  may  be- 
come so  deeply  tanned  that  the  result  does  not  dis- 
appear after  years  of  residence  in  Britain.  Unlike 
the  Ethiopian  he  has  changed  his  skin,  but  he  cannot 
change  it  back  again.  Through  prolonged  disuse 

*A  Theory  of  Heredity,  Contemporary  Review,  XXVII., 
pp.   80-95. 
f  Ueber  die  Vererbung,  Jena,  trans.  Oxford,  1889. 


GEXEOLOGICAL.  413 

from  early  years  onwards  a  muscle  may  pass  into  a 
state  of  atrophy,  through  prolonged  exercise  another 
may  become  exaggerated,  and  the  modifications  in 
either  case  may  last  a  lifetime.  Endless  examples 
might  be  given. 

But  to  understand  the  matter  more  clearly  we 
must  contrast  "  modifications  "  due  to  "  nurture  " 
with  "  variations "  due  to  "  nature."  When  we 
compare  living  creatures  of  the  same  kind,  children 
with  parents,  brother  with  brother,  neighbour  with 
neighbour,  native  with  foreigner,  we  recognise  that 
there  are  many  differences  between  them,  though  they 
all  fall  within  the  range  which  we  call  "  the  same 
species."  To  begin  with,  we  call  these  the  observed 
differences  between  individuals.  As  we  come  to 
analyse  them,  however,  we  discern  that  a  number  are 
definitely  associated  with  particular  functions  and 
surrounding  influences.  They  may  not  be  hinted  at 
in  the  young  forms,  but  they  begin  to  appear  when 
the  particular  conditions  begin  to  operate.  They 
can  be  definitely  related  to  some  alteration  or  dif- 
ference in  environment  or  in  function,  and  they  are 
usually  exhibited  in  some  degree  by  all  organisms 
of  the  same  kind  which  are  subjected  to  the  same 
change  of  conditions.  These  we  call  "  modifica- 
tions "  or  acquired  characters.  Now  when  we  sub- 
tract from  the  total  of  observed  differences  the  modi- 
fications which  we  have  detected,  there  remain  a 
number  of  differences  which  we  call  "  variations." 
We  cannot  causally  relate  them  to  differences  in  habit 
or  surroundings,  they  are  often  hinted  at  even  before 
birth,  and  they  are  not  alike  even  among  forms  whose 
conditions  of  life  seem  absolutely  uniform.  We 
suppose  that  they  have  an  origin  in  changes  of  the 
germinal  material  before  or  after  fertilisation;  we 


414    PEOGRESS  OF  SCIENCE  IN  THE  CENTURY. 

call  them  congenital  or  germinal  variations,  and 
there  is  no  doubt  that  they  are  transmissible.  The 
precise  problem  is,  whether  the  modifications  of 
the  body  can  so  specifically  affect  the  reproductive 
cells  that  the  next  generation  will  inherit  in  some 
measure  the  modification  acquired  by  the  parent  or 
parents.  If  summing  up,  in  Galton's  phrase,  we  call 
the  effects  of  surrounding  influences  "  nurture"  our 
question  is  seen  to  be  an  extraordinarily  important 
one,  May  the  results  of  nurture  be  transmitted,  or  is 
it  the  "  nature  "  alone  that  constitutes  the  inherit- 
ance? 

Widespread  Opinion  in  Favour  of  Affirmative  "An- 
swer.— In  fairness  we  are  bound  to  recognise  that 
the  verdict  of  the  practical  man,  whether  gardener 
or  farmer,  breeder  or  physician,  is  still  predominantly 
in  favour  of  an  affirmative  answer. 

There  is  little  to  be  gained  by  a  citation  of 
opinions,  there  are  equally  great  names  on  both 
sides.  It  cannot  be  an  easy  question  when  we  find 
Spencer  on  one  side  and  Weismann  on  the  other, 
Haeckel  on  one  side  and  Professor  Ray  Lankester 
on  the  other,  Sir  William  Turner  on  one  side  and 
Professor  His  on  the  other,  and  so  on. 

The  reason  why  the  affirmative  position  is  so 
widely  held  is  probably  threefold:  (1)  First,  that 
there  are  many  facts  which  suggest  modification- 
inheritance  until  they  are  examined  critically.  The 
late  Duke  of  Argyll  said  that  the  world  is  strewn 
with  illustrations,  and  Dr.  Haacke  has  compared  the 
evidence  for  the  affirmative  to  the  sand  on  the  sea- 
shore for  multitude,  yet  neither  furnishes  us  with' 
a  single  grain  which  will  bear  analysis.  That  it  is 
an  obvious  interpretation  we  grant,  but  the  obvious 


GENEOLOGICAL.  415 

interpretation  is  seldom  the  right  one.  The  sun  does 
not  go  round  the  earth.  (2)  Second,  it  is  an  inter- 
pretation which  would  seem  to  make  the  theory  of 
organic  evolution  simpler;  it  suggests  a  more  direct 
and  rapid  method  than  the  natural  selection  of  con- 
genital variations.  If  to  a  growing  and  varying 
nature  or  congenital  inheritance  there  be  continually 
added  the  results  of  nurture,  the  rate  of  evolution 
would  be  quickened  both  upwards  and  downwards. 
Our  first  business,  however,  is  to  find  out  whether 
the  hypothesis  actually  consists  with  experience. 
(3)  Third,  we  are  so  accustomed  in  human  affairs 
to  the  entailment  of  gains  from  generation  to  genera- 
tion, to  standing  on  the  shoulders  of  our  ancestors' 
achievements,  that  it  seems  difficult  for  some  to 
refrain  from  projecting  this  on  organic  nature,  for- 
getful of  the  fact  that  the  greater  part  of  our  entail- 
ing process  is  altogether  apart  from  organic  inherit- 
ance. It  comes  about  through  social  inheritance 
embodied  in  tradition,  convention,  institution,  lit- 
erature, art,  law,  etc.,  of  which  there  are  among 
animals  only  vague  analogues. 

A  General  Argument  Against. — Apart  from  the 
fact  that  he  found  the  evidence  brought  forward  in 
favour  of  the  belief  in  the  inheritance  of  acquired 
characters  to  be  "  a  handful  of  anecdotes,"  Professor 
.Weismann  was  led  to  his  position  of  extreme  scepti- 
cism by  his  realisation  of  the  continuity  of  genera- 
tions. 

It  is  evident  that  if  the  germ-plasm  or  the  material 
basis  of  inheritance  be  something  apart  from  the 
general  life  of  the  body,  sometimes  set  apart  from 
a  very  early  stage,  there  is  a  presumption  against  the 
likelihood  of  its  being  readily  affected  in  a  specific 
manner  by  changes  in  the  nature  of  the  body-cells. 


4:16    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

The  germ-plasm  is  in  a  sense  so  apart  that  it  is  diffi- 
cult to  conceive  of  the  mechanism  by  which  it  might 
be  influenced  in  a  specific  or  representative  manner 
by  changes  in  the  cells  of  the  body. 

A  General  Argument  For. — We  have  recognised 
that  the  germ-cells  may  be  early  set  apart  in  the 
building  up  of  the  body,  and  that  they  sometimes 
seem  scarcely  to  share  at  all  in  its  daily  life.  On 
the  other  hand,  in  many  plants  the  distinction  be- 
tween body  and  germ-cells  can  hardly  be  drawn,  and 
even  if  we  keep  to  animals  the  bonds  between  the 
body  and  its  germ-cells  are  often  very  close.  The 
blood  and  lymph  or  other  body  fluids  form  a  common 
medium  for  all  the  parts  of  the  animal;  alteration 
of  diet  in  the  early  youth  of  some  animals  like  tad- 
poles and  caterpillars  may  determine  the  predomi- 
nance of  one  sex  or  the  other  through  influences 
which  must  pass  from  body  to  germ-cells;  various 
poisons  may  affect  the  whole  bodily  system  and  the 
germ-cells  as  well,  and  there  are  real  though  dimly 
understood  correlations  between  the  reproductive  sys- 
tem and  the  rest  of  the  body.  It  is  therefore  erro- 
neous to  think  of  the  germ-cells  as  if  they  led  a 
charmed  life  uninfluenced  by  any  of  the  accidents 
and  incidents  in  the  daily  life  of  the  body  which 
bears  them.  No  one  believes  this,  Weismann  least  of 
all,  for  he  finds  one  of  the  chief  sources  of  congenital 
variation  in  the  nutritive  stimuli  exerted  on  the 
germ-plasm  by  the  varying  state  of  the  body. 

There  are  some  who  find  in  this  "  a  concealed 
abandonment  of  the  central  position  of  Weismann," 
and  one  of  them  has  recently  put  the  argument  thus : 
if  the  germ-plasm  is  affected  by  changes  in  nutrition 
in  the  body,  and  if  acquired  characters  affect  changes 
in  nutrition,  then  "  acquired  characters  or  their  con- 


GENEOLOGICAL.  417 

sequences  will  be  inherited."  But  it  is  quite  illegiti- 
mate to  slump  "  acquired  characters  and  their  con- 
sequences "  as  if  the  distinction  was  immaterial. 
The  illustrious  author  of  the  Germ-Plasm  has 
made  it  quite  clear  that  there  is  a  very  great  differ- 
ence between  admitting  that  the  germ-plasm  has  no 
charmed  life,  insulated  from  bodily  influences,  and 
admitting  the  transmissibility  of  a  particular  ac- 
quired character,  even  in  the  faintest  degree.  The 
point,  let  us  repeat,  is  this:  Does  a  change  in  the 
body,  induced  by  use  or  disuse  or  by  a  change  in 
surroundings,  influence  the  germ-plasm  in  such  a 
specific  or  representative  way  that  the  offspring  will 
exhibit  the  same  modification  which  the  parent  ac- 
quired or  even  a  tendency  towards  it? 

Even  when  we  fully  recognise  the  unity  of  the 
organism,  that  each  part  shares  in  the  life  of  the 
whole,  it  is  very  difficult  for  those  who  accept  the 
belief  in  the  inheritance  of  acquired  characters  to 
suggest  any  modus  operandi  whereby  a  particular 
modification  in  the  brain  or  the  little  toe,  the  root  or 
the  petal,  can  specifically  affect  the  germinal  material 
in  such  a  way  that  the  modification  or  a  tendency 
towards  it  becomes  part  of  the  inheritance.  Did  wo 
accept  Darwin's  provisional  hypothesis  of  pangen- 
esis  according  to  which  the  parts  of  the  body  give 
off  gemmules  which  are  carried  as  samples  to  the 
germ-cells,  the  possibility  of  transfer  might  seem 
more  intelligible.  But  Darwin's  suggestion  remains 
a  pure  hypothesis,  and  is  accepted  by  none  except  in 
extremely  modified  form.  Indeed  it  may  be  recalled 
that  it  was  the  failure  of  his  attempt  to  find  con- 
firmation of  Darwin's  hypothesis  by  experiments  on 
the  transfusion  of  blood  which  led  Galton  many  years 
ago  to  doubt  whether  there  was  any  inheritance  of 


418    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

acquired  characters.  Yet,  in  fairness,  we  must  note 
how  little  we  understand  the  influences  which  pass 
in  the  other  direction  from  reproductive  organs  to 
body,  and  recall  Lloyd  Morgan's  warning  that  al- 
though we  cannot  conceive  how  a  modification  might 
as  such  saturate  from  body  to  germ-cells,  this  does 
not  exclude  the  possibility  that  it  may  actually 
do  so. 

Particular  Evidence  For. — Let  us  now  give  a  few 
examples  of  the  particular  or  a  posteriori  evidence  in 
favour  of  the  inheritance  of  acquired  characters, 
and  to  suggest  some  of  the  difficulties  which  rob  the 
evidence  of  cogency. 

It  has  been  stated  that  the  Panjabis  of  India  show 
certain  peculiarities  of  musculature  and  skeleton 
which  are  plainly  related  to  the  frequency  with  which 
these  people  assume  on  all  possible  occasions  the 
squatting  posture.  Like  so  many  other  pieces  of  so- 
called  evidence  this  does  not  tell  one  enough,  e.g., 
whether  the  peculiarities  are  seen  on  new-born  Pan- 
jabi  babes,  and  whether  the  peculiarities  appear  to 
be  on  an  increase.  As  it  stands,  the  evidence  is  quite 
inconclusive,  and  we  may  place  against  it  the  case 
of  the  compressed  foot  of  Chinese  ladies — in  regard 
to  which  we  have  likewise  few  satisfactory  details, 
but  certainly  not  as  yet  any  evidence  that  the  long- 
continued  deformation  has  resulted  in  any  heredi- 
tary change  in  the  Chinese  baby's  foot.  The  alleged 
dwindling  of  the  little  toe  has  been  impetuously  in- 
stanced as  a  case  in  point — as  a  case  of  the  inherit- 
ance of  a  modification  produced  by  tight  boots.  But 
there  is  no  satisfactory  evidence;  a  dwindling  has 
also  been  alleged  in  savages  who  do  not  wear  boots; 
it  is  possible  that  there  is  in  man  as  there  was  in  the 
horse  a  congenital  variation  in  favour  of  reduction 


GENEOLOGICAL.  419 

of  digits ;  and  there  are  other  possible  explanations. 

About  a  hundred  years  ago  (1796),  an  authority 
on  trotting  horses  stated  that  the  utmost  speed  of  the 
English  trotter  was  a  mile  in  2  minutes,  57  seconds. 
Since  1818,  accurate  trotting  records  have  been  kept, 
and  an  inspection  of  these  shows  that  very  gradu- 
ally, decade  after  decade,  the  speed  and  the  percent- 
age of  swift  trotters  increased.  Finally  there  has 
been  evolved  a  breed  who  can  trot  the  mile  in  2 
minutes,  10  seconds.  It  is  claimed  by  Cope  and 
others  that  we  have  here  evidence  of  the  cumulative 
transmission  of  the  results  of  exercise  or  nurture. 
But  a  sceptical  consideration  leads  one  to  doubt  if 
the  case  is  even  relevant;  the  interpretation  in  terms 
of  use-inheritance  overlooks  the  results  of  selective 
breeding  which  may  have  increased  the  congenital 
swiftness,  and  the  process  of  elimination  which  per- 
sistently weeded  out  the  less  swift  from  the  stud. 

Reference  is  often  made  in  biological  literature 
to  the  observations  and  experiments  of  Schmanke- 
witsch  in  1875  on  certain  brine-shrimps  belonging  to 
the  genus  Artemia.  By  lessening  the  salinity  of 
the  water  he  was  able  to  transform  one  type,  Ar- 
temia salina,  in  the  course  of  generations  into  an- 
other type,  Artemia  milhausenii;  and  conversely,  by 
increasing  the  salinity.  Although  he  did  not  him- 
self make  any  such  claim,  his  work  has  often  been 
referred  to  as  an  illustration  of  changing  one  species 
into  another.  It  had  indeed  the  undeniable  result 
of  showing  that  certain  forms  of  life  are  very  plastic, 
even  to  such  influences  as  altered  salinity.  Apart 
altogether  from  the  criticism  of  experts,  which  has 
been  damaging,  it  may  be  recognised  that  Schmanke- 
witsch  experimented  with  a  progressively  changing 
environment  on  a  series  of  generations,  and  that  the 


420    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

result  is  readily  interpretable  as  due  to  cumulative 
modifications  hammered  on  each  successive  genera- 
tion without  there  being  any  inheritance  of  these 
modifications.  It  is  also  possible  that  the  reproduc- 
tive cells  were  influenced  along  with  the  body  or 
outside  of  the  body  by  the  continuous  change  of 
salinity. 

Another  typical  line  of  evidence  is  that  based  on 
the  study  of  immunity — a  subject  of  great  practical 
importance  and  theoretical  interest.  A  due  discus- 
sion of  it  is  impossible  in  our  space  here,  but  the  par- 
ticular point  admits  of  being  briefly  stated.  It  is 
well  known  that  negroes  and  mongolians  are  rela- 
tively immune  to  yellow  fever,  and  it  is  believed 
by  many  that  a  progressive  immunity  to  various 
diseases  is  observable  in  our  own  country.  Is  not 
this  proof  positive  of  the  inheritance  of  an  acquired 
character?  The  sceptical  answer  is  first  of  all  that 
the  original  immunity  may  have  been  a  congenital 
peculiarity,  which  has  become  dominant  in  the  race 
by  the  elimination  of  those  members  who  were  not 
immune.  And  if  it  be  objected  that  there  are  cases 
where  a  mother-rabbit  or  guinea-pig  has  been  arti- 
ficially rendered  immune  to  certain  diseases,  and  has 
had  young  ones  born  immune,  the  answer  is  again 
ready,  that  this  was  probably  due  to  a  kind  of  infec- 
tion before  birth,  some  anti-toxin  or  other  having 
probably  passed  from  the  mother  to  the  unborn 
young.^ 

Indirect  Importance  of  Modifications. — That 
modifications  are  common,  everyone  admits;  that 
they  are  often  of  great  value  to  the  individuals  who 
acquire  them  is  also  certain ;  the  question  is  whether 
they  are  of  direct  value  to  the  race,  seeing  that  we 
cannot  prove  their  transmissibility. 


GENEOLOGICAL.  421 

In  this  connection  a  recent  suggestion  of  much  in- 
terest has  been  made  by  Professors  Mark  Baldwin, 
Lloyd  Morgan,  and  Osborn,  namely,  that  adaptive 
modifications  may  act  as  the  fostering  nurses  of  con- 
genital variations  in  the  same  direction.  An  illus- 
tration will  make  the  general  idea  clear. 

Let  us  suppose  a  country  in  which  a  change  of 
climate  made  it  year  by  year  of  the  utmost  impor- 
tance that  the  inhabitants  should  become  swarthy. 
Some  individuals  with  a  strong  natural  or  congenital 
tendency  in  this  direction  would  doubtless  exist,  and 
on  them  and  their  similarly  endowed  progeny  the 
permanent  success  of  the  race  might  wholly  de- 
pend. On  the  other  hand,  there  might  be  many  in- 
dividuals in  whom  the  constitutional  tendency  in 
the  direction  of  swarthiness  was  too  weak  and  in- 
cipient to  be  of  use.  If  these,  however,  made  up  for 
their  lack  of  natural  swarthiness  by  a  great  suscepti- 
bility to  acquired  swarthiness,  it  is  conceivable  that 
the  modification,  though  never  taking  organic  root, 
would  serve  as  a  life-saving  screen  until  coincident 
congenital  variations  in  the  direction  of  swarthiness 
had  time  to  grow  strong. 

Practical  Conclusions. — It  seems  then  that  the 
scientific  position  at  present  should  be  one  of  active 
scepticism — leading  on  to  experiment.  It  also  seems 
to  us  necessary  at  present  to  give  a  verdict  of  non- 
proven for  the  affirmative,  with  a  strong  presumption 
in  favour  of  the  negative  answer. 
>  If  this  be  so,  how  should  the  scientific  position  re- 
act upon  conduct?  Supposing  that  the  negative  be 
the  answer,  what  should  be  our  attitude  to  education, 
physical  culture,  amelioration  of  function,  improve- 
ment of  environment,  and  the  like?  There  can  be 
no  doubt  that  these  should  become  increasingly  im- 


422      PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

portant  in  our  eyes.  If  the  results  of  nurture  are 
not  inherited,  it  is  all  the  more  urgent  that  we  should 
secure  that  the  influences  making  for  evolution 
should  be  brought  to  bear  upon  each  successive  gen- 
eration. "  Is  my  grandfather's  environment  not  my 
heredity  ?  "  the  American  asks.  Well,  if  not,  let  me 
secure  my  grandfather's  environment  if  it  made  for 
progress,  and  flee  from  it  if  it  tended  elsewhere.  Is 
nurture  not  inherited? — perhaps  it  is  just  as  well, 
for  we  are  novices  at  nurturing  even  yet.  Is  nature 
alone  inherited  ? — then  we  are  saved  from  undue 
pessimism  when  we  think  of  the  harmful  functions 
and  environments  which  disfigure  our  civilisation. 
Is  there  not  some  result  if  we  are  forced  to  the  con- 
viction that,  to  sustain  and  improve  the  standard  of 
our  race,  we  must  bend  our  energies  more  and  more 
to-  the  development  (in  the  true  sense)  of  our  func- 
tion and  environment.  At  the  same  time,  there  is 
no  denying  the  thought  that  man  is  a  slowly  repro- 
ducing, slowly  varying  organism,  and  that  for  prog- 
ress which  is  really  organic — progress  that  is  in 
nature — we  must  wait  patiently. 

On  the  negative  side — of  inaction — the  scientific 
decision  ought,  however,  to  have  some  effect.  No 
longer  should  we  hear  the  still  frequent  assertion: 
"  Ah,  he  has  got  his  father's  nature,  it  does  not  mat- 
ter much  what  he  learns,  or  what  he  does,  or  where 
he  lives,  he  will  come  all  right  out  of  it,"  forgetting 
that  what  is  called  the  father's  nature  is  much  more 
than  his  inheritance,  it  is  in  adult  life  the  in- 
heritance plus  all  the  results  of  acquired  char- 
acters. No  longer  should  we  hear  the  extreme  pes- 
simism in  regard  to  the  decadence — the  debacle — 
the  abyss — towards  which  those  who  fix  their  atten- 
tion on  the  disagreeable  acquired  characters  of  our 


GENEOLOGICAL.  423 

age  think  we  are  fast  hastening,  for  there  is  at  least 
something  to  be  said  biologically  for  the  view  that 
these  are  but  transient  acquired  characters,  like 
loathsome  paint  on  sound  British  oak.  The  veneer 
on  the  little  boy  pictured  at  the  beginning  of  Cap- 
tains Courageous  was  odious,  but  it  soon  peeled  off 
on  the  Cod-Banks,  where  an  appropriate  nurture — 
both  functional  and  environmental — allowed  the 
constitutional  worth  to  realise  itself. 

//  there  is  little  scientific  warrant  for  our  being 
other  than  sceptical  at  present  as  to  the  transmission 
of  acquired  characters,  this  scepticism  lends  greater 
importance  than  ever,  on  the  one  hand,  to  a  good  "  na- 
ture," to  secure  which  is  the  business  of  careful 
mating;  and,  on  the  other  hand,  to  a  good  "  nur- 
ture," to  secure  which  for  our  children  is  one  of  our 
most  obvious  duties,  the  hopefulness  of  the  task  rest- 
ing upon  the  fact  that,  unlike  the  beasts  that  perish, 
man  has  a  lasting  external  heritage,  capable  of  end- 
less modification  for  the  better,  a  heritage  of  ideas 
and  ideals  embodied  in  prose  and  verse,  in  statue  and 
painting,  in  Cathedral  and  University,  in  tradition 
and  convention,  and  above  all  in  society  itself. 


CHAPTER  XL 
THE  THEOBY  OF  ORGANIC  EVOLUTION. 

THE  general  idea  of  evolution,  like  many  other 
great  ideas,  is  essentially  simple — that  the  present 
is  the  child  of  the  past  and  the  parent  of  the  future. 
It  is  the  same  as  the  scientific  conception  of  human 
history.  In  human  affairs,  what  seems  to  the  care- 
less to  be  quite  new  is  revealed  to  the  student  as  an 
antiquity.  We  see  the  gradual  growth  of  social 
organisations,  the  natural  transition  from  one  estab- 
lished order  of  things  to  another  slightly  different, 
the  transformation  of  one  institution  into  another, 
and  we  formulate  the  growth,  the  transition,  the 
transformation  in  the  general  concept  of  historic 
evolution.  A  process  of  Becoming  leads  to  a  new 
phase  of  Being ;  the  study  of  evolution  is  a  study  of 
Werden  und  Vergehen. 

THE  GENERAL  IDEA  OF  ORGANIC  EVOLUTION". 

Stated  concretely  in  regard  to  living  creatures,  the 
general  doctrine  of  organic  evolution  suggests,  as 
we  all  know,  that  the  plants  and  animals  now  around 
us  are  the  results  of  natural  processes  of  growth  and 
change  working  throughout  the  ages,  that  the  forms 
we  see  are  the  lineal  descendants  of  ancestors  on  the 
whole  somewhat  simpler,  that  these  are  descended 


THE  THEORY  OF  ORGANIC  EVOLUTION.   425 

from  yet  simpler  forms,  and  so  on  backwards,  till  we 
lose  our  clue  in  the  unknown — but  doubtless  momen- 
tous— vital  events  of  pre-Cambrian  ages,  or,  in  other 
words,  in  the  thick  mist  of  life's  beginnings. 

HISTORY  OF  THE  EVOLUTION-IDEA. 

"  Though  the  general  idea  of  organic  evolution  is 
simple,  it  has  been  slowly  evolved,  gaining  content 
as  research  furnished  fuller  illustration,  and  gaining 
clearness  as  criticism  forced  it  to  keep  in  touch  with 
facts.  It  has  slowly  developed  from  the  stage  of 
suggestion  to  the  stage  of  verification ;  from  being  an 
a  priori  anticipation  it  has  become  an  interpretation 
of  nature;  and  from  being  a  modal  interpretation  it 
is  advancing  to  the  rank  of  a  causal  theory."  * 

(1)  In  what  we  may  call  "  the  Greek  Period," 
there  were  many  who  more  or  less  vaguely  suggested 
the    evolution-idea,    notablv    Empedocles    (495-435 
B.C.).     Aristotle    (384-322    B.C.)    speaks    clearly 
of  a  gradual  progression  in  nature  from  the  inor- 
ganic to  the  organic  and  from  one  grade  of  life  to 
another.f     From    Epicurus    (341-270    B.C.),    the 
first  poet  of  evolution,  we  pass  after  a  long  interval 
to  Lucretius  (99-55  B.C.). 

(2)  In  the  mediaeval  period,  though  there  was  a 
general  arrest  of  enquiry,  the  light  of  the  evolution- 
idea  did  not  wholly  die.     Bruno   (1548-1600)   at 
least,  who  proclaimed  that  "  the  investigation  of  Ma- 
ture in  the  unbiased  light  of  reason  is  our  only 
guide  to  truth,"  was  in  some  degree  an  evolutionist. 

*  See  the  writer's  Science  of  Life,  1899  p.  213,  where  this 
section  forms  the  subject  of  a  whole  chapter  "  The  Evolu- 
tion of  Evolution-Theory." 

t  See  E.  Clodd,  Pioneers  of  Evolution  (1897);  H.  F.  Oa- 
born,  From  the  Greeks  to  Darurin  (1894). 


426    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

(3)  As  the  result  of  the  scientific  renaissance  in 
the  seventeenth  century,  when  science  re-asserted  it- 
self as  a .  natural  expression  and  discipline  of  the 
developing  human  spirit,  the  evolution-idea  became 
clear  to  many  minds.     Professor  Osborn  notes  that 
the  philosophers,  rather  than  the  naturalists,  were 
"  upon  the  main  track  of  modern  thought."     Des- 
cartes    (1596-1650)     and    Leibnitz     (1640-1716) 
point  onwards  to  Spinoza  and  Hume,  Lessing  and 
Schelling,  Kant  and  Herder.     On  another  line  we 
have    Francis   Bacon    (1561-1626),    clearly    evolu- 
tionist in  his  outlook. 

In  the  eighteenth  century  there  were  not  a  few 
"  speculative  evolutionists,"  as  Osborn  calls  them, 
such  as  De  Maillet,  Maupertuis,  Diderot,  and  Bon- 
net, whose  methods  were  wrong,  though  their  ideas 
were  often  right.  Many  say  that  the  same  title 
must  also  be  applied  to  Lorenz  Oken  (1776-1851). 

(4)  As  undoubted  pioneers  of  modern  evolution- 
doctrine  we  must  rank  Buffon  (1707-1788),  Eras- 
mus Darwin  (1731-1802),  Lamarck  (1744-1829), 
Goethe     (1749-1832),     Treviranus     (1776-1837), 
fitienne  Geoffroy   Saint-Hilaire    (1772-1844),   and 
Robert  Chambers  (1802-1871)  ;  and  there  are  others 
of  whom  a  complete  history  should  take  notice.    We 
have  elsewhere  given  brief  summaries  of  the  char- 
acteristic views  of  the  pioneers.* 

(5)  It  may  be  said  that  Darwin  did  three  chief 
services  to  evolution-doctrine,     (a)  "  By  his  patient, 
scholarly,   and   pre-eminently  fair-minded   marshal- 
ling of  the  so-called  l  evidences '  which  suggest  the 
doctrine  of  descent,  he  won  the  conviction  of  the  bio- 
logical world.     He  made  the  old  idea  current  intel- 
lectual coin.     In  so  doing  he  was  greatly  aided  by 

*  Science  of  Life,  1899,  pp.  219-223. 


THE  THEORY  OF  ORGANIC  EVOLUTION.   427 

Spencer  and  Wallace,  Haeckel  and  Huxley.  (&) 
He  applied  the  evolution-idea  to  various  sets  of  facts, 
such  as  the  expression  of  the  emotions  and  the  de- 
scent of  man,  and  showed  what  a  powerful  organon 
it  was.  Here,  again,  he  was  greatly  aided  by  his 
contemporaries,  and  Spencer's  work  in  this  direction 
is  even  more  important  than  Darwin's,  (c)  At  the 
same  time  as  Alfred  Kussel  Wallace,  he  elaborated 
the  theory  of  natural  selection,  of  which  there  had 
been  a  few  previous  suggestions."  * 

(6)  Since  Darwin  secured  the  general  acceptance 
of  the  evolution-idea,  the  attention  of  evolutionists 
has  been  chiefly  directed  to  a  discussion  and  criti- 
cism of  the  factors  in  the  evolution-process.  Natu- 
ral Selection  working  on  germinal  variations  has 
seemed  to  some  an  adequate  formula;  and  this  con- 
sistent Darwinism  had  been  strengthened  by  a  recog- 
nition of  the  importance  of  Isolation  (Romanes  and 
Gulick),  while  Weismann  has  added  the  subtle  idea 
of  "  Germinal  Selection."  In  spite  of  the  growing 
scepticism  as  to  the  transmissibility  of  functional 
and  environmental  modifications,  many  adhere  to 
the  Lamarckian  and  Buffonian  position,  that  these 
are  of  direct  importance  in  evolution.  This  may  or 
may  not  be  combined  with  a  recognition  of  the  im- 
portance of  Selection.  Others,  again,  following 
Goethe  and  Nageli,  regard  the  evolution  of  organisms 
as  pre-eminently  a  story  of  self-differentiating  and 
self-integrating  growth, — cumulative,  selective,  defi- 
nite, and  harmonious  like  crystallisation.  Believ- 
ing in  progressive  variations  in  definite  directions  as 
opposed  to  indefinite  sports,  they  find  little  need  to 
invoke  Natural  Selection  except  as  pruning  the  occa- 

*  Op.  cit.  p.  223. 


4:28    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

eional  exuberances  of  the  arbor  vitce.  Thus  we  have 
Darwinian,  Lamarckian,  and  Nagelian  schools,  and 
various  combinations  of  these  up  to  complete  eclecti- 
cism. From  this  others  have  reacted  to  an  agnostic 
position,  which  in  its  more  kinetic  expression  means 
active  scepticism,  and  this  thdtige  Skepsis  seems  to  us 
the  more  useful  mood  for  present-day  evolutionists. 
SUMMARY. — The  evolution-idea  is  not  only  essen- 
tially simple,  but  also  very  ancient.  It  is  perhaps 
as  old  as  clear  thinking,  which  we  may  date  from 
the  (unknown)  time  when  man  discovered  the  year — 
with  its  marvellous  object-lesson  of  recurrent  se- 
quences,— and  realised  that  his  race  had  a  history. 
Whatever  may  have  been  its  origin,  the  idea  was 
familiar  to  several  of  the  ancient  Greek  philoso- 
phers, as  it  was  to  Hume  and  to  Kant;  it  fired  the 
imagination  of  Lucretius  and  linked  him  to  another 
poet  of  evolution — Goethe;  it  persisted,  like  a  latent 
germ,  through  the  centuries  of  other  than  scientific 
pre-occupation;  it  was  made  actual  by  the  pioneers 
of  modern  biology — men  like  Buffon,  Lamarck, 
Erasmus  Darwin,  and  Treviranus; — and  it  became 
current  intellectual  coin  when  Darwin,  Wallace, 
Spencer,  Haeckel,  and  Huxley,  with  united  but 
varied  achievements,  won  the  conviction  of  the  ma- 
jority of  thoughtful  men.  Since  this  achievement, 
there  has  been  a  concentration  of  enquiry  on  the 
originative  and  directive  factors  in  the  evolution- 
process,  but  this  enquiry  is  still  young. 

THE  PRESENT  ASPECT  OF  THE  EVOLUTION  THEORY. 

'Attitude  towards  the  General  Idea  of  Evolution.- 
The  appreciation  of  the  general  idea  of  evolution 
has  changed  for  the  better  since  the  early  Darwinian 


THE  THEORY  OF  ORGANIC  EVOLUTION.      429 

days  of  hot-blooded  controversy.  It  seems  to  be  gen- 
erally recognised,  for  instance,  that  the  evolution 
formula  is  not  antithetic  to  transcendental  formulae. 
The  Theory  of  Descent  tacitly  makes  the  assumption 
— the  basal  hope  of  all  biology — that  it  is  not  only 
legitimate  but  promiseful  to  try  to  interpret  scien- 
tifically the  history  of  life  upon  the  earth.  If  we 
have  good  reasons  for  believing  that  the  long  process 
of  Becoming  which  has  led  eventually  to  ourselves 
and  our  complex  animate  environment  is  altogether 
too  mysterious  or  too  marvellous  to  admit  of  success- 
ful treatment  by  ordinary  scientific  methods,  then  we 
deny  at  the  outset  the  validity  of  the  evolution  for- 
mula. 

Here  is  a  parting  of  the  ways,  and  there  is  no 
via  media.  Is  there  no  hopefulness  in  attempting 
this  scientific  analysis  of  the  confessedly  vast  and 
perplexing  problem? — then  let  us  remain  poets  and 
artists,  philosophers  and  theologians,  and  sigh  over 
a  science  which  started  so  much  in  debt  that  its  bank- 
ruptcy was  a  foregone  conclusion.  On  the  other 
hand,  if  the  scientific  attempt  is  legitimate,  and  if 
it  has  already  made  good  progress,  considering  its 
youth,  then  let  us  rigidly  exclude  from  our  science 
all  other  than  scientific  interpretations ;  let  us  cease 
to  juggle  with  words  in  attempting  a  mongrel  mix- 
ture of  scientific  and  transcendental  formulation ;  let 
us  stop  trying  to  eke  out  demonstrable  factors  by 
assuming,  alongside  of  these,  "  ultra-scientific 
causes,"  "  spiritual  influxes,"  et  hoc  genus  omne:  let 
us  cease  writing  or  buying  books  such  as  God  or 
Natural  Selection,  whose  titular  false  antinomy  is 
an  index  of  their  misunderstanding.  Not  that  we 
are  objecting  for  a  moment  to  any  metaphysical  or 
theological  interpretations  whatsoever ;  we  are  simply 


4:30    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

emphasising  the  so  much  neglected  commonplace 
that  we  cannot  have  scientific  formulae  mixed  up 
with  any  other  interpretations  in  one  sentence;  and 
that  to  place  these  other  interpretations  in  opposition 
to  scientific  formulae  is  to  oppose  incommensurables, 
and  to  display  an  ignorance  of  what  the  aim  of 
science  is. 

