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THE
ADVANCING FRONT
OF SCIENCE
THE
ADVANCING FRONT
OF SCIENCE
by GEORGE W. GRAY
Here stand I as though on a frontier
that divides two peoples, looking both
to the past and to the future.
Petrarch, Book of Memorable Things
New York WHITTLESEY HOUSE London
MCGRAW-HILL BOOK COMPANY, INC.
Copyright, 1937, by GEORGE W. GRAY
All rights reserved. This book, or parts thereof, may not be
reproduced in any form without permission of the author.
First Printing, September, 1937
Second Fritting, October, 1937
PUBLISHED BY WHITTLESEY HOUSE
A division of the McGraw-Hill Book Company, Inc.
PrinUd in the UnM StaUs of Amtrica by Th* MapU Prut Co., York, Pa.
To
JOHN C. MERRIAM
PRESIDENT OF THE CARNEGIE INSTITUTION OF WASHINGTON
A leader in the scientific advance
EFACE
IN a preceding book I undertook to outline the new world
picture of modern physics, and to present briefly the
sequence of discoveries and of guiding theories by which
the new concepts were arrived at. The present book is an
attempt to report news rather than to summarize history.
It is an account of certain current advances in representa-
tive fields of science, of things lately turned up in the
skies, in the atoms and molecules, in the living matter of
cells and tissues findings and intimations which are pro-
viding the basis for further advances, for reinterpretations,
for the new world view of tomorrow. Obviously the experi-
ments and discoveries herein described are only samplings
of a vast teamwork in which men of many nations are
cooperatively engaged. These chapters are largely con-
cerned with activities in the United States, and particularly
with the work of investigators whom I have had oppor-
tunity to consult. It would take many books to cover the
field in any one of the specialties touched on. But perhaps
the samplings can do for the general reader what complete
technical treatises do not: convey something of the spirit,
the purpose, the ingenious methods, and the accomplish-
ments which make the research laboratory the most
romantic spot on the Earth at the present time and
perhaps the most significant. For it is here that the future
comes.
Pascal, in one of his pensees, has chided those authors
who talk of "my book," advising that they would do
[vii]
PREFACE
better to say "our book, our commentary, our history/ 5
The present volume could not have been written but for
the generous response, cooperation, and encouragement
which the author received from men of the laboratories, and
in a quite literal sense this is "our book." I was aided at
every turn, first by the open-door policy which admitted
me to the research workrooms, then by the interest and
patience of the researchers who demonstrated and explained
their experiments and results, and finally by those who
read and checked the chapters in manuscript. In acknowl-
edging a great debt to these collaborators, I do not wish
to imply that they are responsible for any errors or other
maladjustments that may have survived the several revi-
sions, or that they endorse the book. The final product is
my responsibility, and mine alone. I should also add that
the choice of laboratories visited and of work cited is
entirely mine.
Each chapter represents contacts with and contributions
from several workers. Those to whom I am particularly
indebted are the following:
Chapter I: John A. Fleming, L. R. Hafstad, and M. A.
Tuve of the Carnegie Institution's Department of Research
in Terrestrial Magnetism; George B. Pegram of Columbia
University; H. P. Robertson of Princeton University;
Willis R. Whitney of the General Electric Research
Laboratory.
Chapter II: L. V. Berkner and H. W. Wells of the
Carnegie Institution's Department of Research in Ter-
restrial Magnetism; E. O. Hulburt of the Naval Research
Laboratory; Karl G. Jansky of the Bell Telephone Labora-
tories; Harlan T. Stetson of the Massachusetts Institute
of Technology.
Chapter III: Bart J. Bok of Harvard College Observa-
tory; Arthur H. Compton of the University of Chicago;
Heber D. Curtis of the University of Michigan Observa-
[ viii ]
PREFACE
tory; Edwin P. Hubble and Frederick H. Seares of Mount
Wilson Observatory of the Carnegie Institution; J. A.
Pearce of the Dominion Astrophysical Observatory of
Canada.
Chapter IV: Drs. Hubble and Seares of Mount Wilson
Observatory; Dr. Robertson of Princeton.
Chapter V: Walter Clark and C. E. K. Mees of Kodak
Research Laboratories; Dr. Seares of Mount Wilson
Observatory.
Chapter VI: Dr. Compton of the University of Chicago;
Drs. Fleming, S. A. Korff and Tuve of the Carnegie
Institution; Robert A. Millikan of the California Institute
of Technology.
Chapter VII: Drs. Fleming, Hafstad, N. P. Heyden-
burg, and Tuve of the Carnegie Institution.
Chapter VIII: E. E. Free of the Free Laboratories;
Harvey Fletcher of the Bell Telephone Laboratories; Vern
O. Knudsen of the University of California at Los Angeles;
George W. Pierce of Harvard University.
Chapter IX: E. C. Crocker, E. S. Gilfillan, the late
Arthur D. Little, M. Omansky, and E. P. Stevenson of
Arthur D. Little, Inc.; Henry Eyring of Princeton Uni-
versity; S. D. Kirkpatrick of Chemical and Metallurgical
Engineering.
Chapter X : Irving Langmuir of General Electric Research
Laboratory; Arthur C. Langmuir, Dean Langmuir.
Chapter XI: William Arnold of Stanford University;
Frederick S. Brackett of the National Institute of Health;
Dean Burk of the United States Department of Agricul-
ture; James Bryant Conant of Harvard University; Robert
Emerson of the California Institute of Technology; Harold
Mestre of Bard College; Otto Rahn of Cornell University;
H. A. Spoehr of the Carnegie Institution's Division of Plant
Biology; Ralph W. G. Wyckoff of the Rockefeller Institute
for Medical Research.
[ix]
PREFACE
Chapter XII: Albert F. Blakeslee, R. W. Bates, Charles
B. Davenport, M. Demerec, and Oscar Riddle of the
Carnegie Institution's Department of Genetics; Dr. Burk
of the United States Department of Agriculture; Wendell
M. Stanley and Dr. Wyckoff of the Rockefeller Institute;
Theophilus S. Painter of the University of Texas.
Chapter XIII: Alexis Carrel and W. J. V. Osterhout of
the Rockefeller Institute; Selig Hecht of Columbia Uni-
versity; Ralph S. Lillie and N. Rashevsky of the University
of Chicago; D. T. MacDougal and Dr. Spoehr of the
Carnegie Institution.
Chapter XIV: Clark L. Hull and D. C. Ellson of Yale
University; Dr. Rashevsky of the University of Chicago;
Stevenson Smith of the University of Washington.
Chapter XV: Francis G. Benedict, Thone M. Carpenter,
and R. C. Lee of the Carnegie Institution's Nutrition
Laboratory; Hallowell Davis and William T. Salter of
Harvard Medical School; Alfred L. Loomis of the Loomis
Laboratory; Dr. Riddle of the Carnegie Institution's
Department of Genetics.
Chapter XVI: Arthur M. Banta of Brown University;
Lester Ingle of the University of Wisconsin; William Marias
Malisoff of the Montefiore Hospital of New York; C. M.
McCay and L. A. Maynard of Cornell University; Ray-
mond Pearl of Johns Hopkins University; Henry C. Sherman
of Columbia University.
In addition to his laboratory contributions to Chapters
XI and XII, Dean Burk, together with his wife Mildred
Burk, read many of the chapters in manuscript; and I am
under deep obligation to these friends for their check-up
and many helpful suggestions which guided the final
revision. Frank F. Bunker, editor of the Carnegie Institu-
tion of Washington, was a valuable aid in facilitating
contacts with workers in the various Carnegie laboratories.
[x]
PREFACE
Certain chapters or parts of chapters have appeared as
articles in magazines: the Atlantic Monthly, Esquire,
Harper's Magazine, the New York Times Magazine, and
This Week. Thanks are expressed to the editors of these
periodicals for releasing the material for its extension and
development in book form.
G. W. G.
CONTENTS
Preface vii
Prologue The Approach to Science 3
I. New Horizons 8
II. Frontiers of Earth 22
III. The Shining Stars 49
IV. Skies Are Reddening 66
V. The Encircling Darkness 81
VI. The Cosmic Bombardment 99
VII. Deeper into the Atom 113
VIII. The New Science of Sound 133
IX. Chemistry Advancing 154
X. A Chemist on Vacation 168
XI. Life and the Quantum 194
XII. Where Life Begins 215
XIII. Machines Which Imitate Life 241
XIV. Thinking Machines 264
XV. Chemistry and Thinking 285
XVI. Can We Live Longer? 310
Epilogue The Promise of Science 333
Index 355
THE
ADVANCING FRONT
OF SCIENCE
Prologue -THE AP P ROAC H
TO SCIENCE
Science has its showrooms and its workshops. The public
today, I think rightly, is not content to wander round the
showrooms where the tested products are exhibited; the
demand is to see what is going on in the workshops. You
are welcome to enter; but do not judge what you see by the
standards of the showroom.
ARTHUR S. EDDINGTON,
THE EXPANDING UNIVERSE
/-|-\HE slackened activity in industry and trade, which was
JL the most conspicuous aspect of human relations during
the early 1930'$, presents a curious contrast with the
k quickened activity of scientific research. While the be-
wildered world of affairs was at a standstill, or worse, swept
into frantic experiments with discredited social devices,
political dictatorships, and nationalistic insularities, science
pushed progressively into new fields, into wider sharing of
its results, into bolder and more penetrating attacks on the
unknowns of nature.
This is not to imply that scientists escaped the privations
and anxieties of the economic slump. The truth is far
otherwise. Between 1930 and 1934 the American founda-
tions, with endowment funds totaling seven hundred mil-
lion dollars, suffered such shrinkage of income that their
directors deemed it necessary to cut their annual grants
for the support of scientific investigations by nearly three-
[3]
THE ADVANCING FRONT OF SCIENCE
fourths. During the same period, the United States federal
government and many state governments instituted re-
trenchment policies whose first victims were the publicly
supported research centers. Deprivations were even more
severe in some European countries. Science was put on
short rations. Some laboratories sought and found means of
self-support, sacrificing valuable time and talent to financial
pursuit, so it would seem. There is scarcely an institution
that was not handicapped in some way by the depression.
The remarkable circumstance is the accelerated pace of
research in spite of these hardships. And the remarkable
outcome is the fundamental nature of many of the dis-
coveries made in these years of stringency and embarrass-
ment. The advances of our decade are of such brilliance as
to recall the golden years of 1895-1905, when physics
stirred from its long lethargy and sounded the call which
echoed far and awakeningly along all the frontiers of
thought.
The chapters of this book are an account of some of these
recent advances. They represent an attempt to present the
current news of scientific research promptly, in convenient
form, and in terms that will convey the meaning and spirit
of the endeavor without indulgence in false emphasis or
sensationalism. Such tricks are not only alien to science but
unnecessary to its publication, for few subjects are more
interesting to the healthy mind than the drama of dis-
covery. Of all the undertakings of man through the ages,
the exploration of nature is the one that has progressed
consistently toward its objectives, it is the one whose re-
sults have served man most directly, and the one that by
virtue of both its character and its attainments appeals
most surely to the curiosity of the intelligent person. At
the same time it is the human activity that beyond all
others is the most specialized and, by reason of its stand-
ards of exactitude in truth seeking, the most technical in
terminology. Therefore, it needs interpretation.
[4]
THE APPROACH TO SCIENCE
One of the imperative tasks of our day is to interpret the
purposes, methods, and results of science in such wise that
this greatest adventure of the human spirit may be "under-
standed of the people." Science needs to be made use of,
but understanding of it must precede complete utilization.
It needs to be made use of, not only in those practical ways
which lighten burdens, relieve pains, cure diseases, and
increase the comforts and conveniences of civilized life,
but more it needs to be made use of also in those higher
outcomes of the new knowledge: the freeing of the individ-
ual from fear and superstition, the widening of intellectual
horizons, the strengthening of the ties of mutual interest
which alleviate man's inhumanity to man.
"The motive of science," said Ralph Waldo Emerson,
"was the extension of man, on all sides, into nature, till his
hands should touch the stars, his eyes see through the
Earth, his ears understand the language of beast and bird,
and the sense of the wind; and, through his sympathy,
heaven and earth should talk with him. But that is not our
science."
Why not? It can be. Science is not something outside,
immobile, inert, inexorable. It is man's work. Indeed we
may personify it and identify it directly with ourselves, for
science is man abroad in his Universe, adventuring, pros-
pecting, discovering, seeking truth. The motive of natural
science is, literally, the extension of man into all realms, his
conquest of nature's secrets, his harnessing of nature's
forces including the secrets and forces of life, conscious-
ness, and thought which dwell in man himself.
Inevitably the accelerating consequences of scientific
discovery will force men of all nations to recognize the
essential community of their interest in the resources of
this planet. Eventually, inescapably, readjustment will
come. But the adjustment can be made with fewer losses,
less agony, and a minimum of confusion, in a world aware
of the meaning and method of science than in one which is
[si
THE ADVANCING FRONT OF SCIENCE
impressed only by the seeming magic of its applications and
their possible aid in programs of trade, war, and other
predatory competitions.