From  the  Fact  to  the  Factors. — So  far  then  the 
formula,  but  let  us  pass  to  the  more  difficult  ques- 
tion of  the  factors.  Evolution  is  a  certain  mode  of 
becoming,  what  are  the  operative  conditions?  Here 
we  pass  from  practical  certainty  to  perplexing  un- 
certainty, as  is  so  often  the  case  when  we  pass  from 
the  general  to  the  particular,  from  abstract  to  con- 
crete. 

Nature  of  Variations. — The  first  great  question  is 
as  to  what  may  be  called  the  raw  materials  of  prog- 
ress,— the  origin  and  nature  of  those  variations  or 
organic  changes  on  which  the  possibility  of  evolution 
depends. 

Darwin  started  from  the  broad  fact  that  variabil- 
ity exists  (illustrating  it  chiefly  from  domesticated 
animals  and  cultivated  plants)  ;  he  postulated  a  crop 
of  organic  changes,  both  of  tares  and  wheat;  and  he 
pointed  out  how  a  process  of  '  singling '  and  thinning, 
sifting  and  winnowing  would  operate  upon  the  ever- 
growing, ceaselessly  changing  crop  so  that  the  result 
was  progress.  But  all  science  begins  with  measure- 
ment, and  the  great  step  in  advance  that  has  been 
made  of  recent  years  is  in  the  dry  and  tedious,  but 
absolutely  necessary,  task  of  recording  accurately 
the  variations  which  do  actually  occur. 

Without  being  biologists,  simply  as  clear  think- 
ers, we  can  see  the  unsatisfactoriness  of  the  line  of 
argument  which  was  until  recently  prevalent, — that 


THE  THEORY  OF  ORGANIC  EVOLUTION.      431 

of  simply  postulating  variability  without  statisti- 
cally or  otherwise  defining  it.  Life  is  so  abundant 
and  so  Protean  that  biologists  tend  to  draw  cheques 
upon  Nature  as  if  they  had  unlimited  credit,  and 
in  their  impetuosity  scarce  wait  to  see  whether  these 
are  honoured. 

But  we  are  now  changing  all  this.  From  Heli- 
goland to  California,  from  Plymouth  to  ^igg,  we 
have  now  reports  of  fundamentally  important  studies 
on  variation,  which  are  rapidly  helping  us  out  of  the 
slough  of  vagueness  in  which,  to  the  physicist's  con- 
tempt, biology  still  flounders.  The  very  title — Bio- 
metrika — of  a  new  journal  is  a  sign  of  the  times. 

It  is  far  too  soon  to  sum  up  recent  studies  on 
variation,  but  a  few  general  results  are  becoming 
clear.  The  tiresome  objector  who  challenges  the 
evolutionist  to  demonstrate  a  single  case  of  one 
species  being  turned  into  another,  has  an  undevel- 
oped "time-sense"  (all  natural  history  records  em- 
bracing but  a  fraction  of  a  tick  of  the  cosmic  clock)  ; 
and  he  is  a  century  behind  the  times,  with  an  out- 
look like  that  of  the  catastrophic  or  cataclysmal 
school  of  geologists.  Whoever  expects  to  find  big 
"  Jack-in-the-box "  phenomena  in  nature  is  sure  to 
be  disappointed.  What  the  objector  should  do  is 
humbly  to  study  some  of  the  recent  researches  in 
which  the  persistent  patience  of  those  who  can  ap- 
preciate millimetres  has  shown  that  variability  is 
even  greater  than  was  supposed  by  Darwin,  and  is 
certainly  not  less  among  creatures  living  in  a  state 
of  nature  than  among  those  domesticated  or  culti- 
vated forms  on  which  Darwin  concentrated  his  at- 
tention. And  he  should  at  least  give  as  many  days 
as  the  observers  have  given  years  to  the  study  of 
palaeontological  series,  like  those  of  Ammonites  and 


432    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

Brachiopods.  The  fact  is  that  whenever  we  settle 
down  to  measure,  describe,  and  identify,  we  find 
that  specific  diagnoses  are  averages;  that  specific 
characters  require  a  curve  of  frequency  for  their 
expression;  that  the  living  creature  is  usually  a 
Proteus.  There  are  no  doubt  long-lived,  non-plastic, 
conservative  types,  like  Lingula,  and  perhaps  a  score 
of  other  well-known  instances,  where  no  visible  vari- 
ability can  be  proved  even  in  millions  of  years,  but 
to  judge  from  these  as  to  the  march  of  evolutionary 
progress  is  like  estimating  the  rush  of  a  river  from 
the  eddies  of  a  sheltered  pool. 

In  the  study  of  variability  it  seems  possible  to  dis- 
tinguish between  continuous  variation,  in  which  the 
descendant  has  a  little  more  or  a  little  less  of  a  given 
character  than  the  parents  had,  and  discontinuous 
variation,  apparently  frequent,  in  which  a  new  com- 
bination (say,  an  elegant  vase-like  pitcher  on  a  cab- 
bage leaf)  appears  suddenly  without  known  grada- 
tion al  stages  and  with  no  small  degree  of  perfec- 
tion. Though  Lamarck  said  "  Nature  is  never 
brusque,"  though  we  adhere  to  our  statement  about 
the  rarity  of  big  Jack-in-the-box  phenomena,  the  evi- 
dence (e.g.,  of  Bateson)  as  to  the  occurrence  of  dis- 
continuous variations  appears  conclusive.  Such 
words  as  "  freaks  "  and  "  sports  "  are  open  to  ob- 
jection, but  they  suggest  the  idea  of  what  Mr.  Galton 
calls  "  transilient "  variations,  and  the  fact  that  or- 
ganic structure  may  pass  with  seeming  abruptness 
from  one  form  of  equilibrium  to  another. 

It  also  becomes  more  and  more  evident  that  the 
living  creature  in  many  cases  varies  as  a  whole  or 
unity,  so  that  if  there  is  more  of  one  character  there 
is  less  of  another,  and  so  that  one  change  brings  an- 
other in  its  train.  If  this  be  so,  we  are  not  restricted 


THE  THEORY  OF  ORGANIC  EVOLUTION.  433 

to  the  assumption  of  the  piecemeal  variation  of  mi- 
nute parts.  It  seems,  according  to  De  Vries,  as  if 
the  organism  as  a  whole — through  its  germinal  or- 
ganisation, of  course — may  suddenly  pass  from  one 
position  of  organic  equilibrium  to  another.  This  con- 
sideration, and  actual  measurement,  seem  also  to  sug- 
gest that  there  is  a  greater  definiteness  and  a  less 
fortuitousness  in  variation  than  was  previously  sup- 
posed. 

Origin  of  Variations. — In  his  great  work,  Ma- 
terials for  the  Study  of  Variation*  Mr.  Bateson  de- 
votes a  line  to  saying  that  enquiry  into  the  causes  is 
in  his  judgment  premature ;  and  it  must  be  admitted 
that  until  we  know  the  actual  facts  better,  we  can- 
not expect  to  say  much  that  is  wise  in  regard  to  their 
antecedents.  A  number  of  suggestions  have  been 
made,  however,  and  some  of  these  may  be  briefly 
stated. 

A  variation,  which  renders  the  child  different 
from  its  parents,  is  often  interpret  able  as  due  to 
some  incompleteness  of  inheritance  or  in  the  expres- 
sion of  the  inheritance.  It  seems  as  if  the  entail 
were  sometimes  broken  in  regard  to  a  particular 
characteristic.  Oftener,  perhaps,  as  the  third  gen- 
eration shows,  the  inheritance  has  been  complete 
enough  potentially,  but  the  young  creature  has  been 
prevented  from  realising  its  entire  legacy.  Contrari- 
wise, it  may  be  that  the  novelty  of  the  newborn  is 
seen  in  an  intensifying  of  the  inheritance,  for  the 
contributions  from  the  two  parents  may  as  it  were 
corroborate  one  another. 

But  in  many  cases  something  turns  up  to  which 
we  irresistibly  apply  the  word  novel,  some  peculiar 

*See  Fourth  Edition,  1901. 


434    PROGRESS  OP  SCIENCE  IN  THE  CENTURY. 

mental  pattern,  it  may  be,  which  we  feel  bound  to 
call  original,  some  structural  change  which  suggests 
a  new  departure.  We  may  tentatively  interpret  this 
as  due  to  some  fresh  permutation  or  combination  of 
the  complex  nuclear  and  cellular  substances  which 
are  mingled  at  the  outset  of  every  new  life  sexually 
reproduced.  The  plausibility  of  this  interpretation 
is  increased  when  we  remember  that  our  inheritance, 
as  Galton  has  so  clearly  shown,  is  mosaic  rather  than 
dual.  For  it  is  not  merely  in  an  intermingling  of 
maternal  and  paternal  contributions  that  life  be- 
gins, but  of  legacies  through  the  parents  from  re- 
moter ancestors.  The  complexity  of  the  problem 
is  increased,  not  diminished,  if  there  be  reality  in 
the  conception  that  the  different  hereditary  qualities 
may  have  a  struggle  in  nuce,  or  that  there  is  a  "  ger- 
minal selection  "  as  Weismann  calls  it. 

Another  possibility  of  variation  has  been  sought  in 
the  fact  that  the  hereditary  material  is  doubtless 
very  complex  and  has  a  complex  environment  within 
the  parental  body.  If  it  has,  in  spite  of  its  essential 
stability,  a  tendency  to  instability  as  regards  minor 
details,  we  may  perhaps  find  the  change-exciting 
stimuli  in  the  ceaseless  nutritive  oscillations  within 
the  body.  But  enough  has  been  said  to  indicate 
how  uncertain  is  the  voice  of  biology  in  answering 
the  fundamental  questions  as  to  the  nature  and  origin 
of  variations. 

Modifications. — Among  the  observed  differences 
which  mark  man  from  man,  trout  from  trout,  but- 
tercup from  buttercup,  there  are  many  to  which  we 
cannot  apply  the  term  variations.  Quite  apart  from 
constitutional  or  germinal  changes  there  are  differ- 
ences which  are  obviously  impressed  upon  the  body 
from  without,  such  as  sun-burning,  or  which  result 


THE  THEORY  OF  ORGANIC  EVOLUTION.  435 

from  use  and  disuse,  such  as  callosities  on  the 
fingers.  These  do  indeed  presuppose  a  constitution 
capable  of  being  changed,  but  we  can  relate  each  of 
them  (sometimes  with  certainty,  sometimes  only  with 
probability)  to  some  definite  influence  either  of  func- 
tion or  of  environment  which  has  brought  about  a 
structural  change  transcending  the  limits  of  organic 
elasticity.  We  call  these  conveniently  "  modifica- 
tions." Now,  though  organic  "modifications  "  may 
be  of  much  importance  to  the  individuals  possessing 
them,  and  may  serve  as  a  temporary  shield  for  in- 
cipient variations  in  the  same  direction,  they  are 
not  proved  to  be  of  any  direct  importance  in  the 
evolution  of  the  race,  for  the  simple  reason  that  there 
is  no  convincing  evidence  that  they  can  be  as 
such  or  in  any  representative  degree  transmitted 
to  the  offspring. 

So  far  then  we  have  seen  that  the  raw  materials 
of  evolution  consist  of  constitutional  or  germinal 
variations,  and  that  we  are  not  justified  in  including 
modifications  or  acquired  characters  because  their 
transmissibility  is  unproved.  Let  us  now  pass  to  a 
brief  consideration  of  the  secondary  or  directive  fac- 
tors— operating  upon  the  variations  which  crop  up. 

Natural  Selection. — The  first  of  these  directive 
factors  is  natural  selection,  and  it  is  well  known  that 
the  most  distinctive  contribution  which  Darwin  and 
Wallace  made  to  aetiology  was  to  emphasize  its  im- 
portance. The  theory  admits  of  brief  statement. 

Variability  is  a  fact  of  life,  the  members  of  a 
family  or  species  are  not  born  alike;  some  have  qual- 
ities which  give  them  a  little  advantage  both  as  to 
hunger  and  as  to  love;  others  are  relatively  handi- 
capped. But  a  struggle  for  existence  is  also  a  fact 
of  life,  being  necessitated  especially  by  two  facts, 


436    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

first  that  two  parents  usually  produce  many  more 
than  a  pair  of  children,  and  the  population  thus 
tends  to  outrun  the  means  of  subsistence;  and, 
secondly,  because  organisms  are  at  the  best  only  rela- 
tively well-adapted  to  their  conditions,  which,  more- 
over, are  variable.  This  struggle  does  not  express 
itself  merely  as  an  elbowing  and  jostling  around  the 
platter,  but  at  every  point  where  the  effectiveness  of 
the  response  which  the  living  creature  makes  to  the 
stimuli  playing  upon  it,  is  of  critical  moment.  As 
Darwin  said,  though  many  seem  to  have  forgotten, 
the  phrase,  "  struggle  for  existence  "  is  used  "  in  a 
wide  and  metaphorical  sense,"  including  much  more 
than  an  internecine  scramble  for  the  necessities  of 
life, — including,  indeed,  all  endeavours  for  preser- 
vation and  welfare,  not  only  of  the  individual,  but 
of  the  offspring  too.  In  many  cases,  the  struggle  for 
existence  both  among  men  and  beasts  is  more  fairly 
described  as  an  endeavour  after  well-being,  and  what 
may  have  been  primarily  self-regarding  impulses 
become  replaced  by  others  which  are  distinctively 
species-maintaining,  the  self  failing  to  find  full  reali- 
sation apart  from  its  kin  and  society. 

Now,  in  this  struggle  for  existence — manifold  in 
its  expression,  but  never  unreal — the  relatively  less 
fit  forms  tend  to  be  eliminated.  This  does  not 
necessarily  mean  that  they  come  at  once  to  a  violent 
end,  as  when  locust  devours  locust  or  the  cold  deci- 
mates the  birds  in  a  single  night,  but  often  simply 
that  the  less  fit  die  before  the  average  time,  and  are 
less  successful  than  their  neighbours  as  regards  off- 
spring. But  whether  the  eliminative  process  be 
gentle  or  severe,  the  result  is  the  same,  that  the  rela- 
tively more  fit  tend  to  survive;  and  since  many 
variations  (the  argument  continues)  are  transmitted 


THE  THEORY  OF  ORGANIC  EVOLUTION.      437 

from  generation  to  generation,  and  may  through  the 
pairing  of  similar  or  suitable  mates  be  gradually 
increased  in  amount,  the  eliminative  or  selective  proc- 
ess works  towards  the  establishment  of  new  adapta- 
tions and  new  species. 

As  to  that  particular  form  of  natural  selection 
which  is  called  sexual  selection,  to  which  Darwin 
attached  so  much  importance  especially  in  his  later 
work,  we  are  compelled  to  shirk  the  discussion 
of  a  difficult  problem  which  could  not  be  fairly 
treated  within  our  limits  of  space.  Only  a  few 
remarks  can  be  made.  As  is  well  known,  sexual 
selection  takes  two  chief  forms  (a)  where  the  rival 
males  fight  for  the  possession  of  a  desired  mate  or 
mates,  and  in  so  doing  reduce  the  leet ;  and  (b)  where 
the  females  appear  to  choose  certain  individuals 
from  amid  a  crowd  of  suitors.  The  general  verdict 
seems  to  be  that  while  among  some  animals  prefer- 
ential mating  appears  indisputable,  its  range  and  its 
effectiveness  in  evolution  are  much  less  than  Darwin 
believed.  This  is  well  expressed  in  the  work  of 
Darwin's  magnanimous  colleague,  Alfred  Russel 
Wallace,  who  has  given  good  reason  for  believing 
that  too  much  credit  has  been  given  to  this  sexual 
selection  factor.  But  just  as  the  little  child  in  a 
sense  leads  the  race — being  the  expression  of  some 
new  variation, — so  we  may  still  admit  that  there  are 
facts  which  warrant  us  in  saying  that  das  ewig  weib- 
liche  plays  a  part  in  the  upward  march  of  life. 
Cupid's  darts  as  well  as  Death's  arrows  have  some- 
times evolutionary  significance. 

Apart  from  differences  of  opinion  as  to  the  im- 
portance of  sexual  selection,  it  seems  fair  to  say 
that  the  majority  of  naturalists  continue  to  rely  with 
confidence  on  the  general  selective  or  eliminative 


438    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

process.  Whether  the  selection  theory  is  "  all  suf- 
ficient," as  Weismann  calls  it,  or  "  inadequate,"  as 
Spencer  says,  it  remains  a  potent  theory.  Given  a 
sufficiently  abundant  crop  of  variations,  a  persistent 
struggle  for  existence,  and  a  large  draft  on  the  bank 
of  Time,  what  may  the  selective  process  not  ac- 
complish ? 

But  as  £etiology  has  grown  older  and  wiser,  it  has 
begun  to  ask  questions,  the  answers  to  which  will 
mean  much  progress.  Thus  there  is  a  demand  for 
some  serious  attempt  to  measure  the  intensity  of  the 
struggle  in  typical  cases,  and  for  evidence  that  the 
absence  of  a  particular  variation  in  certain  members 
of  the  stock  does  really  determine  their  elimination. 
There  are  enquiries  as  to  the  frequency  of  discontinu- 
ous or  transilient  variations — where  a  new  character 
is  reached  with  apparent  suddenness,  for  if  these 
are  frequent  this  may  lessen  the  claims  which  have 
to  be  made  on  the  selective  process.  It  is  asked 
whether  the  task  of  elimination  will  not  be  further 
lessened  if  the  crop  of  variations  is  more  definite  and 
less  of  the  nature  of  random  freaks  than  used  to  be 
supposed.  Information  is  wanted  as  to  the  degree 
in  which  the  struggle  for  existence  is  directly  com- 
petitive, or  merely  between  the  living  creature  and 
its  inanimate  surroundings.  Especially  is  it  desired 
that  statistics  be  forthcoming  to  show  how  far  the 
elimination  is  discriminate,  as  when  the  pruner  lops 
off  the  less  promiseful  branches,  or  the  breeder  gets 
rid  of  the  unsuitable  members  of  his  stock,  and  how 
far  it  is  indiscriminate,  as  when  the  hastily  driven 
hoe  strikes  the  cluster  of  seedlings.  In  other  words, 
evolutionists  have  awakened  to  the  necessity  of  test- 
ing natural  selection  in  relation  to  actual  cases, 

Isolation. — The  raw  materials  of  progress  are  fur- 


THE  THEORY  OF  ORGANIC  EVOLUTION.      439 

nished,  as  we  have  seen,  by  constitutional  or  germinal 
variations.  What  these  may  amount  to  depends  in 
the  long  run  on  the  potentialities  resident  in  living 
matter,  especially  of  reacting  to  external  influences, 
and  this  forces  us  finally  back  to  the  institution  of 
the  order  of  nature  which  at  some  level  or  other  the 
evolutionist  takes  for  granted.  In  organic  evolution, 
variation  supplies  the  materials;  heredity  (or  the 
relation  of  genetic  continuity  between  successive 
generations)  is  one  of  the  conditions ;  natural  selec- 
tion or  elimination  is  one  of  the  directive  factors. 
But  there  may  be  others,  and  one  has  been  indicated 
in  what  is  called  the  theory  of  isolation. 

A  formidable  objection  to  the  Darwinian  theory, 
first  clearly  stated  by  Professor  Fleeming  Jenkin, 
and  familiar  to  everyone  who  has  thought  out  the 
matter,  is  that  variations  of  small  amount  and  sparse 
occurrence  would  tend  to  be  swamped  out  by  inter- 
crossing. In  artificial  selection,  the  breeder  takes 
measures  to  prevent  this  by  pairing  similar  or  suit- 
able forms  together;  but  what  in  nature  corresponds 
to  the  breeder  ? 

Various  suggestions  have  been  made  in  answer  to 
this  question.  Thus  Professor  Weismann  says, 
"  The  necessary  variations  from  which  transforma- 
tions arise  must  in  all  cases  be  exhibited  over  and 
over  again  by  many  individuals,"  but  there  is  still 
a  lack  of  concrete  evidence  to  bear  this  out  We  do 
not  mean  to  deny  it,  but  before  we  lean  heavily  upon 
it  we  should  like  to  be  able  to  furnish  numerous  ex- 
amples of  many  similar  variations  occurring  at  once 
within  the  same  group. 

The  favourite  answer  of  recent  years  is  that 
worked  out  by  the  late  Dr.  Romanes,  Mr.  Gulick, 
and  others — the  theory  of  isolation.  They  point  to 

2c 


440    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

the  great  variety  of  ways  in  which,  in  the  course  of 
nature,  the  range  of  intercrossing  is  restricted — e.g., 
by  geographical  barriers,  by  differences  in  habit,  by 
psychical  likes  and  dislikes,  by  reproductive  varia- 
tion causing  mutual  sterility  between  two  sections  of 
a  species  living  on  a  common  area,  and  so  on.  Ac- 
cording to  Romanes,  "  without  isolation,  or  the  pre- 
vention of  free  inter-crossing,  organic  evolution  is 
in  no  case  possible."  Again  it  has  to  be  confessed 
that  the  body  of  facts  in  illustration  of  isolation  and 
its  effects  is  unsatisfactorily  small. 

An  interesting  corollary  has  been  recently  indi- 
cated by  Professor  Cossar  Ewart.*  Breeding  with- 
in a  narrow  range  often  occurs  in  nature,  being  neces- 
sitated by  geographical  or  other  barriers.  In  arti- 
ficial conditions,  this  in-breeding  often  results  in 
the  development  of  what  is  called  prepotency.  This 
means  that  certain  forms  have  an  unusual  power  of 
transmitting  their  peculiarities,  even  when  mated 
with  dissimilar  forms.  In  other  words,  certain  varia- 
tions have  a  strong  power  of  persistence.  Therefore, 
wherever  through  in-breeding  (which  implies  isola- 
tion) prepotency  has  developed,  there  is  no  difficulty 
in  understanding  how  even  a  small  idiosyncrasy  may 
come  to  stay,  even  although  the  bridegroom  does  not 
meet  a  bride  endowed  with  a  peculiarity  like  his  own. 

In  Conclusion. — In  conclusion,  or  we  should 
rather  say  in  ending  this  review  whose  point  is  its 
inconclusiveness,  let  us  once  more  emphasise  that 
while  the  general  idea  of  evolution  stands  more  firmly 
than  ever  as  a  reasonable  modal  interpretation  of 
nature,  there  is  great  uncertainty  in  regard  to  the 
factors  in  the  evolution  process.  How  do  variations 

*  Penycuik  Experiments,  1899. 


THE  THEORY  OF  ORGANIC  EVOLUTION.  44! 

arise?  In  what  proportion  are  they  continuous  or 
discontinuous,  definite  or  indefinite?  How  far  is 
natural  elimination  discriminate  ?  To  what  extent 
is  isolation  demonstrable? — before  these  and  a  score 
of  similar  questions  we  stand  not  less  expectant — but 
perhaps  less  confident — than  the  evolutionists  of  a 
third  of  a  century  ago.  It  is  not  that  we  are  where 
we  were  thirty  years  since ;  it  is  rather  that  we  have 
become  more  aware  of  our  ignorance  and  of  the  com- 
plexity of  the  problem. 

It  is  a  critical  mood  that  becomes  us  as  a  reaction 
from  earlier  enthusiasm,  and  the  value  of  this  is 
borne  out  by  the  history  of  science  which  shows  that 
the  rate  of  intellectual  progress  may  be  measured  by 
the  periodicity  of  the  wave  of  scientific  scepticism. 
But  it  is  not  a  hands-in-the-pockets  scepticism  that 
becomes  us  as  evolutionists,  it  is  a  thatige  Skepsis, — 
eager  to  test  and  measure,  to  experiment  and  observe. 
After  half  a  century  of  measurement  and  experi- 
ment, the  voice  of  the  evolutionist  will  probably  re- 
gain confidence.  What  is  especially  needed  is  a 
national  or  inter-national  institute  of  experimental 
evolution  where  the  trials  and  testings  could  be  con- 
tinued for  generations  by  a  carefully  recruited  staff, 
and  thus  remain  unaffected  by  the  death  of  individ- 
ual workers. 


BOOK  FOUR. 

PSYCHOLOGY,  ANTHROPOLOGY,  AND 
SOCIOLOGY. 

(MIND,  MAN,  AND  SOCIETY.) 


CHAPTEK  XII. 

PROGRESS  OF  PSYCHOLOGY.* 

PSYCHOLOGY  is  "  the  positive  science  of  mental 
process  " ;  it  investigates  mental  events  in  their  co- 
existence and  sequence,  or  mental  products  in  their 
subjective  aspect.  It  has  to  do  with  the  racial  evolu- 
tion of  the  mind  and  the  development  of  the  indi- 
vidual consciousness,  but  not  with  what  ought  to  be 
in  thought  or  in  conduct  (logic  and  ethics),  nor  with 
the  nature  of  knowledge  as  such  (metaphysics). 

Its  data  are  obtained  from  a  study  of  the  products 
of  past  mental  processes  and  of  the  stages  of  processes 
presently  occurring  or  just  fading  into  the  past.  Its 
methods  are  introspection  and  retrospection,  observa- 
tion and  experiment.  And  it  aims,  like  other  sci- 
ence, at  restating  the  facts  in  general  formula,  or  in 

*  The  aim  of  this  chapter  is  simply  to  illustrate  four 
noteworthy  changes  in  the  aims  and  methods  of  psychol- 
ogy which  may  be  called  characteristic  of  the  nineteenth 
century. 


PROGRESS  OF  PSYCHOLOGY.  443 

binding  them  into  an  intelligible  system  by  interpre- 
tative hypotheses. 

CHANGES  IN  AIMS  AND  METHODS. 

Even  those  who  insist  that  psychology  is  an  an- 
cient science  (from  Aristotle's  De  Anima)  and  not 
one  of  the  newest,  will  allow  that  the  nineteenth 
century,  especially  in  its  second  half,  witnessed  great 
changes  in  the  aims  and  method  of  psychological 
enquiry.  The  advance  of  physiology  made  a  franker 
recognition  of  the  correlation  of  mind  and  body  im- 
perative; a  growing  intensity  in  the  scientific  mood 
intruded  methods  of  experimentation  into  a  sphere 
wherein  they  were  formerly  conspicuous  by  their  ab- 
sence; the  naturalist  advanced  a  plea  for  the  consid- 
eration of  the  animal  mind  alongside  that  of  man ; 
and  the  grip  of  the  evolution-idea  made  itself  felt 
in  the  conviction  that  the  "  mind  "  must  be  studied 
as  the  product  of  individual  development  and  of 
racial  history. 

As  Prof.  E.  B.  Titchener  expresses  it: — (1) 
"  Modern  psychology  works  upon  the  hypothesis  that 
there  is  no  psychosis  without  neurosis ;  no  sooner  has 
it  analysed  a  mental  complex  than  it  begins  its  search 
for  the  neural  substrate  of  the  elementary  conscious 
processes."  ...  (2)  "  Experiment  has  been  intro- 
duced, not  to  oust  the  old-fashioned  method  of  intro- 
spection or  self-observation,  but  to  control  it  and 
standardise  its  conditions,  lifting  the  '  facts '  of 
psychology  from  the  plane  of  opinion  to  the  plane  of 
knowledge."  ...  (3)  Here  we  would  interpolate 
that  psychology  has  followed  physiology  in  becoming 
comparative.  (4)  "  Mind,  instead  of  being  dissected 
and  classified,  in  purely  logical  terms,  into  static  bits 


444    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

of  knowledge  (ideas)  and  empty  faculties  of  knowl- 
edge (memory,  imagination)  is  looked  upon  as  an 
organic  structure,  that  is,  as  a  structure  that  has 
grown  or  developed,  to  be  investigated  by  analytical 
and  genetic  methods."  * 

"Whether  or  not  we  admit  the  advent  of  a  new 
psychology,  at  least  we  cannot  deny  the  consummation 
of  a  great  and  far-reaching  change  in  psychological 
aims  and  methods."  f 

CORRELATION  OF  MIND  AND  BODY. 

During  the  nineteenth  century  various  views  were 
held  on  this  subject. 

(a)  Ignoring  what  had  been  clearly  shown  even 
by  Descartes,  and  the  truth  in  Hartley's  Observa- 
tions on  Man  (1Y49)  a  certain  school  practi- 
cally denied  that  any  correlation  of  mind  and  body 
existed.  The  body  and  its  organs,  on  one  side,  the 
mind  and  its  organs,  on  the  other,  were  thought 
of  as  entirely  independent  existences.  This  position 
is  untenable.  Certain  lesions  of  the  brain  are 
always  associated  with  certain  disorders  of  language, 
as  in  aphasia.  Conversely,  over  and  over  again,  the 
saving  skill  of  the  surgeon  at  the  best,  or  post-mortem 
examination  at  the  worst,  has  verified  an  inference 
from  a  particular  mental  disorder  to  a  disturbance 
of  a  particular  part  of  the  brain.  The  general  cor- 
respondence throughout  Vertebrates  between  the 
relative  size  and  complexity  of  the  brain  and  the  ani- 
mal's grade  of  intelligence,  cannot  be  a  coincidence. 

Historical  Note. — Although    at    many    different 

*  Siimmarised    from    Recent    Advances    in    Psychology, 
Internat.     Monthly.  II.    (August,  1900).  pp.  154-168. 
f  E.  B.  Titchener  (1900),  loo.  cit.  p.  154. 


PROGRESS  OF  PSYCHOLOGY.  445 

dates  sagacious  thinkers  had  pointed  out  that  the 
flesh  not  only  wars  against  the  spirit,  but  in  a  humili- 
ating way  conditions  its  activity,  the  recognition  of 
the  intimate  correlation  of  body  and  mind  is  practi- 
cally one  of  the  great  results  of  the  nineteenth  cen- 
tury. 

The  new  doctrine  that  the  brain  is  the  organ  of 
the  mind  was  certainly  helped  by  the  industrious 
work  of  Franz  Joseph  Gall  (1758-1828)  and  Johann 
Gaspar  Spurzheim  (1776-1832)  the  founders  of 
phrenology,  doubtless  an  erroneous  system,  but — like 
alchemy  or  astrology — of  some  service  to  science. 
Among  the  other  pioneers  were  Magendie  and  Louis 
Antoine  Desmoulins  who  worked  together  on  the 
nervous  system  of  Vertebrate  animals  (1825) ; 
Charles  Bell  who  in  1811  discovered  the  distinction 
between  motor  and  sensory  nerves,  afterwards  con- 
firmed by  Johannes  Miiller  and  by  Magendie;  Mar- 
shall Hall,  who  first  elucidated  the  phenomenon  of 
reflex  action  (1832)  ;  and  Flourens  who  was  one  of 
the  first  to  enquire  with  precision  into  the  functions 
of  different  parts  of  the  brain. 

In  1825  Boillard,  working  from  the  pathological 
side,  had  tried  in  vain  to  convince  his  contemporaries 
as  to  the  existence  of  an  articulation-centre  in  the 
frontal  lobe  of  the  brain,  and  there  were  other  pio- 
neers. Little  heed  was  paid  to  the  idea  till  1861, 
when  Broca  announced  his  discovery  that  a  definite 
area  in  the  cerebrum  (Broca's  centre)  was  concerned 
with  articulate  speech.  He  thus  initiated  a  more 
intimate  study  of  brain  localisation.  Fritsch  and 
Hitzig,  Ferrier,  Hughlings  Jackson,  Franck  and 
Pitres,  Munk  and  Goltz,  Horsley,  Schafer,  Flechsig, 
Schrader,  Steiner,  have  been  prominent  workers  on 
this  line — endeavouring  to  map  out  the  brain  into 


446    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

specialised  centres  both  sensory  and  motor.  And  to 
this  experimental  investigation  there  has  come  aid 
from  histological  studies,  especially  since  the  refine- 
ment of  methods  due  to  Golgi  and  Ramon  y  Cajal. 

Although  a  splendid  beginning  has  been  made, 
It  is  only  a  beginning,  and  even  among  experts  there 
is  much  diversity  of  opinion  on  important  questions. 
Thus  we  find  Flechsig  mapping  out  three  levels 
of  centres  in  the  cortex,  sense-centres  (also  motor), 
association-centres  (with  indirect  motor  connections), 
and  between  these  in  order  of  development  inter- 
mediate centres;  while,  on  the  other  hand,  we  find 
Loeb  *  maintaining  that  while  there  exists  to  a  cer- 
tain extent  an  anatomical  localisation  in  the  cortex, 
the  assumption  of  a  physical  localisation  is  contra- 
dicted by  the  facts.  ..."  In  processes  of  associa- 
tion the  cerebral  hemispheres  act  as  a  whole,  and  not 
as  a  mosaic  of  a  number  of  independent  parts.  .  .  . 
It  is  just  as  anthropomorphic  to  invent  special  centres 
of  association  as  it  is  to  invent  special  centres  of  co- 
ordination." f 

SUMMARY. — It  must  be  admitted  ~by  all  that 
"  there  exist  manifold  correspondences  of  the  most  in- 
timate and  exact  kind  between  states  and  changes  of 
consciousness  on  the  one  hand,  and  states  and  changes 
of  brain  on  the  other.  As  respects  complexity,  in- 
tensity, and  time-order  the  concomitance  is  appar- 
ently complete.  Mind  and  brain  advance  and  decline 
pari  passu;  the  stimulants  and  narcotics  that  en- 
liven or  depress  the  action  of  the  one  tell  in  like 
manner  upon  the  other.  Local  lesions  that  suspend 
or  destroy,  more  or  less  completely,  the  functions  of 

*Loeb,  Comparative  Physiology  of  the  Brain  (1900), 
p.  262. 

fLoeb,  p.  275. 


PROGRESS  OF  PSYCHOLOGY.  447 

the  centres  of  sight  and  speech,  for  instance,  involve 
an  equivalent  loss,  temporary  or  permanent,  of  words 
and  ideas."  *  The  close  parallelism  of  the  two  sets 
of  facts  is  certain;  the  difficulty  is  how  to  conceive 
of  their  relation. 

(6)  With  the  advance  of  physiological  analysis, 
a  materialistic  school  found  confidence  to  claim  psy- 
chology as  entirely  a  branch  of  physiology.  In  crude 
expression,  it  was  said  that  as  the  liver  secrets  bile, 
so  the  brain  secretes  thought ;  or,  that  as  the  collisions 
in  a  swarm  of  meteors  engender  heat  and  light,  so 
the  whirlpool  of  molecules  within  a  ganglion  has  part 
of  its  energy  expressed  as  consciousness. 