The frontiers of science are man's frontiers. They are his
hard-won outposts against the darkness. And that darkness,
the ignorance of the mysterious universe of things which
surrounds us and of the equally mysterious universe of
consciousness which pervades us, is the enemy, the only
ultimate enemy. Slowly sometimes, it has seemed, crawl-
ing inch by inch man has penetrated the darkness to
capture and control forces of gravitation, steam, electricity,
to wrest the secrets of the microscopic bacillus, to blot out
diseases that his father debited to the discipline of an
omnipotent providence, to probe the hidden springs of life,
bend protoplasm to produce new fruits of the soil to his
taste, remold the very animals better to his heart's desire,
and erase forever the necessity of famine. Onward, ever
onward, and faster! faster the advance continues in our
time. Deeper into the atom, farther into the living cell,
ever more boldly reaching out into the distant realm of the
dim nebulae, pushes Promethean man reconciled to no
permanent boundaries, willing to accept no limitation on
the method of try-and-see-and-try-again.
It is of such trials and glimpses, of methods of seeing,
and of the findings that now and then reward the seeker,
that the following chapters tell. Of necessity their stories
must be fragmentary, incomplete; for bulletins from the
front can be only progress reports, and tomorrow's engage-
ments may carry the outposts farther or perhaps push
them back a bit for a reconsolidation of the line. Five years
from now, perhaps one year from now, it may be necessary
to reappraise the evidence and revise the story. But for the
present, here is a picture of man embattled against certain
unknowns of his Universe, with such personal touches,
biographical details, and laboratory asides as it has seemed
illuminating to include. In some of the chapters, where
[6]
THE APPROACH TO SCIENCE
opportunity offered to do so without overbalancing our
thesis, I have made mention of applications of the new
knowledge events in science comparable to that of the
occupation and settlement of new lands.
But primarily it is borderlands that we are surveying.
There are several respects in which these new discoveries of
the laboratories and observatories conform to this descrip-
tion. Obviously they are borderlands of the known, repre-
sentative tracts, as we have said, of the new fronts of
knowledge. Then too, these new fields of science are border-
lands of the sciences. In these realms astronomy merges
into physics, biology shares with chemistry, and although
the techniques become ever more specialized, their uses
spread into many fields. A mathematician explores the pos-
sibilities of the origin of life; a biologist's concept of organ-
ism becomes useful to the physicist's explanation of atomic
behavior; an acoustician finds sound waves contributing
new knowledge of chemistry; an electrical researcher, ex-
ploring the interior of incandescent lamp bulbs, is led to
discoveries of surface phenomena which throw new light
on the strange ways of living cells. Boundaries lose their
meaning in these shifting vistas of the scientific front. It
is too early to stake out claims. The only dividing line is the
shadowy curve of the horizon, misty and dim in the
twilight, but already brightening with the promise of a
rising sun.
Chapter I-NEW HORIZONS
yearning in desire
To follow knowledge like a sinking star,
Beyond the utmost bound of human thought.
ALFRED TENNYSON, ULYSSES
ETE in the 1920'$ a young European arrived in the
United States from Brazil. He had crossed equatorial
South America by a daring short cut, climbing the Andes
from the Pacific by mule, then coasting the rivers by boat
to the Atlantic. Prior to that he had spent two years in the
Arctic, drifting across the polar sea, enlivening the long
monotony with observations of magnetism, aurorae, and
other natural phenomena. Excitement was in his blood, but
geographical exploration had lost its tang, and he craved
new and challenging experiences. He found them in a
research laboratory in Washington where he became one
of a crew of adventurous physicists prospecting "the genu-
inely new regions inside the atom."
Passage to more than India
Passage to you,
To mastership of you,
Ye strangling problems.
In Pasadena there is an air of expectancy as a group of
technicians uncrate the steel casing which protected the
precious 2OO-inch telescope glass on its journey from the
factory in the East, where it was cast, to the machine shop
[8]
NEW HORIZONS
in California, where it will be ground to its designed con-
cavity. Among them works a veteran, a self-taught optical
expert who was one of Anthony Fiala's right-hand men in
his ill-fated dash for the North Pole. This ex-explorer will
have an important part in the shaping, testing, and in-
stalling of the great telescope whose production is in itself
one of the major scientific experiments of modern times
and here again we have the spectacle of a laboratory and
its methodical regime serving as the successful antidote
for Arctic fever.
In New York an aviator, home from flights to far
countries, turned to a biological laboratory. He found it
not only a refuge from the wearying adulation of crowds
and the annoyance of an obnoxious publicity, but also a
field for his talents, another means of trial of his ingenuity
and patience, a new and fascinating battleground of the
unknown.
The frontier is gone, say geographers the pioneer is
extinct, say historians opportunity is no more, say
economists. Yes, as Kipling anticipated them many years
ago:
Romance is dead and all unseen
Romance brought up the 9:15.
The borderlands today stretch along a front vaster than
the terra incognita of the ancients. The pioneering is more
fundamentally daring, the opportunities richer and more
alluring, than anything the forty-niners knew. The frontiers
are of a different kind, to be sure, and not so obvious; the
pioneering calls more for brains, and for brains of a certain
type, than for brawn or physical endurance; and mere
squatters will not get very far with the sort of opportunities
the laboratories are opening up. New laws, new disciplines,
and new techniques are in the making and in the testing,
and will fundamentally affect our lives, for the future of
[9]
THE ADVANCING FRONT OF SCIENCE
civilization is very likely wrapped up in the future of
science.
The future of science does not mean the future of gadgets
though the gadgets will come, for better or for worse, you
can bank on that. The phrase refers more nearly to the
fundamental knowledge out of which gadgets grow. The
future of exact thinking, of the search for correct ideas
about the Universe, of the quest for the central force which
alike swings the Sun in its orbit among the stars and
energizes the invisible mite of protein into its mechanism
of life: our frontiers lie in those directions. "Pure science,"
some call it, but the trite term is not descriptive. Pride in
the noncommercial pursuits of our pioneering professors
may be arrogance, and in any event is conventional. What
concerns us here is the fundamental nature of the problems
which engage their attention, the value of the new knowl-
edge as bedrock material.
Outsiders sometimes are tempted to dismiss the funda-
mental laboratory experiments as "technical stuff." But
beware! These minutiae are the very stuff of our most
practical dreams the rich loam out of which have sprung
such utilities as bacteriology, immunology, endocrinology,
anesthetics, modern surgery, the electrical industry, tele-
phone, radio, automobile, and the comforts and many of the
taken-for-granted conveniences of civilized living. And
future harvests must look to further extensions of the
frontiers where this virgin soil is to be found.
There were, no doubt, many practical men of the seven-
teenth century who dismissed Isaac Newton's mathema-
tizing as too abstract, too remote from everyday affairs.
Voltaire reports that 40 years after the publication of his
theory of gravitation Newton did not have more than
twenty followers in England. Many professors preferred to
teach the more common-sense and picturable system of
Descartes. But the adventurous mathematics of Newton
changed their world, his discoveries brought to pass our
[10]
NEW HORIZONS
world, and out of the experiments and theorizing now in
course will come the new world of the twenty-first century.
In the history of science, as in that of nations, are epochs
and cycles. There are periods of plodding, periods of
meteoric advance, periods of pause and consolidation.
Today we are in the current of a very rapid advance. And
although no mind is wise enough and no imagination pene-
trating enough to stake out the limits of discovery, we are
capable of glimpses of our borderlands. The present seems
a propitious time for a glance backward, to see by what
trails we have come, and for a general survey of existing
frontiers, to see where we stand in relation to the great
unknowns of nature.
At the turn of the century, the fundamental physical
science found itself in the surge of a great excitement.
Only 5 years before, in 1895, William James had heard a
Harvard professor say that all the fundamental conceptions
of scientific truth had been found and only details re-
mained to be filled in. Nor was this complacency peculiarly
local. The English historian Gerald Brown was writing:
"The great things are discovered. For us there remains
little but the working out of details. " And in Leipzig the
chemist William Ostwald was expressing the same idea.
Before the end of that year, 1895, one of Ostwald's
German colleagues chanced upon a strange influence
radiating from the sides of an activated vacuum tube. It
was Rontgen's discovery of x-rays. The curious behavior
of these rays prompted Becquerel in France to make certain
experiments with uranium which in 1896 gave the first
glimpse of radioactivity. In 1897 J. J. Thomson in England
discovered the electron. And 1898 brought forth, from the
Curies' brilliant searches, radium.
Four supreme discoveries in 4 years! No wonder the
twentieth century opened in an atmosphere of expectancy.
THE ADVANCING FRONT OF SCIENCE
This sudden upturning of strange phenomena, opening new
vistas and posing startling new questions in the moribund
realm of physics, had repercussions in all the sciences
quickening hopes, spurring endeavors, suggesting fresh
trails to be blazed by experiment.
And it suggested, too, the importance of research to many
a thoughtful layman, including, fortunately, some men of
large means. It seems significant that at about the time of
Rontgen's researches, Alfred Nobel decided to set apart
his great fortune as an endowment to provide annual awards
for the encouragement and rewarding of scientific discovery
and other praiseworthy human pursuits.
In 1902 Andrew Carnegie established the Carnegie In-
stitution of Washington, and today its Mount Wilson
Observatory, Geophysical Laboratory, Department of
Research in Terrestrial Magnetism, Department of Genet-
ics, and a dozen other experiment stations are among the
most active outposts of the scientific advance.
Also in 1902 the Rockefeller Institute for Medical Re-
search was established in New York. The quality of its
work and the caliber of its contributions are indicated by
the fact that twice has a Nobel prize come to members of
its staff.
These establishments are representative of scores of in-
stitutions in Europe and America, with a scattering few in
Asia, that have been set up within the last 37 years some
of them privately endowed, some state foundations, some
attached to universities. They are our advance stations,
observation towers, peepholes on the unknown. How far
we penetrate the surrounding mysteries depends on the
reach of our instruments.
Consider, for example, our awareness of cosmic rays
those strange bombardments from outer space. No one can
see a cosmic ray, no one can feel it. The thing was stumbled
upon in the early 1900*5 through the curious fact that elec-
trically charged bodies inevitably lost their charges, an
[12]
NEW HORIZONS
effect that could be accounted for by the influence of in-
visible rays. But what kind of rays ? Physicists competed in
attempts to trap the suspects. Year after year they in-
creased the sensitivity of their detectors, adding some
refinement, some increased delicacy, progressively getting
better results, until at last in 1929 the Russian physicist
Skobelzyn succeeded in photographing the evidence of a
cosmic ray. His camera snapped for a fraction of a second
the track made by an atomic fragment that had been
smashed out of matter by the collision of a cosmic ray.
Now the probability of a ray hitting an atom and frag-
menting it is very small. In the air, where the first detec-
tions were made, it is reckoned that the odds per second are
about one or two to ten million million million. Out of
every ten million million million molecules, one or two may
get hit. The encounter seems exceedingly improbable
billions of times less probable than the occurrence of such
rare human events as the birth of quintuplets. To have
contrived an instrument sensitive to these rarities and
capable of recording them in terms of physical measure-
ment is evidence of the resourcefulness of our cosmic
explorers.
Equally amazing instrumental advances are to be noted
among other techniques. The biologist works with a micro-
dissecting apparatus attached to his microscope and is able
to perform a deft surgery on single cells. The reach of the
microscope has been extended by the use of new illumi-
nants; fluorescence activated by ultra-violet radiation is
showing details beyond the reach of the visible rays.
Recent improvements in photographic speed are being
employed by the cytologist to get microscopic motion
pictures of that world of perpetually changing form which
lies in protoplasm.
Meanwhile, astronomy has extended its grasp to dis-
tances unimaginable. In 1905 the whole universe of stars
was believed to be contained within the Milky Way, whose
[13]
THE ADVANCING FRONT OF SCIENCE
diameter was reckoned as about 7000 light-years. Today
our measurements indicate that the Milky Way has a
diameter of about 100,000 light-years. But large as it is,
we now know that it is far from comprehending the whole
population of stars, that it is only one galaxy among mil-
lions of others. Recently, at Mount Wilson Observatory,
Edwin Hubble photographed one of these outside systems
at a distance estimated to be 500 million light-years.
Thus does our reach progressively extend and the
horizons recede with the increasing sensitivity of the in-
struments through which we prospect the borderlands.
The borderlands are as many, almost, as the specialists
who are exploring them, but perhaps we can focus our
seeing on a few and get some impression of their extent by
considering some of the primary problems on which science
is now engaged. P. A. M. Dirac, successor in the professor-
ship once occupied by Sir Isaac Newton at Cambridge
University, has listed three fundamental problems as
awaiting solution:
1. The relativistic formulation of quantum theory.
2. The nature of the atomic nucleus.
3. The nature of life.
The first two of these problems were unknown at the turn
of our century, for the theory of relativity was yet to be
born, the idea of the quantum had just arrived, and the
existence of the atomic nucleus as we know it was not even
suspected. But the problem of life's mechanism, which
Professor Dirac qualifies as "more difficult," has been with
us since the earliest days of science. Indeed, it is the prob-
lem of problems, the most intimately personal and, for
human beings, the most important.
Machines have been made to simulate certain processes
of life. Chemists and engineers have even designed mecha-
nisms which provide crude analogues of mental activity
NEW HORIZONS
machines that learn, forget, and remember. Other chemists
have succeeded in crystallizing a heavy protein out of a
solution made from living matter a substance which
under certain conditions behaves as an inert chemical and
under other conditions multiplies and reproduces itself
somewhat like a living species.
While biochemists and biologists are attacking the
problem by methods of their specialized techniques, Pro-
fessor Dirac suggests that the secret of the living mechanism
is also a fit subject for the physicist to explore. Vitalists
scoff at the proposal. But on the other side it is reasoned
that life is wholly dependent on matter, that matter be-
haves at times as if it were a structure of electrically
charged entities, therefore that life is basically a field for
the physical scientist.
3
If the physicist eventually is to unravel the mystery of
life, perhaps it will be only by solving the more funda-
mental mystery of matter and this is the theme of the
second item on Professor Dirac's list. Of all the frontiers
inviting the physical scientist today, the atomic nucleus
is the most tempting, and it is the one that is receiving the
most attention. When Sir Herbert Austin, out of his motor
profits, presented the Cavendish Laboratory at Cambridge
with a generous purse in 1936, the director, Lord Rutherford,
announced that the first use of^the money would be to
provide high-voltage apparatus for studies of the nucleus.
In America, where many of the new types of atom-smash-
ing machines were invented, there is a veritable race for high-
powered armament. At least a dozen laboratories are now
armed, or in process of arming, in this intensifying cam-
paign against the invisible citadel of physical reality the
atomic nucleus.
Our present knowledge of the nucleus may be likened to
our knowledge of the atom in 1912. At that time we knew
1 15]
THE ADVANCING FRONT OF SCIENCE
that the atom consisted of a central massive core and
encircling electrons. Today we know that the core is a
complex structure or aggregate of different parts, or at
least we know that we are able to smash different things
out.
Prior to 1931 it was believed that these interior parts
were of two kinds only: lightweight negatively charged
electrons, and heavyweight positively charged protons. But
around Thanksgiving Day in 1931, at Columbia Univer-
sity, Harold C. Urey discovered a hydrogen atom of double-
weight nucleus a thing so strange that it suggested a new
element, almost. Urey named it "deuterium." Just as
Rontgen's x-rays were the opening shot of the revolutionary
decade of 40 years ago, so Urey's deuterium was the be-
ginning of the breath-taking succession of atomic finds of
today.
Early in 1932, only a few weeks after Urey had made
his discovery in New York, James Chadwick was experi-
menting at the Cavendish Laboratory in Cambridge to test
a peculiar effect that had been sighted by investigators on
the Continent. They had misunderstood the effect and
misinterpreted its cause, but Chadwick now recognized
the phenomenon for what it was and attributed it to the
presence of an unknown particle. The new particle was
massive, like the proton, but unlike the proton it carried
no electric charge, it was neutral, therefore Chadwick
named it neutron. The neutron helped to explain Urey's
deuterium, for was not that heavyweight hydrogen
nucleus simply a proton and a neutron interlocked? This
seemed a reasonable explanation of the double weight, and
is still the accepted idea.
Later in that same 1932, by a brilliant stroke at the
California Institute of Technology in Pasadena, Carl D.
Anderson detected the presence of another particle appar-
ently coming out of the nucleus a lightweight positively
charged something which he named positron.
[16]
NEW HORIZONS
A year following, at the Radium Institute in Paris, the
Joliot-Curies were exploring the metal boron by bom-
barding it with alpha particles, when accidentally they
discovered that the boron had become radioactive in some-
what the manner of radium. It was firing back, out of its
invisible nucleus. And its projectiles turned out to be
Anderson's positrons. Since then more than sixty other
familiar elements have been bombarded in turn, and each
has been converted into a furious geyser of energy, dis-
charging positrons, electrons, and even gamma rays com-
parable to those emitted by radium.
Do you wonder that the nuclear explorers are excited?
Anderson did not get to sleep the night after he discovered
the positron. Sitting one day in the office of another atom
chaser, I picked up a book from his desk, and, opening it
at the flyleaf, chanced to read a hastily scribbled date and
a jubilant memorandum: "Proton tracks today!"
There is endless fascination here, the everlasting
whisper of the unknown, the tantalizing call of the hidden
but not unattainable reality "Proton tracks today!"
Perhaps in the nucleus will be found the answer to that
other problem in Dr. Dirac's list the reconciliation of
relativity and quantum theories. The task here is more
recondite than the others, but no less fundamental to the
integrity of our knowledge.
The theory of relativity dates from 1905, its generaliza-
tion from 1915, and today it is basic in the scientific inter-
pretation of celestial mechanics and other phenomena
involving large bodies, vast distances, and high velocities.
The theory of the quantum, first introduced in 1900 to
explain certain strangenesses in the behavior of radiation,
was applied to the atom in 1913, and extended and for-
malized into more satisfactory theories of atomic mechanics
[17]
THE ADVANCING FRONT OF SCIENCE
in 1926 and the years immediately following. We may say
that, as relativity best accounts for the large-scale phe-
nomena of stars and planets, quantum theory best accounts
for the small-scale phenomena of atoms and electrons.
But between the two theories are discrepancies, or at
least restrictions. The more glaring of these are, para-
doxically, too subtile for brief and simple exposition, but
perhaps we may glimpse the nature of the dilemma from
the following comparison.
In relativity theory the physical reality is described in
terms of the familiar three dimensions of space and one
dimension of time, so that at a given moment each star,
each planet, and even each particle has a certain position
and direction with reference to other stars, planets, and
particles. Each object is said to describe a " world line" as
it courses its way through the Universe, traveling a track
ordained for it by the curvature of space, which curvature
in turn is ordained by the masses of the bodies which
inhabit space.
In quantum theory the case is quite different. Here the
dominating law appears to be the uncertainty principle
which says that exact position and precise velocity cannot
be measured, and therefore are not known to exist. Thus,
the space-time definition of events becomes indefinite.
Indeed, in the quantum concept, as F. A. Lindemann of
Oxford points out, "We must conclude that there are no
such things as world lines. As a first approximation they
would be represented as world tubes. The tubes must not
be thought of as having rigid boundaries, but rather as
shading off from the center outward according to a form of
error law."
There are certain relativity effects which have been
found to operate in the atom, first pointed out by Arnold
Sommerfeld some years ago, and Dirac himself is the
author of a number of interesting developments of theory
combining ideas of relativity with those of quantum
[18]
NEW HORIZONS
mechanics. But the consolidation of relativity theory with
quantum theory, or the discovery of the unified system
which includes them both, is yet to be attained. Recent
projects in this direction have been essayed by Albert
Einstein, Arthur S. Eddington, and George D. Birkhoff.
So the riddle is not rusting. All these approaches are
significant and helpful, but the difficulties still are very real,
and the problem remains one of the most formidable
frontiers of science. It will continue to be an inviting field
for exploration so long as there are those who believe that
nature is coherent, orderly, and subject in all its members
to law.
The approach to problems of science those of astron-
omy, physics, chemistry, biology, and all the rest is
limited by the conditions of man's environment. It is
granted that creatures living at the bottom of the sea,
where no visible rays ever penetrate, and where the sur-
rounding medium is a dense liquid, would have a different
impression of the cosmos and therefore a different cos-
mology from creatures living as the human race does at
the bottom of an ocean of air. A scientist on the planet
Venus, which is always swathed in dense clouds and from
whose surface no image of Sun or other star is visible, would
picture the firmament quite differently from an observer
on the arid surface of Mercury, on whose cloudless horizon
the Sun never sets; and still different would be the outlook
of an investigator resident on the giant Jupiter, with its
surface still plastic and its atmosphere impregnated with
ammonia gas and methane. Nor is it only the view upward
to the skies that is colored and transfigured by these plane-
tary differences, but also the outlook downward to the
planets themselves, to their surface features: the solids and
liquids, polar zones, equatorial belts, and the thin films of
[19]
THE ADVANCING FRONT OF SCIENCE
life that may (or may not) overlay certain favorable
surface areas of these spinning orbs.
The specter of life haunts all human hypotheses about the
other planets, and doubtless it will continue to plague our
conjecturing until the first rocket ship makes a successful
landing abroad and is able to send back a message of its
discoveries. Our speculation of life in other worlds is not
unnatural. Man is lonely in his new-found Universe, this
deepening shadow of space-time, and seeing "other little
ships" cannot but wonder "whether in yonder spheres
there is also an Above and a Below," the living and the
not-living. Life on the Earth ranges from the invisible
microbe, which can endure both boiling water and liquid
air, to man, who cannot long survive so much as a i per
cent change in his body temperature. With the demon-
strated existence of this wide range of protoplasmic
sensitivity on the Earth, who can deny that life of some
kind may be possible on hot Mercury or cold Pluto or in
any of the planetary arrangements between these two
extremes? Human life, no; or hardly; for it is conditioned
on a finely balanced internal environment which in turn is
dependent on a certain balance of external forces : the solar
constant of radiation, the atmospheric constant of oxygen,
the presence of water and other minerals a combination
that exists perhaps nowhere in the Solar System but on
Planet 3. But it is not impossible that the resonance
phenomena which we call life may assume other forms,
given other environmental conditions. The probability of
life existing on other planets, or, as Sir Francis Young-
husband would have it, on or in the stars, reduces to a
definition of what life is. The living unit, as we shall see in
a later chapter, is exceedingly difficult to define.
Our knowledge of nature is limited by our ability to
apprehend the materials and the forces which meet us
both those of the Earth, which we encounter in their
hurryings to and fro, and those of the Universe outside,
[20]
NEW HORIZONS
which beat upon us from the stars and the darkness beyond
the stars. Nor is it only our five senses that limit the
boundaries of the known. Ingenious man has devised appa-
ratus for translating the invisible, the inaudible, and the
imponderable into a code intelligible to human sense
organs. By means of lenses, mirrors, prisms, magnets,
fluorescent salts, electrically sensitive filaments, photo-
graphic plates, and other extensions of eyes, ears, and
fingers, scientific man has discovered much that to the
unaided senses is nonexistent. The story of modern dis-
covery is very largely a story of increasing ingenuity of
instruments.
But the reach of our instruments, and indeed the very
biological nature of our observers, is conditioned, as we
have said, by the nature of the observation post from which
we view our world. The rotating, revolving Earth is subject
to certain restrictions imposed by its mass, its distance
from the Sun, its motions, the constitution of its enveloping
atmosphere, and the perpetual panorama of change which
attends its flight through space. Our observation post is
not constant. It is not the poet's
round and delicious globe,
moving so exactly in its orbit forever and ever,
without one jolt or the untruth of a single second.
On the contrary, it is a quite bulgy, irregular, tempest-
tossed spherule of air, as well as a globe of land and sea. And
what we glimpse, and how we interpret our snatches of
the unknown, depends very directly on these terrestrial
conditions. Therefore we begin our quest of the border-
lands with a look at our observation post our little ship
plowing its trackless world line among the stars.
Chapter II FRONTIERS
OF EARTH
The Earth never tires,
The Earth is rude, silent, incomprehensible at first,
Nature is rude, silent, incomprehensible at first;
Be not discouraged, keep on, there are divine things
well envelop'd,
I swear to you there are divine things more beautiful
than words can tell.
WALT WHITMAN, SONG OF THE OPEN ROAD
THE terrestrial reality indeed is "well envelop'd." A
star is obvious, the simplest thing in nature Eddington
has called it, a globe of gas implicitly obeying the gas
laws. And since we know the gaseous state of matter
better than we know the liquid or solid state, it follows that
we can know stars better than planets simply because
stars are made of the stuff with which we are most familiar.
A star is a glowing system, self-revealing, self-advertising
a vast aggregate of matter in a primitive state of motion,
fragmentation, and organization, which ceaselessly broad-
casts the most intimate news of itself. But a planet, the
cooled fragment of star stuff that is something different.
The planet broadcasts no radiation of its own that we can
discern at a distance; it only gives back the reflected rays
of the Sun which warm and illumine it. The planet hides
its internal nature within a crust of rocks and metals, and
[22]
FRONTIERS OF EARTH
complicates our seeing the solid phases of its continents
and islands and the liquid phases of its seas by an envelop-
ing gaseous phase of atmosphere. There is nothing per-
ceptibly energizing, or generative, in its behavior. It is a
dependent body, subservient, inert. William Bolitho, in
one of his essays, described the human race as " blood clots
on a clod." His picture is obviously incomplete and super-
ficial for great and "well enveloped" is the might of
hemoglobin but I suppose most of us who wince at being
called blood clots would readily agree that the Earth is a
clod. The Earth never tires because it has no capacity for
fatigue. It is brute matter, clay. And while the majesty of
man and all his company of conscious creatures has arisen
from this terrestrial compost, that only lends the more
dignity to man, elevating him the higher by contrast with
the lowly dust of his origin. So we celebrate, in our moments
of inspiration and emotion, our testament of faith in the
inerrant course of evolution, forgetting or ignoring the
testament of fossils the mute evidence of species that
also once flourished and proliferated but perished aeons
ago under the scourging changes of this spinning clod that
eternally calls the tune for our dance of life.