This  conclusion  includes  two  distinct  assump- 
tions:— (1)  that  material  agency  is  the  only  real 
condition  of  protoplasmic  metabolism  (or  bodily 
life),  and  so  likewise  of  consciousness  or  mental  life, 
and  (2)  that  physiological  interpretations  are  suffi- 
cient for  mental  occurrences.  The  first  assumption 
is  a  metaphysical  dream  involving  the  fallacy  of 
"  postulating  mechanism  as  the  substratum  and  not  as 
the  conceptional  expression  of  certain  groups  of  sense- 
impressions  "  (Pearson)  ;  the  second  assumption  has 
not  been  justified  by  any  success.  Xo  one  has  suc- 
ceeded in  giving  a  physiological  interpretation  of 
any  mental  process;  though  the  physical  conditions 
attendant  on  many  mental  processes  are  known,  the 
relations  between  the  two  have  not  been  apprehended. 

A  quotation  from  Dr.  G.  F.  Stout's  Analytic  Psy- 
chology (1896)  may  be  permitted  here: — 

"  Those  who  deny  agency  to  consciousness,  finding 
that  mental  events  occur  which  are  not  immediately 

*  Prof.  James  Ward,  Naturalism  and  Agnosticism,  1899, 
Vol.  I.  p.  10. 


448    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

traceable  to  other  mental  events,  assume  that  they  are 
due  to  material  agency.  Similarly  those  confronted  by 
material  changes  not  easily  traceable  to  mechanical 
antecedents,  have  often  assumed  that  they  are  due  to 
spiritual  agency.  How  can  the  modern  materialist 
show  that  he  has  any  better  guarantee  for  his  position 
than  the  untutored  Indian  has  for  his?  ...  If  the 
continuity  of  the  mechanical  process  debars  us  from 
regarding  a  movement  as  due  to  a  volition,  it  must  in 
like  manner  debar  us  from  regarding  a  volition  as  due 
to  movement,  even  of  brain  particles.  ...  No  analysis 
can  discover  in  the  psychological  fact  any  traces  of  its 
supposed  physical  factors."  * 

(c)  As  physiology  has  become  more  modest  in 
realising  its  own  limits  of  interpretation,  and  as  the 
psychologist  has  without  mistrust  sought  to  avail 
himself  of  all  the  help  the  physiologist  can  give,  a 
more  reasonable  position  has  been  attained.  "  Psy- 
chology is  distinguished  from  the  physical  sciences 
inasmuch  as  their  aim  is  to  know  the  material 
world,  whereas  it  deals  with  the  question  how  this 
knowledge  arises."  f  "  Mental  processes  cannot  be 
explained  as  special  complications  of  processes  which 
are  not  mental,  nor  can  they  enter  into  the  composi- 
tion of  such  processes."  $  "  No  consideration  of  the 
physical  antecedents  as  such  needs  to  be  included  in 
any  strictly  psychological  proposition.  We  take  ac- 
count of  them  only  in  so  far  as  they  are  indispensable 
helps  in  determining  and  defining  the  nature  and 
order  of  changes  produced  in  the  mind  from  without. 
The  psychologist  is  primarily  concerned  not  with  the 
antecedents  of  externally  initiated  changes,  but  with 
these  changes  themselves,  inasmuch  as  they  modify 

*  Stout,  pp.  5-6. 

t  G.  F.  Stout,  Analytic  Psychology,  Vol.  I.,  1896,  p.  8. 
%  Op.  cit.,  p.  6. 


PROGRESS  OF  PSYCHOLOGY.  449 

preceding  and  determine  succeeding  mental  states. 
Thus,  though  these  physical  facts  supply  data  indis- 
pensable to  the  solution  of  psychological  problems, 
yet  they  do  not  themselves  belong  to  the  essential 
subject-matter  of  psychology."  * 

But  the  position  of  this  acute  thinker  might  be 
misunderstood  if  we  did  not  quote  further.  "  The 
life  of  the  brain  is  part  of  the  life  of  the  organism 
as  a  "whole,  and  inasmuch  as  consciousness  is  the 
correlate  of  brain-process,  it  is  conditioned  by  organic 
process  in  general.  It  is  clear  that  the  unity  and 
connection  of  psychical  states  cannot  be  clearly  con- 
ceived without  taking  into  account  the  unity  and 
connection  of  the  processes  of  the  organism  as  a 
whole."  f 

No  enthusiast  for  physiological  interpretation, 
could  at  present  wish  for  a  more  friendly  greeting. 

But  what  of  the  future,  since  physiology  is  advanc- 
ing by  leaps  and  bounds  ?  "  Let  us  consider  what 
would  happen  under  ideally  perfect  conditions.  If 
the  physiologist  were  to  attain  to  as  clear  and  definite 
a  conception  of  brain  processes  as  the  physicist  pos- 
sesses of  light  and  sound  vibrations;  if  he  had  also 
an  acquaintance  with  psychology  sufficient  to  enable 
him  to  set  about  establishing  definite  connections  be- 
tween elementary  mental  and  elementary  physiolog- 
ical occurrences ;  if,  finally,  he  had  at  his  command 
psycho-physical  means  and  methods  adequate  to  this 
undertaking — then,  indeed,  we  might  hope  for  abun- 
dant and  valuable  results.  Indeed,  it  would  seem 
that  under  such  conditions  psychology  would  be 
wholly  absorbed  into  physiology  so  that  a  single  in- 
divisible science  would  result.  But  at  present  we 
appear  to  be  as  far  from  such  a  consummation  as 

*  Stout,  p.  27.  f  Stout,  p.   23. 


4:50    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

from  the  establishment  of  a  penny-post  between  the 
planets  of  the  solar  system."  *  This  is  one  of  the 
finest  specimens  of  ironical  scientific  literature  since 
science  began. 

When  the  question  is  asked  in  this  form : — Do  the 
formula  of  biology,  of  physiology,  of  chemistry  and 
physics,  suffice  to  restate  the  facts  of  mental  life  ? 
there  is  at  present  no  manner  of  doubt  that  the 
answer  should  be  an  emphatic  "  No." 

Whether  the  development  (personal)  and  evolu- 
tion (racial)  of  that  synthesis  which  we  call  Mind 
("the  unity  of  manifold  successive  and  simulta- 
neous modes  of  consciousness  in  an  individual 
whole")  can  be  traced  is  another  question,  to  which 
the  sanguine  would — with  some  justification — an- 
swer "Yes." 

Whether  we  shall  ever  be  able  to  conceive  how  it  is 
that  protoplasmic  metabolism  comes  to  be  in  certain 
cases  attended  by  consciousness  (which  we  cannot  posi- 
tively define)  is  another  question,  answers  to  which 
are  mere  matters  of  opinion.  The  correlation  and 
parallelism  of  metabolism  and  mentality,  of  neuroses 
and  psychoses  must  be  admitted,  but  the  two  sets  of 
facts  cannot  be  identified,  and  science  'as  such  has 
at  present  no  answer  to  give  in  regard  to  the  nature 
of  the  relation  between  them.  We  may  simply  state 
the  three  metaphysical  alternatives: — (a)  that  the 
brain  is  the  only  real  agency  and  consciousness  one 
of  its  phenomena;  (6)  that  consciousness  is  the  real- 
ity of  which  the  correlated  brain-process  is  a  phenom- 
enon; or  (c)  that  brain-process  and  consciousness  are 
two  aspects  of  the  same  reality. 

SUMMARY. — The  physiologist  who  devotes  himself 
to  the  study  of  nervous  functions  often  speaks  as  if 

*  Stout,  loc.  cit. 


PROGRESS  OF  PSYCHOLOGY.       451 

his  science  was  in  process  of  absorbing  psychology, 
or  rather  of  showing  that  psychology  is  illusory,  for 
he  will  replace  such  metaphysical  conceptions  as 
soul,  consciousness,  and  will  by  "  real  physiological 
processes  "  (Loeb).  He  has  not  yet  succeeded  in  this 
process  of  substitution,  and  it  appears  to  us  that  his 
expectation  or  his  mode  of  stating  it  reveals  a  misun- 
derstanding. 

At  the  same  time,  this  anti-metaphysical  physi- 
ology, of  which  Professor  Ernst  Mach  *  of  Vienna 
is  an  outstanding  champion,  expresses  a  true  ideal 
for  physiology.  For  there  the  terms  of  interpreta- 
tion ought  to  be  entirely  objective  (i.e.,  as  objective 
as  any  general  terms  like  stimuli,  neuron,  neuroses, 
can  be),  and  terms  like  consciousness  and  will  are 
irrelevant. 

EXPEEIMEXTAL,  PSYCHOLOGY. 

The  introduction  of  experimental  methods  into 
psychological  research  was  one  of  the  distinctive 
steps  of  the  nineteenth  century,  but  as  most  of  the 
results  have  been  gained  since  1878  when  Wundt 
opened  his  laboratory  of  physiological  psychology  at 
Leipzig,  it  is  still  too  soon  to  estimate  their  value. 
Although  Wundt  has  been  the  direct  inspirer  of  most 
of  the  modern  work — whether  in  opposition  or  in 
agreement — we  may  go  further  back  to  Johannes 
Miiller  and  Weber,  to  Fechner  and  Helmholtz. 

Johannes  Miiller  (1801-1858). — To  this  genius 
we  owe  the  discovery  of  the  law  of  the  "  specific 
energy  of  the  senses," — that  the  same  stimulus,  the 
same  external  phenomenon,  acting  on  different 

*E.  Mach,  Contributions  to  the  Analysis  of  the  Sensa- 
tions, trans.  Chicago,  1897. 


452    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

organs  of  sense  always  produces  different  sensations ; 
and  that  different  stimuli  acting  on  the  same  organ 
of  sense  always  produce  the  same  sensation.  Bunge, 
from  whom  we  have  quoted  the  statement  of  the 
law,  calls  it  "  the  greatest  achievement  both  of  physi- 
ology and  psychology,"  "  the  greatest  and  deepest 
truth  ever  thought  out  by  the  human  intellect." 
"  There  is,"  Verworn  f  says,  "  scarcely  any  physio- 
logical discovery  which  has  a  more  important  bear- 
ing upon  all  psychology  and  the  theory  of  knowl- 
edge— although  unfortunately  it  is  not  generally 
appreciated — than  the  doctrine  of  the  specific  energy 
of  the  nerves  or  organs  of  the  special  senses."  The 
doctrine  implies  "  that  the  external  world  is  not  in 
reality  what  it  appears  to  us  to  be  when  perceived 
through  the  spectacles  of  our  sense-organs;  and  that 
by  the  path  of  our  sense-organs  we  cannot  arrive  at 
an  adequate  knowledge  of  the  world." 

We  have  already  noted  that  Miiller  was  mistaken 
in  referring  to  the  specific  effects  of  stimulation  to  the 
nerves,  for  since  the  work  of  Yulpian  (1866)  it  has 
been  recognised  that  nerves  are  simply  conducting 
threads;  the  specific  functions  had  to  be  shifted  to 
the  cells  of  the  nerve-centres.  Moreover,  Dr.  Hill  ^ 
refers  to  the  remarkable  experiment  by  which  "  the 
vagus  nerve,  which  ought  to  be  supervising  digestion 
and  the  beating  of  the  heart "  can  be  made  "  to  con- 
trol blushing,  dilation  of  the  pupil,  and  the  other  ac- 
tions which  were  formerly  (are  normally)  within 
the  province  of  the  cervical  sympathetic.  This  up- 

*  G.  Bunge,  Text-BooJc  of  Physiological  and  Pathological 
Chemistry,  trans.  1890,  p.  12. 

t  M.  Verworn,  General  Physiology,  trans.  1899,  p.  21. 
$  An  Introduction  to  Science,  1900,  p.  125. 


PROGRESS  OF  PSYCHOLOGY.  453 

sets  our  notions  of  the  specific  functions  of  nerve- 
centres." 

There  is  reason  to  suspect  that  Miiller's  law,  while 
expressing  an  important  truth,  has  inclined  many 
physiologists  to  put  in  a  full  stop  prematurely.  Let 
us  notice  how  Loeb  regards  it;  his  revolutionary  or 
evolutionary  outlook  is  always  stimulating. 

"  Whether  a  blow,  an  electric  current,  or  ether-vibra- 
tions of  about  0.0008-0.0004  millimetres  wave  length 
stimulate  the  retina,  the  sensation  is  always  a  specific 
one,  namely,  light,  while  a  blow  or  an  electric  current 
produces  sensations  of  sound  in  the  ear.  This  so- 
called  law  of  the  specific  energy  of  the  sense-organs  is 
not  peculiar  to  the  sense-organs;  it  applies,  as  was 
emphasised  by  Sachs,  to  all  living  matter ;  it  even  holds 
good  for  machines.  It  is  in  reality  only  another  ex- 
pression for  the  fact  that  the  eye,  the  ear,  and  every 
living  organ  are  able  to  convert  energy  in  but  one 
definite  form — that  is,  that  they  are  special  machines. 
The  determination  of  the  way  in  which  this  transforma- 
tion of  energy  occurs  in  the  various  organs  would  be 
the  explanation  of  the  specific  energy  of  the  various 
senses." 

"  Physiology  gives  us  no  answer  to  the  latter  ques- 
tion. The  idea  of  specific  energy  has  always  been  re- 
garded as  the  terminus  for  the  investigation  of  the 
sense-organs.  All  the  more  credit  is  due  Mach  and 
Hering  for  first  having  advanced  beyond  that  limit 
with  their  chemical  theory  of  colour  sensations. 
Mach  has  recently  expressed  the  opinion  that  chemical 
conditions  lie  at  the  foundation  of  sensations  in  gen- 
eral." * 

E.  H.  Weber  (1795-18T8).— Weber  was  one  of 
those  who  introduced  precise  physical  methods  into 
physiological  investigation.  He  belongs  to  the 

*  Comparative  Physiology  of  the  Brain  and  Comparative 
Psychology,  1901,  pp.  290-291. 


454    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

school  whose  illustrious  roll  includes  the  names  of 
Volkmann,  Ludwig,  Helmholtz,  E.  du  Bois-Rey- 
mond,  and  Marey;  and  he  deserves  a  place  in  this 
psychological  chapter  for  his  formulation  of  a  law 
which  perpetuates  his  name  and  has  had  a  far-reach- 
ing influence.  It  was  one  of  the  initiatives  in  psycho- 
physics. 

What  Weber  tried  to  find  out  was  the  relation 
between  the  intensity  of  sense-stimulus  (readily  meas- 
ured objectively)  and  the  intensity  of  the  associated 
sensation.  He  found  that  the  degree  of  keenness  in 
our  discrimination  between  two  sensations  of  weight, 
light,  or  sound,  varies  in  constant  rates  with  the  total 
magnitude  of  the  stimuli. 

The  generalisation  may  be  thus  expressed: — 
"  There  will  be  the  same  sensible  difference  of  in- 
tensity between  two  sensations,  provided  the  relative 
intensities  of  the  stimuli  producing  them  remain 
the  same.  Thus  an  increase  of  1  to  a  stimulus  whose 
strength  is  expressed  by  100  will  be  experienced  as 
of  the  same  intensity  as  an  increase  of  2  to  a  stimulus 
whose  strength  is  200,  or  of  3  to  a  stimulus  whose 
strength  is  300,  etc.  The  literature  of  psycho- 
physics  is  occupied  with  the  experimental  verifica- 
tion, the  mathematical  development,  and  the  inter- 
pretation of  this  law.  But  neither  its  experimental 
basis  nor  its  interpretation  is  quite  satisfactory." 
Its  experimental  verification  is  only  approximate, 
especially  in  regard  to  light  and  sound,  and  there 
is  abundant  room  for  difference  of  opinion  as  to  its 
psychological  importance.  There  is  a  critical  sum- 
mary in  Professor  Sorley's  article  from  which  our 
quotation  is  taken. 

*  Prof.  W.  R.  Sorley,  article,  Psychology,  Chambers'a 
Encyclopaedia. 


PROGRESS  OF  PSYCHOLOGY.  455 

The  history  of  psycho-physics  should  give  prom- 
inence to  Gustav  Fechner  who  invented  (1860)  the 
term  (Psycliophysik)  and  first  spoke  of  "  physiologi- 
cal psychology,"  who  was  also  mainly  concerned  with 
a  vindication  and  elaboration  of  "  Weber's  Law " 
(as  he  called  it)  ;  and  to  Helmholtz,  who  measured 
the  velocity  of  nerve-messages  (1851),  supplied  a 
provisional  physiological  basis  for  the  interpreta- 
tion of  visual  and  auditory  sensations,  and  stood  firm 
by  Miiller's  conclusion  that  our  senses  afford  us  only 
symbols  of  the  outer  world.  Mention  should  also 
be  made  of  two  general  works  which  had  a  strong 
influence:  Hermann  Lotze's  Medicinische  Psychol- 
ogie,  oder  Physiologie  der  Seele  (1852)  and  Herbert 
Spencer's  Principles  of  Psychology  (1855).  Dur- 
ing the  last  twenty-five  years  the  most  prominent 
figure  in  Psycho-physics  has  been  Wilhelm  Wundt. 
Among  those  who  have  followed  him  or  have  struck 
out  on  independent  lines  we  may  note: — Baldwin; 
Bethe;  Ebbinghaus;  James;  Pierre  Janet;  Kraepe- 
lin;  Ladd;  Lange;  Lipps;  Loeb;  Lloyd  Morgan; 
Miinsterberg ;  Kibot ;  Titchener. 

The  utility  of  the  experimental  method  is  (1)  in 
giving  point  and  precision  to  introspection,  (2)  in 
making  a  certain  amount  of  measurement  possible, 
and  (3)  in  correlating  definite  variations  in  mental 
process  with  definite  variations  in  the  conditions. 


COMPAEATIVE  PSYCHOLOGY. 

A  new  day  began  in  Physiology  when  Johannes 
Miiller  made  it  a  comparative  study;  and  although 
the  study  of  the  animal  mind  has  not,  as  yet,  yielded 
such  rich  results  to  the  psychology  of  man  as  might 

2D 


456    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

perhaps  have  been  expected,  an  auspicious  beginning 
has  been  made. 

Historical  Outline. — Though  Descartes  set  a 
splendid  example,  there  were  few  in  pre-Darwinian 
days  who  even  attempted  a  scientific  study  of  the 
animal  mind.  Even  those  who  were  careful  ob- 
servers usually  remained  content  with  theological  or 
metaphysical  interpretations.  H.  S.  Reimarus,  who 
published  a  large  work  on  Instincts  in  1760,  and  the 
philosopher  Schelling  may  be  named  as  representa- 
tive. 

The  development  of  physiology  (e.g.,  the  theory 
of  reflexes)  and  of  human  psychology,  and  the  in- 
fluence of  the  evolution-idea,  led  to  a  more  scientific 
outlook.  Alfred  Russel  Wallace  and  others  showed 
that  many  cases  of  alleged  instinctive  activity  were 
really  cases  of  rapid  learning  and  that  "  instincts  " 
were  neither  so  perfect,  unerring,  or  stereotyped  as 
had  been  supposed.  An  attempt  was  made  to  arrange 
vital  activities  in  a  psychological  series — as  if  on 
an  inclined  plane — automatic  physiological  rhythms, 
simple  reflexes,  complex  reflexes,  instinctive  activi- 
ties, habitual  intelligent  actions,  intelligent  behav- 
iour, and  rational  conduct.  Theories  as  to  the 
origin  of  instincts  began  to  abound,  the  Lamarckian 
school  regarding  them  as  the  outcrop  of  inherited 
habits  (either  intelligent  activities  or  complex  re- 
flexes to  start  with),  the  strict  Darwinian  school  re- 
garding them  as  the  result  of  the  action  of  Natural 
Selection  on  congenital  cerebral  variations. 

Although  the  term  "  instinctive  activity  "  is  still 
used  to  include  several  different  modes  of  action,  we 
have  placed  it  on  the  inclined  plane  between  reflex 
action  and  habitual  intelligent  action.  Instinctive 
activities  differ  from  habitual-intelligent  activities  in 


PROGRESS  OF  PSYCHOLOGY.  457 

beng  inborn  or  innate,  requiring  a  liberating  stimu- 
lus, but  neither  experience  nor  education,  though  they 
are  often  perfected  thereby.  They  seem  to  be  shared 
by  all  the  members  of  the  species  in  almost  the  same 
degree,  though  those  of  the  male  may  differ  from 
those  of  the  female,  and  they  are  of  critical  moment 
in  the  struggle  for  existence.  They  differ  from 
simple  reflexes  in  involving  the  activity  of  the  higher 
nerve-centres,  and  there  seems  no  sufficient  reason 
for  denying  that  they  may  be  accompanied  by  some 
measure  of  consciousness. 

Among  the  many  contributions  to  the  study  of 
instincts,  we  recall  those  of  Bethe,  Biichner,  Darwin, 
Forel,  Groos,  G.  H.  Lewes,  Wesley  Mills,  Lloyd 
Morgan,  J.  J.  Murphy,  Romanes,  Schneider,  Spald- 
ing,  Spencer,  Thorndike,  Vogt,  A.  JR.  Wallace,  Was- 
mann,  Weismann,  C.  O.  Whitman,  Ziegler. 

Although  the  progress  of  research  has  already 
made  many  of  his  conclusions  more  than  doubtful, 
George  John  Romanes  (1848-1894)  should,  in  our 
opinion,  be  remembered  as  one  who  did  much  to 
place  the  study  of  comparative  psychology  on  a  scien- 
tific basis.  In  his  Animal  Intelligence  (1881)  he 
tried  to  sift  the  wheat  of  facts  from  the  chaff  of  an- 
ecdotes; in  his  Mental  Evolution  in  Animals  he 
distinguished  primary  instincts,  which  arise,  apart 
from  intelligence,  in  the  course  of  natural  selection, 
and  secondary  instincts,  which  arise  by  the  habitua- 
tion  and  inheritance  of  originally  intelligent  be- 
haviour; in  the  same  volume  and  in  his  Mental  Evo- 
lution in  Man  (1888)  he  made  a  detailed  comparison 
of  the  mental  life  of  man  and  of  animals. 

Some  Lines  of  Modern  W&rk. — An  escape  from 
"  the  muddy  quagmire  of  verbal  dispute  and  the  will- 
o'-the-wisps  of  irresponsible  speculation "  is  indi- 


458    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

cated  in  the  beginning  of  the  experimental  study 
of  instinct.  This  is  well  expressed  in  the  work  of 
Prof.  C.  Lloyd  Morgan,  e.g.,  in  his  study  (following 
Spalding)  of  young  chicks  hatched  in  an  incubator, 
away  therefore  from  all  parental  influence.* 

Bethe — another  careful  experimenter — has  recent- 
ly done  good  service  in  bringing  to  a  focus  the  inter- 
pretation of  the  behaviour  of  ants  and  bees  as  that  of 
reflex  machines  or  automata, — a  return  to  the  posi- 
tion of  Descartes.  After  intricate  meanderings 
(marked  on  smoked  paper)  an  ant  finds  a  food-treas- 
ure ;  it  returns  to  the  nest  and  comes  back  to  the  spoil 
with  reinforcements;  but  it  is  only  in  the  course  of 
many  journeys  that  the  circuitous  path  becomes 
straightened,  as  the  scent-marked  trail  is  definitised. 
It  seems  all  "  chemo-reflex."  A  strange  ant,  dipped 
in  a  solution  of  the  pounded  ants  of  another  nest, 
is  received  by  its  normal  enemies  with  friendliness. 
The  home-coming  bees  which  usually  fly  to  the  door- 
way of  the  hive,  like  arrows  to  their  mark,  are  quite 
nonplussed  if  the  hive  be  shifted  a  few  yards  aside. 
Even  if  the  hive  be  simply  reversed  they  cluster  in 
futile  excitement  at  the  back  wall. 

In  1889,  Verworn  published  an  account  of  his 
experiments  and  observations  on  Protozoa  in  which 
he  showed  that  most  of  their  actions  are  reflexes, 
though  some  show  as  it  were  traces  of  being  impul- 
sive, t  A  different  view  was  maintained  by  A.  Bi- 
net  £  (1891),  who  convinced  himself  that  unicellular 
organisms  exhibit  genuine  selective  actions.  But 

*  See  his  Animal  Life  and  Intelligence  (revised  under 
the  title  Animal  Behaviour),  also  his  Introduction  to  Com- 
parative Psychology  and  Habit  and  Instinct. 

t  Psychophysiologische  Protistenstudien,  1889. 

$  La  vie  psychique  des  micro-organismes,  1891. 


PROGRESS  OF  PSYCHOLOGY.  459 

Verworn's  researches  are  much  more  convincing,  and 
have  been  recently  corroborated  by  H.  S.  Jennings.* 

In  his  study  of  the  slipper  animalcule  (Para- 
mcecium)  and  some  other  Protozoa,  Jennings  has 
shown  that  in  all  the  seeming  to  seek  food  or  to  evade 
the  inimical,  there  is  but  one  typical  motor  reaction, 
like  that  of  a  strip  of  muscle.  It  may  be  that  a 
vestige  of  consciousness  persists  and  that  the  observ- 
able reflex  was  once  represented  by  a  conscious  im- 
pulsive movement,  but  the  fact  seems  to  be  that  the 
slipper  animalcule  now  responds  to  all  sorts  of  stim- 
uli by  one  constant  kind  of  movement. 

Reference  should  also  be  made  to  the  psychological 
study  of  some  of  the  outstanding  phenomena  which 
occur  in  the  life  of  many  different  kinds  of  animals, 
e.g.,  mating  (Darwin,  Wallace,  Biichner,  Lloyd 
Morgan,  Groos),  or  play  (Groos).  In  a  most  in- 
teresting study,  Groos  seeks  to  show  that  play  is  the 
outcrop  of  instincts,  evolved  like  other  instincts  from 
congenital  variations,  and  fostered  in  virtue  of  their 
utility.  But  what  can  be  the  utility  of  play,  which 
by  definition  has  no  serious  purpose  ?  To  which  it 
is  answered  that  play  is  the  young  form  of  work,  a 
rehearsal  without  responsibilities, — that  it  lightens 
the  burden  of  inheritance  by  affording  opportunity 
for  the  exercise  and  perfecting  of  instinctive  activi- 
ties, and  that  the  play  period  allows  scope  for  the 
rise  and  progress  of  new  variations,  initiatives,  idio- 
syncrasies, etc.,  which  form  the  raw  material  of  prog- 
ress, before  the  struggle  for  existence  has  become 
keen. 

Open  Questions. — We  have  elsewhere  referred  to 

*  "  Studies  on  Reactions  to  Stimuli  in  Unicellular  Organisms." 
Numerous  papers  in  Amer.  Journ.  Physiol.  and  Amer.  Naturalist, 
from  1899  onwards. 


460    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

some  of  the  many  open  questions*  in  comparative 
psychology.  Are  there  any  cases  of  animal  behav- 
iour which  cannot  be  interpreted  without  assuming 
a  conceived,  as  contrasted  with  a  perceived  purpose 
(reason  as  contrasted  with  intelligence)  ?  In  what 
proportion  of  cases  can  it  be  shown  that  animals  util- 
ise their  individually  acquired  experience,  adapting 
their  behaviour  in  reference  to  what  they  have 
learned,  or  in  relation  to  some  quite  novel  situation  ? 
To  what  extent  can  we  interpret  the  routine  life  of 
an  animal,  say  ant  or  bee,  as  a  series  of  reflex  actions  ? 
How  have  instincts  been  evolved? 

Nervous  Mechanism. — Before  we  try  to  make 
clear  the  present-day  antithesis  between  the  two 
schools  of  "  comparative  psychologists  " — those  who 
would  interpret  all  the  phenomena  in  objective  phys- 
iological terms,  and  those  who  maintain  that  psychi- 
cal interpretations  are  equally  essential, — we  must 
devote  a  few  paragraphs  to  stating  the  generally  ac- 
cepted conclusions  in  regard  to  nervous  mechanism. 

In  the  simplest  animals  (Protozoa),  there  is 
irritability  and  conductibility  in  the  protoplasm; 
there  is  nervous  function,  in  short;  and  there  are 
many  interesting  modes  of  behaviour,  but  there 
is  no  distinctly  nervous  structure.  Some  of  the 
polypes  show  in  simple  form  the  essential  ground 
plan  of  all  the  nervous  mechanisms  of  higher 
animals.  A  superficial  sensitive  cell  is  connected  by 
a  fibre  with  a  more  internal  nerve-cell  or  gan- 
glion-cell, which  gives  off  a  fibre  to  a  muscle-cell. 
If  we  multiply  each  of  these  component  parts  a 
thousand-fold,  we  have  a  sense-organ  receiving 
stimuli,  a  sensory  nerve  transmitting  these,  a  nerve- 
centre  or  ganglion  receiving,  storing,  co-ordinating 
*  Science  of  Life,  p.  207. 


PROGRESS  OF  PSYCHOLOGY.  461 

and  shunting  the  stimuli,  and  a  motor  nerve  passing 
from  the  ganglion  to  a  muscle. 

Up  to  a  certain  level  in  the  animal  kingdom  the 
behaviour  is  on  the  whole  very  simple,  and  from  a 
physiological  point  of  view  may  be  summed  up  in 
the  phrase  "  reflex  action." 

"A  reflex  is  a  reaction  which  is  caused  by  an  ex- 
ternal stimulus,  and  which  results  in  a  co-ordinated 
movement,  the  closing  of  the  eyelid,  for  example, 
when  the  conjunctiva  is  touched  by  a  foreign  body,  or 
the  narrowing  of  the  pupil  under  the  influence  of  light. 
In  each  of  these  cases,  changes  in  the  sensory  nerve- 
endings  are  produced  which  bring  about  change  of  con- 
dition in  the  nerves.  This  change  travels  to  the  cen- 
tral nervous  system,  passes  from  there  to  the  motor 
nerves,  and  terminates  in  the  muscle-fibres,  producing 
there  a  contraction.  This  passage  from  the  stimulated 
part  to  the  central  nervous  system,  and  back  again  to 
the  peripheral  muscles,  is  called  a  reflex.  There  has 
been  a  growing  tendency  in  physiology  to  make  reflexes 
the  basis  of  the  analysis  of  the  functions  of  the  central 
nervous  system,  consequently  much  importance  has 
been  attached  to  the  underlying  processes  and  the  nec- 
essary mechanism."  * 

The  question  to  which  so  much  attention  has  been 
turned  in  the  closing  years  of  the  nineteenth  century 
is  as  to  the  proportion  of  animal  behaviour  which 
can  be  covered  by  this  concept  of  reflex  action.  At 
what  level  do  animals  begin  to  learn,  to  profit  by 
experience,  to  adapt  their  behaviour  to  novel  condi- 
tions ?  Moreover,  what  security  is  there  in  the  as- 
sumption that  the  reflex  actions  which  are  simplest 
are  also  the  most  primitive  ?  To  what  extent  may  they 

*  J.  Loeb,  Comparative  Physiology  of  the  Brain,  1901, 
pp.  1-2. 


462    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

be  the  degenerate  descendants  of  impulsive  (or  even 
more  complicated)  actions  ? 

There  can  be  no  doubt  that  a  healthy  intact  frog 
or  newt  controls  and  selects  some  of  its  modes  of 
activity,  while  it  is,  to  say  the  least,  very  difficult 
to  prove  that  a  jelly-fish  does  so.  Yet  the  jelly-fish 
has  got  complex  sense-organs  and  a  well-developed, 
though  not  very  complex,  system  of  nerve-cells. 
What  is  it  that  makes  all  the  difference  between  frog 
and  jelly-fish?  The  answer  is  given  in  part  by  a 
familiar  experiment.  "  Eemove  the  brain  of  the 
frog  (an  operation  which  it  bears  with  remarkable 
impunity),  and  carefully  keep  it  moist  and  fed,  and 
for  the  rest  of  its  life,  which  may  easily  be  prolonged 
for  a  year  or  eighteen  months,  we  have  in  our  hands 
a  machine  which  responds  infallibly  to  every  stimu- 
lus, but  never  makes  a  move  in  the  absence  of  an 
easily  recognised  provoking  cause."  * 

But  while  the  above  experiment  shows  that  the 
brain  is  the  seat  of  control,  we  require  some  more 
precise  answer,  for  the  brain  has  many  different 
parts.  And  here  we  are  helped  by  one  of  the  ele- 
mentary facts  of  minute  anatomy,  that  while  the 
grey  matter  (a  network  of  nerve-cells)  in  the  spinal 
cord  and  in  certain  parts  of  the  brain  receives  sen- 
sory nerves  and  gives  origin  to  motor  nerves,  the  grey 
matter  of  the  surface  or  cortex  of  the  brain  is  in  a 
measure  apart,  acting  and  being  acted  upon  through 
the  mediation  of  the  other  grey  matter  in  the  lower 
parts  of  the  brain  or  in  the  spinal  cord.  It  is  then 
in  this  cortical  grey  matter  that  we  look  for  the  seat 
of  that  power  of  choice  and  control  that  distinguishes 
the  higher  animals. 

*  Dr.  A.  Hill,  Trans.  Viet.  Inst.,  XXVI.,  1892-93,  p.  38. 


PROGRESS  OF  PSYCHOLOGY.  463 

Minute  anatomy  has  made  it  possible  to  map  out 
many  of  the  possible  routes  in  the  spinal  cord  and 
brain  which  was  no  long  time  ago  an  un-mapped 
country.  But  it  is  like  a  country  in  which,  though 
the  roads  are  known,  no  passenger  has  ever  been 
seen,  and  where  the  possibilities  of  short-cuts  across 
the  fields  are  endless.  "  One  thing  is  quite  certain, 
namely,  that  the  routes  which  are  most  frequently 
used  are  the  most  open,  and  therefore  the  most  easily 
traversed."  Measurements  of  the  time  taken  by 
nervous  impulses  in  travelling  from  part  to  part  of 
the  body  make  this  clear. 

It  is  usual  to  call  the  possible  path  of  a  sensory 
stimulus  from,  let  us  say,  the  finger  to  the  spinal 
or  basal  brain  ganglia,  and  of  a  resulting  motor 
stimulus  from  the  ganglion  via  motor  nerve  fibres 
to  the  muscles,  a  complete  arc.  And  what  we  have  to 
conceive  of  is  that  part  of  the  impulse  may  be  in  many 
cases  diverted  from  the  short  arc  and  ascend  to  the 
brain-cortex,  there  provoking  impulses  which  de- 
scending fibres  carry  back  to  the  short  arc.  It  19 
in  some  such  way  that  reflex  actions  may  be  strength- 
ened or  restrained  by  the  control  of  the  higher  nerve 
centres. 

The  familiar  "  knee-jerk  "  is  a  good  example  of 
a  pure  reflex,  occurring  in  sleep,  in  the  hypnotic 
state,  in  unconsciousness, — not  much  of  an  action, 
indeed,  but  enough  to  link  us  back  physiologically  to 
the  jelly-fish  with  its  pulsating  disc.  From  this 
simple  reflex,  with  consciousness  at  zero  as  far  as  it 
is  concerned,  we  can  make  a  long  inclined  plane  on 
which  are  arranged  more  complex  reflexes,  compound 
reflexes,  reflexes  which  are  apt  to  arouse  conscious- 
ness, and  reflexes  which  are  very  liable  to  be  in- 
fluenced by  conscious  control. 