Perhaps the Earth is a clod, but if so it is a vibrant clod,
responsive to an endless symphony or cacophony of
cosmic influences. In truth, so sensitive is the planet to
its environment, that one might accurately liken our
"round and delicious globe" to a tuning fork, or to a deli-
cately poised magnetic needle, or to one of those highly
vibrant quartz crystals used to detect frequencies beyond
the range of audibility. In the vast span of the Universe
our dwelling place is relatively a point, smaller in the
scale of the whole than a pollen grain is in the scale of the
Solar System. And yet, it is this minute point that picks
out of space the energy that drives our terrestrial machine
its flow of winds and of water, its growth of living things,
its invisible pulses of electricity and magnetism.
[23]
THE ADVANCING FRONT OF SCIENCE
If you look at the planet Mars, a small bright red spot in
the night sky, you see an object that is considerably
nearer the Earth than the Earth is to the Sun. To an ob-
server on the Sun, the Earth would appear not much larger
than Mars appears to us. Imagine, then, such an observer
peering out through the thin solar corona into the sur-
rounding void and seeing these dots of borrowed light:
Earth, Mars, Jupiter, and the others. It would seem a
slight probability that any object so small, covering so
diminutive an area of the sky, would be able to capture any
considerable portion of the energy flooding space. The
answer is, of course, that it can capture only so much as its
surface intercepts and this suggests two actualities: first,
the tremendous volume of energy poured out by the stars;
and second, the sensitivity of our planet to these influences.
Our nearest star is the master influence, so far as knowl-
edge goes. Whether or not the Earth owes its origin to the
Sun is an unsolved problem. One recently proposed
hypothesis inclines to the belief that both Sun and planets
emerged simultaneously from some cosmic event of a few
thousand million years ago. But this is only one of many
surmises. Whatever the planetary genesis may have been,
there is no question that the Earth's destiny is inexorably
bound up with the Sun's, and that our planet owes much of
the present form of its surface features to solar radiation.
The torrent of outgoing energy totals five hundred million
million million horsepower continuously, and the Earth's
surface is sufficient to intercept only the two thousand-
millionth part of this a quota that averages about one
horsepower to each square yard of the sunlit Earth. Only
a small fraction of this horsepower is absorbed and put to
work, but that is quite enough to keep oceans liquid and
atmosphere gaseous, to generate our weather, and in these
and other ways to mold and remold the fabric of our planet.
FRONTIERS OF EARTH
The Moon is a far lesser mass. Its weight is only the
twenty-seven millionth part of the weight of the Sun, but
the Moon is four hundred times nearer than the Sun, and
it makes up in proximity for its bantam weight. The tides
of our seas are largely an effect of the gravitational influence
of the Moon. Less known is the fact that the lunar gravita-
tion lifts a tidal wave of air which heaves along the upper
surface of our atmosphere and also a lesser tide down in the
rocky crust of the Earth.
Several evidences of this crustal tide have been offered.
Alfred L. Loomis and Harlan T. Stetson report that when
the Moon is passing over the North Atlantic Ocean, the
city of Washington is a few feet nearer London than it is
at other times. Total differences sometimes amount to as
much as 60 feet. The change in the variation seems to follow
the Earth's seasons, indicating that solar influences also
may enter into the situation. Such part of the shift as
keeps step with the Moon's position suggests that our
satellite through its gravitational influence causes the
rocky layer beneath the sea to rise and by virtue of that
movement to shorten the distance between our continent
and England. Recently scientists at a Chinese observatory
compared the time signals between Shanghai and Berlin
and found a difference of 60 feet in the distance between
these two cities, a shift apparently related to the position
of the Moon. In Pittsburgh, P. D. Foote used a delicate
gravitational instrument which detects minute differences
in the distance to the center of the Earth. Dr. Foote found
that when the Moon was at its zenith over Pittsburgh the
crust of the Earth apparently rose, and when it was on the
opposite side of the Earth the crust fell, the difference
being about twenty-three inches. All these reports must be
disquieting to astronomers and other surveyors, accus-
tomed to determining the latitude and longitude of their
observatories, and proceeding to work on the assumption
that the places are fixtures. A difference of mere feet
1*5]
THE ADVANCING FRONT OF SCIENCE
between America and Europe is not enough to affect steam-
ship fares or cable tolls, but it is enormous to those who
must measure longitude, reckon time in split seconds, and
determine star positions within hair's breadths. Stetson
has also compared the dates of earthquakes with the
lunar calendar, and reports that the quakes are most
frequent when our satellite is in such positions as to exert
its maximum tidal forces.
Smaller, numerous, and with effects different from that
of the Moon are the meteors. They come closer and actually
add themselves to our mass. Estimates based on counts
made in different parts of the Earth show that approxi-
mately one hundred thousand million meteors dart into
pur atmosphere every twenty-four hours. Most of them are
mere granules of dust, motes from interplanetary space,
and are consumed in the upper air; but some are huge
chunks and, despite the terrific heating engendered by their
swift flights and friction with air molecules, may finally
reach the surface of the Earth as solid bodies. The largest
known is the great Ahmighito meteorite, a part of the
exhibit at the Hayden Planetarium in New York, a roughly
triangular lump of iron-nickel which weighs more than
36 tons. It was found in Greenland, and brought to New
York by Admiral Peary. There are a few others in our
museums that weigh tons, but most of the ten or eleven
thousand meteorites that have been recovered weigh only
pounds or fractions thereof. Doubtless innumerable mil-
lions lie buried in oceans and waste lands. F. G. Watson and
J. L. Greenstein, of the Harvard College Observatory, re-
cently made a study of this continual rain of "shooting
stars/' and they reckon that the mass of the Earth is in-
creased about 3^ tons annually by these additions. This
yearly accretion is negligible in proportion to the total
mass of the Earth: 6570 million million million tons,
according to the determination of Paul R. Heyl, made at
the Bureau of Standards in Washington. Meanwhile it
[26]
FRONTIERS OF EARTH
may be that we are losing as much or possibly even more
through the escape of light gases from our atmosphere and
through the disintegration of matter by radioactivity or
other forces of transmutation.
Meteors seem to have another terrestrial influence. It is
possible that they contribute to the ionization or electrifica-
tion of the upper air. The probable reality of such an effect
is suggested by the behavior of radio signals; these seem to
increase their strength at times of meteoric showers. As a
meteor plunges into the atmosphere from interplanetary
space, traveling at speeds which range from 10 to 100
miles a second, it is heated to incandescence by the impact
and friction of air particles. Temperatures of 3000 to
7OOOF. are generated, intense darts of ultra-violet light
are released, and some of these may collide with air mole-
cules and smash them. Thus the meteor, as it plows through
the atmosphere, leaves a trail of mutilation in its wake.
There have been instances in which a radio investigator
saw a meteor shoot across the sky at the moment when he
was making a test, and the sudden increase of static in the
earphones was unmistakable.
But these things that the eye sees the Sun, the Moon,
and the darting meteors are only the obvious among the
influences that ring their changes on our vibrant Earth.
There are also more hidden bombardments cosmic rays,
for example. Although they are invisible and imperceptible
to any human sense organ, cosmic rays have disclosed
themselves as the superlative energy carriers of the world.
An electron in a thunderbolt may move with a pressure of
1000 million volts, but some of the electrons knocked out
of matter by cosmic rays exhibit energies of 20,000 million
volts and even more, according to certain estimates.
It seems improbable that the Earth could be under con-
tinuous battering by such forces without being affected,
and many have been the speculations on the nature of the
effects. Several years ago John Joly, of Dublin University,
[27]
THE ADVANCING FRONT OF SCIENCE
suggested that the incidence of cancer on the Earth might
bear some relationship to cosmic radiation. It remains a
provocative idea, without proof.
Later, when H. J. Muller at the University of Texas dis-
covered that the genetic patterns of living creatures can be
changed by x-ray bombardment, causing the descendants
of the radiated individuals to develop new physical char-
acteristics, the idea was proposed that cosmic radiation
might be continuously acting in this same way in nature,
and thus furnish the key to organic evolution. This hy-
pothesis, born of experiment, is entirely reasonable. And
while it appears on statistical grounds that the density of
cosmic rays (the number of rays falling on each square yard
of the Earth's surface per second) is not sufficient to account
for all the mutations occurring in nature, there is no reason
to doubt that some of them are attributable to this source.
Since the outer frontiers of the Earth lie in its atmos-
phere, one would naturally expect that any effects of out-
side influences would show themselves there first. Such is
the case, though we are still fumbling for exact knowledge.
Much has been discovered with the aid of radio. In truth,
the capital achievement of modern terrestrial exploration is
the radio discovery of the electrical structure of the
atmosphere.
It is not obvious that our atmosphere is an electrical
ceiling, with an electrical roof above the ceiling. The old
idea pictured a halo of gas surrounding the more solid
globe, and presumably the gas thinned to the vanishing
point a hundred miles or so above sea level.
When Hertz discovered radio in the i88o's, and inventors
began to speculate on the possibilities of wireless com-
munication, it was assumed that such communication
:ould connect only relatively near points on the Earth's
surface. Radio waves are undulations in space rather than
[28]
FRONTIERS OF EARTH
n air; therefore the waves could not be expected to conform
:o the spherical contour of the atmosphere. They would go
>ut from the broadcasting antenna in all directions, like
:he upper half of an expanding bubble, but they could not
:>end round the planet's curve. Light did not bend round
:hat curve, and radio was a species of light. The only way
:he theorists saw to bridge distance by wireless was to
>uild very tall transmitting and receiving antennae. As
vith a lighthouse so with an antenna : the higher it was, the
nore distant its horizon.
Marconi's early experiments gave strength to this sup-
position. On Salisbury Plain, England, in 1896, he trans-
nitted signals over 2 miles. In a few months, with taller
mtennae and more powerful apparatus, he had doubled
:his distance; and so progressively as he improved his
nstruments and increased the height of his antenna, he
ncreased his range. By 1900 he was spanning 60 miles with
>ase, and occasionally, under favorable conditions, picked
ip a message at 100 miles. Early in 1901 two of his stations
[86 miles apart were clicking off messages to each other.
Svery gain whetted his appetite for more distance, and in
;he summer of 1901 he set himself an audacious test. He
vould build a yet more powerful transmitter and install it
vith a yet more lofty antenna on the Cornish coast. Then
le would cross to America and listen for its signals.
Marconi shared the secret plan with only a few intimates
vhose cooperation was necessary. Others thought he was
embarking for more of his ship-to-shore experiments when
le sailed in late November. He landed in Newfoundland
vithout publicity. The rest is history. On December 12,
vhile his men struggled with an enormous kite to support
:he slender wire aerial above the windswept coast, Marconi
;at alone in a barracks-like room of the hospital with a pair
>f headphones clamped over his ears. For an hour he waited,
ike a man in a waxworks, motionless, tense, listening. At
lalf-past twelve, noon, a faint staccato quivered in the
[29]
THE ADVANCING FRONT OF SCIENCE
phones the three short dots of the letter s repeated over
and over again. It was the prearranged signal. He called
his men. Nervously, almost violently, he handed the
phones to one of them, saying, "Can you hear anything?"
The instrument was passed to the next man, and to the
next. Each in turn heard the feeble click of the code, "zip-
zip-zip." Wireless power had swung its mysterious reso-
nance across the Western Ocean to be heard by a human
ear for the first time.
How had it done this ? asked Lord Rayleigh. The waves
could not travel through the Earth; how could they
curve round it ?
Almost immediately the right explanation was suggested.
If the waves could not bend of their own accord, perhaps
they might be bent by some outside agency. It was known
that an electrical conductor, a sheet of copper or a wire
screen, for example, would reflect radio waves in the
laboratory. Assume such a conductor in the upper air. A
layer of ions (mutilated air particles) would serve the
purpose quite as effectively as a metal screen. If there
existed this ionized sphere of electrification high above the
Earth's surface, the long-distance transmission of radio
waves could be explained. It could be explained as a con-
sequence of a mirror effect. The waves striking the concave
undersurface of this layer of ions would be reflected back
at the same angle with which they struck it and on reach-
ing the ground would be reflected upward at a similar
angle. And so, alternately bouncing the ceiling and the
ground, they would zigzag round the globe as far as their
strength carried.
Such, in brief, was the theory proposed by two electrical
engineers, Oliver Heaviside in England and A. E. Kennelly
in the United States. The idea of an ionized upper region
was not new. It had been suggested some years before by
the British magnetician Balfour Stewart on other evidence.
But Kennelly and Heaviside were the first to apply it to
[30]
FRONTIERS OF EARTH
explanation of radio transmission. The explanation re-
mained merely a hypothesis for more than twenty years.