464:    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

"  In  its  first  origin  the  nervous  system  is  like  an 
open  moor,  equally  easy  and  equally  difficult  of  pas- 
sage in  all  directions,  but  the  nervous  system  as  we 
inherit  it  is  a  labyrinth  of  paths."  Some  of  these 
paths  are  trodden  down  in  antenatal  life,  but  of 
many  of  them  we  can  only  say  that  their  making  is 
part  of  our  inheritance.  But  here,  as  elsewhere,  the 
question  of  origins  cannot  at  present  be  answered 
with  any  confidence. 

Animal  Behaviour. — Let  us  take  a  broad  survey 
of  animal  behaviour.  All  around  us,  except  in  our 
cities,  there  is  a  busy  animal  life,  swayed  by  the 
twin  impulses  of  "  Hunger  "  and  "  Love."  There 
is  eager  endeavour  after  individual  well-being,  there 
is  not  less  careful  effort  which  secures  the  welfare  of 
the  young.  The  former  varies  from  a  keen  and 
literal  struggle  for  subsistence  to  a  gay  pursuit  of 
aesthetic  luxuries;  the  latter  rises  from  physiolog- 
ically necessary  life-losing  and  instinctive  parental 
industry  to  remarkable  heights  of  what  seem  to  us 
like  deliberate  sacrifice  and  affectionate  devotion. 

On  the  one  hand,  we  see  struggle,  between  mates, 
between  rival  suitors,  between  nearly  related  fellows, 
between  foes  of  entirely  diverse  nature,  between  the 
powers  of  life  and  the  merciless  forces  of  the  in- 
organic world.  On  the  other  hand,  we  see  the  love 
of  mates,  family  affection,  mutual  aid  among  kin- 
dred, many  quaint  partnerships  and  strange  friend- 
ships and  infinite  inter-relations  implying  at  least 
some  measure  of  mutual  yielding. 

We  watch  the  wondrous  industry  of  birds  and  bees 
who  work  from  the  dawn  until  the  dusk  brings  en- 
forced rest  to  their  brains,  which  we  know  to  suffer 
fatigue  as  ours  do;  on  the  other  hand  we  see  the 


PROGRESS  OF  PSYCHOLOGY.  465 

parasite's  drifting  life  of  ease.  Here  locust  eats 
locust,  and  rat  rat ;  there  in  the  combat  of  stags  lover 
fights  with  lover  till  death  conquers  both ;  and  again 
we  see  a  mother  animal  losing  her  life  in  seeking 
to  save  her  children.  At  one  pole  we  see  simple 
brainless  creatures  pursuing  their  daily  life  in  what 
we  can  hardly  call  more  than  dull  sentience;  again 
we  marvel  at  an  instinctive  skill  whose  expression, 
is  unconscious  art;  finally  we  are  face  to  face  with 
an  intelligent  behaviour  which  seems  at  once  a  carica- 
ture and  prototype  of  our  own. 

When  we  talk  to  naturalists  or  read  a  num- 
ber of  works  on  natural  history,  we  soon  recog- 
nise that  there  are  two  extreme  positions.  One  of 
these  has  been  briefly  described  in  the  phrase  "  The 
man  in  the  beast."  It  is  that  which  interprets  an 
animal's  action  forthwith  as  if  it  were  human,  which 
credits  the  beast  with  the  man's  qualities  of  feeling 
and  reasoning  without  seeking  to  prove  their  pres- 
ence, which,  in  short,  reads  the  man  into  the  beast. 
Now  this  is  generous,  and  the  interpretation  of  ani- 
mal life  which  results  is  pleasing,  and  free  from 
the  usual  self-conceit  of  human  intelligence.  Most 
children  pass  through  it,  some  naturalists  die  peace- 
fully in  the  faith  of  it.  But  if  comparative  psy- 
chology has  taught  us  anything,  it  is  that  this  posi- 
tion is  fallacious.  He  is  still  at  the  feet  of  Uncle 
Remus,  who  credits  animals  with  his  own  qualities 
without  proving  his  pleasant  poetry. 

The  other  extreme  is  that  of  those  who  erect  be- 
tween themselves  and  the  beast  a  high  wall.  At  no 
price  will  they  let  the  man  into  the  beast,  nor  admit 
the  man  in  the  beast.  They  are  far  from  agreeing 
with  Scheitlin,  the  author  of  a  Versuch  einer  voll- 
stdndigen  Thierseelenkunde  (1840),  who  said, 


466    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

"  JSTicht  aller  Mensch  ist  im  Thier,  aber  alles  Thier 
1st  im  Menschen."  The  construction  of  this  high 
wall  between  man  and  beast  varies  considerably.  It 
is  not  of  course  without  the  hard  stones  of  fact,  but 
is  usually  cemented  with  superstition.  Those  who 
build  it  seldom  look  over  it,  not  that  they  do  not 
exalt  themselves,  but  they  suffer  from  timidity  or 
from  lack  of  the  curious  spirit. 

If  they  happen  to  observe  how  like  to  human  con- 
duct the  behaviour  of  animals  often  is,  the  resem- 
blance is  hastily  explained  away  as  a  mere  analogy. 
In  comparing  human  conduct  with  that  of  animals, 
we  must,  we  are  told,  ever  remember  that  it  is  a 
person,  a  soul,  a  homo  sapiens,  a  man  who  acts. 
Sometimes  the  distinction  is  confessedly  apparent; 
at  other  times  we  wish  we  could  forget  it. 

Sometimes  the  height  of  the  separating  wall  is 
made  to  depend  not  so  much  on  "  the  unique  maj- 
esty of  human  nature  "  as  on  the  "  marked  infer- 
iority of  the  brute."  The  animal  is  seen  as  an  eft 
in  the  moat  around  the  human  citadel.  It  is  said  to 
have  no  soul,  no  intelligence,  no  control,  even  no  con- 
sciousness. 

Such  then,  sufficiently  outlined  for  our  purpose, 
are  the  two  extreme  views,  that  which  reads  the  man 
into  the  beast,  and  that  which  rears  an  unsurmount- 
able  wall  between  them,  that  which  makes  of  an 
individual  Lepus  cuniculus  frisking  on  the  links  a 
Brer-rabbit,  or  that  which  regards  him  as  a  whimsi- 
cal automatic  machine. 

A  Compromise. — Between  the  two  extreme  inter- 
pretations indicated  above  it  seems  necessary  to  find 
a  compromise.  We  are  sure  of  a  conscious  mental 
life  in  ourselves, — it  is  our  greatest  certainty ;  we  in- 
fer it  in  other  people, — without  this  postulate  there 


PROGRESS  OF  PSYCHOLOGY.  467 

could  have  been  no  science  at  all ;  we  usually  admit 
its  existence  in  the  higher  animals,  like  birds  and 
mammals,  partly  because  it  seems  the  simplest  postu- 
late that  will  cover  the  facts,  and  partly  from  our 
general  acceptance  of  the  idea  of  evolution;  but  as 
we  descend  to  ants  and  bees,  earthworms  and  jelly- 
fishes,  the  impression  of  automatism  grows  upon  us, 
we  are  without  any  criterion  that  will  enable  us  to 
decide  as  to  the  presence  or  absence  of  conscious  con- 
trol or  intelligence  or  the  like,  and  in  particular  cases 
it  is  often  a  matter  of  opinion  whether  the  behaviour 
of  the  animal  requires  psychical  terms  at  all  for  its 
re-description. 

If  we  adhere  to  the  law  of  parcimony,  we  must 
seek  to  interpret  as  reflexes  as  much  of  animal  be- 
haviour as  will  bear  this  interpretation,  but  no 
amount  of  success  in  so  doing  can  prove  the  absence 
of  consciousness.  Furthermore,  when  we  reflect  that 
it  often  requires  close  acquaintance  to  discover  intel- 
ligence in  the  behaviour  of  our  fellow-men, — whose 
actions  are  often  complex  reflexes  or  automatic — we 
are  induced  to  be  cautious  in  our  inferences  as  to 
animals.  Especially  with  subjects  like  ants  and  bees, 
we  feel  the  difficulty  of  getting  sufficiently  near  them 
to  detect  the  individual  peculiarities  of  behaviour  in 
which  intelligence  may  reveal  itself. 

Our  opinion  at  present  is  that  since  a  number  of 
lower  animals  give  evidence  of  memory  for  local- 
ities, for  sounds,  for  particular  kinds  of  food,  etc. ; 
since  others  show  some  power  of  profiting  by  experi- 
ence, or  of  educability;  since  others  seem  able  to 
depart  from  the  usual  responses  of  their  reflexes  when 
novel  circumstances  demand  a  departure  from  rou- 
tine, and  so  on,  we  cannot  give  even  a  descriptive 
account  of  their  behaviour  without  introducing  psy- 


468    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

chical  terms,  such  as  intelligence  and  conscious  con- 
trol. And  this  position  is  strengthened  by  the  fact 
that  we  find  structural  nervous  complications,  in  a 
gradually  ascending  series,  comparable  to  those  which 
we  know  to  be  the  physical  basis  of  mentality  in 
ourselves.  We  need  not  be  so  generous  as  the 
earlier  observers  who  made  each  animal  a  homun- 
culus;  but  we  cannot  pretend  to  be  convinced  that 
the  progress  of  physiology  has  yet  justified  us  in  ac- 
cepting the  phrase  "  reflex-machine  "  as  an  adequate 
description  of  even  a  pismire. 

Father  Wasmann,*  who  has  done  splendid  work 
as  an  entomologist,  especially  in  connection  with  the 
partners  and  guests  of  ants,  has  recently  sought  to 
uphold  the  view  that  many  animals  must  be  regarded 
as  actively  intelligent,  or  with  psychical  life  which, 
within  its  acknowledged  limits,  is  as  essential  to 
their  behaviour  as  ours  is  to  our  daily  conduct.  In 
other  words,  he  has  argued  against  the  purely  objec- 
tive interpretation  of  animals  as  "reflex-machines." 
In  referring  to  this  Professor  Loeb  notes  that  the 
answer  to  the  question  whether  or  not  animals  possess 
intelligence  varies  with  the  definition  of  the  word, 
and  that  the  discussion  is  purely  scholastic.  "  The 
aim  of  modern  biology  is  no  longer  word-discussion, 
but  the  control  of  life-phenomena.  Accordingly  we 
do  not  raise  and  discuss  the  question  as  to  whether 
animals  possess  intelligence,  but  we  consider  it  our 
aim  to  work  out  the  dynamics  of  the  processes  of 
association,  and  find  out  the  physical  and  chemical 
conditions  which  determine  the  variation  in  the  ca- 
pacity of  memory  in  the  various  organisms."  f  And 

*  Instinct  und  Intelligenz  im  Thierreich,  1897. 
t  Comparative  Physiology  of  the  Brain  and  Comparative  Psy- 
chology, 1901,  p.  287. 


PROGRESS  OF  PSYCHOLOGY.  469 

he  looks  for  the  interpretation  of  memory  in  terms 
of  the  nature  of  the  colloidal  substances  which  make 
up  protoplasm. 

This  seems  to  us  an  admirable  position  for  the 
physiologist,  to  whom  subjective  terms  are  irrele- 
vant, but  "  comparative  psychology  "  is  part  of  the 
title  of  Loeb's  book,  and  therefore  we  doubt  if 
the  author  is  justified  in  calling  the  question  of 
presence  or  absence  of  intelligence  a  scholastic  dis- 
cussion. 

Our  point  is  simply  this,  that  while  the  purely 
physiological  interpretation  may  seem  sufficient  (we 
are  only  half-convinced)  to  account  for  certain 
events  in  the  behaviour  of  sea-anemones,  jelly-fishes, 
worms,  etc.,  as  most  graphically  depicted  by  Loeb, 
it  is  not  as  yet  even  approximately  sufficient  to  ac- 
count for  the  general  behaviour  of  the  majority  of 
animals.  We  admit  that  where  no  evidence  of  even 
associative  memory  can  be  found,  it  is  difficult  to 
show  (except  on  general  grounds)  why  the  hypothesis 
of  psychoses  as  well  as  neuroses  is  necessary.  But 
when  we  take  a  broad  view  of  the  behaviour  of 
animals,  we  find  the  psychological  interpretation 
necessary. 

If  it  be  shown  that  not  only  the  bee  but  the  bird 
can  be  adequately  described  physiologically,  that  the 
hypothesis  of  crediting  either  with  a  mental  life 
is  gratuitous,  that  comparative  psychology,  in  short, 
has  disappeared  as  comparative  physiology  has  ad- 
vanced, then  the  number  of  scientific  formula?  has 
been  reduced  by  one, — that  is  all.  But,  in  the  mean- 
time, this  reduction  not  having  been  achieved,  we  are 
in  the  habit  of  studying  the  behaviour  of  bees  and 
birds,  and  must  have  a  theoretical  linkage  for  our 
facts.  We  find  no  other  linkage  available  except 


4:70    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

the  psychological  one,  since  that  afforded  by  physi- 
ology seems  to  us  inadequate  to  fit  the  facts. 

Another  View. — As  we  wish  that  our  historical 
balance-sheet,  necessarily  condensed,  should  be  at 
least  fair,  we  may  direct  the  reader's  attention  to  the 
work  of  Prof.  Loeb  (already  cited  as  an  instance  of 
the  purely  physiological  position).  According  to  Loeb, 
reflexes  may  occur  without  a  reflex  arc,  they  are  not 
necessarily  bound  up  with  the  central  nervous  system 
or  the  ganglion-cells;  the  central  nervous  system  is 
only  a  convenient  conductor;  instincts  are  bundles 
of  tropisms ;  neither  for  spontaneous  activity  nor  for 
co-ordination  are  ganglion-cells  essential;  the  only 
specific  function  of  the  brain,  or  certain  parts  of  it, 
which  Loeb  has  been  able  to  find,  is  the  activity  of 
associative  memory;  and  this  is  made  possible  by 
peculiarities  (still  quite  obscure)  in  the  nature  of  the 
colloidal  substances  which  form  the  physical  basis  of 
life. 

DEVELOPMENT  AND  EVOLUTION  OF  MIND. 

"  We  may  define  psychology,"  says  Dr.  G.  F. 
Stout,  "  as  the  science  of  the  development  of  mind." 
The  definition  indicates  the  modern  outlook  of  the 
science,  but  the  problems  involved  are  so  difficult  that 
we  have  restricted  ourselves  to  pointing  out  the  vari- 
ous sources  of  information. 

The  Data. — From  four  sets  of  facts  the  psycholo- 
gist may  obtain  development  and  material  for  his 
conclusions  as  to  the  individual  and  racial  evolution 
of  mind. 

'*  Analytic  Psychology,  Vol.  L,  189G,  p.  9. 


PROGRESS  OF  PSYCHOLOGY.  471 

(a)  He  may  utilise  past  mental  products, — the 
words  and  structure  of  language  in  which  thought 
is  embodied,  the  beliefs  and  customs  of  races,  their 
works  of  art,  and  so  on. 

(&)  Valuable  data  are  also  obtainable  by  the  study 
of  children, — a  line  of  investigation  practically  be- 
gun by  Preyer,  and  at  present  well  represented  by 
Prof.  Mark  Baldwin  *  and  Stanley  Hall. 

(c)  From  experimental  work — in  which  the  stages 
of  a  mental  product  can  sometimes  be  detected ;  and 
from  comparisons  of  normal  subjects  with  the  blind 
or  the  deaf,  another  set  of  data  are  obtainable. 

(d)  Lastly,  some  help  has  been  forthcoming  from 
the  studies  of  those  who,  like  Romanes  and  Lloyd 
Morgan,  have  paid  particular  attention  to  the  animal 
mind. 

CONCLUSION. 

We  have,  in  this  chapter,  briefly  illustrated  four 
steps  of  recent  progress  in  psychology: — (a)  the 
fuller  recognition  of  the  correlations  between  body 
and  mind,  (6)  the  rapidly  increasing  habit  of  resort- 
ing to  experiment,  (c)  the  broadening  of  the  science 
on  comparative  lines,  and  (d)  the  endeavour  to  look 
at  all  the  facts  from  a  genealogical  or  evolutionary 
standpoint. 

We  are  reminded  that  there  are  other  important 
steps, — the  beginning  of  a  social  psychology  (Tarde, 
Baldwin,  Eoyce,  Le  Bon)  ;  the  beginning  of  a  care- 
ful psychology  of  sex  (Havelock  Ellis)  ;  the  develop- 
ment of  practical  psychology  in  reference  to  educa- 
tion (James,  Lloyd  Morgan,  and  many  others)  ;  the 

*  Mental  Development  in  the  Child  and  the  Race,  2  vols. 
2  E 


472    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

application  of  psycho-physical  methods  to  the  study 
of  the  abnormal  mind ;  and  so  on.  For  here,  as  else- 
where, we  can  only  illustrate  the  scientific  progress 
of  the  century  by  the  unsatisfactory  method  of  sam- 
pling. 


CHAPTEE  XIIT. 
ADVANCE  OF  ANTHROPOLOGY.* 

The  Subject. — Anthropology  has  mankind  for  its 
subject,  just  as  ornithology  deals  with  bird-kind  and 
entomology  with  insect-kind.  It  is,  from  one  point 
of  view,  a  specialised  department  of  zoology,  deal- 
ing with  one  particular  species — Man,  and  it  applies 
zoological  methods  to  the  study  of  human  variations 
and  modifications,  and  to  the  interpretation  of  the 
characteristic  features  in  structure,  habit,  and  social 
organisation  which  distinguish  the  different  human 
races.  It  is,  from  another  point  of  view,  concerned 
with  what  may  be  called  the  prolegomena  to  the 
scientific  study  of  history,  for  through  linguistics, 
folk-lore,  and  the  study  of  the  ancient  (often  pre- 
historic) remains  of  human  activity  it  passes  grad- 
ually into  the  historical  discipline,  in  the  narrower 
and  stricter  sense,  which  takes  to  do  with  the  period 
of  which  we  have  intentional  records. 

Anthropology  is,  like  geography,  a  synthesis  or 
combination  of  contributions  from  a  number  of 
sciences  towards  the  interpretation  of  a  particular 
problem — the  human  species  as  such.  "  We  must 
be  prepared  to  take  anthropology  more  as  the  study 
of  man  in  relation  to  various  and  often  independent 

*  The  aim  of  this  chapter  is  simply  to  indicate  six  of  the 
most  important  problems  which  have  engaged  the  attention 
of  anthropologists  during  the  nineteenth  century. 


474    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

subjects  than  as  an  organic  and  self-contained 
science."  * 

Anthropology  has  its  physical  side,  based  on  anat- 
omy and  physiology;  it  has  also  its  psychical  side, 
based  (theoretically)  on  psychology;  it  has  also  its 
social  aspect,  and  leads  gradually  on  to  the  incipient 
science  of  inductive  sociology  which  concentrates  its 
attention  on  the  various  forms  of  social  organisation 
and  on  their  correlation  with  particular  conditions 
of  existence.  In  the  study  of  skulls,  etc.,  anthro- 
pology meets  anatomy;  but  in  the  study  of  in- 
teresting problems  like  that  of  a  primitive  matri- 
archate  (or  maternal  group)  and  its  possible  rela- 
tions to  the  recognition  of  the  family-tie  and  tribal 
development,  it  obviously  joins  hands  with  sociology. 
It  is  easy  enough  to  confine  anthropology  by  a  defi- 
nition to  the  study  of  individual  bodily  characters 
and  to  make  ethnology  the  science  of  the  races  of  men, 
but  the  distinction  is  untenable,  since  man  is  charac- 
teristically social. 

Impulses. — There  were  at  least  three  impulses 
which  prompted  the  noteworthy  advance  of  anthro- 
pology in  the  second  half  of  the  nineteenth  century. 
(1)  In  many  ways  travelling  had  become  easier,  dis- 
tant parts  of  the  earth  became  practically  near  at 
hand,  and  materials  which  were  formerly  scanty  and 
uncertain  became  abundant  and  secure.  (2)  The 
increase  of  colonisation  and  the  expanding  exploita- 
tion of  the  earth  brought  men  into  familiar  touch 
with  races  whose  names  were  unknown  to  their 
fathers,  and  anthropology  came  to  have  great  practi- 
cal as  well  as  theoretical  interest.  (3)  The  influ- 
ence of  Darwin's  work  was  especially  momentous, 

*  Prof.  W.  M.  Flinders-Petrie,  Address  Anthropol.  Section, 
Rep.  Brit.  Ass.,  1885.  p.  816. 


ADVANCE  OF  ANTHROPOLOGY.  475 

for  he  showed  the  value  of  discussing  man  from  a 
natural  history  point  of  view,  and  shed  the  light  of 
the  evolution-idea  on  a  mass  of  anthropological  facts 
which  had  previously  been  little  more  than  curi- 
osities. 

Associated  with  these  there  is  now  another  sad  im- 
pulse, that  certain  races  are  in  process  of  rapid 
elimination ;  their  scientific  lesson  must  be  read  now 
or  never.  An  anthropological  expedition  is  urgently 
needed  to  study  fleeting  customs,  as  E.  H.  31an  and 
M.  V.  Portman  did  for  the  natives  of  the  Andaman 
Islands,  as  Prof.  A.  C.  Haddon  did  at  the  Torres 
Straits,  as  Profs.  Baldwin  Spencer  and  Gillen  have 
been  doing  in  Australia,  as  Government  officials  and 
others  are  doing  for  the  American  aboriginal  popula- 
tion. 

Perhaps  another  impulse  to  careful  anthropologi- 
cal study  has  come  from  the  insistent  importance  of 
criminology.  The  great  practical  interest  of  this 
enquiry  has  reacted  on  the  science  of  anthropology 
from  which  it  had  its  origin. 

MAN'S    PLACE   IN   NATURE. 

We  use  this  time-honoured  phrase  to  designate 
the  problem — still  far  from  solution — of  man's 
genetic  relationship  to  some  pre-human  or  Simian 
stock.  Even  Sir  Richard  Owen,  conservative  as  he 
was,  recognised  the  "  all-pervading  similitude  of 
structure  "  between  man  and  the  apes,  and  since  Dar- 
win's Descent  of  Man  and  Huxley's  essay  on  Mans 
Place  in  Nature,  it  has  seemed  quite  fair  to  reject 
any  interpretation  which  denies  man's  structural  re- 
semblance to  some  Simian  or  ape-like  type.  So  far 
as  bodily  structure  is  concerned,  Man  is  plainly  one 
of  the  Primates.  As  regards  the  psychical  charac- 


476    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

teristics  of  man, — language,  reason,  morality, — every; 
fair-minded  enquirer  must  admit  that  it  is  difficult 
to  disclose  the  factors  which  evoked  them,  but  that  is 
hardly  an  argument  against  deciding  that  their  mode 
of  origin  was  evolutionary. 

Although  the  structural  resemblances  between  man 
and  the  anthropoid  apes  are  numerous  and  plain, 
no  one  now  dreams  of  arguing  that  man  is  descended 
from  any  existing  form.  Different  living  forms  ap- 
proach man  in  different  ways.  At  what  point  the 
human  stock  diverged  from  the  Simian  remains  quite 
obscure;  no  certain  intermediate  links  are  as  yet 
known, — though  some  of  the  oldest  known  human 
skulls  are  primitive  in  some  of  their  features. 

ISTor  can  it  be  ignored  that,  as  regards  various 
structural  characters,  some  experts  have  found  it 
necessary  to  look  for  man's  ancestry  even  deeper  than 
in  the  monkey  race, — down  to  the  Prosimiee  or  Lemu- 
roids.* 

Dr.  E.  Dubois'  discovery  of  remains  at  Trinil 
in  Java  (which  he  calls  Pithecanthropus  erectus)  is 
interesting  and  valuable,  but  they  are  fragmentary 
(skull-cap  and  femur),  and  experts  differ  greatly  in 
their  interpretation  of  them.  The  Trinil  femur 
seems  to  have  been  that  of  a  being  who  stood  up- 
right; the  capacity  of  the  skull  (inferred  from  the 
cap)  was  greater  than  that  of  any  known  anthropoid 
ape,  but  inferior  to  that  of  human  skulls  of  low  type 
belonging  to  the  Stone  Age.  The  remains  are  either 
those  of  a  missing  link  or  of  a  low  and  ancient  type 
of  man. 

"The  antiquity  of  the  human  race  is  much  greater 
than  was  previously  supposed;  we  must  go  back  to  the 

*  Prof.  H.  Klaatsch,  Globus,  LXXVI.,  1899. 


ADVANCE  OF  ANTHROPOLOGY.  477 

Early  Tertiary,  and  to  the  roots  of  the  Primate  stock 
to  find  the  origin  of  the  species  Homo.  A  precise  in- 
vestigation of  the  whole  Primate-group,  of  its  extinct 
as  well  as  of  its  extant  members,  forms  the  only  basis 
on  which  a  scientific  physical  anthropology  can  be 
established.  Without  this  comparative  anatomical 
foundation,  all  theories  as  to  the  origin  of  the  human 
race  remain,  in  my  opinion,  wholly  in  the  air."  * 

Apart  from  mental  development,  the  distinctively 
human  characters  are  thus  summarised  by  Sir  Wil- 
liam Turner : — "  the  capability  of  erecting  the  trunk, 
the  power  of  extending  and  fixing  the  hip  and  knee 
joints  when  standing,  the  stability  of  the  foot,  the 
range  and  variety  of  movement  of  the  joints  of  the 
upper  limb,  the  balancing  of  the  head  on  the  sum- 
mit of  the  spine,  the  mass  and  weight  of  the  brain, 
and  the  perfection  of  its  internal  mechanism."  f 

But,  as  is  well  known,  the  great  gap  between  man 
and  other  living  creatures  is  in  mental  life,  some 
indication  of  which  is  given  by  man's  superiority  in 
brain-development.  A  man  may  have  a  brain  three 
times  as  heavy  as  a  gorilla's ;  the  average  human 
brain  weighs  48-49  ounces,  the  heaviest  gorilla  brain 
does  not  exceed  20  ounces.  The  figures  for  volume 
or  cranial  capacity  are  not  less  striking.  (  See  Keane's 
Ethnology.,  p.  40.)  But  these  figures  will  be  seen  in 
an  altogether  false  light  unless  we  compare  them  with 
the  differences  between  the  various  kinds  of  monkeys. 
The  marmoset  is  farther  below  the  gorilla  than  man 
is  above  it.  It  is  also  necessary  to  take  into  account 
the  enormous  variations  that  occur  within  the  hu- 

*  Prof.  Rudolf  Martin,  AntJiropologie  als   Wissenschaft 
und  Lehrfach.  Jena,  1901,  p.  23. 
t  Rep.  Brit.  Ass.,  1897,  p.  788. 


478    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

man  species.  Similarly,  as  to  characters  which  can- 
not be  measured  or  weighed,  it  is  obvious  that  it  is 
the  mind  of  a  Fuegian  and  not  that  of  a  Newton 
which  should  be  compared  with  that  of  the  higher 
animals. 

Although  anthropologists  are  not  in  a  position  at 
present  to  do  more  than  speculate  in  regard  to  the 
factors  which  may  account  for  the  evolution  of  man's 
big  l}rain}  the  great  majority  are  unhesitating  in  their 
acceptance  of  the  general  conclusion  of  Darwin's 
Descent  of  Man,  that  man  arose  from  an  ancestral 
stock  common  to  him  and  to  the  higher  apes. 

ANTIQUITY  OF   MAN. 

"  Man's  immense  antiquity  is  now  accepted  by  a 
vast  majority  of  the  most  thoughtful  men."  *  The 
word  "  immense  "  is  suitable,  for  it  remains  impos- 
sible to  arrive  at  incontrovertible  data  by  which  to 
measure  the  prolonged  period  which  has  certainly 
elapsed  since  the  human  race  began.  We  have  al- 
ready referred  to  the  uncertainty  which  besets  any 
estimate  of  the  age  of  the  earth,  and  similar  remarks 
apply  to  the  case  of  man.  There  are  traces  of  man, 
or  of  some  immediate  precursor  in  the  New  or  Late 
Pliocene  deposits,  along  with  remains  of  the  mam- 
moth, the  woolly  rhinoceros,  the  cave-lion,  the  cave- 
bear,  the  Irish  elk,  and  other  extinct  mammals  once 
wide-spread  throughout  Europe  and  Britain.  That 
man  appeared  before  the  last  of  the  Pleistocene  ice- 
ages  seems  undeniable,  and  it  is  possible  that  he  had 
appeared  before  the  first  of  them.  "  The  most  ra- 
tional hypothesis,"  Mr.  Keane  says,  "  seems  that  of 

*  Dr.  Robert  Munro,  Address  Anthropological  Sec.,  Rep.  Brit. 
Ass.,  1893. 


ADVANCE  OF  ANTHROPOLOGY.  479 

inter-glacial  Hominidce  specialised  not  less,  probably 
much  more,  than  half  a  million  years  ago/'  *  Giglioli 
may  be  named  as  another  expert  anthropologist  who 
regards  man's  origin  as  inter-glacial.  For  our 
present  purpose,  the  long  and  weary  discussions  on 
this  subject  are  of  little  moment,  for  though  there 
may  be  doubts  whether  a  million  or  half  a  million 
or  a  quarter  of  a  million  of  years  should  be  claimed, 
the  general  tendency  among  those  who  know  most 
about  it  is  towards  the  larger  figures,  and  while,  on 
the  other  hand,  man  is  but  a  child  of  yesterday  when 
the  age  of  the  earth  is  considered. 

Let  us  recall  the  great  periods  in  man's  unwritten 
history. 

(a)  Since  man  is  certainly  not  derivable  from 
any  of  the  known  anthropoid  apes,  and  since  it  is 
likely  that  he  sprang  from  an  ancestral  stock  com- 
mon to  them  and  to  him,  we  seem  almost  bound  to 
conclude  that  the  divergence  which  led  on  to  the  hu- 
man line  of  evolution  must  have  occurred  before  the 
appearance  of  the  anthropoid  family.  But  the  an- 
thropoids (e.g.,  Pliopiiliecus,  Dryopiihecus)  were  in 
existence  in  Miocene  times,  and  the  inference  is  that 
man's  direct  precursors  had  also  appeared. 

(&)  Before  man  became  habitually  a  user  of  tools 
and  weapons,  there  probably  was  a  long  period  when 
he  used  such  sticks  and  stones  as  came  readily  to 
hand.  Even  monkeys  occasionally  do  so.  Although 
we  do  not  know  with  security  of  any  implements 
older  than  palaeolithic  axes  and  hammers  and  the 
like,  it  is  plain  that  the  making  of  these  implied  no 
small  skill  and  a  previous  period  of  apprenticeship. 

(c)  The  data  for  the  study  of  the  prehistoric  evo- 

*  Ethnology,  1896,  p.  69. 


480    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

lution  of  man  are  derived  from  his  bones,  from  his 
implements,  and  from  the  remains  of  his  homes  and 
monuments.  To  Sir  John  Lubbock  is  due  the  now 
universally  used  term  "  palaeolithic  "  for  the  first  of 
the  prehistoric  periods  with  definite  data,  and  the 
second  half  of  the  nineteenth  century  is  rich  in  re- 
searches on  this  ancient  era.  It  is  probable  that 
palaeolithic  man  (defined  by  remains  in  the  inter- 
glacial  epoch)  had  already  spread  over  nearly  the 
whole  world,  that  he  knew  naturally-kindled  fire, 
that  his  diet,  at  first  mainly  vegetarian,  became  more 
carnivorous  as  hunting  and  fishing  developed,  that 
he  had  no  cultivated  plants,  no  houses,  no  monuments, 
that  he  made  stone  implements  but  did  not  grind 
or  polish  them,  that  he  made  a  few  personal  orna- 
ments, that  he  could  sew,  and  that  he  sometimes  drew 
with  considerable  skill.  In  this  period  the  state  of 
man  is  often  described  as  "  savage."  See  A.  H. 
Keane's  Ethnology  (1896),  p.  110,  and  Tyler's  An- 
thropology (1881). 

(d*)  In  Neolithic  times,  man  seems  to  have  been 
able  to  make  fire  and  to  have  sometimes  cooked  his 
food;  to  hunting  and  fishing  he  had  added  stock- 
breeding  and  tillage;  there  were  many  cultivated 
plants;  he  had  houses,  barrows,  graves,  and  monu- 
ments (single  blocks  or  polylithic  cells)  ;  his  indus- 
tries extended  to  making  polished  stone  instruments, 
spinning,  weaving,  mining,  pottery-making,  carpen- 
try, and  boat-building.  In  this  period  the  state  of 
man  is  often  described  as*  " barbaric"  Between  the 
palaeolithic  and  the  neolithic  periods,  there  often 
seems  a  hiatus  (as  in  Britain),  but  there  is  evidence 
elsewhere  (in  southern  and  south-eastern  lands)  of 
continuous  evolution. 


ADVANCE  OF  ANTHROPOLOGY.  481 

(e)  After  the  neolithic  ages,  but  still  prehistoric, 
come  the  metal  ages, — the  copper  age  ("  crowded 
out  almost  everywhere  in  the  Old  World "),  the 
bronze  age,  and  the  iron  age  (the  two  last  sometimes 
coalescing). 

Even  a  moderate  estimate  would  grant  10,000 
years  to  the  historical  period  in  Egypt  and  Mesopo- 
tamia, 20,000  to  the  metal  ages,  70,000  to  the  neo- 
lithic period,  and  behind  that  total  of  100,000  years 
(since  the  close  of  the  last  ice  age)  there  stretches 
the  vista  of  the  palaeolithic,  and  even  then  man  had  a 
long  history  behind  him. 

The  interest  of  these  figures  is  merely  to  sug- 
gest that  there  was  plenty  of  time  for  much  evolution. 
"  Many  things  may  happen  in  a  long  time,"  and  the 
acknowledged  difficulty  of  interpreting  human  evo- 
lution must  not  be  exaggerated  by  forgetting  that  he 
is  not  so  young  as  he  looks. 

Although  the  date  of  man's  origin  remains  quite 
uncertain,  the  work  of  the  nineteenth  century  has 
secured  this  result  at  least  that  man  is  of  great  an- 
tiquity. It  is  a  moderate  estimate  to  suggest  half 
a  million  years. 


THE  HUMAN  SPECIES. 

The  literature  on  the  subject  of  the  human 
species  is  enormous,  and  when  we  seek  for  the  result, 
it  seems  preposterously  small.  Is  there  one  species 
of  man  or  are  there  several  ?  It  seems  for  the  most 
part  a  verbal  discussion,  depending  on  the  definition 
of  the  term  species. 