Finally, in 1925, its truth was established independently
by three convincing experiments.
At the laboratory in Washington of the Carnegie Institu-
tion's Department of Research in Terrestrial Magnetism,
Gregory Breit and M. A. Tuve directed a radio impulse
straight up, and in a fraction of a second the echo came
bounding back clear evidence of the existence of some
sort of electrical mirror.
At the Naval Research Laboratory near Washington,
A. H. Taylor and E. O. Hulburt sent up a series of short-
wave impulses at an angle, and measured the skip distance
to the first ground reflection of the wave another bit of
testimony from the upper-air reflector.
And in England, near London, W. A. Appleton and
M. A. F. Barnett reached up and touched the invisible by
still another method. They radioed signals of different
wave lengths, and, by measuring the patterns of inter-
ferences which resulted when the returning waves bashed
into the outgoing waves, they were able to demonstrate the
presence of the reflector and to gauge its height.
Thus the Kennelly-Heaviside Layer, the ionosphere,
took its place on the chart of the planet Earth as a known
but as yet unexplored borderland.
Perpendicular exploration has advanced swiftly since
then. While Byrd and Ellsworth were edging perilously
into unknown stretches of Antarctica, adding new moun-
tain chains and plateaus and other features to the surface
map of the Earth, these radio explorers, comfortably
seated in their laboratories in Washington, London, and
other congenial bases, have been pushing steadily into the
ionosphere. They have discovered lofty mountains, wide
plateaus, sometimes sagging valleys in this ever-changing
realm of the upper air. The aerial mountains, valleys, and
plateaus never stay put, but forever are shifting their
[31]
THE ADVANCING FRONT OF SCIENCE
positions and altering their dimensions under the pressure
of sunlight, the heat and electrolysis of the solar rays, and
other causes.
The varied influences produce a varied structure whose
complicated pattern we are just now in process of dis-
entangling. Indeed, we may liken the ionosphere to a
section of a geological stratification, with one sky land piled
on another, each continually changing its density, its
thickness, and perhaps its topographical features. The
whole subject is very much "up in the air" at present,
but this much we know.
If you send out a radio signal of long wave length, such
as is used by the general broadcasting stations, the reflec-
tions come from a height of about 70 miles. But if your
impulse is of short waves, such as were used to communicate
with Admiral Byrd in Little America and such as are com-
monly used for transoceanic broadcasts, the reflections will
be longer and the distance between reflections will be
greater, indicating that the height of the mirror is from
115 to 150 miles. These levels vary from season to season,
from hour to hour at times, and are different for different
latitudes; but the two sharply distinguished regions are
discernible at all hours and from every part of the Earth's
surface, and therefore appear to be permanent features.
The Kennelly-Heaviside Layer thus turns out to be two
layers: the lower, or E layer, serving to reflect long radio
waves, and the upper, or F layer, being a reflector for
shorter waves to which the lower layer is transparent.
The discovery that some wave lengths are reflected from
a lower level than other wave lengths provides the radio
explorer with a master tool a combination hand and eye
which can reach into the ionosphere and spy out the
hidden lands. By starting a transmission at one wave
length and gradually changing the signal to shorter and
yet shorter waves, one may discover the critical wave
length at which the pounding of the invisible vibrations
FRONTIERS OF EARTH
against the invisible barrier becomes sharp enough to pierce
through the Earth's ceiling, the E layer, and strike the
Earth's roof, or F layer. This type of investigation was
pursued at the National Bureau of Standards by a trio of
researchers S. S. Kirby, L. V. Berkner, and D. M. Stuart
with the result that they discovered still another sky
land. It, however, is an intermittent reality, appearing
during daytime and fading at night. This new-found
reflector forms in the upper part of the F region. It begins
to show its presence right after dawn, grows steadily in
reflecting strength, reaches a maximum shortly after noon,
and then begins to shrink. After sunset it has disappeared,
and the F layer resumes its function as the radio roof. Most
of the authorities regard this daylight upper region as a
temporary tent over the more permanent F layer or roof;
therefore it is called the F* layer, while during this double
phase the original F layer is known as FI.
Still more transitory atmospheric structures are reported.
Sometimes the lower or E layer splits into two, while the F
layer on occasions shows not only its daytime FI and F%
but also an F*. And occasionally yet another stratum
appears midway between the uppermost E and the lowest
F. Thus, three sporadic ledges are added to the two perma-
nent and the one sunlit layer, making occasionally as many
as six stories in our electrical superstructure, each with its
individual characteristics, each a reflector of all radio waves
longer than a certain critical wave length, a transparency to
all waves of shorter length. No wonder radio has a
temperament!
3
Although no pilot balloon, rocket, or other aerial vehicle
has been able to sample the ionosphere for our benefit, it is
possible by means of radio waves to sample it indirectly.
We know, from laboratory tests, what a gas of a certain
density will do to waves. When the gas is ionized it will
[33]
THE ADVANCING FRONT OF SCIENCE
reflect radio waves of a certain wave length and pass all
shorter than that wave length. Ionize the gas to a still
higher state of electrification, and its opacity increases
waves that got through before are now turned back.
Many experiments prove that the critical wave length is a
direct index to the density of ionization. Therefore, by
measuring the precise wave length at which a layer of
atmosphere ceases to reflect signals and allows them to
pass, our radio explorers are able to tell the state of ioniza-
tion of the layer. Very exact studies of this kind have been
carried on for several years at widely separated points on
the Earth's surface, and we now know pretty closely the
ionic density of each of the atmospheric layers and their
changes. The records cover daily and seasonal changes, the
progressive changes that have taken place over a period of
years, and the sporadic changes that occur at irregular
intervals. Since the ionization is accomplished presumably
by radiation from the Sun, and since the amount of radia-
tion reaching a given latitude of the Earth may vary from
month to month with the seasons, and from year to year
with the sunspot cycle of about n^j years, these changes
in the state of ionization are to be expected.
But I doubt if many users of radio have any conception
of the extent of the changes that have taken place recently
in these upper regions of our planet these aerial lands of
thinnest gossamer, their material more diffuse than that
of the highest vacuum ever attained in a laboratory, and
yet of a substantiality so real and so indispensable to the
operation of long-distance radio communication that any
subtraction from or addition to the density is instantly
apparent. Before we look at the record of startling changes,
let us get clearly in mind the general picture of what is
happening up there beyond the blue stratosphere.
The Sun's radiation must travel some 93 million miles to
reach the Earth. But it travels through the vacuum of
interplanetary space, and in consequence of the high
[34]
FRONTIERS OF EARTH
transparency of its medium it strikes the upper atmosphere
with an energy not much different from that with which it
leaves the Sun. This means a temperature of approximately
io,oooF. Whether or not the temperature of our outer-
most air is 10,000 we do not know, but the point is that
whatever radiation arrives carries with it the possibilities
of that degree of excitation. The solar radiation is of a
wide range of vibrations, including ultra-violet light,
visible light, the invisible infra-red, and corpuscles or par-
ticles of exploded sun stuff.
The thin outlying fringe of the atmosphere gets the full
force of this solar bombardment. Perhaps every one of its
atoms that chances to get hit is violently mutilated, and
so the greatest slaughter of particles takes place here. This
maximum ionization forms the daylight tent which we
have called the Fz layer.
The solar radiation that survives these outer collisions
passes on into deeper and denser zones of air, and its
chance encounters smash other atoms here to form the
stratum which we have called the F\ layer.
Still deeper penetrates the remaining torrent of Sun rays,
reaching yet denser areas of air, and performing the mutila-
tions whose fragmented atoms constitute the still lower
level, our radio ceiling, the E layer.
The sporadic intermediate layers alluded to in the
preceding section are no part of the normal picture; they
are supposed to be consequences of unusual eruptions from
the Sun, and frequently occur at times of magnetic disturb-
ances in the Earth and auroral displays in the skies; and to
keep the present discussion simple and uncomplicated we
shall ignore the exceptions here.
What we have at high noon over the city of Washington,
for example, on an ordinary summer day, is this invisible
structure of electrified gases: the E layer, about 70 miles
overhead, with a relatively sparce population of ions; then
the FI layer, about 115 miles from the ground, with a
[35]
THE ADVANCING FRONT OF SCIENCE
higher number of ions, though the atmosphere itself is
thinner here; and finally, at about 200 miles (sometimes
higher), the uppermost or F* layer, a still finer tissue of
matter but an enormously higher number of ions. The radio
program that comes to you from your local broadcast
station is reflected by the bottom or E layer. That which
comes across the Atlantic from London may be reflected
by the intermediate or FI layer, while messages from
Antarctica or Australia are likely to use such short wave
length that they penetrate both E and FI and are reflected
only by the Ft mirror. Since the density of its ionization
determines whether a layer will pass a certain wave length
or reflect it, we can be sure that any considerable change
in the ionization of the upper air is bound to influence man's
wireless communications.
And considerable changes have been taking place. For
instance:
In the year 1934, at summer noon, in Washington, the
uppermost or Ft layer averaged 700,000 ions per unit. 1 The
longest wave that was just able to penetrate this barrier
was one of 40 meters wave length. Everything longer was
turned back. But in 1936 the case was quite different, for
by then 4O-meter waves were unable to get through. The
explorers, sounding that outer barrier with shorter and yet
shorter waves, found that the signal must be reduced to
21 meters wave length before it could escape. There were
more ions up there in 1936 than in 1934, the wave length
21 meters gave a direct clue to the ionization, and the
reckoning showed the enormous average of 2,500,000 per
cubic centimeter. The density had more than tripled in the
2 years!
Corresponding changes, though in lesser degree, showed
in the lower layers. In 1934 the density of FI was 250,000,
and its critical wave length 65 meters; in 1936 density
1 Equivalent electrons per cubic centimeter.
[36]
FRONTIERS OF EARTH
was 350,000, and critical wave length about 57 meters.
For the E layer, in 1934 the density was 150,000, the critical
wave length 85 meters; by 1936 density had increased to
185,000, critical wave length had decreased to 77 meters.
While these striking differences were measured in the
daylight conditions of 1934 and 1936, it is worth noting
that a smaller change showed in the night conditions. As
soon as the rotating Earth removes Washington from the
field of the Sun's radiation, the mutilated particles of the
upper air tend to repair their wreckage. An electron in its
wanderings will encounter a broken atom that is minus an
electron, and the two join to form a whole again. By this
process of mutual repair the uppermost layer of ionization
soon disappears or its residue merges with the intermediate
region. At the same time the intermediate region and the
lower region have been undergoing similar atomic restora-
tions, and by midnight this is the state of affairs: The
upper or F region has thinned to a density of only 100,000
ions per unit, and in consequence a loo-meter wave is able
to get through it. The lower or E region has thinned to
only 7000 ions per unit, and waves of 400 meters readily
pierce its depleted screen. In citing the critical wave lengths
here, as in other parts of this discussion, the values given
are those for waves striking the layers at the normal angles
of incidence. For reflections at other angles, other wave
lengths become critical.
Despite the far greater number of mutilations occurring
during the daylight of 1936, repairs were made so swiftly
after dark that by midnight the ion density showed rela-
tively only a small increase over that of 1934 midnight.
Perhaps from these comparisons we may gather a broad
hint of why radio reception is generally more steady at
night than during the sunlit hours. For surely it is the
Sun that electrifies the atmosphere into an ionosphere;
if so, it is reasonable that changes in position of the Sun
in the sky, changes in the distance of the Sun from the
[37]
THE ADVANCING FRONT OF SCIENCE
Earth, and changes of the surface features on the face of
the Sun may affect the degree of our electrification.
There are, of course, bombardments other than the solar
radiation, and these cannot be ignored. Recently A. M.
Skellett of the Bell Laboratories made a list of all the
radiant sources of atmospheric ionization known to us,
computed their probable energies, and arrived at this
line-up :
Ultra-violet light from the Sun 28 . 35
Meteors during morning meteor shower 2.4 (maximum)
Ultra-violet light from the stars 0.014
Cosmic rays 0.00031
Meteors, average for normal day, A.M 0.00024
Meteors, average for normal day, P.M 0.00012
Ultra-violet light from full Moon 0.000044
The numerals refer to units of energy per unit of area
intercepted by the Earth per second. Note that the solar
ultra-violet represents more than ten times the energy of
all the other sources combined. This is not because it is more
energetic than the stellar ultra-violet or the cosmic rays,
but because there is so much more of it. All authorities
agree that the solar ultra-violet is one of the most active
agencies of atmospheric ionization. E. O. Hulburt and H. B.
Maris, of the Naval Research Laboratory, regard the solar
ultra-violet as the dominating agency, responsible for more
than 99 per cent of the ionization of all the various layers of
sky lands. It is known that enormously more ultra-violet
sunlight reaches the upper air than ever gets through to
the Earth. It is also known that fluctuations occur in the
ultra-violet radiation of the Sun, sudden outbursts at times
of sunspot appearance, and these bursts and spots often are
followed instantly by violent shifts in the ionosphere. The
evidence for ultra-violet influence as a leading actor in the
invisible drama of ionization is strong. But some authorities
have doubted whether the ultra-violet was the whole show.
Several years ago S. Chapman of the University of
London suggested that high-speed electrons or other par-
[38]
FRONTIERS OF EARTH
tides ejected by the Sun could account for some of the
ionization. More recently another corpuscular theory has
been proposed by L. V. Berkner and H. W. Wells on the
basis of late findings at three widely separated observatories
of the Carnegie Institution's Department of Terrestrial
Magnetism the station near Washington, D. C., another
at Huancayo in Peru, and the third at Watheroo, Australia.
A curious discrepancy has shown up in the records of these
three stations with regard to the jF 2 layer, whereas their
records with regard to the lower layers remain in agreement
with former conceptions.
The point is this : if the ionization is caused by the light
of the Sun, the results should be most prominent when
the Sun is directly overhead. In the latitude of Washington
and other parts of the northern hemisphere this vertical
position is attained in summer, in Australia and other
southern latitudes in winter. Therefore we should expect the
ion density in July to be at a maximum over Washington
and at a minimum over Watheroo, and in January to be at
a minimum over Washington and at a maximum over
Watheroo. This is exactly what happens so far as layers
E and F\ are concerned, but F% follows a different pattern
of behavior. For, curiously, the F^ ionization is at its high-
est density during the months of November, December,
January, and February both at Washington and at
Watheroo, and at its lowest during the summer months
at both stations. Reports from the equatorial station at
Huancayo show the same conditions for F% over Peru.
Apparently F 2 is at its maximum at all latitudes at the
same time, irrespective of the altitude of the Sun, while
the density of the two lower layers of ionization follows the
Sun's course along the ecliptic rather closely. From these
and other considerations Berkner and Wells reason that
the agency which smashes the molecules of the uppermost
atmosphere to form the sunlit bulge we call F* is not the
same as the agency which penetrates deeper to form FI
[39]
THE ADVANCING FRONT OF SCIENCE
and E layers. And yet both agencies must come from the
Sun, since there are certain daily and seasonal and sporadic
effects in all layers which seem to keep step with certain
solar changes. It is the hypothesis of Berkner and Wells
that ultra-violet light is responsible for E and FI ionization
in the normal phases of these lower layers, and that par-
ticles of matter shot out of the Sun are responsible for the
Fa ionization. It is known that vagrant calcium is abundant
in the solar atmosphere, and atoms or molecules of such an
element ejected from the Sun at high speeds might mutilate
and agitate the particles of our upper atmosphere in the
peculiar rhythms of the ^2 layer. Another item cited in
favor of this corpuscular theory is the behavior of the
ionosphere during the solar eclipse of June, 1936. As soon
as the Moon covered the face of the Sun, there was a
pronounced drop in the ion density of both E and FI layers,
suggesting that their source of ionization had been shut off.
But the ion density of F^ showed very little change.
Ultra-violet light travels at the speed of 186,000 miles a
second, and any interruption of its beams at the Moon's
distance should be felt in less than 2 seconds; whereas cor-
puscles, such as molecules or atoms, travel only a few
miles a second, and those already past the Moon would
require many minutes of travel to reach the Earth.
The corpuscular hypothesis is proposed by its authors as
a tentative explanation, subject to the testing of more
extensive observations. Recently they perfected an auto-
matic radio sounding device which is expected to provide
the more complete record that is wanted. This apparatus
is driven by a motor and operates continuously, twenty-
four hours a day. It transmits a series of signals of chang-
ing wave length, beginning at 18.8 meters and gradually
shifting to longer and longer lengths until 583 meters is
reached, whereupon it reverses and repeats the sequence.
Fifteen minutes are required to each series; therefore the
machine runs the gamut of its wave lengths four times
[40]
FRONTIERS OF EARTH
every hour. At the same time, a photographic device records
the reflections and other behavior of the waves. One of
these machines is now operating in the station near Wash-
ington, another at Huancayo, a third at Watheroo; and
others may be installed at strategic points on other con-
tinents. The idea is to obtain a continuous record of what
is happening in the upper air and this robot has shown
up in all tests as a peculiarly apt, dependable, and never-
sleeping observer.
4
The lowest ledge within the ionosphere averages about
70 miles above ground, and the highest occasionally reaches
300 miles. The material of this upper region cannot be called
air in the strict sense, for only the lightest atoms could
rise to such altitude, and perhaps only the lightest fragments
of these exist there; consequently the texture of this outer
atmospheric stuff is the thinnest imaginable. And yet,
rare as it is, the gas is hot. It bulges ever toward the Sun,
the author of its heat. Here, in this thin, hot, continually
changing bulge of electrification, is the radio's last barrier.
Any wave that can pierce it would be lost or so we
think.
But one night in 1927, J. Hals, a radio engineer of Nor-
way, was listening in Bygdo to code signals vibrated by a
short-wave sending station at Eindhoven, Holland. The
signals were coming through sharp and clear, when pres-
ently Hals became aware of a delayed echo. He timed the
echo and found a lag of 3 seconds. This was amazing!
Radio travels 186,000 miles a second; therefore a 3 -second
delay in the reception of the echo suggested that the wave
had traversed three times that distance or about 279,000
miles out and an equal span back. This is beyond the
Moon's orbit, and it seemed incredible that any wave
which had escaped that far could be reflected back to the
small target which is the Earth.
[41]
THE ADVANCING FRONT OF SCIENCE
Hals's announcement caused a stir, and preparations
were made for special tests. Signals of enormous strength
were propagated, so strong indeed as to be painful to the
ear; and to several listeners in northern Europe the echoes
came back firm and distinct some 3 seconds later, some
5, a few 15. A French eclipse party in Indo-China in 1929
reported hearing delayed echoes of 30 seconds time enough
for a radio impulse to travel more than 5 million miles.
Who can explain this mysterious effect ?
Appleton, of London, and van der Pol, of Holland, have
suggested that the delay may be caused by a trapping of
the radio waves in the ionosphere. Possibly the impulses are
caught between the changing layers of ions and oscillate
back and forth in their prison for a while, until some fluc-
tuation opens a way of escape and they bounce back to the
ground.
More attractive to the imagination is the hypothesis
proposed by Carl Stormer, the distinguished Norse geo-
physicist. Professor Stormer believes that the aurorae,
those flickering arcs and curtains of light which are familiar
sights in the polar skies, are caused by streams of solar
electrons impinging on the magnetic field of the Earth.
The fact that the Earth is a rotating magnet necessitates
that there be such a field, or peculiar configuration of space,
extending out from it and surrounding it; and the fact that
compass needles respond and point as they do is direct
evidence of the existence of the field.
Now, this magnetic field extends far beyond the atmos-
phere, possibly for hundreds of thousands of miles. It
operates to shield off from the equatorial and temperate
zones of the Earth the continual rain of electrons shot out
from the Sun, and causes these particles to flow in long
curving paths toward the two magnetic poles so Stormer
infers. Such a flow would constitute a continually moving
but fairly uniform electronic structure in the form of a vast
hollow ring surrounding our planet, a sort of vacuous
FRONTIERS OF EARTH
doughnut with the Earth at its center. The inner, opposite
surface of this hollow ring, according to Stormer, is the
distant mirror that reflects the echoes which Hals and
others have heard.
Neither of the explanations is free from serious criticism,
and science is still groping for light on this peculiar phe-
nomenon. A curious detail is the fact that the echoes have
never been heard in North America, though on several
occasions special signals have been sent on very powerful
transmissions, and delicate detectors have waited attuned
to pick up the echo.
5
An investigator in the United States has discovered what
may prove to be an even more significant gesture from Out
There. He is Karl G. Jansky, an engineer of the Bell Tele-
phone Laboratories. His work is centered at the short-
wave experiment station near Holmdel, New Jersey, where
three farms were bought and consolidated into a tract of
four hundred acres. Here radio researchers find elbow room
and sanctuary from interruption, and in this quiet retreat,
isolated from surface noises, they try to unscramble etherial
noises static, for example.
The familiar static that occasionally rasps its atmospheric
jazz into a Metropolitan Opera broadcast or, with equal
indifference, into the antics of a tooth-paste comedian
has been the subject of much study by a group of able
analysts of long-wave radio phenomena. But scarcely any
attention had been given to static affecting short-wave
reception until the present decade, when Jansky took up
the problem. In particular, the authorities needed to know
if the static came from a definite direction. To get at that
question Jansky rigged up an antenna on a rotating
platform.
G. K. Chesterton used to sponsor a precious notion to the
effect that useful devices of civilization originate as toys or
[43]
THE ADVANCING FRONT OF SCIENCE
playthings. Jansky's rotating antenna would fit neatly into
Chesterton's theorem, for here is a merry-go-round turned
to scientific research. The thing is 90 feet long; it rides on
wheels fitted to a circular track and is driven by a motor
which moves the frame so leisurely that 20 minutes are
required to make a revolution. All night and all day it
rotates, as constant as the Earth on the polar axis. And as
it thus inclines an ear to each point of the compass in turn,
a sensitive apparatus traces a continuous record of what-
ever is heard.
Soon after this scientific eavesdropping began, Jansky
recognized among his records three distinct kinds of static.
First, there were intermittent noises of the crash type which
were traced to local thunderstorms. Then, classed as a second
type, he heard a weaker but more steady crash-and-rumble,
attributable to discharges of distant thunderstorms whose
radiations are reflected from the Kennelly-Heaviside layers.
Finally, the third type, a steady hiss. The source of this hiss
was not obvious, and eventually all Jansky's attention was
concentrated on it.
The crashes and rumbles of the first and second types of
static might come from any direction, but the hiss betrayed
a definite point of origin, though the point progressively
changed during each day, and from day to day. It was as
though someone out in space were broadcasting messages
and at the same time were revolving round the Earth.
"It never quite completed the circuit, though," observed
Jansky, "but when it reached the northwest the hiss would
die, and at the same time a similar hiss from the northeast
began to make itself heard. This new source of static would
then gradually shift in direction throughout the day until
the northwest position was attained, when it died and so
the process repeated itself, day after day."
At first Jansky thought the Sun marked the direction of
origin of this mysterious signal, but as the year advanced
and the Sun changed its position among the stars, the static
[44]
FRONTIERS OF EARTH
did not follow it. Then the whisper seemed to proceed from
the point in the sky opposite the Sun, but again continued
observations showed that this was not so. Finally, evidence
pointed to the position of the Milky Way system of stars
as the direction; and subsequent observations and mathe-
matical analysis of the whole body of data confirm this.
The effect is weak. Only a sensitive apparatus can detect
it, but to this acute radio ear it is unmistakable. As soon
as the rotating antenna turns toward the Milky Way the
disturbance begins ; it grows in strength until the region of
the constellation Sagittarius is reached; after that it
weakens and gradually ceases as the opposite side of the
galaxy is reached. Since the Sagittarius region marks the
center of the Milky Way, and is believed to be the most
densely packed zone of our stellar system, it seems reason-
able to attribute the effect to the stars. Accordingly the
hiss has been named, "cosmic static."
Cosmic static is not to be confused with cosmic rays. The
latter are detected as an ionizing agency in vacuum tubes
and electroscopes, whereas cosmic static has made itself
known only as a wave attuned to a radio receptor of 14.6
meters. That happens to be the wave length of the antenna
used by Jansky in his discovery. A further investigation is
planned, to use antennae of various wave lengths. By
these means it should be possible to go up and down
the scale to find the limiting wave lengths within which the
cosmic static operates. While it manifests itself in the
detector as a wave, it may possibly be a secondary effect
caused by missiles of a corpuscular nature striking the
atoms of the upper atmosphere. Here is a rich and inviting
field for further research.
There is still another apparition, a luminosity of the
night sky that may be seen by the unaided eye. It is difficult
to detect when the Moon is up, or where there are street
[45]
THE ADVANCING FRONT OF SCIENCE
lights or the glare of a neighboring city; but under favorable
conditions, and especially in the spring, the effect becomes
visible shortly after sunset a faint band of haze arching
up from the western horizon. In the autumn it assumes the
same form in the eastern sky before sunrise. For centuries
this has been called the zodiacal light. On a very clear night,
particularly in the tropics, the zodiacal light may be traced
entirely across the sky as a luminous belt. And at midnight
the part of this belt which is overhead glows more brightly.
This more luminous patch is called the counterglow, or
gegenschein. But naming a thing does not solve its enigma,
and the zodiacal light and its counterglow have long been
an astronomical puzzle. Numerous theories have been ad-
vanced. They range all the way from Cassini's idea of a
cloud of meteoric particles surrounding the Sun to E. E.
Barnard's less spectacular idea of refracted sunlight.
But more recent, and particularly fascinating because of
the graphic picture of our planet which it presents, is the
hypothesis proposed by E. O. Hulburt as a result of his
study of the ionosphere. Hulburt, as I have mentioned
earlier, explains the ionosphere in all its layers as produced
by the bombardment of ultra-violet rays from the Sun.