The  Linnaean  conception  of  species,  from  which 
Biology  has  not  even  yet  quite  freed  itself,  was  that 


482    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

of  an  assemblage  of  forms  with  characters  constant 
to  this  extent  that  the  species  was  permanent  and 
discontinuous  from  other  species.  But  the  evolu- 
tion-idea has  changed  this,  and  we  regard  species  as 
stages  in  a  progressive  development  whose  flux  is  so 
slow  that  the  shortness  of  any  man's  observational 
period  is  almost  inadequate  to  detect  it.  But  the 
flow  of  glaciers  is  not  negatived  by  the  fact  that  they 
cannot  be  used  as  means  of  transport. 

It  seems  fairly  certain  that  had  not  the  enquirer 
been  man  himself  (with  obvious  vested  interests) 
there  would  never  have  been  any  discussion  as  to  the 
unity  of  the  human  species.  The  numerous  races 
are  quite  comparable  to  the  races  of  pigeons  (all 
descendants  of  the  wild  rock-dove,  Columba  livia), 
or  to  the  races  of  cabbages  (all  derived  from  the  wild 
kale)  ;  they  are  all,  so  far  as  we  know,  fertile  inter 
se}  but  precise  data  on  this  subject  are  within 
a  comparatively  narrow  range;  they  shade  off  into 
one  another  most  perplexingly  when  identification 
or  definition  is  the  object;  in  a  word,  they  are 
varieties.  There  are  no  certain  cases  comparable 
to  mules  among  mankind. 

It  is  possible,  of  course,  that  some  of  the  re- 
mains doubtfully  identified  as  human  may  be  those 
of  a  precursor  species;  it  is  possible,  also,  that  some 
form  of  "  isolation,"  e.g.,  psychical  antipathy,  might 
even  now  lead  to  the  evolution  of  a  distinct  human 
species  non-fertile  with  the  rest  of  mainkind;  but, 
at  present,  the  conclusion  seems  secure  that  zoologi- 
cally considered  mankind  represents  one  species. 

We  have,  however,  no  enthusiasm  on  the  subject, 
remembering  Darwin's  verdict : — "  It  is  almost  a 
matter  of  indifference  whether  the  so-called  races  of 
man  are  thus  designated,  or  ranked  as  '  species '  or 


ADVANCE  OF  ANTHROPOLOGY.  483 

'  sub-species,'  but  the  latter  term  appears  the  most 
appropriate." 

Whether  we  should  regard  the  races  of  mankind 
as  distinct  species,  or  as  sub-species,  or  as  varieties, 
remains  a  subject  of  verbal  discussion,  but  the  mod- 
ern evolutionary  conception  of  "  species "  has 
robbed  the  problem  of  most  of  the  interest  it  once 
had.  The  important  thing  is  that  the  modern  statis- 
tical method  of  talcing  account  of  specific  characters 
should  be  applied  to  the  races  of  men,  that  actually 
occurring  variations  should  be  recorded,  and  that, 
as  far  as  possible,  all  non-congenital  differences  (due 
to  individual  modification}  and  all  artificial  differ- 
ences (e.  g.,  politically  defined  nationality}  should 
be  separated  from  the  congenital  characters  which 
alone  are  indicative  of  genetic  affinity. 

EACES  OF  MANKIXD. 

The  difficulty  that  has  been  felt  in  distinguishing 
human  races  is  parallel  to  that  which  is  familiar  to 
the  zoologist  in  regard,  for  instance,  to  dogs,  or  to 
the  botanist  in  regard  to  willows  or  brambles. 

"  All  being  fertile  inter  se,  although  possibly  in 
different  degrees,  and  several  having  early  acquired 
migratory  habits,  endless  new  varieties  have  constantly 
been  formed  since  remote  prehistoric  times,  both  by 
segmentation  of  early  groups,  and  by  countless  fresh 
combinations  of  early  established  varieties.  Outward 
modifying  influences  must  have  been  brought  into 
play  as  soon  as  the  first-named  groups  began  to  migrate 
from  their  original  homes,  and  such  influences,  inten- 
sified by  the  climatic  changes  accompanying  the 
advance  and  retreat  of  glacial  phenomena,  would  in- 


484    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

crease  in  activity  according  as  the  primitive  tribes 
spread  farther  afield.  To  these  influences  of  the  sur- 
roundings were  soon  added  the  far  more  potent  effects 
of  interminglings  seen  to  be  at  work  already  in  neolithic 
times,  and  thus  the  development  of  fresh  sub-varieties 
of  all  sorts  proceeded  at  an  accelerated  rate.  This 
process  has  necessarily  continued  down  to  the  present 
time,  resulting  in  ever-increasing  confusion  of  funda- 
mental elements,  and  blurring  of  primeval  types. 
Hence  it  is  not  surprising  that  many  ethnologists 
should  accept  as  a  truism  the  statement  that  e  there  are 
no  longer  any  pure  races  in  the  world.' "  * 

The  history  of  the  classification  of  mankind  into 
races  is  not  very  instructive.  The  complexion,  the 
character  of  the  hair,  and  the  shape  of  skull  have 
supplied  the  chief  basis,  sometimes  in  combination, 
but  oftener  singly.  Consideration  of  language  has 
also  been  introduced,  but  it  has  been  perhaps  as 
much  a  hindrance  as  a  help.  Only  of  recent  years 
has  it  been  possible  to  utilise  mental,  as  well  as 
bodily,  distinctions,  and  their  usefulness  depends  on 
the  discrimination  of  the  enquirer. 

The  first  serious  attempt  at  classification  is  said 
to  be  F.  Bernier's  (1672),  but  that  of  Linne,  a 
century  later,  has  had  more  lasting  influence.  After 
setting  aside  Homo  monstruosus  and  Homo  ferus, 
Linnaeus  divided  Homo  sapiens  into  fair-haired,  blue- 
eyed,  light-skinned  Europeans;  yellowish,  brown- 
eyed,  black-haired  Asiatics;  black-haired,  beardless, 
tawny  Americans ;  and  black,  woolly-haired,  flat-nosed 
Africans.  A  close  approximation  to  this  classifica- 
tion is  now  used  by  many  experts. 

The  work  of  'Buff on   and   Dr.   J.    C.   Prichard 

*  A.  H.  Keane,  Ethnology,  1896,  p.  163. 


ADVANCE  OF  ANTHROPOLOGY.  485 

(1785-1846)  lies  at  the  foundation  of  ethnology, 
but  neither  indulged  in  any  special  classification. 
Broca,  De  Quatrefages,  Haeckel,  Huxley,  and  many 
others  suggested  schemes,  none  of  -which  has  been 
found  altogether  satisfactory.  The  present  tendency 
seems  to  be  to  postpone  further  construction  until 
the  criteria  of  race  have  been  more  thoroughly  and 
more  critically  studied.  The  practice  of  anthropo- 
metry was  greatly  increased  in  exactness  by  the  -work 
of  Quetelet,  Gafton,  and  others;  but  there  is  still 
need  for  careful  criticism.  Thus  the  zoological  dis- 
tinction between  "  variations  "  and  "  modifications  " 
has  to  be  worked  out  in  regard  to  racial  distinctions ; 
and  the  occurrence  of  "  convergence  "  or  "  homoplas- 
tic  resemblance  "  familiar  to  the  biologist,  must  be 
carefully  looked  for. 

It  seems  fairly  clear  that  in  regard  to  physical 
characters  no  reliance  can  be  based  on  one  character 
by  itself.  Men  cannot  be  classified  by  skull-char- 
acters (especially  if  the  observations  be  restricted 
to  adults)  as  crystals  by  their  facets.  The  diagnostic 
distinctions  of  races  must  rest  on  a  combination  of 
characters.  It  seems  also  clear  that  speech  and  race 
are  anything  but  convertible  terms,  and  that  simili- 
tudes in  customs  and  belief  afford  no  criterion  of 
genetic  affinities.  They  are  analogies,  not  homolo- 
gies. 

Mr.  Keane's  picture  of  the  chief  branchings  of 
the  human  genealogical  tree  is  briefly  as  follows: — 
(I.)  The  first  ramification  from  the  main  stock  is 
that  of  the  "  generalised  negro "  (Homo  cethiopi- 
cus),  branching  off  in  various  directions  towards 
Africa,  Oceania,  and  Australia;  (II.  and  III.)  after 
the  negro  dispersion  the  main  stem  throws  off  a 
generalised  Mongolo- American  limb,  which  pres- 


486    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

ently  breaks  into  two  great  divisions  (Homo  mon- 
golicus  and  Homo  americanus)  ;  (IV.)  between  the 
negro  and  the  Mongolo-American  boughs  the  main 
stem  passes  upwards,  developing  a  generalised  Cau- 
casic  type  (Homo  caucasicus),  which  also  at  an 
early  date  ramifies  into  three  great  branches,  filling 
all  the  intervening  central  space,  overshadowing  the 
negro,  overtopping  the  mongol,  and  shooting  still 
upwards,  one  might  say,  into  almost  illimitable 
space.  Such  is  the  dominant  position  of  the  highest 
of  the  Hominidse,  which  seems  alone  destined  to  a 
great  future,  as  it  is  alone  heir  to  a  great  past.  All 
the  works  of  man  worthy  of  record  have,  with  few 
or  doubtful  exceptions,  emanated  from  the  large  and 
much  convoluted  brain  of  the  white  Homo  caucasi- 
cus.* 

EVOLUTION  OF  LANGUAGE. 

For  millions  of  years  the  silence  of  nature  was 
broken  only  by  the  "  inanimate  "  voices  of  wind  and 
wave,  of  thunder-clap  and  cataract.  There  was  no 
voice  of  life,  until  this  began  among  insects,  and 
at  a  much  later  stage  once  again  among  amphibians. 
The  croaking  of  frogs  is  effected  by  a  mechanism 
(of  larynx  and  vocal  cords)  essentially  similar  to 
that  of  the  prima  donna's  song.  Even  a  brief  study 
of  the  vocal  sounds  made  by  birds  and  mammals 
shows  that  certain  sounds  are  restricted  to  certain 
occasions  and  have  a  certain  meaning.  They  express 
particular  emotional  states,  and  they  often  indicate 
the  discovery  of  danger  or  of  food.  In  this  sense, 
there  is  no  doubt  that  the  young  chick  or  the  dog 
has  a  few  definite  words.  That  fairly  definite  in- 
*  From  Keane,  p.  226. 


ADVANCE  OF  ANTHROPOLOGY.  487 

formation  may  be  conveyed  by  one  animal  to  another 
without  words  at  all  seems  a  legitimate  conclusion 
from  studies  on  the  behaviour  of  ants,  while,  on  the 
other  hand,  there  is  no  evidence  that  any  animals, 
even  monkeys,  have  language  (logos)  in  the  stricter 
sense;  that  is  to  say,  the  use  of  words  in  expressing 
judgments. 

From  his  pre-human  ancestry  man  doubtless  in- 
herited the  structural  arrangements  which  make 
language  possible, — the  vocal  cords  and  their  ner- 
vous connection  with  a  cerebral  centre;  but  it  seems 
extremely  improbable  that  any  hint  as  to  human 
phonetics  will  be  furnished  by  the  most  careful  study 
of  jabbering  monkeys.  It  seems  likely  that  lan- 
guage in  the  strict  sense  was  altogether  a  human 
product,  following  in  the  wake  of  that  marvellous 
stride  in  evolution  which  gave  man  his  big  and  richly 
convoluted  brain.  That  speech  helps  intellectual  de- 
velopment (unless  overdone)  is  certain,  but  there 
seems  more  reason  to  say  that  man  spoke  because 
he  thought  than  that  man  thought  because  he  was  able 
to  speak.  And  it  would  be  still  more  correct  to  say 
that  man  became  able  to  speak  partly  in  virtue  of 
higher  cerebral  organisation  and  intelligence  gener- 
ally, and  partly  because  he  had  gained  somewhat 
subtle  nervous  connections  between  the  brain  and  the 
mouth  and  larynx.  There  may  have  been,  as  there 
still  is,  communication  of  judgments  without  a  single 
sentence. 

We  look  back  in  imagination  to  the  early  days  of 
our  race,  and  we  suppose  that  then,  as  in  the  early 
days  of  individual  infancy,  there  was  "  no  language 
but  a  cry."  We  remember  also  that  the  physio- 
logical "  emotional  circuit "  within  our  body  affects 
the  muscular  movements  of  heart  and  lungs,  of 

2r 


488    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

larynx  and  bladder.  We  look  back  to  the  first 
sentence  as  a  subtle  mixture  of  cry  and  gesture. 
It  may  seem  that  a  great  gulf  is  fixed  between  the 
first  jabbering  sentence  and  the  orations  of  Demos- 
thenes, but  the  students  of  phonesis  and  language 
have  detected  many  a  hint  of  the  bridge.  The  child 
remains  as  a  perpetual  illustration,  whose  signifi- 
cance is  by  no  means  exhausted. 

That  there  are  great  difficulties  in  accounting  for 
the  evolution  of  language  must  be  frankly  admitted, 
but  the  enquiry  is  still  young.  We  must  remember 
the  importance  of  sociality;  the  possible  influence 
of  periods  of  enforced  leisure  (which  seem  to  have 
been  important  in  the  evolution  of  bird-song)  ;  the 
excitements  of  the  chase,  of  the  conflict,  of  the  court- 
ship; the  imitative  instinct  and  the  hints  to  inven- 
tion afforded  by  the  many  voices  of  nature  which 
fell  upon  the  ear  of  primitive  man ;  and  many  other 
considerations. 

Apart  from  the  problem  of  its  origin  and  evolu- 
tion, language  is  of  great  interest  to  anthropolo- 
gists as  an  index  of  mental  character  in  different 
races  and  as  a  possible  aid  in  their  classification. 
We  are  no  longer  liable  to  the  error  of  making  it  the 
sole  criterion  of  race,  as  some  of  the  earlier  philolo- 
gists maintained  in  their  enthusiasm,  but  the  oppo- 
site error  of  rejecting  the  philologist's  assistance 
must  be  Avoided.  Although  data  are  still  few,  there 
seems  evidence  of  structural  differences  in  the 
organs  of  speech  in  different  races,  and  there  is  no 
doubt  as  to  the  value  of  the  old  "  shibboleth  "  test 
which  depends  on  the  auditory  as  well  as  on  the  vocal 
organs.  The  value  of  the  linguistic  test  is  increased 
by  the  remarkable  fact  that  while  peoples  mix,  lan- 
guages never  do  (apart  from  word-borrowing).  The 


ADVANCE  OF  A3TTHROPOLOGY.  489 

Basques  are  shown  by  their  speech  to  be  at  least 
partly  descended  from  a  pre-Aryan  or  a  non-Aryan 
race  (African  Hamite  ?),  and  similarly  it  may  be 
said  of  Finns  atnd  of  Magyars  that  their  speech  be- 
trayeth  them.  "  Language  used  -with,  judgment  is 
thus  seen  to  be  a  great  aid  to  the  ethnologist  in  de- 
termining racial  affinities  and  in  solving  many  an- 
thropological difficulties"  (Keane).  Into  the  ques- 
tion of  the  various  lines  of  language-evolution — Ag- 
glutinating, Polysynthetic,  Inflecting,  and  Isolating 
— it  is  beyond  our  scope  to  enter. 

On  the  other  hand,  we  must  remember  Prof. 
Sayce's  caution :  "  A  common  language  is  not  a  test 
of  race,  it  is  a  test  of  social  contact.  .  .  .  "While  the 
characteristics  of  race  seem  almost  indelible,  lan- 
guage is  as  fluctuating  and  variable  as  the  waves  of 
the  sea." 

APPRECIATION  OF  FOLK-LORE. 

The  advance  of  anthropology  in  the  nineteenth 
century  has  involved  a  quite  new  appreciation  of 
folk-lore,  and  this  has  brought  much  gain  to  the 
science.  What  was  formerly  regarded  as  the  some- 
what mysterious  romance  of  young  peoples  is  now 
part  of  the  anthropologist's  data.  So  much  has  it 
been  used,  indeed,  that  the  taunt  has  arisen  that  an- 
thropology is  founded  on  romance.  Let  us  give 
one  familiar  illustration,  in  reference  to  folk-lore 
about  the  fairies. 

It  seems  that  there  are  fairies  and  fairies.  There 
are  divinities  associated  with  rivers  and  lakes,  and 
there  are  dead  ancestors,  but  "  in  far  the  greater 
number  of  cases  we  seem  to  have  something  histori- 
cal, or,  at  any  rate,  something  which  may  be  con- 


490    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

templated  as  historical.  The  key  to  the  fairy  idea 
is  that  there  once  was  a  real  race  of  people  to  whom 
all  kinds  of  attributes,  possible  and  impossible,  have 
been  given  in  the  course  of  uncounted  centuries  of 
story-telling  by  races  endowed  with  a  lively  imagi- 
nation." *  From  British  folk-lore  about  fairies, 
Prof.  Rhys  has  constructed  a  picture  of  an  ancient 
race  in  Britain,  "  small,  swarthy  mound-dwellers,  of 
an  unwarlike  disposition,  much  given  to  magic  and 
wizardry,  and  living  underground:  its  attributes 
have  been  exaggerated  or  otherwise  distorted  in  the 
evolution  of  the  Little  People  of  our  fairy  tales."  f 

With  the  help  of  folk-lore  and  linguistics  it  may 
thus  became  possible  to  trace  a  probable  succession  of 
British  peoples — the  Little  People,  the  taller  Pict8 
who  enslaved  them,  the  Celts,  and  so  on. 

Though  we  must  not  make  a  dogma  of  it,  there 
seems  much  to  be  said  for  the  generalisation  that 
similar  interpretations  and  similar  modes  of  fanciful 
expression  crop  up  at  similar  stages  in  the  intellec- 
tual evolution  of  different  races.  The  wide  dissemi- 
nation of  many  old  stories,  like  that  of  Cinderella, 
suggests  this.  "  If  we  view  them  in  their  wealth 
of  detail,  we  shall  deem  it  impossible  that  they 
could  have  been  disseminated  over  the  world  as 
they  are,  otherwise  than  by  actual  contact  of  the 
several  peoples  with  each  other.  If  we  view  them 
in  their  simplicity  of  idea,  we  shall  be  more  dis- 
posed to  think  that  the  mind  of  man  naturally  pro- 
duces the  same  result  in  the  like  circumstances,  and 
that  it  is  not  necessary  to  postulate  any  communica- 

*  Prof.  John  Rhys,  Address  to  Anthropological  Section, 
Rep.  Brit.  Ass.  for  1900,  p.  885. 

f  Op.  cit.,  p.  896. 


ADVANCE  OF  ANTHROPOLOGY.  491 

tion  between  the  peoples  to  account  for  the  identity. 
It  does  not  surprise  us  that  the  same  complicated 
physical  operations  should  be  performed  by  far- 
distant  peoples  without  any  communication  with 
each  other.  Why  should  it  be  more  surprising 
that  mental  operations,  not  nearly  so  complex,  should 
be  produced  in  the  same  order  by  different  peoples 
without  any  such  communication?  Where  commu- 
nication is  proved  or  probable,  it  may  be  accepted 
as  a  sufficient  explanation ;  where  it  is  not  provable, 
there  is  uo  need  that  we  should  assume  its  existence."* 
In  this  connection  reference  should  be  made  to  the 
researches  of  Dr.  J.  G.  Frazer,  Mr.  E.  Sidney  Hart- 
land  and  Mr.  Gomme. 

There  is  need  to  be  exceedingly  careful  with 
the  generalisation  that  children  in  their  fancies  and 
games,  speech  and  ideas,  recapitulate  stages  in  the 
evolution  of  mankind.  Changed  conditions  and  the 
influences  of  education  tend  to  modify  such  recapitu- 
lation as  there  may  be.  At  the  same  time,  this  line 
of  enquiry,  cautiously  followed,  has  led  to  valuable 
results.  Thus  the  antiquity  of  many  child-games  is 
indubitable ;  they  persist  unchanged  with  remarkable 
conservatism;  to  some  extent  they  are  vestiges  of 
ancient  customs.  As  Lord  Bacon  said  of  fables,  we 
may  find  in  the  games  of  children  "  sacred  relics, 
gentle  whispers,  and  the  breath  of  better  times."  The 
works  of  Mrs.  Gomme  and  Professor  Groos  may  be 
especially  mentioned. 

Increasing  attention  is  also  being  paid  to  the 
anthropological  value  of  the  decorative  arts.  In 
many  cases  there  is  a  "  racial  style,"  as  persistent 
as  a  physical  feature,  recognisable  through  periods  of 

*  E.  B.  Bradbrook,  Address  Anthropological  Section,  Rep. 
Brit.  Ass.,  1808,  p.  1005. 


492     PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

thousands  of  years.  The  works  of  Dr.  Grosse,  Dr. 
H.  Balfour,  Prof.  A.  C.  Haddon,  and  Him  may  be 
particularly  referred  to. 

FACTORS  IN  THE  EVOLUTION  OF  MAN. 

Enquiry  into  the  factors  of  evolution  is  still  so 
young  that  we  find  little  sure  foothold  before  such 
a  difficult  problem  as  the  origin  and  descent  of  man. 
The  same  may  be  said  in  regard  to  the  origin  and 
descent  of  Vertebrates,  or  of  Birds,  or  of  Mammals, 
in  fact  all  round.  But  the  difficulty  seems  great  in 
regard  to  man,  because  man's  mental  characteristics 
raise  him  so  high  above  the  animals.  Indeed,  the 
difficulty  of  accounting  for  mathematical,  musical, 
artistic,  and  moral  faculties  in  terms  of  the  evolu- 
tion-formula led  Alfred  Russel  Wallace — the  Nestor 
of  Nineteenth  Century  biology — to  give  up  the 
problem,  and  to  conclude  that  these  faculties  must 
have  had  another  mode  of  origin,  for  which  "  we  can 
only  find  an  adequate  cause  in  the  unseen  universe 
of  Spirit." 

It  seems  premature,  however,  to  make  man — or 
rather  one  aspect  of  man — the  great  exception,  and 
to  abandon  the  scientific  problem  as  insoluble,  after 
a  trial  of  less  than  half  a  century. 

The  difficulty  is  doubtless  exaggerated  by  ignoring 
the  facts  of  anthropology,  by  thinking  too  much  of 
Plato  and  Aristotle,  Newton  and  Goethe,  and  too 
little  of  the  savage. 

The  difficulty  is  also  exaggerated  unnecessarily 
by  the  relative  youth  of  comparative  psychology ;  we 
are  only  beginning  to  be  precisely  informed  in  re- 
gard to  the  intellectual  development  of  the  higher 
animals.  We  readily  refer  to  them  our  heritage  of 


ADVANCE  OF  ANTHROPOLOGY.  493 

evil  dispositions  and  ignoble  propensities  which 
cling  about  the  ascending  life  as  the  grave-clothes  on 
the  resurrected  Lazarus — but  we  are  apt  to  forget 
our  heritage  of  good, — the  wrinkled  brain,  the  quick 
sense,  the  interest  in  kin,  and  how  much  more. 
Such  a  work  as  Sutherland's  Evolution  of  the  Moral 
Instincts  may  be  cited  for  its  wealth  of  evidence  as 
to  the  content  of  morality  in  which  man's  precursors 
might  well  have  shared,  though  we  do  not  think  that 
it  fairly  faces  the  difficulty  of  interpreting  the 
origin  of  the  ethical  judgment, 

Must  we  simply  fall  back  upon  the  general  evo- 
lution-factors which  the  biologist  seeks  to  test: — 
Variation,  sometimes  transilient,  often  definite ;  nat- 
ural selection,  whose  subtlety  of  influence  is  becom- 
ing ever  clearer ;  and  isolation  in  its  many  forms  ? 
Or  are  there  any  particular  factors,  which,  though 
included  in  the  above  categories,  may  be  specially 
relevant  to  the  case  of  man  ?  Or  is  there  some  un- 
known factor  in  evolution  which  will  make  the  whole 
matter  clear  ? 

(a)  Dr.  Robert  Munro  has  emphasised  the  impor- 
tance to  the  evolving  man  of  the  erect  attitude,  which 
Pithecanthropus  erectus — whatever  he  was — seems  to 
have  had,  which  the  anthropoid  apes  (especially  the 
gibbon)  have  in  some  degree.  It  left  the  hands 
more  free  for  manipulation,  for  using  a  tool  or 
weapon,  for  feeling  round  things  and  appreciating 
their  three  dimensions;  it  reacted  on  other  parts  of 
the  body,  such  as  the  spinal  column  and  the  pelvis, 
even  perhaps  on  the  larynx,  as  Jaeger  suggested. 
In  his  address  to  the  Anthropological  Section  of  the 
British  Association  in  1893,  Dr.  Munro  directed  at- 
tention to  three  propositions: — (1)  the  mechanical 
and  physical  advantages  of  the  erect  position,  (2) 


494    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

the  consequent  differentiation  of  the  limbs  into  hands 
and  feet,  and  (3)  the  casual  relation  between  this  and 
the  development  of  the  brain.  But  what  prompted 
man  or  his  forerunners  to  abandon  arboreal  life  and 
stand  erect  upon  the  earth  remains  a  riddle. 

(&)  If  we  grant  the  primitive  man  an  erect  atti- 
tude, the  habit  of  using  his  hands,  a  big  brain,  some 
words  at  least,  some  family  life,  and  so  on,  as  far 
as  the  anthropoid  analogy  will  in  fairness  admit,  but 
deny  him  strength  enough  to  keep  his  foothold  by 
that  virtue,  it  may  seem  more  than  a  platitude  to 
say  that  natural  selection  would  favour  the  develop- 
ment of  wits,  and  not  only  wits,  but,  in  the  widest 
sense,  "  love,"  which  became  a  new  source  of 
strength. 

(c)  The  influence  of  the  family  was  probably  an 
important  factor,  fostering  sympathy  and  gentleness, 
prompting  talk  and  division  of  labour.  Even  in 
early  days  children  would  educate  their  parents. 
As  rudimentary  forms  of  family  life  are  exhibited  by 
gorillas,  chimpanzees,  etc.,  there  is  no  reason  to 
make  any  particular  difficulty  over  its  human 
origin.  We  are  certainly  not  compelled  to  believe 
in  original  promiscuity,  though  such  phases  may 
have  occurred.  The  conclusions  of  McLennan  and 
Morgan  have  to  be  corrected  in  the  light  of  the  criti- 
cisms of  Westermarck,  Hale,  and  others.  And  again 
it  must  be  remembered  that  pairing  for  life  or  for 
prolonged  periods  occurs  both  among  mammals  and 
birds. 

(d~)  As  the  prolonged  helpless  infancy,  character- 
istic of  human  offspring,  tightened  the  family  bond, 
and  helped  to  evolve  gentleness;  as  related  families 
combined  in  a  rudimentary  clan  for  protection 
against  wild  beasts  and  other  rudimentary  clans,  there 


ADVANCE  OF  ANTHROPOLOGY.  495 

might  arise  a  heightened  sociality  rich  in  progressive 
influence. 

(e)  With  the  development  of  tool-using  and  sen- 
tence-making, with  the  gaining  of  firmer  foothold  in 
nature,  with  the  occasional  emergence  of  the  genius, 
there  might  arise — in  permanent  products,  in  sym- 
bols, in  traditions — an  external  heritage,  which,  it 
appears  to  us,  has  been  the  most  potent  factor  in  se- 
curing and  furthering  human  progress.  For  man  is 
relatively  a  slowly  reproducing,  slowly  varying  or- 
ganism. 

We  have  not  expanded  these  suggestions,  for  mere 
may-be's  have  no  place  in  science,  and  a  further 
elucidation  of  the  factors  in  the  evolution  of  man 
must  be  one  of  the  tasks  of  the  twentieth  century. 


CHAPTER  XIV. 

SUGGESTIONS  OF  SOCIOLOGY.* 

SCOPE  OF  SOCIOLOGY. 

SOCIOLOGY,  though  still  a  very  young  science,  is 
past  the  stage  of  being  scoffingly  dismissed  as  "  a 
mass  of  facts  about  society."  It  proposes  to  give 
a  scientific  account  of  social  life  as  a  concrete  unity, 
whose  constituents  have  their  significance  from  their 
relations  to  the  whole.  It  proposes  to  do  this  by 
analytic  and  historical  investigation. 

Aristotle  looked  upon  man  as  "  by  nature  a  politi- 
cal animal,"  and  Darwin  agreed  with  him  in  suppos- 
ing that  man  was  born  a  social  being.  That  this  is 
usually  true  now  is  certain;  to  suppose  that  it  was 
so  originally  seems  gratuitous.  It  is  easy  to  refer 
to  the  fact  that  man  is  derived  from  a  characteris- 
tically gregarious  stock,  but  the  apes  nearest  man  do 
not  live  in  societies;  it  is  easy  to  assert  that  in  his 
primitive  weakness  man  could  not  have  survived  in 
a  Robinson  Crusoe  condition,  even  with  a  mate  to 
help  him,  but  we  know  of  many  savages  who  get 
along  fairly  well  with  nothing  beyond  domestic  or- 
ganisation. 

But  by  some  means  or  other,  probably  along  vari- 
ous paths,  man  became  definitely  social,  and  evolved 

*  The  aim  of  this  chapter  is  to  indicate  some  of  the  lines 
which  are  now  being  followed  in  sociological  inquiry. 


SUGGESTIONS  OF  SOCIOLOGY.  497 

around  himself  a  social  environment.  On  this  he 
acts,  and  it  reacts  on  him.  This  social  environ- 
ment, called  in  hrief  a  society,  is  a  more  or  less  com- 
plex system  of  inter-relations  of  thought,  feeling,  and 
action,  which  find  expression  in  traditions  and  cus- 
toms, in  laws  and  institutions,  in  science  and  litera- 
ture, in  arts  and  crafts,  and  so  on.  Sociology  aims 
at  the  scientific  study  of  this  society — in  its  present 
structure  and  functions,  in  its  origin  and  develop- 
ment (looking  forward  as  well  as  backward) ;  and 
thus,  at  certain  points,  it  necessarily  comes  into  con- 
tact with  psychology,  anthropology,  and  history, 
not  to  speak  of  economics  (which  has  primarily  to 
do  with  industrial  organisation)  or  of  politics  (which 
has  primarily  to  do  with  the  affairs  of  the  state  as 
such). 

Just  as  Biology  includes  Botany  and  Zoology, 
Anatomy  and  Physiology,  hut  is  their  synthesis 
rather  than  their  sum,  having  to  do  with  the  funda- 
mental problems  of  the  nature  and  origin,  continu- 
ance and  progress  of  living  organisms,  so  sociology, 
while  embracing  a  number  of  more  special  enquiries 
(which  may  be  separated  off  if  this  is  found  conven- 
ient), has  to  do  with  the  general  phenomena  of  the 
structure  and  activity,  development  and  evolution 
of  social  groups  or  of  social  forms.  But  just  as 
there  has  been  some  disadvantage  in  separating  Biol- 
ogy from  the  more  special  disciplines — namely,  that 
many  investigators  ignore  general  problems ;  so  there 
is  some  disadvantage  in  defining  off  Sociology,  in  so 
far  as  it  furnishes  an  excuse  for  experts — whether 
historians  or  economists,  anthropologists  or  psychol- 
ogists— to  pursue  their  enquiries  without  recogni- 
tion of  the  sociological  basis. 

To  sum  up  the  section,  the  justification  of  social- 


498    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

ogy  as  a  separate  science  rests  upon  the  fact,  that 
"  man  is  (now,  if  not  from  the  first)  a  social  being; 
his  existence  is  bound  up  with  the  community  .  .  . 
and  no  individual  is  complete  by  himself " 
(Schaffle).  Every  societary  form  is,  in  other  words, 
to  some  degree  an  organic  unity,  and  more  than  the 
sum  of  its  parts. 

HISTORICAL    NOTE. 

In  one  sense  sociology  is  old;  from  Aristotle  and 
Plato  to  Hobbes  and  Locke,  many  had  pondered 
over  the  problems  of  society  and  said  wise  things 
about  them.  But  if  this  be  put  aside  as  being  not 
u  science,"  but  "  philosophy,"  political  or  social, 
then  sociology  is  indeed  young  and  dates  from  Comte 
and  Spencer. 

(1)  The  term  "  Sociologie "  is  due  to  Comte 
(1839),  who  had  clearly  before  him  the  ideal  of  a 
study  of  society  which  should  be  dispassionate  and 
free  from  transcendental  assumptions,  which  should 
in  fact  follow  the  scientific  method.  His  remarkable 
combination  of  mathematical  and  historical  attain- 
ments enabled  him  to  give  an  outline  of  what  the 
work  of  the  sociologist  should  be — an  analytic  and 
historical  study  of  social  statics  and  social  dynamics ; 
but  he  lacked  the  key  which  the  Evolution-idea  af- 
fords. Moreover,  he  meant  by  the  term  sociology  to 
include  more  than  is  now  implied, — he  thought  of  a 
summation  or  synthesis  of  all  science  with  practical 
reference  to  the  regulation  of  human  society. 
Comte's  Sociologie  was  to  supplant  politics,  econo- 
mics, and  much  more;  but  the  modern  sociologist's 
dream  is  rather  that  of  affording  the  special  depart- 
ments a  more  secure  foundation. 


SUGGESTIONS  OF  SOCIOLOGY.  499 

(2)  Herbert  Spencer,  on  the  other  hand,  ap- 
proached the  subject  as  an  evolutionist,  and  al- 
though his  first  book  was  called  Social  Statics 
(1850),  he  consistently  regarded  man  and  his  so- 
cial institutions  as  products, — as  the  results  of  long 
processes  of  change,  and  as  still  subject  to 
change.  Whether  the  problem  be  that  of  the 
transition  from  militarism  to  industrialism,  or 
the  status  of  women,  or  the  development  of  law, 
he  showed  that  the  facts  were  illumined  by  the 
light  of  the  evolution-idea.  Through  the  ages  man 
has  been  adapting  himself  to  the  physical  environ- 
ment, becoming  more  and  more  its  master  as  he 
became  its  more  skilled  interpreter,  and  likewise 
adapting  himself  to  his  social  environment  which  is 
his  truest  discipline  of  character.  From  the  antag- 
onism of  small  groups  competing  for  the  means  of 
subsistence  to  the  co-operation  of  nations  in  a 
"  Friedenspiel"  there  is  a  long  evolution,  but  the 
steps,  through  pain  to  further  progress,  through 
struggle  to  greater  sociality,  are  still  in  part  discern- 
ible for  our  guidance;  and  it  is  part  of  the 
sociologist's  task  to  make  them  clear. 

The  central  ideas  of  Spencer's  sociological  work 
are  thus  summed  up  by  Prof.  F.  H.  Giddings, — 

"Mr.  Spencer's  propositions  could  be  arranged  in 
the  following  order :  (1)  Society  is  an  organism ;  (2)  in 
the  struggle  of  social  organisms  for  existence  and  their 
consequent  differentiation,  fear  of  both  the  living  and 
the  dead  arises,  and  for  countless  ages  is  a  controlling 
emotion ;  (3)  dominated  by  fear,  men  for  ages  are  habit- 
ually engaged  in  military  activities;  (4)  the  transition 
from  militarism  to  industrialism,  made  possible  by  the 
consolidation  of  small  social  groups  into  large  ones, 
which  war  accomplishes,  to  its  own  ultimate  decline, 


500      PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

transforms  human  nature  and  social  institutions  ;  and 
this  fact  affords  the  true  interpretation  of  all  social 
progress." 