He sees the zodiacal light as of a piece with these other
phenomena of the upper atmosphere. It too is an effect of
air particles electrified by the solar ultra-violet.
Originally, of course, our air particles are neutral, i.e.,
unsmashed molecules. But like the molecules of all gases
they are perpetually on the go, and as the atmosphere
heats under the Sun's rays the particles move faster, with
a general tendency to move upward. Many of them acquire
speeds that carry them through the sunlit FZ region and
far beyond, to distances 20,000 to 50,000 miles from the
Earth. But by the time they have attained these dis-
tances the solar ultra-violet has got in its work; practically
every air molecule is now ionized. Once ionized they are
charged fragments, and as such are trapped by the Earth's
[46]
FRONTIERS OF EARTH
magnetic field, their outward flight being checked by the
attractive forces of our rotating terrestrial magnet. There-
after the ionized fragments go wherever the force of gravi-
tation and the pressure of light take them. The combined
effect of these two forces is to cause the particles to drift
horizontally eastward and westward around the Earth and
finally, under the pressure of sunlight, to trail off in the
direction away from the Sun. Thus on the day side of the
Earth the particles never rise higher than about 50,000
miles, but on the night side they trail off into space, and the
sunlight whose pressure distends them also stimulates them
to fluoresce. Hence they are visible, and this stream of
visibility may extend into the Earth's night shadow for as
far as a million miles, according to Hulburt's computation.
Such then is the zodiacal light. This distended cloud of
electrified fluorescing particles is what we see after sunset,
and before sunrise, as the arching band of haze pointing
upward and away from the sunken Sun.
At midnight the distended cloud is directly above us, and
it is then that there appears at the zenith the brighter area of
the counterglow. The counterglow, says Hulburt, is only
the center of the cone of the zodiacal light seen from
below.
What a picture! Our "round and delicious globe"
attended by this thin cometlike tail a million-mile plume
of electrified particles that we trail through space as we ride
our annual circuit round the Sun at 19 miles a second, and
travel with the Sun toward Vega at 12 miles a second, and
partake of the rotational motion of the Milky Way in still
another direction at an estimated 175 to 185 miles a second.
One might think that, with all these motions to accom-
modate itself to, our plume of electricity might get bent or
tangled. But not so, says the theory: the persistent pres-
sure of light both creates and molds it; so the plume
always points away from the Sun, always trails the night
side of the Earth.
[47]
THE ADVANCING FRONT OF SCIENCE
Thus, according to physicist Hulburt, the zodiacal light
is the last vestige of the Earth's atmosphere. This outer-
most stuff of our planet is too thin and subtile to reflect
radio waves. Perhaps it may be thought of as dust from
the radio roof cosmic dust blown into space by the wind
of light that forever is rushing through the world. Perhaps
some of this far-driven Earth stuff is captured by a passing
planet or meteor. Or it may escape, to travel its own course
for millions of years solitary, relic of Earth, stuff for the
future, symbol of man adrift, tugged at by all the Universe,
beaten upon by all the radiant forces, but persisting some-
how in that unity of nature which makes the whole creation
kin man and stars.
[48]
Chapter III -THE SHINING
STARS
The Daughter: Still, the stars are shining.
The Uncle: Ah! stars that's nothing.
M. MAETERLINCK, THE INTRUDER
THE nature and behavior of the shining stars are be-
trayed by their invisible atoms, and lately these have
been telling some astounding facts of the stellar energy we
live by and the stellar universe we live in. Perhaps no
quarter century since Galileo's time has opened such astro-
nomical vistas for the mind to explore as has ours. New in-
struments of research, new methods of decoding the
messages that continually bombard us, fresh attitudes of
mind, and unconventional approaches to ancient enigmas
have given astronomy a golden age. Perhaps it is only a
prelude to what we shall have in the 1940*5 when the zoo-
inch telescope is safely poised on its mountaintop and the
Otherness beyond our present seeing becomes dominions
of man: this curious, prying, stumbling, aspiring, per-
sistently hopeful creature, half brute who clings to his
practical clod, half god who looks through distant light-
years where the stars are shining.
They shine by a mystery of motion which seems to under-
lie all things. It is exciting to realize that in a fiery tempest
of particles deep in the Sun the weather in our streets is
[49]
THE ADVANCING FRONT OF SCIENCE
forged, the green magic of chlorophyll is activated, and the
delicate rhythms of protoplasm, of consciousness, of mind,
are shaped. From the shining stars we learn of processes
of degeneration which issue at last in the massive, collapsed,
opaque, nonluminous lumps known as black dwarf stars,
the dark destiny that may mark the end of shining. Thus,
from present stellar news we read the past and are enabled
to peer somewhat into the future.
The news comes by one motion the motion of light rays
traveling at the constant rate of 186,000 miles a second
but the messages these vibrant signals bring are of three
kinds of movement: the motions of atoms within stars,
of stars within galaxies, and of galaxies within the Universe.
The motions of stellar atoms are detected by means of
the spectroscope. The heart of this device is a transparent
prism which breaks up light into its rainbow pattern of
colors; but in practice the prism requires a complicated
mounting of accessory apparatus, including a telescope
mirror or lens to collect and focus the light and a photo-
graphic plate or film to record the image. Some years ago
George Ellery Hale added still further auxiliary equipment
to the prism device, and, by an ingenious mechanical
arrangement, provided an apparatus which would show the
image of the Sun as seen in the light of a single one of its
incandescent elements. With Dr. Male's spectroheliograph
it was possible to make a photograph of the Sun in the
violet light of its glowing calcium, or in the red light of its
glowing hydrogen, or in the other tints that glow with
sufficient intensity in the solar crucible. Such photographs,
by shutting out other rays and giving a hydrogen view of
the Sun, or a calcium view, reveal details which are lost in
the tumult of mixed elements, each vibrating its distinctive
spectral colors. By means of Rale's device, moreover, it
was possible to eclipse the Sun artificially, and thereby to
[so]
THE SHINING STARS
bring into sight at will the great tongues of flame known as
"prominences" which continually lick out from the Sun's
edge. The existence of these solar flames was known long
before this time, and by opening the slit of the spectroscope
wide it was possible to observe an individual prominence.
But Hale's spectroheliograph added an important advan-
tage: with it the astronomer could photograph on a single
plate all the prominences flaring out from the solar disk at
a given moment, and thus obtain a complete record of the
Sun's encircling flames.
In the summer of 1936 still another advance in our
apprehension of star stuff was made by Robert R. McMath
and his associates of the University of Michigan. They
adapted Hale's apparatus to a motion-picture technique,
building for the purpose a huge movie camera in the form
of a 5O-foot tower at Lake Angelus, Michigan. By a reflec-
tion of sunlight from the clock-driven mirror at the top of
the tower, down to the lens at its bottom, and thence
through the spectroheliograph to the moving ribbon of film,
McMath and Edison Pettit (the latter from Mount Wilson)
obtained a series of pictures of the Sun in action action of
a sort that astonished the professionals of the American
Astronomical Society when the first public showing of the
solar movies was given at the society's dinner in Cambridge
in the autumn of 1936.
Here was a continuous record of the swift vicissitudes of
calcium gas in the Sun's hot atmosphere. Flaming streamers
were seen to form and lick upward, some of them for tens
of thousands of miles, others flaring horizontally along the
curving edge of our star like a vast prairie fire fanned by a
hurricane. There were successive fiery jets of matter
apparently shot out of sunspots or other disturbed areas,
dart after dazzling dart like the successive discharges of a
roman candle, spurting upward in long parabolas at 60
miles a second and faster. Most surprising of all were the
prominences that formed as luminous clouds in the high
THE ADVANCING FRONT OF SCIENCE
atmosphere of the Sun, to descend in falling streamers,
sweeping downward for thousands of miles toward the
surface. Other pictures showed prominences of hydrogen
gas, equally varied and spectacular.
"We knew from earlier studies that prominences must
change their form/* said Heber D. Curtis, introducing the
pictures to his fellow astronomers at the Cambridge meet-
ing, "but this is the first unbroken record of the processes
of development as they occur in the different types of
prominences. It seems out of the question now to regard
the pressure of light as the sole cause, or even as the most
important factor in such displays. The apparent start of
the clouds or streamers in the high atmosphere of the Sun
seems to argue some important contribution of electrical
action. "
Perhaps our star, like our planet, has its peculiar roof of
electrification. We know that the corona, the pearly crown
which is visible only at times of solar eclipse as a sur-
rounding halo, changes its form as the sunspot cycle waxes
and wanes. Sometimes it is an oblong arrowlike shape, as
though the forces which distend it were greatest along one
line of direction; at other times it is more nearly circular,
but always the outer edges are ragged and irregular.
Characteristically the brightness of the corona about equals
that of the full Moon. But at the 1936 eclipse, as photo-
graphed in Asia by the expedition from Harvard College
Observatory and Massachusetts Institute of Technology,
the corona shone with the brilliance of more than fifty full
Moons. Logically we should expect a variable star to have
a variable envelope.
Just how this envelope forms, and of what substance, is
unknown; but it is probably safe to say that in the corona
we see sun stuff at its thinnest, that here we have the outer
mists of the solar atmosphere. Suppose, in our asbestos-
clad imagination, we penetrate the corona and push
through it to the central Sun. We encounter denser and yet
[52]
THE SHINING STARS
denser concentrations of gas, and higher temperatures, until
we reach a level at which the solar material becomes opaque.
Ripples continually mottle this stratum, appearing as a
granulated structure whose perpetually undulating "rice
grains" measure more than 2000 miles across. The tem-
perature here is about io,oooF., generally known as the
surface temperature of the Sun. This turbulent "surface"
is still gaseous, however, and beneath it the density in-
creases and the temperature rises until we reach the center
of our star. The central temperature measures about
15,000,000 and it appears that practically all stars,
irrespective of their considerable differences in size, have
approximately this same central temperature, although
surface temperature varies from star to star over a wide
range. At the solar center the material is compressed to a
mass denser than solid metal. And yet, amazingly, this
central stuff is not solid, not even liquid it is a gas
throughout!
There was a time, not many years ago, when it was be-
lieved that the Sun is a liquid star. This idea arose from the
fact that if you take the mass of the Sun and proportion
it to the volume, you arrive at an average density about
one and a half times that of water. Other stars similarly
proportioned show an average density greater than that of
solid iron: the red dwarf known as Krueger 60 is an ex-
ample. Still others are yet more dense the white dwarf
Companion of Sirius has stuff so concentrated that it
averages about a ton to the cubic inch. At the opposite
extreme of stardom are the red giants such as Antares and
Betelgeuse enormous balloon like bodies with an average
density less than that of the Earth's atmosphere. Sir Arthur
Eddington found a certain relationship for the gaseous
stars a ratio such that if you know the mass of a star you
can determine its absolute brightness (or, if you know
its brightness you can determine its mass), and then from
these two values you may derive its other conditions and
[53]
THE ADVANCING FRONT OF SCIENCE
so describe the internal mechanism. One day, just to see
what would happen, Professor Eddington tried his formula
for gaseous stars on the Sun. He was surprised to find that
it worked. Then he tried it on the denser Krueger 60, and
again the mass-luminosity relation as prescribed by the
law agreed very closely with the observational evidence.
But this mass-luminosity relation could work only for
gaseous material; it had no applicability for liquids and
solids. There was just one reasonable conclusion: the Sun,
though denser than water, and Krueger 60, though denser
than iron, must be accepted as gaseous stars.
But how can a substance be so closely packed, so concen-
trated, and yet remain a mobile gas ? The secret, answer the
physicists, lies in the process of ionization that process
of atomic mutilation with which we are already familiar
from our studies of the Kennelly-Heaviside layers of our
atmosphere. Atom smashing facilitates atom packing. The
atom of iron, for example, a metal that exists in abundance
in the Sun, consists of a central nucleus surrounded by
twenty-six revolving electrons. The electrons move in
orbits at various distances from the nucleus. The distances
are such that if an atom of iron could be magnified until its
central nucleus became just visible (about the size of a pin
point), the outermost electron orbit would be about 6 feet
from that center. If you detached the two electrons which
travel this outermost path, your iron atom would be con-
siderably smaller, slightly mutilated, but still iron. If you
then removed the fourteen electrons which ride the next
outer orbits, you would drastically reduce the diameter of
the atom; but since the nucleus would remain intact, and
since the nucleus is the predominant determiner of atomic
character, this reduced structure would still be recognizable
as iron. Under extreme conditions it might be possible to
strip off the eight electrons of the next shell of orbits, and
leave a residue consisting only of the iron nucleus and the
two innermost encircling electrons a structure so small
[54]
THE SHINING STARS
that millions of such fragments could be contained in the
space that originally was occupied by the whole atom.
In addition to iron there are platinum, copper, sodium,
oxygen, helium, and fifty-five other chemical elements in the
Sun. All are subject to the pressures generated by the
gravitational effect of this huge aggregate of particles, each
atomic mass attracting its neighbor masses, and also subject
to the random movement which is characteristic of gas
particles. The greater the gravitational pressure, the heavier
is the crushing effect, the more violent is the agitation, and
in general the higher is the temperature. It is these processes
that cause atoms to bump head on, to knock particles out
of one another, to strip off whole shells of electrons in the
case of some, and to turn the interior of the Sun into a
turbulent mob of almost naked nuclei and free electrons.