"  Such,  in  its  chief  theoretical  conceptions,  is  the 
great  sociological  system  put  forth  by  a  master  mind, 
to  which  all  other  modern  systems  of  sociological 
thought,  and  all  more  special  sociological  studies,  in 
one  or  another  way  are  related."  * 

(3)  As  it  seems  to  us,  a  third  historical  step  of  the 
greatest  moment  is  marked  by  the  work  of 

"  Frederic  Le  Play,  an  economist  whose  name  is 
strange  to  most  people,  even  to  most  Frenchmen,  but 
whose  thought  has  none  the  less  been  in  many  ways 
widely  and  popularly  active  throughout  the  century, 
and  has  been  and  is  even  now  silently  working  in  many 
channels,  at  first  mainly  practical,  but  now  also  theo- 
retic and  speculative.  There  are  social  workers  and 
social  students  who  would  estimate  his  influence  on 
action  and  his  impulse  towards  thought  as  alike  quite 
among  the  very  greatest  in  actual  value  and  in  probable 
usefulness  which  the  nineteenth  century  is  handing 
towards  the  twentieth,  and  this  with  no  disrespect  to  or 
forgetfulness  of  its  many  great  and  better-known  per- 
sonalities and  forces."  t 

Le  Play  turned  a  fertile  brain  and  a  remarkable 
organising  genius  to  the  problem  of  the  concrete  in- 
terpretation of  existing  social  groups  in  terms  of 
the  three  biological  categories, — Environment,  Func- 
tion, and  Kinship,  or,  as  he  phrased  it,  "Lieu, 
Travail,  Famille"  We  shall  return  to  this  three- 
fold interpretation  in  a  subsequent  section. 

*  Modern  Sociology,  Internal .  Monthly,  Nov.,  1900,  p.  543. 
See  also  his  Principles  of  Sociology. 

f  Prof.  Patrick  Geddes,  Man  and  the  Environment,  Intemat. 
Monthly,  1.  (1900),  p.  179. 


SUGGESTIONS  OF  SOCIOLOGY.  501 


LINES    OF   SOCIOLOGICAL   ENQUIRY. 

The  lines  of  sociological  work  are  parallel  to  those 
in  biology:  — 


(A)  "SS-O-*  to  Mor- 
Statics. 


Dynamics. 

I  Comparable  to  Gen- 

(C)    Inquiring    into    the    growth    of  I      eology    (Embryol- 
eociety  in  whole  or  in  part.  (     ogy,  Palaeontology, 

J      etc.)' 


"]  Comparable  to 
(D)  Inquiring  into  the  factors  of  social        ology,  but  it  need 
evolution  (variation,  selection,  |      not  be  separated  as 
etc.),  or  into  the  factors  in  the  }•     a    special    depart- 


evolution  of  any  particular  form 
or  function  of  society. 


ment  as  it  must  be 
our  way  of  looking 
at  the  whole. 


It  may  be  of  service  to  illustrate  this  classifica- 
tion by  means  of  some  representative  examples. 
These  are  indicative  of  some  of  the  steps  of  nine- 
teenth-century sociological  work,  but  it  should  be 
noted  (1)  that  many  of  the  best  pieces  of  work  tra- 
verse the  whole  field,  and  that  even  when  an  investi- 
gator refrains  from  enquiring  into  the  historical  or 
evolutionary  aspect,  he  usually  brings  some  evolu- 
tionist ideas  into  his  morphology;  (2)  that,  as  be- 
fore said,  the  lines  separating  sociological  enquiry 
from  anthropology,  psychology,  and  history  (in  the 
narrow  sense)  are  artificial  lines  of  convenience ;  and 
(3)  that  the  great  bulk  of  sociological  work  (we  do 
not  refer  to  sociological  ideas}  is  subsequent  to  Her- 
bert Spencer's  finely  conceived  introduction  to  the 


502    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

study*  (1873)  which  was  a  powerful  influence  in 
awakening  and  diffusing  interest  in  the  subject. 

A.  Morphological: 
1850.  Spencer,  Social  Statics. 

1875-8.  Schaffle,  Bau  und  Leben  des  socialen  Korpers. 

1889.  Comte  de  Lestrades,  Elements  de  Sociologie. 

B.  Physiological: 

1883-1897.     Lester  Ward,  Dynamic  Sociology. 

1893.  Emile  Durkheim,  De  la  division  du  travail  sociale. 

1893.  Loria,  Les  Bases  economiques  de  la  constitution  sociale. 

Grosse,  Die  Anfcinge  der  Kunst. 

Wallaschek,  Primitive  Music. 
1896.  Lilienfeld,  La  pathologic  sociale. 

C.  Genealogical  : 

1861.  Sir  Henry  Maine,  Ancient  Law  (Patriarchal  Theory). 

1861.  Bachhofen,Das  Mutterrecht. 

1877.  Lewis  H.  Morgan,  Ancient  Society. 

1885.  McLennan,  The  Patriarchal  Theory. 

1888.  Starcke,  Die  Primitive  Familie. 

1891.  Westermarck,  The  History  of  Human  Marriage. 

1896.  Giddings,  Principles  of  Sociology,  Book  III. 

D.  ^tiological: 

Buckle,  History  of  Civilisation. 

J.   Stuart  Glennie,    Tlieory  of  the   Conflict  of  Racest 

New  Philosophy  of  History.} 
1883.  L.  Gumplowicz,  Der  Rassenkampf. 

1890.  Simmel,  Ueber  Sociale  Differ enzierung. 
1893.  Novicow,  Les  Luttes  entre  societes  humaines. 
1893.  Lester  Ward,  Psychic  Factors  in  Civilisation. 
1893.  Ammon,  Die  naturliche  Auslese  beim  Menschen. 
1837.  Baldwin,  Social  and  Ethical  Interpretations. 

*  The  Study  of  Sociology,  International  Science  Series,  1873. 

f  I  beg  to  be  allowed  as  a  grateful  personal  tribute  to  direct 
attention  to  the  importance  of  Mr.  Stuart  Glennie's  work,  not 
only  as  a  sociological  investigator  and  original  thinker  ;  but 
also  as  an  evolutionist  whose  early  theory  of  the  importance 
of  the  conflict  of  races  (long  previous  to  that  of  Gumplowicz 
and  contemporary  with  Darwin's)  has  been  unjustly  lost  sight 
of.  He  is  also  one  of  those  who  have  persistently  endeavoured 
to  carry  on  into  the  sciences  dealing  with  organisms  the  laws 
and  lessons  of  inorganic  phenomena. 


SUGGESTIONS  OF  SOCIOLOGY.  503 


THE  SOCIAL  ORGANISM. 

The  comparison  of  society  to  an  organism  is  at 
least  as  old  as  the  philosophy  of  Plato  and  Aristotle, 
and  the  analogy  has  been  a  favourite  one  in  many 
minds.  It  has  been  made  the  keynote  of  what  is 
often  called  "  biological  sociology,"  it  is  especially 
valuable  in  correcting  mechanical  ideas;  but  like 
many  another  analogy,  it  has  been  overworked. 

As  Spencer  was  one  of  the  first  to  fill  in  the 
analogy  with  biological  detail,  we  may  refer  to  his 
comparison.  In  a  famous  essay  in  1860  he  com- 
pared government  to  the  central  nervous  system, 
agriculture  and  industry  to  the  alimentary  tract, 
transport  and  exchange  to  the  vascular  system  of  the 
animal.  He  also  pointed  out  that,  like  an  organism, 
a  society  grows  and  differentiates,  and  so  on. 

While  Spencer  is  largely  responsible  for  the  dif- 
fusion of  the  analogy  between  a  society  and  an 
organism,  it  should  be  carefully  noted  that  it  was 
he  who  introduced  the  term  "  super-organic  "  as  de- 
scriptive of  society,  indicating  thereby  that  the  bio- 
logical conceptions  may  require  considerable  modi- 
fication before  they  can  be  safely  used  in  sociology. 

It  is  obvious  that  the  analogy  may  be  pursued  far. 
A  society  may  be  compared  to  an  organism  as  re- 
gards the  genetic  kinship  of  the  component  units 
(the  cell  =  the  individual  or  the  family?)  ;  in  the 
power  of  retaining  integrity  or  equilibrium  in  spite 
of  ceaseless  changes  both  internal  and  external;  in 
the  internal  struggle  of  parts  which  co-exists  with 
some  measure  of  mutual  subordination ;  in  owing  its 
peculiar  virtue  to  the  subtle  inter-relations  between 

2G 


504    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

its  elements ;  in  its  power  of  coalescing  with  another 
form  or  of  giving  birth  to  another  form;  in  its 
habit  of  competing  with  other  forms,  as  the  result 
of  which  adaptation  or  elimination  may  ensue;  and 
so  on.  The  analogy  is  far-reaching  and  persuasive, 
and  it  is  helped  over  some  of  its  difficulties  by  the 
consideration  that  just  as  there  are  many  forms  of 
social-group,  from  the  nomad  herd  to  the  French 
Republic,  so  there  are  many  forms  of  organism  from 
sponge  to  eagle. 

Schaffle,  in  his  famous  work  on  the  Structure  and 
Life  of  the  Social  Body  (1875),  carried  the  meta- 
phor of  the  social  organism  to  an  extreme  which  has 
induced  many  to  recoil  from  it  altogether.  The 
family  is  the  cell,  and  the  body  consists  of  simple 
connective  tissue  (expressed  in  unity  of  speech,  etc.) 
and  of  various  differentiated  tissues,  including  a 
sensory  and  motor  apparatus,  and  so  on.  The  com- 
parison is  as  interesting  as  a  game. 

In  his  lucid  exposition  of  the  modern  outlook,* 
Professor  Fairbanks  admits  that  a  society  deserves 
to  be  called  organic,  because  of  its  structural  com- 
plexity; its  dynamical  unity  of  correlated  parts; 
its  unity  and  development  determined  from  within 
(surely  not  wholly?)  ;  its  dependence  on  the  environ- 
ment, both  physical  and  social;  and  its  intelligibility 
only  as  part  of  a  larger  process, — the  evolution  of 
human  society  as  a  whole.  But  he  adds  that  a  so- 
ciety differs  from  a  "  biological  organism,"  let  us 
say  a  bird,  in  the  greater  original  discreteness  of  its 
elements,  in  its  less  fixed  and  permanent  form,  in 
the  greater  interdependence  of  the  parts,  and  in  the 
fact  that  consciousness  remains  centered  in  the 
discrete  individual  elements.  Perhaps  the  enthu- 
*  Internal.  Journ.  Ethics,  VIII.,  1897,  p.  61. 


SUGGESTIONS  OF  SOCIOLOGY.  505 

siast  for  the  "  social  organism  "  idea  would  argue 
each  of  these  points. 

There  are  many  other  objections  to  the  analogy. 
Thus  Mr.  E.  Montgomery  writes : — "  Vital  organi- 
sation is  not  brought  about  like  social  organisation 
through  the  consensus  of  autonomous  units.  It  is 
wrought  within  a  unitary  being,  whose  organic  dif- 
ferentiations and  specifications  were  gradually  elab- 
orated through  interaction  with  the  medium.  The 
end  of  vital  organisation  is  realised  in  the  co-opera- 
tive efficiency  of  its  constituent  parts  in  total  sub- 
serviency to  the  organism  as  an  integral  being, 
whilst  the  true  end  of  social  organisation  among  us 
human  beings  is  realised  in  the  social  consciousness 
of  each  constituent  individual."  * 

But  it  might  be  maintained  that  there  is  some 
consensus  of  units  in  the  making  of  an  animal  body, 
and  that  in  early  human  societies  the  consensus  was 
rather  enforced  than  deliberate. 

The  ideal  society  is  synonymous  with  humanity, 
but  the  reality  is  far  otherwise.  For  the  purposes 
of  scientific  study,  we  must  abstract  our  ideal  concep- 
tions, and  recognise  numerous  social  groups  of  men 
who  have,  with  some  bond  of  unity  and  with  some 
persistence,  come  to  share  a  common  life.  Such  a 
social  group  is  the  unit  in  sociological  study.  It  is 
more  than  a  sum  of  individuals  just  as  an  organism 
is  more  than  the  multitude  of  its  cells,  just  as  a  mole- 
cule is  more  than  the  sum  of  its  atoms;  in  other 
words,  it  has  a  unity,  it  is  an  integrate.  The  unity 
might  be  more  assured,  the  integration  might  be 
more  perfect,  but  without  some  unity  or  integration 
there  is  no  social  group  in  the  sociological  sense.  A 
casual  assortment  of  individuals,  isolated  for  in- 
*  Internat.  Journal  Ethics,  VII.,  1897,  pp.  414-434. 


506    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

stance  by  shipwreck,  is  not  a  social  group,  though 
it  might  become  one.  The  Pilgrim  Fathers,  on  the 
other  hand,  formed  a  social  group.  Until  there  is 
enough  of  unity  for  the  group  to  act,  however  imper- 
fectly, as  a  group,  contradicting  the  egoism  of  the 
isolated  individual,  there  is  no  society. 

The  chief  objections  to  the  analogy,  as  it  seems  to 
us,  are: — (1)  that  every  societary  form  we  know 
is  an  imperfectly  unified  integrate  of  organisms,  and 
that  the  analogy  is  rather  between  society  and  ant- 
hill or  bee-hive  or  beaver-village  than  between  a 
society  and  an  animal  body;  (2)  that  the  unity  which 
the  social  philosopher  looks  for  is  "  a  unity  which 
is  the  end  of  its  parts,"  but  though  this  is  clearly 
distinct  from  a  mechanical  unity,  it  is  rather  an  ideal 
than  a  reality  either  in  society  or  in  an  individual 
body;  and  (3)  that  since  the  biologist  has  not  yet 
been  able  to  discover  the  secret  of  the  individual 
organism,  notably  the  secret  of  its  unity,  the  compar- 
ison is  suggestive  of  an  attempt  to  interpret  dbscurum 
per  obscurius. 

In  thinking  of  the  unity  of  the  individual  organ- 
ism— which  seems  to  us  an  unsolved  problem — we 
have  to  distinguish  (a)  ilie  physical  unity  which 
rests  on  the  fact  that  all  the  component  units  are 
closely  akin,  being  lineal  descendants  of  the  fertilised 
ovum,  and  on  the  fact  that  they  are  subtly  con- 
nected with  each  other,  whether  by  intercellular 
bridges  or  by  the  commonalty  established  by  the 
vascular  and  nervous  systems;  and  (&)  the  psychical 
unity,  the  esprit  de  corps,  which  in  a  manner  incon- 
ceivable to  us  makes  the  whole  body  one.  There  are 
organisms,  like  sponges,  in  which  the  psychical  unity 
cannot  be  verified. 

The  same  is  true  in  regard  to  the  social  organism ; 


SUGGESTIONS  OF  SOCIOLOGY.  507 

we  have  to  distinguish  (a)  the  physical  unity  -which 
rests  on  hereditary  kinship  (what  Giddings  calls 
"  the  consciousness  of  kind  ")  and  on  similar  life-con- 
ditions and  (6)  the  psychical  unity,  which  rests  on 
the  unity  of  psychical  life — the  "  social  mind  " — 
developed  within  the  social  group  and  with  relations 
to  certain  ends.  It  seems  probable  that  in  early 
days  the  physical  unity  was  more  important  than 
it  was  later  on,  when,  in  some  cases  of  mixed  nations, 
the  psychical  bond  is  practically  supreme;  and  we 
may  still  distinguish  between  groups  whose  unity 
is  determined  by  genetic  and  environmental  bonds, 
from  others  in  which  the  association  is  also  definitely 
determined  to  the  accomplishment  of  particular  ends. 
If,  then,  we  continue  to  speak  of  society  as  a 
social  organism,  we  must  safeguard  the  analogy  by 
remembering  that  its  character  as  organism  exists 
in  the  thoughts,  feelings,  and  activities  of  the  com- 
ponent individuals.  The  social  bond  is  not  one  of 
sympathy  and  synergy  only,  for  the  rational  life  is 
intrinsically  social.  As  Green  said  "social  life  is 
to  personality  what  language  is  to  thought." 

"  LIEU,    TEA V ALL,    FAMILLE." 

Apart  from  a  corroboration  of  the  evolution- 
formula,  the  chief  service  that  biology  has  rendered 
to  sociology  is  in  indicating  the  three  main  factors  in 
interpretation, — namely,  the  environment,  the  func- 
tion, and  the  genetic  relations  of  the  organism. 
(1)  The  living  creature  exists  in  the  midst  of  a 
sphere  of  influence  (soil,  temperature,  illumination, 
weather,  other  unrelated  living  creatures,  and  so  on) 
— which  constitutes  its  environment.  That  this  en- 
vironment has  its  grip  upon  the  organism,  modifying 


508    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

it,  prompting  it  to  vary,  eliminating  it,  is  obvious. 
(2)  To  this  environment,  however,  the  organism  re- 
acts, modifying  it,  utilising  it,  and  in  some  measure, 
perhaps,  mastering  it.  In  other  words,  function 
consists  of  action  and  reaction  between  the  organism 
and  the  environment.  (3)  But  in  the  third  place, 
the  organism  is  in  genetic  continuity  with  its  ances- 
try, it  is  the  expression  of  an  inheritance,  it  has  kin 
and  it  produces  more.  All  biological  interpretations 
must  take  account  of  the  three  facts: — environment, 
function,  and  kinship. 

As  biology  came  of  age,  its  modes  of  interpreta- 
tion were  bound  to  have  their  influence  on  other 
studies ;  and  this  influence  on  sociology  has  been  far 
more  important  than  the  idea  of  "  a  social  organism." 
A  method  is  better  than  a  metaphor. 

(I.)  To  interpret  a  social  form  we  have  to  take  ac- 
count of  locality,  climate,  fauna,  and  flora,  and  so  on, 
in  a  word,  Lieu;  (II.)  of  the  mode  of  life,  the  occu- 
pations, the  doing  and  not-doing,  in  a  word,  Travail; 
and  (III.)  of  natural  inheritance  and  the  facts  of 
kinship,  in  a  word,  Famille. 

(I.)  Environment. — Although  precise  facts  as  to 
the  influence  of  the  environment  on  the  organism 
are  now  more  abundant  for  plants  and  animals  than 
for  man,  it  was  apparently  in  reference  to  man  that 
the  idea  first  took  hold.  The  theory  that  man  was 
moulded  by  his  surroundings  is  much  older  than 
Buffon  and  Erasmus  Darwin,  Lamarck  and  Trevi- 
ranus  who  insisted,  in  various  ways,  on  the  environ- 
mental factor.  But  just  as  exact  biological  facts  of 
environmental  influence  were  scarce  before  the  work 
of  men  like  Semper,  though  interpretations  in  terms 
of  supposed  environmental  influence  were  rife,  so  it 
must  be  confessed  that  most  of  the  human  illustra- 


SUGGESTIONS  OF  SOCIOLOGY.  509 

tions  still  remain  on  the  merely  interpretative  plane. 
Nor  can  it  readily  be  otherwise,  for  experimenting 
on  man  can  only  be  done  indirectly.  It  is,  however, 
of  much  interest  to  observe  how  many  workers,  from 
many  different  sides,  are  now  emphasising  the  en- 
vironmental— the  geographic — factor.  There  is  a 
renewal  of  confidence  in  the  aphorism — Histories 
alter  oculus  geographia!  "Tell  me  the  geography 
of  a  country,"  Victor  Cousin  said,  "  and  I  will  tell 
you  its  future." 

That  the  characteristics  of  a  race  are  in  part  due 
to  the  influence  of  the  physical  environment  was  an 
idea  familiar  to  Montesquieu  and  to  Humboldt  and 
characteristic  of  Le  Play  and  of  Buckle,  and  perhaps 
there  is  no  one  who  would  now  think  of  maintaining 
a  direct  negative.  But  those  who  admit  the  reality 
of  the  factor  are  not  unanimous  as  to  its  power.  The 
question  is,  how  much  we  can  legitimately  make  the 
environment  responsible  for.  Thus  Buckle  regarded 
the  environmental  factor  as  of  special  importance  in 
relation  to  what  he  called  primary  civilisations,  while 
later  on  the  influence  of  people  on  people  became 
more  momentous.  In  other  words,  man  has  loosened 
the  grip  of  the  environment,  and  in  many  cases  his 
emancipation  has  made  him  callous. 

It  is  obvious  that  the  configuration  of  a  country 
may  imply  concentration,  isolation,  accessibility; 
that  climate  may  partly  account  for  sluggishness 
or  industry,  for  carelessness  or  forethought;  and 
that  many  consequences  will  follow  from  the  re- 
sources of  the  soil,  and  the  nature  of  the  fauna  and 
flora.  The  influence  of  the  environmental  factor  is 
expounded  in  many  books,  e.g.,  Fairbanks'  Outlines 
of  Sociology;  it  seems  more  appropriate  to  our  pur- 
pose to  borrow  from  that  work  a  quotation  from 


510    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

Humboldt : — "  The  final  and  highest  truths  of  the 
geographical  sciences  are  included  in  the  statement 
that  the  structure  of  the  earth's  surface,  and  the 
differences  of  climate  dependent  upon  it,  visibly  rule 
the  course  of  development  for  our  race,  and  have  de- 
termined the  paths  for  the  changes  of  the  seats  of 
culture;  so  that  a  glance  at  the  earth's  surface  per- 
mits us  to  see  the  course  of  human  history  as  deter- 
mined (or,  one  may  say,  purposed)  from  the  begin- 
ning, in  the  distribution  of  land  and  water,  of  plains 
and  heights." 

In  this  section,  we  are  dealing  with  the  interpreta- 
tion of  peculiarities  in  various  societary  forms.  It 
may  be  difficult  to  decide  whether  a  characteristic 
should  be  compared  to  an  "  environmental  modifica- 
tion "  (i.e.,  the  direct  effect  of  external  influence, 
producing  a  change  which  transcends  the  limits  of 
elasticity  and  therefore  persists),  or  to  an  environ- 
mental adaptation  resulting  more  indirectly  from 
the  selection  of  "  variations."  But  in  either  case  it 
has  to  be  interpreted  in  relation  to  the  environment. 
It  is  hardly  necessary  to  say  that  this  line  of  inter- 
pretation is  not  restricted  to  physical  features,  but 
applies  to  the  whole  character  of  the  societary  form. 
Thus,  without  pressing  the  point,  we  may  simply 
allude  to  the  thesis  that  morality  is  cl'osely  correlated 
to  the  environmental  conditions. 

To  sum  up:  The  environmental  influences  in  the 
widest  sense  cannot  be  overlooked  in  social  interpre- 
tations. They  affect  both  body  and  mind,  both  the 
individual  and  the  group.  But  it  should  be  noted 
that  they  are  conditions  rather  than  causes  of  social 
evolution.  "  Outer  nature,"  Keasbey  says  tersely, 
"may  determine  the  form,  but  cannot  account  for 
the  fact  of  society." 


SUGGESTIONS  OF  SOCIOLOGY.  5H 

(II.)  Function. — Biology  has  also  brought  to 
sociology  the  idea  that  the  structural  features  of  an 
organ  are  to  be  interpreted  in  relation  to  its  function 
or  activity.  The  various  forms  of  activity — so 
numerous  in  a  modern  complex  society — are  for  the 
most  parts  referable  to  the  obvious  needs  of  mankind. 
Many  of  them  are  pre-figured  in  the  pursuits  and 
industries  of  animals,  which  include  hunting  and 
fishing,  even  hints  of  agriculture  and  shepherding 
(in  ants),  securing  shelter  and  protection,  and  so  on. 
Love  and  hunger,  if  we  use  the  words  widely,  are 
the  fundamental  impulses  which  sway  both  animal 
and  human  life.  We  recall  Goethe's  question: — 
"  Warum  treibt  sich  das  Voile  so,  v/nd  schreit  ?  "  and 
the  answer,  "  Es  wiU  sich  emdhren,  Kinder  zeugen, 
und  sie  ndhren  so  gut  es  vermag" 

To  get  food,  shelter,  and  clothing;  to  replace  the 
feeling  of  fear  (for  dead  as  well  as  living!)  by  a 
sense  of  security;  to  satisfy  the  sexual  impulse  and 
the  desire  for  companionship — these  are  at  once  pri- 
mary and  fundamental  needs,  each  of  which  has  been 
the  subject  of  much  sociological  research.  In  many 
a  social  group  they  may  be,  as  it  were,  masked  in 
the  garments  of  culture,  but  the  fundamental  needs 
remain  none  the  less.  When  they  are  unrecognis- 
able, it  usually  means  some  morbid  condition  of 
body  or  mind. 

We  can  imagine  how  long  ago  in  paleolithic  days, 
when  men  were  perhaps  for  the  most  part  vegeta- 
rians, the  ravaging  of  the  home  by  some  wild  beast, 
led  to  an  organised  chase,  and  how  the  pursuers,  at 
last  circumventing  their  enemy,  satisfied  at  once  rage 
and  hunger  with  the  warm  flesh.  We  can  imagine 
how  more  adventurous  spirits  took  to  hunting  for 
other  reasons,  how  they  brought  home  the  young 


512     PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

jackal  or  the  kid,  and  the  domestication  of  wild  ani- 
mals began.  We  can  imagine  how  men  imitated  the 
wolves  by  hunting  in  packs,  or  the  pelicans  in  driv- 
ing the  fish  shorewards  to  capture.  Even  monkeys 
may  use  a  stone  as  an  instrument  or  co-operate  to 
lift  some  heavy  object,  and  there  seems  no  difficult 
riddle  in  man's  going  much  further.  A  shelter  is 
desirable,  and  it  often  needs  combined  labour  to  build 
it  or  make  it  safe.  The  home  got  a  hearth,  and  the 
fire  made  itself  felt  as  a  socialiser.  With  home  and 
clothing  property  began.  Not  only  were  beasts 
brought  into  service,  but  men  unconsciously  followed 
the  ants  in  making  slaves  of  their  captured  human 
enemies,  and  the  resulting  greater  leisure  implied 
time  for  thought  and  for  art.  From  simple  stimuli 
long  continued  the  framework  of  a  society  was  grad- 
ually evolved. 

From  a  study  of  origins,  always  so  misty,  the 
sociologist  passes  to  surer  ground  when  he  traces  the 
evolution  of  tools  and  weapons,  through  the  stone, 
the  copper,  the  bronze,  the  iron  ages,  and  from  simple 
to  complex  forms;  or  when  he  shows  how  division 
of  labour,  implied  in  the  very  fact  of  sex,  becomes 
more  and  more  marked,  the  tool-maker  being  special- 
ised from  the  tool-user,  the  warrior  from  the  food- 
provider,  the  preparer  of  skins  from  the  hunter,  and 
so  on  through  the  whole  list,  and  often  with  the  most 
circumstantial  verification  in  existing  uncivilised 
social  groups. 

Or,  again,  the  sociologist  may  follow  another  line 
of  investigation,  which  is  perhaps  most  characteristic 
of  the  school  of  Le  Play  and  well  represented  in 
Britain  by  the  teaching  of  Prof.  Patrick  Geddes,  that 
of  showing  the  social  effects  of  the  particular  modes 
of  life, — hunting,  shepherding,  farming,  and  so  on. 


SUGGESTIONS  OF  SOCIOLOGY.  513 

Just  as  Dr.  Arbutknot  Lane  and  Dr.  Havelock 
Charles  tell  us  of  the  modifications  wrought  on  the 
shoemaker's  and  tailor's  body  by  his  habits  of  work ; 
just  as  Dr.  Arlidge  has  given  us  a  monograph  on  the 
diseases  causally  connected  with,  the  different  modern 
occupations;  so  the  sociologist  seeks  to  trace  the  far- 
reaching  influences  of  the  different  primary  modes  of 
food-getting.  Thus  hunting  may  be  said  to  imply 
a  roving,  unsettled  life,  a  small  tribe  with  perhaps 
only  a  rendezvous,  and  the  evolution  of  independ- 
ence, bravery,  and  wariness;  shepherding  may  be 
said  to  imply  a  larger  tribe,  less  individualism,  more 
corporate  life,  and  the  evolution  of  protective  organi- 
sation and  rights  of  property;  agriculture  may  be 
said  to  imply  a  still  larger  population,  a  settled  life, 
a  relief  from  anxiety,  a  greater  opportunity  to  use 
slaves,  more  leisure,  and  thence  perhaps  more  civili- 
sation. The  importance  of  the  different  kinds  of  diet 
has  been  often  pointed  out,  but  Prof.  Patten  has 
more  than  anyone  done  justice  or  more  than  justice 
to  the  sociological  import  of  food.  We  recall 
Claude  Bernard's  remark  in  regard  to  nutrition: — 
"  IS  evolution,  CQ  n'est  pas  que  la  nutrition,  vue  au 
travers  du  temps/'  and  ]Moleschott's  aphorism  "  Der 
Mensch  ist  was  er  isst." 

We  need  not,  however,  give  further  illustration; 
the  general  thesis  is  plain  that  physical  needs, 
changing  in  expression  with  the  natural  inheritance 
of  each  race,  determine  the  fundamental  functions 
which  are  adapted  to  particular  environments;  and 
on  the  economic  life  thus  resulting  the  structure  of 
a  society  in  greater  part  depends. 

(III.)  Kinship. — The  third  great  set  of  factors 
to  be  borne  in  mind  in  all  sociological  interpreta- 
tion may  be  summed  up  in  the  phrase  genetic  rela- 


514    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

tionship.  In  virtue  of  natural  inheritance  the  prim- 
itive social  group  or  small  tribe  has  a  physical  unity, 
which  rises  into  a  psychical  one.  As  blood-relations, 
they  have  certain  characteristics  in  common,  they 
respond  similarly  to  similar  stimuli,  the  sense  of  kin- 
ship grows.  Peculiarities  may  be  fixed  by  in-breed- 
ing, and  a  consciousness  of  distinctiveness  may  be- 
come vivid  enough  to  be  expressed  in  word  or  symbol. 
A  primitive  sense  of  kinship  may  rise  into  an  esprit 
de  corps,  and  that  to  a  race-ideal  and  patriotism.  It 
must  be  remembered  that  the  natural  inheritance 
(which  includes  psychical  as  well  as  physical  fea- 
tures, and  not  only  obvious  characters  like  shape  of 
nose,  lips,  and  eyes  but  less  definable  characters  like 
fertility)  must  be  distinguished  from  the  hardly  less 
important  external  heritage  expressed  in  custom  and 
myth,  law  and  institution.  Both  are  part  of  the 
racial  entail,  but  only  the  former  is  organically 
transmitted. 

The  sociological  importance  of  the  family  can 
hardly  be  over-estimated,  and  it  should  be  remem- 
bered that  the  researches  of  Starcke,  Westermarck, 
E.  Grosse,  H.  Ounow,  and  others,  have  tended  to  un- 
dermine the  old  conclusion  of  McLennan  and  Lub- 
bock  that  a  lawless  promiscuity  prevailed  in  the 
early  stages  of  social  evolution.  There  seems  no 
good  reason  to  doubt  that  monogamy  was  primitive. 

While  carefully  distinguishing  the  question  of 
validity  from  that  of  origin,  it  is  important  to  con- 
sider the  evolutionist  thesis  that  morality  had  and 
has  one  of  its  centres  around  the  hearth  and  the 
cradle. 

According  to  Mr.  Sutherland,  the  content  of  moral- 
ity arises  from  parental,  conjugal,  and  social  sym- 
pathy, and  the  sentiment  of  Duty  is  regarded  as  a  sys- 


SUGGESTIONS  OF  SOCIOLOGY.  515 

tematisation  or  standardising  of  sympathy.  Although 
this  seems  to  us  to  avoid  the  difficulty  of  account- 
ing for  the  distinctively  ethical  quality  of  "  thinking 
the  ought"  it  sets  forth  admirably  the  pre-human 
expressions  of  sympathy  at  many  different  levels. 

Prof.  F.  H.  Giddings  in  more  than  one  book  has 
elaborated  the  thesis  that  like-mindedness,  i.e.,  like- 
responsiveness  to  given  stimuli,  with  correlated  simi- 
larity in  cerebral  structure,  is  the  basis  of  social 
organisation.  Sympathetic  like-mindedness  results 
in  impulsive  social  action ;  formal  like-mindedness  is 
expressed  in  tradition  and  in  conformity  to  existing 
social  standards;  rational  like-mindedness  leads  to 
the  development  of  a  public  opinion  which  becomes 
an  intelligent  guide  to  progress. 

To  sum  up,  the  three  categories  of  interpretation, 
Environment,  Function,  and  Kinship — Lieu,  Tra- 
vail, Famille — seem  sufficient  for  a  descriptive  ac- 
count of  societary  forms,  but  must  not  be  regarded 
in  a  merely  physical  way.  Each  is  rich  in  psychical 
meaning.  The  physical  and  psychical  lines  of  ad- 
vance are  parallel,  and  the  outcome  is  an  integration 
of  persons. 

CLASSIFICATION  OF  THE  GENERAL  FACTOES  OF  SOCIAL 
EVOLUTION. 

Our  knowledge  of  the  factors  in  social  evolution  is 
still  vague  partly  because  of  the  intrinsic  complexity 
of  the  problem,  and  partly  because  of  our  ignorance 
of  the  early  prehistoric  stages.  It  is  unsatisfactory 
to  use  the  past  as  the  interpretative  key  to  the  pres- 
ent, if  we  have  previously  invented  many  of  the  fea- 
tures of  that  past.  It  is  unsatisfactory  to  adopt 
biological  conclusions  as  if  they  must  hold  good  in 
society,  and  this  is  the  more  precarious  since  some 


516    PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

of  the  leading  biological  ideas  were  originally  sug- 
gested to  biology  by  students  of  social  phenomena. 
There  is  no  other  basis  than  that  furnished  by  histor- 
ical research,  helped  by  the  present  persistence  of 
simple  societary  forms  which,  if  not  exactly  primi- 
tive, do  to  some  extent  suggest  what  primitive  condi- 
tions may  have  been  like. 

Beginning  of  Society.  The  problem  of  the  origin 
of  the  primitive  social  group  is  so  difficult  that  we 
are  forced  at  present  to  an  eclectic  position,  admit- 
ting the  value  of  quite  a  number  of  distinct  sug- 
gestions. 

(a)  Some,  like  Rousseau,  have  pointed  to  man's 
genetic  filiation  to  a  stock  which  shows  many  illus- 
trations of  family  organisation  and  gregariousness. 
His  view  may  be  summed  up  in  the  words: — Man 
did  not   make   society,    (pre-human)    society  made 
man.     To  this  it  may  be  objected  that  the  apes  most 
nearly  related  to  man  are  not  strictly  gregarious. 

(b)  Darwin  and  others  have  supposed  that  primi- 
tive man  was  too  weak  to  stand  alone,  and  that  he 
was  forced  in  self-defence  to  be  social.     To  this  it 
may  be  objected  that  not  a  few  uncivilized  races  live 
in  small  and  scattered  groups,  with  no  more  sociabil- 
ity than  the  mild  and  timorous  chimpanzees. 

(c)  Many  have  emphasised  the  function  of  the 
family   in   developing   sympathetic   feelings,    which 
diffused  to  a  wider  circle.     Thus   Prof.   Fiske  in 
his    Cosmic    Philosophy    has    maintained    that    the 
transition  from  animal  gregariousness  to  human  so- 
ciality was  due  to  the  relations  of  parents  to  off- 
spring,   the   prolonged   period    of   helpless    infancy 
being  of  especial  importance.     But  the  difficulty  is 
to  account  for  the  diffusion  of  domesticity,  and  it 
is   evident   that   the   consciousness   of   kind,    which 


SUGGESTIONS  OF  SOCIOLOGY.  517 

Prof.  Giddings  emphasises,  requires  material — some 
association  wider  than  the  family — in  order  that  it 
may  develop. 

(d)  Spencer  and  others  look  to  "co-operation  in 
war  as  the  chief  cause  of  social  integration."     But 
while  the  importance  of  this  factor  is  almost  unani- 
mously admitted,  there  is  room  for  doubting  whether 
it  was  primitive.     Many  simple  peoples   are  very 
peaceful. 

(e)  There  seems  much  force  in  the  thesis  ably 
expounded  by  Prof.  L.  M.  Keasbey  that  the  social 
cement    is    primarily    economic.     "  A    local    food- 
supply  inevitably  causes  families  to  congregate,  and 
the  more  concentrated  and  permanent  the  source  of 
subsistence,    the   closer    and   more    enduring   is  the 
resulting   tribal    aggregation.     Forest   hunters    and 
river-fishers    are   thus    naturally   tribal    economists. 
Isolation  is  not  economically    advantageous    under 
such  environmental  circumstances,  and  being  brought 
together  in  their  own  interests,  such  people  are  led 
to  become  at  least  semi-social."  * 

In  short,  the  clan  with  which  sociology  begins  is  an 
economic  institution.  "  Sociality  arose  in  the  first 
place  out  of  the  economic  necessity  of  productive 
co-operation."  But  the  historical  evolution  of  so- 
ciety is  obviously  too  difficult  a  subject  to  be  discussed 
in  a  few  paragraphs.  We  may  refer  for  a  fine  exam- 
ple of  the  modern  mode  of  treatment  to  Prof.  Gid- 
dings' Principles  of  Sociology  (1896)  Book  III., 
where  he  distinguishes  a  series  of  stages: — the  an- 
thropogenic stage,  the  metronymic  tribe,  the  patro- 
nymic tribe,  the  military-religious  civilisation,  and 
the  economico-ethiaal  civilisation. 

Factors  in  Social  Evolution.     As  in  biology,  it 

*  The  Institution  of  Society,  Intemat.  Monthly,  I.  (1900), 
pp.  355-398. 


518     PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

seems  useful  to  distinguish  (a)  the  primary  or  origi- 
native factors  which  evoke  change  in  the  societary 
form,  and  (b)  the  secondary  or  directive  factors 
which  determine  the  persistence  of  particular  lines 
of  change. 

(A)  Originative  Factors.  Social  variations  may 
have  an  individual  or  a  social  origin.  "  The  indi- 
vidual," Baldwin  says,  "  produces  the  new  varia- 
tions, the  new  things  in  social  matter."  *  "  The  in- 
dividual particularises  on  the  basis  of  the  generali- 
sations which  society  has  already  effected,  and  his 
activity  supplies  the  essential  material  of  all  human 
and  social  progress."  f  The  genius— who  must  be 
interpreted  as  an  individual  "  transilient  "  variation 
— may  be  powerful  enough  to  bring  about  a  social 
variation.  This  is  the  truth  in  "  the-great-man- 
theory  "  of  history. 

Social  variations  may  also  have  a  social  origin. 
Increase  of  population  implies  the  internal  growth 
of  society,  and  the  structural  arrangements  which 
were  adequate  yesterday  may  be  incoherent  to-mor- 
row unless  there  be  differentiating  and  integrating 
changes.  The  societary  form  passes  from  one  state 
of  approximate  equilibrium  to  another. 

One  may  doubt  whether  the  biologist  has  a  right 
to  speak  of  self -differentiation  or  self-integration  in 
regard  to  a  plant  or  animal,  but  there  is  no  doubt 
that  the  terms  are  often  appropriate  to  what  occurs 
in  a  societary  form,  which  is  conscious  of  itself  and 
actually  changes  itself. 

Another  source  of  variation,  corresponding  to  the 
biological  amphimixis  (or  fertilisation)  is  to  be 
found  in  the  coalescence  of  two  societary  forms. 

*  Social  and  Ethical  Interpretation.     1897,  p.  455. 
t  P.  456. 


SUGGESTIONS  OF  SOCIOLOGY.  519 

This  never  occurs  as  an  accretion  from  without ;  it 
always  implies  some  measure  of  amalgamation  and 
intermixture,  in  ideas,  if  not  also  physically,  and  the 
result  is  variation.  Strong  societary  forms  may 
exterminate  weak  ones,  but  they  cannot  swallow 
them  as  Pharaoh's  lean  kine  did,  and  be  unaffected. 
The  incidentally  weaker  organisation  may  pro- 
foundly change  the  stronger,  and  victory  may  be 
after  all  to  the  vanquished. 

An  important  consideration,  which  seems  to  have 
been  overlooked  by  some  writers,  is  that  the  ques- 
tion of  the  inheritance  of  acquired  characters  (trans- 
mission of  modifications)  assumes  quite  a  different 
aspect  when  we  pass  from  plants  and  animals  or  in- 
dividual men  to  societary  forms.  While  it  remains 
true  that  the  natural  inheritance  of  the  component 
individuals  probably  does  not  include  modifications, 
and  that  the  changes  most  to  be  trusted  are  the  slow 
organic  or  constitutional  variations,  it  must  not  be 
forgotten  that  the  external  heritage  embodied  in  tra- 
dition and  custom,  in  laws  written  and  unwritten, 
in  literature  and  art,  and  so  on,  admits  of  what  is 
practically  the  transmission  of  acquired  characters. 
Thus  social  modifications  induced  by  environment 
or  function  have  in  social  evolution  a  direct  signifi- 
cance. 

This  note  on  social  inheritance  suggests  a  cross 
reference  to  Galton's  work  on  filial  regression,  which 
shows  us,  he  says,  that  even  a  nation  moves  as  a 
great  fraternity. 

(B)  Directive  Factors.  The  essay  of  Malthus  in 
1798  contains  the  first  modern  recognition  of  the 
sociological  importance  of  "  the  struggle  for  exist- 
ence," a  phrase  which  he  used.  In  the  hands  of  Dar- 
win, Wallace,  Spencer,  Huxley,  and  Haeckel,  the  idea 
acquired  sufficient  validity  to  form  the  basis  of  a 

2H 


520     PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

sociological  theory.  Independently  of  Darwin,  in 
1859  Mr.  J.  S.  Stuart-Glenn ie  laid  emphasis  on  the 
sociological  importance  of  the  conflict  of  races,  a 
process  in  which  the  conquerors  were  often  the  con- 
quered, becoming  merged  in  and  modified  by  those 
whom  they  had  physically  subdued. 

The  same  general  idea  has  been  more  recently 
worked  out  in  detail  by  Gumplowicz  in  his  Rassen- 
Tcampf  (1883)  and  Grundriss  der  Sociologie 
{1885),  who,  while  rejecting  biological  analogy,  has 
an  essentially  Darwinian  outlook.  He  emphasises 
the  ceaseless  struggle,  alike  in  peace  and  in  war,  and 
the  resulting  re-adjustments  of  social  groups,  the 
strong  becoming  barons,  captains  of  industry,  or  a 
cultured  caste;  the  weak  becoming  serfs,  wage- 
earners,  or  "  the  uneducated."  But  the  antagonism 
ends  in  some  mutual  re-adjustments;  the  weaker  are 
rarely  eliminated,  at  least  not  rapidly;  they  are 
subjected  by  the  stronger  to  new  ends ;  and  the  struc- 
ture of  society  becomes  more  complex.  "  The  great 
merit  of  Gumplowicz's  work  is  that  he  constructs  his 
sociology  out  of  strictly  sociological  materials." 

The  use  of  the  selection-formula  in  accounting  for 
social  evolution  has  been  denounced  by  many  as  il- 
legitimate, but,  so  far  as  we  can  judge,  the  objections 
mainly  refer  to  the  mistake  that  some  biological  so- 
ciologists have  made  in  supposing  that  the  form  of 
the  selective  process  in  mankind  might  be  inferred 
a  priori  from  the  form  of  the  selective  process  in 
plants  and  animals.  As  Prof.  D.  G.  Ritchie  says: 
"  Biological  conceptions  are  certainly  less  inadequate 
than  mathematical,  physical,  or  chemical  conceptions 
in  the  treatment  of  the  problems  of  human  society; 
but  an  uncritical  use  of  them  in  a  more  complex  ma- 


SUGGESTIONS  OF  SOCIOLOGY.  521 

terinl  means  a  constant  risk  of  mistaking  metaphors 
for  scientific  laws.  To  adapt  a  phrase  of  Bacon's, 
we  might  say  that  the  conception  of  evolution  which 
is  adequate  in  the  biological  sphere,  is  nevertheless 
siibtilitati  rerum  humanarum  longe  impar, — "  no 
match  for  the  subtilitj  of  human  history."  * 

(a)  In  looking  to  biology  for  hints  as  to  the  fac- 
tors in  social  evolution,  it  is  necessary  to  bear  in 
mind  the  present  security  of  biological  conclusions 
on  the  problem  of  evolution  (see  Chap.  XI),  and 
the  fact  that  the  biologist  has  himself  often  followed 
the  clew  suggested  by  social  processes.  There  is  no 
small  risk  of  a  lamentably  vicious  circle.  We  would 
suggest  that  sociologists  should  as  far  as  possible 
focus  their  attention  rather  on  the  animal  social- 
group  (the  herd,  the  flock,  the  bee-hive,  the  ant-hill, 
the  beaver-village,  the  rookery)  than  on  the  individ- 
ual organism,  for  in  the  latter  case  the  analogy  is 
more  remote,  and  therefore  more  apt  to  be  illusive. 
It  should  be  evident  that  there  is  no  strict  analogy 
between  struggle  in  non-social  species  and  the  compe- 
tition of  social  groups.  Among  individual  men  it 
is,  indeed,  easy  to  find  analogues  of  what  occurs 
among  animals,  e.g.,  in  the  struggle  with  climate 
or  with  Bacteria ;  but  in  the  distinctively  social 
struggle  it  is  a  case  of  one  organisation  against  an- 
other organisation,  and  physical  victory  over  the 
component  individuals  may  mean  victory  for  the 
organisation  (as  expressed  in  ideas)  of  the  defeated. 

Furthermore,  in  using  the  selection-formula, 
we  must  be  careful  to  bear  in  mind  that  the  selec- 
tion in  a  progressive  society  is  in  part  conscious,  de- 
liberate, and  rational.  Selection  determined  by 

*  Social  Evolution,  Internal.  Journal  Ethics,  vi.  (1896).  p. 
16G. 


522     PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

conscious  purpose  may  be  called  artificial  or  ra- 
tional, as  opposed  to  natural  selection,  but  the  dis- 
tinction is  apt  to  disguise  the  fact  that  the  general 
formula  remains  the  same.  And  if  the  philosopher 
wishes  to  show  in  the  end  that  we  can  only  under- 
stand the  whole  sweep  of  the  evolution-process  in 
the  light  of  the  self-conscious  personality  towards 
which  it  has  been  making,  that  morality  is  not  only 
an  element  in  cosmic  life  but  the  reality  of  it,  he 
should  not  dwell  on  the  supposed  contrast  between 
the  cosmic  and  the  ethical  process. 

But  it  must  be  clearly  recognised  that  the  selec- 
tive process  may  be  varied  in  its  form,  at  dif- 
ferent times  and  in  different  spheres.  It  is  always 
a  sifting,  but  the  nature  of  the  sieve  is  variable.  A 
struggle  for  subsistence  around  the  platter  may  be 
replaced  by  an  endeavour  after  well-being;  military 
competition  may  give  place  to  industrial;  a  pre- 
mium may  be  put  on  mutual  aid  just  as  markedly  as 
on  self-assertion.  But  the  cruder  forms  of  struggle 
are  often  persistent,  both  at  the  margin  of  industrial 
society  and  in  international  relations.  While  we  see 
in  the  course  of  history  a  raising  of  the  level  of  com- 
petition— from  a  war  with  weapons  to  a  battle  of 
wits,  from  individualistic  to  co-operative  endeavour, 
and  so  on — what  Huxley  chose  to  call  a  checking  of 
the  cosmic  process  by  substituting  for  it  the  ethical 
process,  we  see,  on  the  other  hand,  that  the  pressure 
of  destructive  competition  still  falls  heavily  upon  the 
laggards,  and  that  if  it  be  not  allowed  so  to  fall, 
evil  results. 

Even  those  who,  like  Novicow,  seem  to  accept 
the  old  words  "  strife  the  parent  of  all," 
recognise  that  the  universal  conflict  has  had  many 
forms.  Thus  Novicow  distinguishes  the  slow  and 


SUGGESTIONS  OF  SOCIOLOGY.  523 

irrational  conflict  (of  the  past,  in  great  part),  in- 
cluding massacres,  homicides,  brigandage,  slavery, 
persecution,  etc.,  from  the  more  rapid  and  rational 
conflict  (of  the  future)  which  is  competitive  and 
argumentative.  There  is  a  gradual  elimination  of 
certain  forms  of  conflict ;  even  in  war  all  destructive 
devices  are  no  longer  considered  fair.  The  most 
difficult  of  social  dilemmas  is,  that  if  the  cruder 
forms  of  struggle  be  too  mercifully  relaxed  there  is 
apt  to  be  an  undue  multiplication  of  the  unfit,  who, 
in  sterner  conditions,  would  have  gone  under, — 
while,  on  the  other  hand,  a  persistence  of  the  lower 
forms  of  struggle  is  apt  to  be  prejudicial  to  the  de- 
velopment of  genius  and  of  art,  and  other  flowers  of 
civilisation. 

To  sum  up :  even  those  who  agree  with  Schaffle,  for 
instance,  that  "  all  processes  of  social  development 
are  subject  to  the  law  of  natural  selection,"  or  go  the 
length  of  saying  with  him  that  "  the  law  of  the  sur- 
vival of  the  fittest  is  the  only  clear  formula  for  a 
moral  order  of  the  world,"  must  in  clearness  admit 
that  when  all  is  said  and  done  selection  is  only  the 
knife  which  prunes  the  tree;  it  directs  but  does  not 
originate  the  vital  impulse,  the  persistent  growth,  the 
new  initiative.  And,  furthermore,  while  the  logical 
form  of  the  selection  theory  remains  the  same,  a  real 
and  practical  difference  did  ensue  when  man  became 
conscious,  if  not  master,  of  his  fate,  and  began,  as 
it  were,  to  swim  in  the  current  in  which  he  found 
himself  floating. 

Isolation.  A  general  survey  of  racial  evolution 
discloses  two  directly  opposite  processes : — on  the  one 
hand,  (a)  dispersion,  expansion,  with  (it  may  be)  re- 
sulting differentiation  as  isolation  became  more 
marked;  and,  on  the  other  hand,  (b)  consolidation, 


524:     PROGRESS  OF  SCIENCE  IN  THE  CENTURY. 

amalgamation,  unification,  with  (it  may  be)  result- 
ing integration  as  the  social  relations  became  more 
subtly  interwoven. 

In  both  processes  the  factor  which  biologists 
call  "  isolation  "  may  operate ;  thus  the  expansion 
of  groups  may  involve  the  geographical  isolation  of 
some  of  their  offshoots,  &nd  the  consolidation  of 
groups  may  mean  a  restricted  range  of  cross-fertili- 
sation. 

Of  no  little  importance,  as  it  seems  to  us,  is  some 
consideration  of  in-breeding  (i.  e.,  pairing  within  a 
limited  range  of  relationship)  and  cross-breeding 
(i.  e.,  the  pairing  of  members  of  distinct  stocks). 
Thus  Dr.  A.  Reibmayr  has  argued  that  the  establish- 
ment of  a  successful  tribe  or  race  involves  periods  of 
in-breeding,  with  the  effect  of  "  fixing  "  or  engraining 
constitutional  characteristics,  and  periods  of  cross- 
breeding, with  the  effect  of  promoting  a  new  crop 
of  variations  or"  initiatives. 

While  there  is — and,  at  present,  must  be — great 
diversity  of  opinion  as  to  the  best  means  of  securing 
a  healthier  "  social  organism,"  there  is  practical  un- 
animity as  to  the  end  in  view,  which  may  be  ex- 
pressed in  the  words  with  which  Mr.  Spencer  closes 
the  third  volume  of  his  Principles  of  Sociology 
(1897): — "Long  studies  .  .  .  have  not  caused 
me  to  recede  from  the  belief  expressed  nearly  fifty 
years  ago :  '  The  ultimate  individual  will  be  one 
whose  private  requirements  coincide  with  public 
ones.  He  will  be  that  manner  of  man  who,  in 
spontaneously  fulfilling  his  own  nature,  incidentally 
performs  the  functions  of  a  social  unit,  and  yet  is 
only  enabled  so  to  fulfil  his  own  nature  by  all  others 
doing  the  like.'  " 


INDEX. 


Abstract  Sciences,  28. 

Achromatin,  360. 

Acids,  125. 

Acquired  characters  or  modifica- 
tions, 402,  412. 

Adams,  185. 

Adhemar,  265. 

Agassiz,  Alexander,  876. 

Agassiz,  Louis,  260,  351,  376 ;  on  the 
cell-doctrine,  358. 

Age  of  the  Earth,  241. 

Agricultural  chemistry,  1C4. 

Aim  of  Science,  16,  18. 

Airy,  205. 

Algol,  197,  219. 

Alkalis,  125. 

Altmann,  360. 

Amoeba  and  man,  27. 

Ampere,  90,  102,  158,  159. 

Anabolism,  320. 

Analogy,  337. 

Analysis,  biological,  288. 

Analysis,  minute,  of  organic  struc- 
ture, 352. 

Andrews,  95,  96,  115. 

Angstrom,  214,  216. 

Animal  behaviour,  461. 

Animal  intelligence,  468. 

Animals,  influence  of,  upon  the 
Earth,  268. 

Animals,  words  of,  42. 

Anthropology,  scope  of,  473 ;  ad- 
vance of,  474. 

Antiquity  of  man,  477. 

Ants,  psychological  appreciation  of, 
42. 

Arago,  153,  205. 

Archaeopteryx,  351. 

Argelander,  200. 

Argon,  discovery  of,  73. 

Argyll,  the  late  Duke  of,  414. 

Arnold,  360. 

Arrestetl  development,  343. 

Arrhenius,  119;  relation  of  electrical 
and  chemical  properties  (1884), 
130. 

Association-centres,  810. 

Asteroids,  183. 


Astronomical  systems,  ISO. 
Astronomy,  179. 
Astronomy,  physical,  203. 
Atavism,  409. 
Atomic  Theory,  80. 
Atomic  view  of  nature,  168. 
Atomic  weights,  83. 
Atoms,  166,  169. 
Anerbach,  360,  371. 
Avogadro's  Law,  88,  90 

B. 

Bacteria,  363. 

Bacteria  of  the  soil,  1ZL 

Baer.  see  Von  Baer. 

Baily,  205. 

Balance  of  organs,  295. 

Balbiani,  315. 

Baldwin,  421,  471 ;  quoted,  518. 

Balfour,  369. 

Balfour  Stewart,  179  ;  spectroscopy, 

Ball,  Sir  Robert,  210 ;  quoted,  206. 

Barbaric  man,  480. 

Barfurth,  396. 

Barry,  Martin,  357,  371. 

Bateson,  433 ;  variation  on  organ- 
isms (1894),  56. 

Beale,  358. 

Beard,  thymus  gland,  298  ;  origin  of 
leucocytes,  299. 

Beaumont,  Elie  de,  252,  257. 

Becher,  77. 

Becquerel,  157. 

Beer,  202. 

Beevor,  310. 

Bell,  Sir  Charles,  302.  445. 

Beneden,  see  Van  Beneden. 

Berghaus,  277. 

Bergmann.  274. 

Bernard,  Claude,  296,  300;  on  glyco- 
genic  function  of  the  liver,  293  ;  on 
metabolism,  319. 

Bernoulli!,  68,  93,  150,  170. 

Berry,  quoted,  182,  223:  on  the 
nebular  hypothesis,  822. 

Berthelot,  115,  124. 

Bertrand,  quoted,  258. 


526 


INDEX. 


Berzelius,  71,  80,  87,  98, 127,  128,  274  ; 
isomerism,  101 ;  radical  theory, 
102. 

Bessel,  measurement  of  the  distance 
of  a  star  (1838),  191;  quoted, 
190,  193. 

Bethe,  experimental  study  of  in- 
stincts, 458. 

Bichat,  312,  355;  Anatomic  Gene- 
rale,  301,  331  ;  on  correlation, 
295  ;  on  tissues,  286. 

Biedermann,  306. 

Binet,  behavior  of  Protozoa,  458. 

Biogenesis,  law  of,  60. 

Biogenetic  law,  375. 

Biometrika,  431. 

Bionomics  or  OEcology,  289. 

Bischof ,  271,  871. 

Bode's  Law,  183. 

Boisbaudran,  Lecoq  de,  73 ;  discovery 
of  gallium,  112. 

Bois-Reymond,  300. 

Boltzmann,  149. 

Bonney,  quoted,  253. 

Bordage,  396. 

Born,  391  ;  experimental  embryology, 
386. 

Boscovich,  theory  of  matter,  166. 

Bothlingk,  262. 

Boveri,  373,  403 ;  his  remarkable  ex- 
periment, 389. 

Bower,  344. 

Boyle,  88. 

Bradley,  191 ;  velocity  of  light,  155. 

Brain,  305. 

Braun,  Alex. ,338. 

Brewster,  Sir  David,  213. 

Brine-shrimps,  experiments  on,  419. 

Broca,  on  brain  localisation,  445. 

Brongniart,  234,  249,  344. 

Bronn,  249,  262,  351. 

Brooks,  402,  404. 

Brown,  Robert,  338,  356. 

Briicke,  300,  358;  complexity  of 
cell-substance,  316 ;  Elementar- 
organismen,  861. 

Bruckner,  264. 

Buch,  Leopold  von,  252,  257,  262. 

BUtschli,  360,  364,  371 ;  structure  of 
emulsions,  361. 

Buffon,  225. 

Bunge,  294 ;  quoted,  803,  323,  324, 
326,  452. 

Bunsen,  98,  117,  271 ;  radical  theory, 
102 ;  spectroscopy,  214. 

Burdon-Sanderson,  Sir  John,  300; 
on  Johannes  Miiller,  290 ;  on 
protoplasm,  317. 

Butler,  Samuel,  404. 

C. 

Cailletet,  95,  96. 

Caird,  John,  on  the  unity  of  science, 


on  the   progressiveness  of   sci- 
ence, 43. 

Cajori,  quoted,  141. 
Caloric,  1-12. 
Campbell,  344. 
Cannizzaro,  88. 
Carbohydrates,  318. 
Carlisle,  127. 
Carnelley,  111. 
Carnot's  work  on  heat,  144. 
Carnoy,  360. 
Carpenter,  202. 
Cataclysmal   school   of  geologists, 

225. 

Cathode  rays,  164. 
Cauchy,   heterogeneity  of  matter, 

171. 

Cavendish,  77, 127, 159, 161. 
Cell,    or   unit  area  of  living  matter, 

48 ;   defined,   363 ;   complexity  of, 

316. 

Cell-division,  362. 
Cell-lineage,  375. 
Cells,  286,  300,  313,  331 ;  discovery  of. 

354. 

Cell-structure,  360. 
Cell-substance,  structure  of,  360. 
Cell-Theory,  311,  831,  356,   369,   397; 

stated,  286,  311 ;  its  importance, 

359. 

Centres  of  force,  166. 
Centrosome,  360,  372  ;  of  the  animal 

cell,  49. 

Centrosphere  9f  the  earth,  238. 
Cerebral  localisation,  310. 
Ceres,  183. 

Challenger  expedition,  269,  279. 
Challis,  185. 
Chamberlin,  266. 
Charles'  Law,  89. 
Charpentier,  260. 
Chemical  affinity,  125. 
Chemistry,    fundamental    problem 

of,  72. 

Chromatin,  360. 
Chun,  384. 

Circulation  of  Matter,  120. 
Classification,  problem  of,  107. 
Clausius,  93,  119,  148,  149,  171. 
Clerk  Maxwell,  93,  149,  156,  157,  158, 

184  ;    definition  of  conservation 

of  energy,  139  ;   on  energy,  187  ; 

dynamical     theory    of     gases, 

171 ;  theory  of  electricity,  162. 
Clerke,  A.  M.,  quoted,  187,  188,  190, 

192,  194,  204. 
Coal,  268. 

Coal-tar  products,  98. 
Cohn,  358,  364. 
Colding,  139,  146. 
Combustion,  76. 
Comets,  186. 
Comte,  classification  of  the  sciences, 

26 ;  conception  of  sociology,  498. 


INDEX. 


527 


Conclusions   of   the    first   magnitude, 

49. 

Concrete  sciences,  28. 
Conservation    of    energy,     115,     136, 

138. 

Conservation  of  Matter,  76. 
Continental  areas,  23!X 
Continuity  of  generations,  399,  415. 
Continuity  of  the  germ-plasm,  403, 

415. 

Control  Experiments,  23. 
Control,  seat  of,  in  the  brain,  462. 
Conybeare,  249. 

Cope,  344,  351  ;  on  inheritance,  419. 
Coral-reefs,  868. 
Cordier,  271. 

Cornu,  155  ;  quoted,  152,  153,  156. 
Correlation  of  knowledge,  29. 
Correlation  of  organs,  295. 
Correlation  of  parts,  333. 
Correlation  of  the  sciences,  60. 
Couper,  104. 

Creationist  and  evolutionist,  37. 
Cretinism,  292. 
Critical  point,  96. 
Croll,  265. 
Cronstedt,  274. 
Crookes,  Sir  William,  75,  163 ;  on  pro- 

tyle,  113. 

Crust-movements,  256. 
Cuenot,  297. 

Cuvier,  225,  234,  241,  249,  333,  344, 
Cytology,  360. 
Cytoplasm,  316,  360. 


D. 

Dagnerre,  photography  (183S),  116. 

Dalton,  81,  113,  126. 

Dalton  on  diffusion  of  gases,  147. 

Darnes,  351. 

Dana,  257. 

Danuemann,  194. 

Dareste,  experimental  teratology, 
380. 

Darwin,  Charles,  30,  262,  266,  290, 
417 ;  on  earthworms,  269 ;  Origin 
of  Species  (1859),  351,  397;  pan- 
genesis,  402  ;  question  of  human 
species,  483 ;  services  to  evolu- 
tion -  doctrine,  426 ;  theory  of 
Natural  Selection,  430,  435 ;  on 
variability,  431. 

Darwin,  G.  H.,  242;  tidal  friction, 
223. 

Daubeny,  252. 

Davenport,"  Physiological  Morphology, 
314,  363. 

Davy,  Sir  Humphry,  71,  73,  95,  139 ; 
electrolysis,  127 ;  experiments 
on  heat,  1799,  144. 

De  Bary.  338, 364,  371 ;  on  cell-forma- 
tion, 363. 


De  Blainville,  319. 
Deep-Sea  deposits,  281. 
Deep-Sea  exploration,  278. 
Degeneration,  343. 
Deiters,  306. 
De  La  Beche,  262. 

Delage,    373,    405 ;    on    protoplasm, 
359 ;  experiments  on  merogony 
(1898),  390. 
Denudation,  243. 
Deshayes,  249. 
Desmarest,  238. 

Development,    365  ;    arrested,   343  ; 
factors  in,  380  ;  progressive,  349 ; 
without     sperm  -  nucleus,    388  ; 
without  ovum-nucleus,  390. 
Developmental  mechanics,  379. 
Deville,  H.  de  St  Claire,  Disassocia- 

tion,  92. 

De  Vries,  404,  433. 
Dewar.    liquefaction    of    hydrogen 

(1898),  97. 

D'Halloy,  d'Omallius,  249. 
Diabetes,  294. 
Dielectrics,  161. 
Differentiation,  339. 
Division  of  Labour,  295. 
Dobereiner,  109. 

Dohrn,  298  ;  function-change,  341. 
Donati,  186. 
Donders,  358. 
Doppler,  218. 
Double  stars,  189. 
Draper,  117. 
Driesch,  315,  389. 
Driesch,  experimental  embryology. 

384,  386,  387. 
Drift,  203. 
Drift-Theory,  262. 
Dubois,  350. 

Dubois,  his  Pithecanthropus,  476. 
Duclaux,  364. 
Dufrenoy,  252. 

Dujardiu.  332,  356,  364  ;  sarcode,  357. 
Dulong  and  Petit,   144;    Law  of,   86. 

91. 

Dumas,  88,  98,  109,  129,  357,  369 ;  isom- 
erism,    101;    radical    theory,    102; 
theory  of  substitution,  103. 
Diising,  391. 
Dutrochet,  355. 
Duval,  theory  of  sleep,  307. 

E. 

Earth,  age  of  the,  241 ;  history  oi 

the,  236. 

Earth-sculpture,  250. 
Earthquakes,  254. 
Earthworms,  importance  of,  269. 
Ecker,  358. 

Ectoderm  or  epiblast,  373. 
Ehrenberg,  269,  364. 
Ehrlich,  306. 


528 


INDEX. 


Electricity     and     chemical     affinity, 

126. 

Electricity,  theory  of,  157. 
Electro-chemical  theories,  129. 
Electro-chemistry,  118. 
Electrolysis,  127. 
Elements  and  compounds,  71. 
Elements,  search  for  the,  70. 
Elimination  of  races,  475. 
Elimination,  theory  of  natural,  437. 
Elkin,  193. 

Embryology,  experimental,  380 ;  gene- 
ralisations of,  378 ;  physiological, 

378  ;  progress  of,  365. 
Encke,  186. 

Endoderm  or  hypoblast,  373. 
Energy,  maintenance  of  solar,  207. 
Energy,  transformations  of,  116,  138; 

conservation   of,   138;   dissipation 

of,  138,  139. 
Engelmann,  117. 
Epigenesis,  defined,  366. 
Epigenesis  versus  Evolution,  368. 
Ether,  168,  169,  174,  176;  theories  of 

the,  177. 
Ethnology,  474. 
Evolution,  evidences  of,  377 ;   factors 

in,  430;  inorganic,  112. 
Evolution -idea,    history   of,    425;    in 

astronomy,  220. 
Evolution    in    the   old   embryological 

sense,  368. 

Evolution  of  Sex,  391. 
Evolution  of  the  subject-matter  of  the 

sciences,  49. 

Evolution,  theory  of,  424. 
Evolution   theory,  present  aspect  of. 

428. 

Evolutionary  geology,  225,  234. 
Ewart,    Cossar,    on   breeding,  440 ; 

Penycuik  Experiments,  394,  401, 

410. 

Experiment  and  observation,  22. 
Experimental  geology,  233. 
Explanation  and  interpretation,  322. 
Extinct  Types,  346. 
Extinction  of  races,  the  problem  of 

the,  847. 

F. 

Fairbanks,  on  the  social  organism, 
504. 

Fairies,  489. 

Falb,  on  earthquakes,  255. 

Family,  sociological  import  of  the, 
514. 

Faraday,  13,  94,  95,  96,  101, 144, 156; 
discovery  of  induced  currents, 
160 ;  discovery  of  magneto- 
electricity  (1831),  160  ;  dynami- 
cal theory  of  electricity,  161 ; 
electrolysis,  129,  161 ;  electro- 
lytes, 118, 119. 


Fatigue  of  nerve-cells,  308. 

Faye,  meteoritic  hypothesis.  223. 

Fechner,  300,  455. 

Fere,  381. 

Ferrier,  304  ;  on  cerebral  localisa- 
tion, 310. 

Fertilisation,  371. 

Fick,  808. 

Fischer,  81. 

Fiske,  on  origin  of  human  sociality, 
516. 

Fison,  quoted,  193,  196,  197,  198,  200, 
218 

Fitzgerald,  quoted,  131 ;  electro-mag- 
netic waves,  162. 

Fizeau,  218. 

Fizeau,  velocity  of  light,  155. 

Flateau,  308. 

Flechsig,  810;  on  cerebral  localisa- 
tion, 446. 

Flemming,  360. 

Fleurian  de  Bellevue,  271. 

Flinders-Petrie,  quoted,  474. 

Flourens,  304,  445. 

Fluorine,  73. 

Fol,  359,  360,  871. 

Folk-lore,  489. 

Forchhammer,  262. 

Forel,  307. 

Fossils,  844  ;  value  of,  234,  248,  250. 

Foster,  Sir  Michael,  300 ;  on  proto- 
plasm, 317 ;  on  nervous  tissue, 
802 ;  on  scientific  spirit,  7. 

Foucault,  214  ;  velocity  of  light,  154. 

Fouque,  275. 

Fourier,  235. 

Frankland,  74,  104. 

Frapolli,  262. 

Fraunhof er,  217 ;  spectroscope,  212. 

Fraunhofer's  lines,  213. 

Fresnel,  experiments  on  light,  151. 

Friedel,  275. 

Fritsch,  304,  310. 

Frommann,  860. 

Fuchs,  274. 

Function,  complexity  of,  293. 

Functional  compensation,  295. 

Function-change,  341. 

Functions  of  organs,  290. 

G. 

Qadow,  quoted,  355. 

Galle,  185. 

Gallium,  112. 

Galton,  399,  402,  412,  417,  485;  on 
filial  regression,  408 ;  genetic 
continuity,  399  ;  law  of  ancestral 
inheritance,  411  ;  transilient 
variations,  43B  ;  Natural  In- 
heritance (1889),  401. 

Galvani,  157. 

Games,  491. 

Gaskell,  on  metabolism,  819. 


INDEX. 


529 


Gastrsea-theory,  875. 
Gaudry,  quoted,  347,  348. 
Gauss,  183,  205. 
Gautier,  A.  A.,  205. 
Gay-Lussac's  Law,  86,  89,  98. 
Geddes,   Patrick,  356,  891 ;   quoted, 
334,  500;  on  history  of  biology, 

Gegenbaur,  297.  335. 
Geikie,  Sir   Archibald,  quoted.  228, 
229,    233,    250,   261;    Age  of  the 
Earth,  244 ;    ancient  volcanoes, 
253  ;  on  denudation.  243. 

Geikie,  James,  quoted,  254.  264  ; 
Great  Ice  Age,  263;  Earth  Sculp* 
ture,  251. 

Geneology,  defined,  365. 

Genetic  continuity,  370,  39J,  415. 

Geoffrey  Saint -Hilaire,  IStienne,  295. 
336. 

Geography,  275. 

Geological  record,  its  incompleteness, 
349. 

Geological  succession,  idea  of,  230. 

Geology,  225;  dynamical,  225:  ex- 
perimental, 233 ;  foundation 
stones  of,  228;  stratigraphical, 
233. 

Gerhardt,  103. 

Germanium,  73, 112. 

Germ-cells,  369,  370,  416. 

Germinal  continuity,  403. 

Germinal  selection,  434. 

Germ-layers,  373. 

Germ-plasm,  399. 

Gibbs,  Willard,  120. 

Giddings.  quoted,  499. 

Gill,  Sir  Thomas,  193. 

Glaciation,  259. 

Glands,  291  ;  ductless,  291,  298. 

Glazebrook,  quoted,  167,  170. 

Glennie,  J.  Stuart,  contributions, 
502. 

Glycogen,  293. 

Glycogenic  function  of  liver,  293 

Goebel,  344. 

Goethe,  376,  427 ;  as  morphologist, 

Goitre,  292. 

Goldschneider,  308. 

Goldstein,  163. 

Golgi,  305,  306. 

Goltz,  304,  310. 

Goodchild,  Age  of  the  Earth.  245. 

Goodsir,  312,  359,  362 ;  on  cells,  313  ; 
origin  of  cells,  357. 

Gould,  200. 

Graham,  93 ;  on  diffusion  of  gases, 
147. 

Gravitation,  181 ;  law  of,  131 ;  theory 
of  law  of,  135;  formula,  appli- 
cations of  the,  182. 

Grey  matter  of  brain,  305. 

Groos,  on  play,  459. 


Grove,     correlation     of     physical 

forces,  120. 
Gruber,  315. 
Gudden,  Von,  307. 
Guerrini.  308. 
Guettard,  228. 
Guignard,  360. 
Gulick,  427,  439. 
Gulland,  298 ;  tonsils,  299. 
Gumplowicz,   "  Ratsenkampf,"  530. 

H. 

Haacke,  414. 

Haeckel,  338,  350,  364,  402,  404,  414, 
427 ;  biogenetic  law,  375,  376 ; 
Gastraea-theory,  375 ;  CEcology, 
289. 

Haldane,  J.  S.,  324. 

Hall,  Sir  James,  232,  257,  275. 

Hall,  Marshall,  445. 

Hall,  Stanley,  471. 

Halliburton.  300. 

Hanstein,  338. 

Haugergues.  144. 

Haiiy,  94,  273.  274. 

Heape,  experiments,  394. 

Heat  as  a  mode  of  motion,  141. 

Heer,  266. 

Hegel,  183. 

Heidenhain,  300. 

Heim,  288. 

Helium,  74. 

Hellriegel  on  bacteroids,  124. 

Helmholtz,  120,  129,  196,  222,  235,  300, 
306  ;  Die  Erhaltung  der  Kraft, 
141  ;  on  sun's  heat,  208  ;  velocity 
of  nerve-messages,  455 ;  on  vor- 
tex rings,  167. 

Henderson,  191,  193. 

Henle,  356,  357. 

Henneberg,  391. 

Hennell,  synthesis  of  ethylene 
(1826-8),  100. 

Henry,  induction  currents,  161 

Hensen,  392. 

Herapath,  93,  148,  170. 

Herbst,    315 ;    experimental    embryo- 
logy, 3SS. 

Heredity,  397  ;  defined,  399. 

Hering,  404.  453 :  on  metabolism,  319. 

Herschel,  Sir  John.  F.  W.,  spect- 
roscopy,  213 ;  on  the  sun's  heat, 
206. 

Herschel,  Sir  William,  his  work,  188 ; 
on  the  sun,  204  ;  on  sun-spots, 
205. 

Hertwig,  O.,  315,  359,  360,  372,  381 ;  on 
cell-theory,  311  ;  experimental 
embryology,  886 ;  experiments 
on  frog's  eggs,  382. 

Hertwig,  O.  and  R.,  experimental 
embryology,  387,  389 ;  germ- 
layers,  874. 


530 


INDEX. 


Hertz,  electro-magnetic  theory  of 
light,  156;  theory  of  electricity, 
162. 

Hess,  115. 

Hildebrand,  74. 

Hill,  Alexander,  quoted,  304,  452, 462. 

His,  298,  414  ;  development  of  nerve- 
cells,  306 ;  Unsere  Korperform 
(1875),  378. 

Hisinger,  127.  • 

Hitzig,  304,  310. 

Hoche,  on  Neuron-Theory,  309. 

Hodge,  fatigue  of  nerve-cells,  308. 

Hofacker  and  Sadler,  392. 

Hofer,  315. 

Hoffmann,  253. 

Hofmann,  98,  103,  104. 

Hofmeister,  338,  356,  359. 

Holcombe,  155. 

Homogeny  and  homoplasty,  338. 

Homology,  337,  374. 

Hopkins,  235. 

Hoppe-Seyler,  300. 

Horsley,  304,  310. 

Huggins,  Sir  William,  186,  196,  218  ; 
quoted,  196,  200,  221,  222 ;  origin 
of  nebulae,  223 ;  spectroscopy, 
219  ;  stellar  spectroscopy,  217. 

Hugi,  260. 

Humboldt,  Alexander  von,  89,  205, 
252,  254,  277 ;  on  the  influence  of 
the  environment,  610. 

Hutchins,  216. 

Hutton,  226,  230,  241,  257;  quoted, 
231 ;  earth-sculpture,  250. 

Huxley,  335,  358,  427 ;  quoted,  140  ; 
germ-layers,  374 ;  palaeontology, 
345 ;  physical  bases  of  life,  287, 
316. 

Hyatt,»350. 

Hybridisation,  394. 

Hybrids,  410. 

Hydrosphere,  of  the  earth,  276. 

Hypothesis,  178. 


I. 


Ice- Ages,  recognition  of,  259;  causes 

of,  265. 

Idiosomes,  361. 

Immortality  of  Protozoa,  395. 
Immunity,  420. 
Impact-theory,  211. 
Imperfection  of  geological  record, 

349. 

Imponderable  matter,  142. 
In-breeding,  394,  440. 
Indestructibility  of  matter,  114. 
Inertia,  174. 
Inheritance,  397. 
Inheritance,  ancestral, 411  ;  blended, 

407  ;  dual  nature  of,  404  ;    mul- 


tiple, 405,  409  ;  particulate,  407  ; 
physical  bases  of,  889,  440  ;  so- 
cial, 415 ;  unilateral,  405. 

Inheritance,  degrees  of  complete- 
ness in  expression  of,  405. 

Inheritance  of  acquired  characters 
or  modifications,  412. 

Inheritance,  of  fecundity,  fertility, 
and  longevity,  406. 

Instinct,  456. 

Integration,  340. 

Internal  secretions,  296. 

Inter-relations  of  things,  15,  277. 

louisation  theory,  129. 

Ions,  119,  129. 

Irmisch.  338. 

Isolation^  a  factor  in  evolution,  438. 

Isomerisrn,  100. 

Isomorphism,  274. 

Isotherms,  277. 


J. 


Jaeger,  402,  404, 493. 

Jahn,  120. 

James,  Alex.,  cell-division,  362. 

Janssen,  206. 

Jenkin,  Fleeming,  439. 

Jennings,  behaviour  of  Protozoa,  459. 

Joly,  245 ;  age  of  the  earth,  238. 

Joule,  93,  139,  146,  170 ;  on  light,  154 ; 
mechanical  equivalent  of  heat, 
114, 140;  velocity  of  particles  of 
a  gas,  147. 

E. 

Kant,  400,  412. 

Katabolism.  320. 

Keane,  on  man's  inter-glacial 
origin,  479 ;  on  races  of  man- 
kind, 484 ;  on  classification  of 
human  races,  485. 

Keasbey,  on  origin  of  human  soci- 
ality, 517. 

Kekule,  104. 

Kelvin,  Lord,  210;  age  of  earth,  237, 
242 ;  dissipation  of  energy,  139 ; 
grained  structure  of  matter,172 ; 
theory  of  Vortex-Atoms,  167. 

Kestner,  101. 

Kielmeyer,  376. 

Killian,  tonsils,  299. 

Kinetic  theory  of  gases,  68,  93,  147, 
170. 

Kirchhoff,  217. 

Kirchhoff's  law,  211,  315. 

Klaproth,  94,  98. 

Klebs,  experiments,  394. 

Kleinenberg,  341. 

Knee-jerk,  an  example  of  pure  reflex, 
463. 


INDEX. 


531 


Knott.  quoted,  160. 

Koch,  364. 

Kolbe,  104. 

Kolliker,  296,  905,  306,  331,  357,  359, 
369. 

Kopp,  114 

Kossel.  300,  815. 

Kowalevsky,  297. 

Kronig,  93, 150. 

Krukenberg,  comparative  physiol- 
ogy; 297. 

Kuhne,  300,  358. 


Ladenburg.  quoted,  216. 

Lamarck.  344. 

Lament.  205. 

Lane's  theorem.  209. 

Langley,  206. 

Language,  evolution  of,  486. 

Lankester.  E.  Ray,  338,  844,  414 :  on 
instinctive  and  educable  brains, 
43. 

Laplace,  nebular  hypothesis,  220, 
222. 

Lapworth,  249. 

Larmor,  theory  of  atoms.  175. 

Latent  characters,  407,  419. 

Laurent,  92,  103. 

Laurie.  111. 

Lavoisier,  71,  77,  78,  79,  98,  114. 

Laws  of  nature,  meaning,  of,  17,  52. 

Le  Bel,  105. 

Le  Chatelier,  207. 

Le  Conte,  258. 

Legallois,  296. 

Lenard,  his  rays,  168. 

LenhosseTr,  306. 

Lenssen,  109. 

Le  Play,  his  contribution  to  socio- 
logy, 500. 

Lesage.  135. 

Leasona's  law  (1868),  896. 

Leuckart,  cell-division,  362. 

Leuckart-Spencer  principle,  863. 

Leucocytes,  298. 

Levecrier.158. 

Leydig,  358. 

Leydig,  comparative  histology,  831 . 

Liebig,  86.  88,  98, 100, 800 ;  circulation 
of  matter,  124;  on  the  radical 
cyanogen,  102. 

Life,  its  influence  upon  the  earth, 
266. 

Life-Lore.  283. 

Light,  Corpuscular  Theory,  150; 
Undulatory  Theory,  150;  Elec- 
tro-magnetic Theory,  156 ;  Velo- 
city of,  155;  Invisible,  157;  an 
electrical  phenomenon,  162. 


Light,  destructive  action  of,  on 
microbes,  117. 

Light,  influence  of,  on  green  plants, 
bacteria,  retina,  etc.,  117. 

Lilienfeld,  815. 

Lister,  364. 

Lithosphere  of  the  earth,  888. 

Liver,  functions  of,  293. 

Living  matter.  121  ;  analysis  of,  861. 

Localisation  of  cerebral  functions, 
310. 

Lockyer,  Sir  Norman,  74,  216 ; 
inorganic  evolution,  113  ;  me- 
teoritic  hypothesis,  223. 

Lodge,  quoted,  186,  137;  electro- 
magnetic waves,  162 ;  on  the 
ether,  169 ;  on  theories  of  matter, 
168. 

Loeb,  297,  396,  405  ;  on  animal  intelli- 
gence, 468 ;  artificial  partheno- 
genesis, 373,  888 ;  on  cerebral 
localisation,  446 :  on  Muller's  law, 
453 ;  on  reflex  action,  461. 

Loew,  315. 

Lohrruann,  202. 

Lotze,  378,  455. 

Lowit,  315. 

Lubbock.  Sir  John  (Lord  Avebory;, 
Ml 

Lucas,  heredity,  397. 

Ludwig,  300. 

Lugaro,  308. 

Lyell,  249,  262,  265 ;  uniformitarian- 


Mach,  451,  453 ;  quoted,  134. 

McKendrick,  356. 

MacKinder,  H.  J.,  on  geography,  277. 

Madler,  208. 

Magendie,  445. 

Mallet,  R.  and  J.  W.,  on  earth- 
quakes, 255 ;  volcanoes,  858. 

Malthus,  519. 

Man,  evolution  of,  492 :  place  in 
nature,  475  ;  antiquity  of,  477, 
478 ;  palaeolithic,  480  ;  neolithic, 
480. 

Man  and  animals  contrasted,  4S,  465. 

Mann,  308. 

Marchi,  305. 

Marey,  300. 

Marconi,  163. 

Marinesco,  308. 

Mariotte,  88. 

Marr,  quoted,  227. 

Mars,  maps  of,  203  ;  supposed  canals 
of,  203 

Marsh,  on  evolutionary  palaeonto- 
logy, 352. 

Marshall.  A.  Milnes,  376. 

Martin,  Rudolf,  quoted,  477. 


532 


INDEX. 


Matter,  Theories  of,  165 ;  perfectly 
hard  atoms,  166;  centres  of 
forces,  16(5 ;  heterogeneous 
structure,  82,  166,  167  ;  vortex 
atoms,  167 ;  aggregate  of  elec- 
tric charges  of  opposite  sign,  168. 

Maupas,  891  ;  his  experiments,  394. 

Maurer,  298. 

Maxwell,  see  Clerk  Maxwell. 

Mayer,  148  ;  Sun's  heat,  208. 

Mayow,  77. 

Measurement,  the  beginning  of 
science,  898,  430. 

Mechanical  theory  of  heat,  140. 

Mechanism  and  vitalism,  328. 

Meckel,  336,  376. 

Meinecke,  88, 108, 113. 

Meldola,  106. 

Memory,  469  ;  organic,  404. 

Mendelejeff,  73,  88,  95. 

Mendelejeff,  periodic  law,  106,  109  ; 
prophecies,  111. 

Mering,  on  pancreas,  294,  296. 

Merogony,  390. 

Merz,  quoted,  134,  148. 

Metabolism,  319. 

Metal  ages,  481. 

Metaplasm,  316. 

Metchnikoff,  297. 

Meteoric  theory,  184,  208. 

Meteorites,  237. 

Meteoritic  hypothesis,  222. 

Meteors,  187. 

Meyen,  355. 

Meyer,  E.  von,  quoted,  214,  275. 

Meyer,  Lothar,  88,  111 ;  periodic  law, 
109. 

Meyer,  O.  E.,  150. 

Michel,  396. 

Michel-Levy,  275. 

Michelson,  155. 

Microscope,  its  influence,  853. 

Microscopic  analysis,  270. 

Miescher,  315. 

Milky  way,  199. 

Mill,  H.  R.,  on  geography,  276. 

Miller,  spectroscopy,  214 ;  stellar 
spectroscopy,  217. 

Milne,  seismology,  255. 

Milne -Ed  wards,  Henri,  division  of 
labour,  295. 

Mind  and  body,  correlation  of,  444. 

Mind,  evolution  of,  470. 

Minkowski,  on  pancreas,  294,  296. 

Mirbel,  355. 

Missing  links,  349. 

Mitscherlich,  94,  274. 

Modifications  or  acquired  char- 
acters, defined,  412,  434 ;  indirect 
importance  of,  420. 

Mohl,  see  Von  Mohl. 

Moissan,  78. 

Monakow,  Von,  307. 

Montgomery,  quoted,  606. 


Montlosier,  253. 

Moon,  study  of  the,  202;  origin  of 
the,  236. 

Morgan,  C.  Lloyd,  418,  421. 

Morgan,  T.  H.,  experiments  on  eggs. 
383,  388,  389,  396. 

Morphology,  329 ;  history,  332 ; 
methods,  332 ;  foundations  of. 
333 

Mortillet,  Gabriel  de,  263. 

Mountain-making,  257. 

Miiller,  E.,  896. 

Miiller,  Fritz,  376. 

Miiller,  Johannes,  29,  290,  326,  837, 
856,  445;  foundation  of  com- 
parative physiology,  297 ;  influ- 
ence on  physiology,  285;  motor 
and  sensory  nerves,  303 :  specific 
energy  of  the  senses,  303,  451. 

Munk,  304,  310. 

Munro,  Robert,  quoted,  478 ;  on 
man's  erect  attitude,  493. 

Murchison,  Sir  Roderick,  249,  262. 

Murray,  Sir  John,  269;  quoted,  235, 
239 ;  oceanography,  278. 

Myxoedema,  291. 

N. 

Nftgeli,  338,  356,  358,  359,  427. 
Nansen,  262  ;  on  nerves,  308. 
Nasmyth,  202. 
Natural  History,  287 ;  old  and  new, 

288. 

Natural  Law,  meaning  of,  52. 
Natural  Selection,  435  ;  discriminate 

and  indiscriminate,  438. 
Nebulas,  189,  195. 
Nebular  hypothesis,  220. 
Necrology,  danger  of,  288. 
Neison,  202. 
Neolithic,  480. 
Neptune,  discovery  of,  184. 
Neptunists,  232. 

Nerve-cells,  their  complexity,  307. 
Nerves,  sensory  and  motor,  301,  802, 

803. 

Nervous  arc,  463. 
Nervous  mechanism,  460. 
Nervous  tissue,  301. 
Neumann,  115. 
Neuroblasts,  305. 
Neuron-Theory,  306. 
Newcomb,  155. 
Newlands,  Law  of  Octaves  (1863-4), 

109. 
Newtonian  foundation   of   physics, 

133 

Nicholson,  127. 
Nicol,  William,  271. 
Nilson,  73. 

Nilson,  discovery  of  scandium,  112. 
Nissl,  306, 308. 


INDEX. 


533 


Nitrogen,  circulation  of,  123. 
Nobili,  159. 

Nuclei,  theory  of  chemical,  103. 
Nucleus  of  the  cell,  356,  360. 
Nussbaum,  391,  402. 

O. 

Oceanography,  278. 

Odling,  serial  relations  of  elements, 

109. 

(Ecology,  289. 

Oersted,  electro-magnetism,  158. 
Ohm,  law  of  electrical  resistance, 

159.  160. 

Oken,  335,  355,  376. 
Olbers,  183, 186. 
Olszewski,  95,  96. 
Ontogeny  and  Phylogeny,  376. 
Ontogeny,  defined,  365. 
Organic    chemistry,    development   of, 

98. 
Organism,  different  aspects,  283,  321 ; 

unity  of,  288,  322  ;  unsolved  secret 

of  the,  320. 
Organs,   balance   of,  295 ;   correlation 

of,    295 ;    enigmatical,    291,    297 ; 

functions    of,     290 ;    rudimentary 

or  vestigial,  342 ;  substitution  of, 

341. 

Osborn,  351,  421. 
Ostwald,  79,   111,  114;   measure  of 

chemical  affinity  (1889),  130. 
Ovum,  370. 
Owen,  Sir  Richard,  337,  351,  402,  475. 

P. 


Palaeolithic,  480. 

Palaeontological  series,  350, 

Palaeontology,  344 ;  evolutionary, 
351. 

Palseospondylus,  351. 

Pallas,  183,  229. 

Palmieri,  74. 

Pancreas,  294.  296. 

Pander,  368,  378. 

Pangenesis,  402,  417. 

Parallax,  191. 

Parthenogenesis,  artificial,  373. 

Parry,  262. 

Pasteur,  23,  29,  33,  67,  105,  266,  270, 
364. 

Patten,  sociological  import  of  food, 
513. 

Pearson,  K.,  399,  406;  quoted,  134, 
137 ;  on  scientific  method,  24, 
327 ;  filial  regression,  408  ;  mul- 
tiple inheritance,  409 ;  statistical 
study  of  inheritance,  408. 

Penck,  262,  264,  278. 

Periodic  Law,  106,  110. 

Perkin,  aniline  dyes,  99. 


Perrey,  Alexis,  earthquakes,  254, 
255. 

Perthes,  278. 

Peschel,  278. 

Petrography,  270. 

Pettenkofer,  109,  300. 

Pfliiger,  300,  391. 

Phagocytosis,  299. 

Pheuacodus.  350. 

Philips,  W.,  249. 

Phillips,  Jokn,  233. 

Phlogiston,  76. 

Photochemistry,  116, 

Photography,  stellar,  201. 

Photometry,  202. 

Phylogeny,  defined,  365. 

Physical  basis  of  life,  316. 

Physics,  definition  of,  131 ;  method 
of,  131 ;  aim  of,  132. 

Physiological  analysis,  237. 

Physiology,  history  of,  283 ;  com- 
parative, 296;  experimental,  299; 
of  tissues,  300;  of  cells,  313;  of 
protoplasm,  315. 

Piazzi,  discovered  Ceres,  183. 

Pickering,  197,  200,  219. 

Pictet,  95,  96. 

Pithecanthropus  erectus,  350,  476. 

Planck,  119. 

Planets,  discovery  of  minor,  183. 

Plants,  influence  of,  on  the  earth, 
267. 

Play  on  animals,  459. 

Playfair,  226,  232,  241. 

Plutonists,  232. 

Pogson,  202. 

Poisson,  235. 

Pouillet,  159;  on  the  sun's  heat,  206. 

Poulett-Scrope,  257 ;  on  volcanoes, 
252. 

Poulton,  on  age  of  the  Earth,  246. 

Poynting,  quoted,  131,  132,  166,  181 ; 
on  nature  of  matter,  175. 

Practical  Mood,  3. 

Preformation-theory.  366. 

Prenant,  298. 

Prepotency,  405,  440. 

Prevost,253,  357,  369. 

Prichard,  400,  412,  484. 

Priestley,  77. 

Pringsheim,  364. 

Proctor,  200. 

Progress  in  the  organic  world,  348. 

Progress  of  Science,  its  necessity,  46. 

Prophecy  in  science,  111. 

Proteids,  318. 

Protophytes,  364,  395. 

Protoplasm,  287,  315,  331 ;  different 
uses  of  the  term,  316;  physio- 
logical conceptions  of,  317. 

Protozoa,  364,  395 ;  behaviour  of,  458. 

Protyle  or  prothyle,  108,  113. 

Proust,  80,  98. 

Prout  88,  108,  113. 


534 


INDEX. 


Psychology,  definition,  442 ;  changes 
in  its  aims  and  methods,  44;! ; 
experimental,  451 ;  comparative, 
455. 

Pure  science,  66. 

Purkinje,  356 ;  protoplasm,  358. 

Putrefaction  due  to  micro-organ- 
isms, 23. 


Quetelet,  485. 


Q. 


B. 


Rabl,  378. 

Races  of  mankind,  483. 

Radical  theory,  101. 

Ram6n  y  Cajal,  305,  306. 

Ramsay,  A.  C.,  glaciation,  262. 

Ramsay,  W.,  and  Argon,  74. 

Ranvier,  307. 

Raspail,  355. 

Ratke,  335. 

Rauber,  381 ;  Formbildung,  379. 

Rayleigh,  Lord,  and  Argon,  73. 

Recapitulation,  306. 

Recapitulation-doctrine,  50,  375. 

Reflex  action,  461. 

Regeneration-experiments,  395. 

Regnault,  115. 

Regression,  408. 

Reibmayr,  on  in-breeding  and  cross- 
breeding, 584. 

Reichenbach,  on  Goethe,  336. 

Reichert,  335,  357. 

Remak,  306,  357,  359. 

Renard,  269,  281. 

Rennie,  266. 

Reproductive  organs,  296. 

Retrogression,  343. 

Retzius,  306. 

Reversion,  394  ;  defined,  409. 

Rhys,  on  fairies,  490. 

Richter.  109. 

Richter  s  Stoicheiometry,  80. 

Richthofen,  von,  278. 

Rink,  262. 

Ritter,  277. 

Ritzema-Bos,  894. 

Roberts,  221. 

Rocks,  the  record  of  the,  248,  349. 

Romanes,  427,  439,  457. 

Rontgen  rays,  157. 

Rontgen,  X-rays,  163. 

Rorig,  296. 

Roscoe,    Sir     Henry,    82,    117,    129; 
quoted,  141,  147. 

Rosenbusch,  273. 

Ross,  262. 

Rossi,  de,  254. 

Roux,  315,  364 ;  developmental  me- 
chanics, 379 ;  experiments  on 
frog's  eggs,  383. 


Rowland,  216. 
Rudimentary  organs,  348. 
Rumford,  139. 

Rumford's  experiments  on  heat, 
143. 

8. 

Sabine,  Sir  Edward,  205. 

Sachs,  338 ;  on  cell-formation,  363. 

Saltness  of  the  sea.  245. 

Salts,  125. 

Sarasin,  275, 

Saturn's  rings,  184. 

Saussure,  229,  260. 

Savage  man,  480. 

Sayce,  on  language,  489. 

Scandium,  73,  112. 

Schafer,  310 ;  on  thyroid  gland,  292. 

Schtiffle,  on  the  social  organism,  504. 

Scheele,  71,  77. 

Scherer,  275. 

Schimper,  260. 

Schleiden,  312,  331,  338,  356,  359; 
quoted,  313. 

Schmankewitsch,  on  brine-shrimps, 
419. 

Schmidt,  202. 

Schonbein,  124. 

SchrSter,  202. 

Schultze,  Max,  332,  359 ;  defined  the 
cell,  358. 

Schultze,  O.,  298. 

Schwabe,  on  sun-spots,  205. 

Schwann,  812,  331,  356,  359  ;  quoted, 
313. 

Schwann  and  Schleiden,  Cell-Theory 
(1838-9),  286. 

Schwartz,  315. 

Schweigger,  159. 

Science,  aim  of,  16  ;  correlation  of, 
29 ;  criticism  of,  31  ;  definition 
of,  1,  2 ;  factors  on  progress  of, 
41,  55  ;  justification  of,  62 ; 
method  of,  2, 19  ;  unity  of,  25. 

Science  and  Utility,  65. 

Sciences,  classification  of,  25. 

Scientific  Mood,  defined,  6 ;  its 
characteristics,  7. 

Scoresby,  262. 

Secchi,  202. 

Secretions,  internal,  296. 

Sedgwick,  A.,  249. 

Seeliger,  389. 

Seismometers,  256. 

Seguin  and  Mayer,  146. 

Semper,  influence  of  the  environ- 
ment, 508. 

Sex,  determination  of,  391. 

Sexual  selection,  437. 

Shaler,  258. 

Shooting  stars,  187. 

Siebold,  Von,  parasites,  28. 

Simms,  spectroscope,  218. 


INDEX. 


535 


Smith,  Wmisra,  «7,  241,  249,  844;  his 
epoch-making  Geological  Map  of 
England,  233. 

Social  evolution,  factors  in,  517. 

Social  organism,  theory  of,  503. 

Society,  as  a  vast  fraternity,  408. 

Sociology,  scope  of,  496  ;  outline  of 
its  development,  498 ;  lines  of 
enquiry,  501 ;  factors  in  sociolo- 
gical interpretation,  508. 

Solar  Energy,  207. 

Sollas,  age  of  the  earth,  244 ;  history 
of  the  earth,  238;  quoted,  286. 
228,  239,  240,  246. 

Sorby,  272. 

Sorley,  on  Weber's  law,  454. 

Species,  the  human,  481. 

Specific  average,  408. 

Spectroscope,  uses  inastronomy,211. 

Spectroscopic  study  of  the  stars. 
217. 

Spectroscopy,  establishment  of  by 
Kirchhoff  and  Bunsen,  31. 

Spectrum  analysis,  67,  211. 

Spectrum  analysis,  history,  214. 

Spencer,  Herbert,  338,  376,  414,  427, 
438,  455  ;  cell-division,862  ;  classi- 
fication of  the  sciences,  28 ;  here- 
dity, 402 ;  his  conception  of  soci- 
ology, 499 ;  on  the  social  organ- 
ism, 503. 

Spermatozoon,  370. 

Spleen,  291. 

Spongioblasts,  305. 

Stahl,  77, 141. 

Starkweather,  392. 

Stars,  188 ;  distance  of,  191 ;  life  of, 
195 ;  weighing  the,  194  ;  variable, 
197;  fixed,  198;  dead,  197. 

Stas,  88, 108. 

Stellar  spectra,  217. 

Stieda,  298. 

Stohr,  tonsils,  299. 

Stokes,  Sir  Gabriel,  214. 

Stoney,  Johnstone,  75. 

Stout,  on  mind  and  brain,  447 ;  defini- 
tion of  psychology,  470. 

Strasburger,  359,  360,  371. 

Stratigraphical  geology,  233, 248. 

Struggle  for  existence,  436. 

Struve,  father  and  son,  190, 191. 

Struve,  F.  G.  W.,  194,  205. 

Stuart  Glennie,  520. 

Substitution  of  organs,  342. 

Substitution-theory,  103. 

Succession,  idea  of  geological,  233. 

Suess,  work  of,  258  ;  earthquakes  255  • 
Antlitz  der  Erde,  257,  258. 

Sun,  its  heat,  206. 

Sun-spots,  204. 

Sutherland,  Evolution  of  the  Moral 
Instincts,  493. 

Button,  392. 

Swan,  spectroscopy,  213,  214. 


T. 

Tait,  235  ;  quoted,  135,  139,  145,  808  ; 
age  of  the  earth,  242;  comets, 
186 ;  grained  structure  of  mat- 
ter, 172  ;  solar  energy,  207  ; 
theory  of  matter,  167. 

Talbot,  spectroscopy,  213. 

Teall,  quoted,  251. 

Tektosphere  of  the  earth,  238. 

Telluric  lines,  213. 

Thenno-chemistry,  114. 

Thilorier,  96. 

Thomsen,  Julius,  115. 

Thomson,  Elihu,  quoted,  162. 

Thomson,  J.  J.,  164  ;  quoted,  157. 

Thomson  (Lord  Kelvin),  148,  203,  235, 
241 ;  galvanometer,  159. 

Thomson,  Thomas,  113. 

Thomson  and  Tait,  134,  139. 

Thury,  891,  392. 

Thymus  gland,  297. 


Thyroid  gland,  291. 
Tidal  friction,  223. 


Tissues,  330  ;  defined,  801 ;  phvsio- 
logy  of,  300. 

Titchener,  on  modern  psychology, 
443. 

Tonsils,  299. 

Torell,  262. 

Transformations  of  energy,  138. 

Transmissibility  of  acquired  char- 
acters, 412. 

Traquair,  quoted,  346  ;  on  Palaeos- 
pondylus,  351 ;  on  palaeontology, 
345,351. 

Trowbridge.  216. 

Turner,  Sir  William,  356, 414 ;  quoted, 
311,  314,  477. 

Turpin,  355. 

Tylor,  480. 

Tyndall,  208. 

Types,  theory  of  chemical,  103, 

U. 

Unger,  356,  858. 

Uniformitarian   school   of  geologists 

225. 

Uniformity  illustrated,  251. 
Uniformity  of  Nature,  51,  53. 
Unity  of  life,  34 
Unity  of  nature,  39. 
Unity  of  science,  38. 
Unity  of  the  organism,  28S,  296. 


V. 
Valency,  theory  of  chemical,  104, 

Valentin,  856. 
Van  Beneden,  359,  360,  871. 
Van  der  Waals,  150. 
Van  Gehuchten,  306. 


2i 


536 


INDEX. 


Van't  Hoff,  chemistry  in  space,  94, 
105. 

Variability  in  nature,  431. 

Variation,  continuous,  482;  discon- 
tinuous, 432  ;  definite,  433,  438  ; 
fortuitous,  433  ;  indefinite,  438. 

Variations,  56,  246,  342,  406,  413. 

Variations,  nature  of  organic,  430 ; 
origin  of,  433. 

Vauquelin,  98. 

V^jdovsky,  387. 

Venetz,  260. 

Vernon,  894. 

Vertebral  theory  of  skull,  335. 

Verworn,  297,  314,  315  ;  behaviour  of 
Protozoa,  458 ;  on  cellular  phy- 
siology. 313 ;  Neuron  theory, 
306,  309;  on  Johannes  Mttller, 
286 ;  quoted,  315,  452  ;  proto- 
plasm, 318. 

Vestigial  organs,  342. 

Virchow,  812,  359,  362 ;  quoted,  313  ; 
genetic  continuity,  370,  397 ; 
origin  of  cells,  357. 

Vital  force,  286,  321,  322,  326. 

Vitalism,  321. 

Vogel,  197, 218. 

Vogelsang,  273. 

Vogler,  219. 

Voit,  300. 

Volcanoes,  251. 

Volkmann,  300. 

Volta,  158. 

Volvox,  300. 

Von  Baer,  369,  876 ;  quoted,  355. 

Von  Mohl,  332,  338,  356,  358. 

Vulpian,  452 ;  on  nerves,  304. 

W. 

Walcott,  350. 

Waldeyer,  Neuron  theory,  306. 
Walker,  S.  C.,  on  Neptune,  185. 
Wallace,  Alfred  Russel,  427,  435, 

456, 492 ;  on  sexual  selection,  437. 
Waller,  807. 
Wallich,  278. 
Ward,  on  correlation  of  mind  and 

brain,  446. 

Wasmann,  on  animal  behaviour,  468. 
Waterston,  93, 148,  170,  208. 
Weber,  800,  458. 
Weber's  law,  454. 
Weismann,  400,  402,  403,  414,  415,  427. 

438,  439 ;  genetic  continuity,  399 ; 

Germ-Plasm  (1893),  401 ;  germi- 


nal selection,  434 ;  non-transmis- 
sion of  acquired  characters,  412  ; 
origin  of  variations,  416  ;  regen- 
eration, 396. 

Weldon,  245. 

Werner,  251,  396. 

Wheatstone,  160. 

Wheeler,  396. 

White,  Gilbert,  on  earthworms,  269. 

Whitman,  on  protoplasm,  362. 

Willfarth,  on  bacteroids,  124. 

Williamson,  119 ;  on  etheriflcation, 
103. 

Willis,  304. 

Wilson,  E.  B.,  quoted,  355,  859,  370, 
889,  398  ;  cell-theory,  311 ;  experi- 
mental embryology,  884 ;  proto- 
plasm, 817,  858 ;  The  Cell  in  De- 
velopment and  Inheritance,  401. 

Wilson,  J.  T.,  quoted,  823. 

Windle,  381. 

Winkler,  53,  73  ;  discovery  of  germa- 
nium, 112 ;  supposed  uniformity 
of  nature,  54. 

Wislicenus,  105. 

Wohler,  98,  800 ;  radicals,  102 ;  syn- 
thesis of  urea,  99. 

Wolf,  205. 

Wolff,  396. 

Wollaston,  105.  212. 

Words  of  animals,  42. 

Wroblewski,  95,  96. 

Wundt,  455;  physiological  psychol- 
ogy, 451. 

Wurtz,  103,  104,  274. 


X-rays,  163. 


Y. 


Young,  James,  155. 

Young,  Thomas,  144,  206 ;  on  Light, 

151, 152. 
Yung,  391. 

Z. 

Zach,  von,  183. 
Zacharias,  815. 
Zinin,  99. 
Zirkel,  272. 

Zittel,  K.  A.  von,  quoted,  258,  851. 
Zittel's    history     of    geology  and 
palaeontology,  225. 


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