Because they are so stripped they require less than normal
space, and, despite the excessive concentration, the particles
enjoy a freedom of movement sufficient to class them as a
gas. I have mentioned the Companion of Sirius, in which
the gas is so dense that it weighs a ton to the cubic inch.
Recently G. P. Kuiper studied another white dwarf star
of even more extraordinary properties. Its diameter is only
half the Earth's, but its mass is nearly three times the
Sun's which means that its material averages about 620
tons to the cubic inch. A penny minted of such material
would weigh more than a motor truck.
No eye can pierce the opaque undulations of the solar
body. But, knowing that the material is gaseous through-
out, and knowing by laboratory experiment what happens
to gases with increase in pressure and temperature, astro-
physicists are able to picture the tumultuous interior of the
Sun. They find that at 15,000,000 the gas will generate all
its radiation in the form of x-rays. And they can calculate the
congestion and the collisions that such temperature produces.
" Crowded together within a cubic centimeter there are
more than a quadrillion atoms, about twice as many free
[551
THE ADVANCING FRONT OF SCIENCE
electrons, and 20,600 trillion x-rays," reports Eddington,
and his units are of the British order which reckons a
trillion as a million million million. "The x-rays are travel-
ing with the speed of light, and the electrons at 10,000 miles
a second. Most of the atoms are hydrogen, or rather, since
they have lost their satellite electrons, simply protons [i.^.,
hydrogen nuclei] traveling at 300 miles a second. Here and
there will be heavier atoms, such as iron, lumbering along
at 40 miles a second. I have told you the speeds and the
state of congestion of the road; and I will leave you to
imagine the collisions."
The Sun thus may be likened to a huge x-ray tube. The
beneficent heat and light which flood from it through space
are simply the softened residue of such solar x-rays as
manage to escape. It takes only about 8 minutes for a dart
of sunlight to travel from the " surface" of the Sun to the
Earth, but that same dart may have caromed about within
the crowded interior for thousands and even millions of
years, repeatedly robbed of energy in its innumerable col-
lisions with atoms, until finally what started within the
dense central tumult as a short wave of invisible x-radiation
escapes as a long wave of blue, green, red, or some other
visible color.
The source of this energy we do not know positively, but
an increasing number of investigators are inclined to believe
it is by atomic synthesis, rather than by atomic annihila-
tion, that the solar x-ray tube is empowered. One-third of
the Sun's mass is hydrogen, which leaves the remainder to
be distributed among the sixty other known solar elements.
Perhaps there was a time when the proportion of hydrogen
was greater. Indeed, some theorists suggest that "in the
beginning was hydrogen," and that all the more massive
and more complicated atoms are the results of mergers of
hydrogen atoms. A hydrogen atom weighs 1.008 units.
Four hydrogens, weighing 4.032, may combine to form
one atom of helium. But by oft-repeated test it has been
[56]
THE SHINING STARS
found that helium weighs only 4.003, which means that
.029 of the hydrogens does not enter into the helium. What
becomes of it? The answer, say the physicists, is simple:
this surplus hydrogen stuff is transformed in the process
from mass into energy, and is radiated as an x-ray. Simi-
larly, sixteen hydrogen atoms (or four helium atoms) may
merge to make one oxygen atom, with an even larger dif-
ference in mass translated into energy. We believe it is in
such ways, by repeated fabrication and rebuilding of their
units of matter, that the stars continue to shine.
An important factor in these changes is the balancing of
two effects: the effect of gravitation, tending to contract
the star, and the effect of the outpouring radiation, oper-
ating to distend it. If the equilibrium is disturbed in one
direction, the star may expand. This response may be fol-
lowed by a contraction, and thus the star appears to
pulsate. With a more violent or more critical disturbance
of its balance, the star might even explode.
Most of the hundreds of thousands of stars that have been
studied appear to be in a state of fair stability, but there are
a few thousands that vary quite noticeably. Some of them
change irregularly. In October of 1936, for instance, the
second magnitude star Gamma in the constellation Cas-
siopeia increased its brightness 60 per cent within a day,
and then over a period of weeks slowly faded to normal
luminosity. Other variables are more regular, and the group
known as Cepheids appear to be true pulsating stars, alter-
nately brightening and dimming in fixed periods of hours,
days, and weeks.
Whether the upflare of Gamma Cassiopeiae represents a
thwarted explosion, or is preliminary to a future one, we do
not know; but there are other recent stellar events whose
explosive nature can hardly be questioned. Thus, during
1936, four faint stars within the Milky Way suddenly, over-
night, became very bright. One of these novae or new
stars, as they are called lighted up in June in the con-
[57]
THE ADVANCING FRONT OF SCIENCE
stellation Lacerta, the Lizard. The next appeared in July
in Aquila, the Eagle, and in September still another nova
burst forth in this same constellation Aquila. Finally, in
October, came the appearance of yet another new star in
Sagittarius. In each case, the star increased its output of
radiation by several magnitudes within a few days.
The nova in the Lizard was especially brilliant. Photo-
graphs taken a few hours apart showed the formation of four
successive shells of expanding gas, one moving 2200 miles a
second. The intensity of the calcium lines in the spectrum of
this star enabled J. A. Pearce, at the Dominion Astro-
physical Observatory in Canada, to measure its distance as
about 2600 light-years. Independently C. S. Beales made
the measurement at the same observatory, and Merrill
and Wilson did so at Mount Wilson, and all obtained the
same value. It is the past that we are studying in the light
of these distant orbs: the explosion which brought an un-
known star into conspicuous view of the Earth in A.D.
1936 really occurred centuries before Christ. Soon after its
discovery in June this nova showed as of the second
magnitude; but by the beginning of 1937 it had faded to
the tenth and could be seen only with the aid of a telescope.
There is much speculation as to what happens in these
gigantic outbursts, and what follows the fading of the star
to mediocrity. Do the shells of expanding gas escape from
the star? Or are they held by its gravitational influence,
perhaps to cool and condense into smaller bodies sub-
sidiary to the main body? Gustav Stromberg, of Mount
Wilson Observatory, has suggested that planets may be
condensed fragments of a nova explosion. "If this is true,"
says Dr. Stromberg, "a nova outburst is a signal that
construction work on new abodes of organic life has been
started." Perhaps a new Earth, destined after its geological
evolution to produce its peculiar flowering of life, was
spawned out there in the direction of the celestial Lizard
2600 years ago. It may be that our Sun too had its nova
outburst, in some remote past, and by the grace of that
[58]
THE SHINING STARS
catastrophe gave birth to Mercury, Venus, Earth, and the
other planets of the Solar System merely a surmise, but
interesting.
It is possible that an explosion such as produces a nova
may split the star in two, or at least break off a sizable part
of it. This seems to have happened to the nova which flared
up in Hercules just before Christmas of 1934. Watching
this magnificent luminary at Lick Observatory in the sum-
mer of 1935, Dr, Kuiper saw that the star had separated
into two pieces, one shining about half a magnitude brighter
than the other. With the 4O-inch refracting telescope at
Yerkes Observatory, George van Biesbroeck followed the
movements of these two large fragments over a period of
months. They continued to separate, and at the beginning
of 1937 the distance between them was more than two hun-
dred times the distance of the Earth from the Sun. It is
possible, of course, that we are witnessing here the birth
of a double star, but many astronomers are inclined to
doubt this. They think that the "companion" which is
about half a magnitude fainter than the other is really a
smaller mass of gas at high temperature i.e., a part of the
ejected material and that the main body of the star re-
mains intact.
A more plausible theory of the birth of double stars
attributes the event to the capture of one star by another.
Similarly, a nova has been explained as the result of a near
approach of two stars.
The light rays which report these far-off events, remote
in time as in space, tell the temperatures, the nature of the
agitated gases, their tumults of atomic action and reaction.
But as to causes of these catastrophes their messages are
less definite. And we are left to speculate.
Superficially, the motions of stars through space appear
to be almost as random as the motions of atoms and
electrons within a star. Each of these shining bodies seems
[59]
THE ADVANCING FRONT OF SCIENCE
to have its individual direction of going: some advancing,
some receding, some heading eastward, others westward,
still others along diagonal paths. Many are traveling alone,
like the free electrons in the stellar interior. Others are mov-
ing in couples as double stars, or in families as clusters of
many stars. The velocities range all the way from the Sun's
12 miles a second, and even slower for a few sloths, to 700
miles a second for a swift giant in Cepheus, the King. In spite
of these diverse directions and velocities, the stars do not
barge off into outer space. They appear to be held by some
primal law into a unified system, the swarm which the
Greeks named the Milky Way. One of the great detections
of our time is the discovery that the vast swarm itself
turns in a whirlpool motion of rotation.
Rotation, it would seem, is a universal principle of
physical nature. The electrons within atoms spin on their
axes as they revolve round their central nuclei, and there is
evidence that the nuclei also rotate. The Earth, as it travels
its orbit round the Sun, imitates the rotating electrons, and
so do the other planets. We know by observational tests
that the Sun rotates. By virtue of the Sun's rotation and the
revolutions of the planets, each at its individual velocity,
the Solar System continually turns as it plows its course
through space in the gravitational grip that directs it. And
now we detect, amid the medley of apparently random
stellar motions, this overruling systematic motion of
rotation round a dynamical center.
We have found, first by Harlow Shapley's researches,
later confirmed by others, that this center lies in the direc-
tion of the great star cloud in Sagittarius.
We have measured the velocity of the rotation, guided
by the theory of B. Lindblad of Sweden, tested by the ob-
servations of J. H. Oort of Holland, then confirmed and
extended by the more numerous observations of J. S.
Plaskett and J. A. Pearce of Canada. Just as the planets
move round the Sun at velocities which vary with the dis-
THE SHINING STARS
tance, the nearer' the planet the faster its speed, so do the
stars move round the dynamical center of the Galaxy. At
the Sun's distance from the center, the rate appears to be
about 175 miles a second some authorities say 185. And
the period of rotation of the system is 225 million years it
takes that long for the Milky Way to make one turn.
Most of these findings rest on actual measurements of
individual stellar motions. The rotational effect is not dis-
cernable in the light of near-by stars but becomes more
apparent as the distances increase. Because of this our sur-
veyors have confined their search to beacons not nearer than
1000 light-years, Oort had measurements for about 300
such stars; Plaskett and Pearce clocked the speeds of about
850 others. Thus, close to 1200 star records were available.
Their testimony was remarkably unanimous. Each showed
a motion which spoke of the Milky Way rotation.
But our Galaxy contains millions of stars. According to
the estimate of Frederick H. Scares, made at Mount Wilson
Observatory on the basis of counts of stars in representative
regions of the skies, the Milky Way aggregate must be not
less than 30,000 million stars and may be 40,000 million.
But whatever the luminous population of the Milky Way
may be, it is certainly many thousands of millions and
what are 1200 measured stars among that multitude?
Astronomers wish to extend their evidence. They want
thousands instead of hundreds of witnesses. And they
are eager for news of yet more distant members of this
celestial swarm. Recently, at the Harvard College Observa-
tory, Bart J. Bok and S. W. McCuskey put to use an
improved technique of measurement which should add a
thousand stars a year to our list, and swiftly accumulate the
fuller data which the galactic surveyors desire.
Bok and McCuskey's method is not so much new as it
is a refinement of a proposed extension of an old method.
In the old method, a telescope is focused on a star, and the
light from the star is then passed through a prism and
[61]
THE ADVANCING FRONT OF SCIENCE
spread into its spectrum. Meanwhile, light from some source
in the laboratory is also passed through the prism, and both
the spectrum from the star and the spectrum from the
laboratory are photographed on the same plate. If the lines
of the stellar rainbow do not coincide in position with lines
of the corresponding element in the laboratory rainbow, the
astronomer concludes that the star is in motion approach-
ing, if the displacement is toward the violet end of the
spectrum; receding, if toward the red. For distant stars
the work is tedious. Hours and sometimes days are spent
getting a legible record from a single star.
Some years ago E. C. Pickering, G. E. Hale, and F. L. O.
Wadsworth suggested a variation in this strategy. Instead
of directing the light from the telescope into the prism,
place the prism in front of the telescope lens and take a
photograph of the result at the focus of the telescope. In
this way, the light of all the stars within view of the
telescope is first passed through the prism, and each
stellar image is separated into its spectral lines before it
reaches the lens. The resulting photograph shows not one
spectrum, but many one for each star in the field and
in this way as many as 200 stars have been spectrographed
at the same time on a single photographic plate.
But the problem is not only to get the spectral images of
stars, but also to add a laboratory spectrum to each
stellar spectrum so that the shift of the lines may become
apparent. R. W. Wood pointed out that there are certain
chemicals neodymium compounds, for example which
might be used to provide the comparison. And it is this
chemical device that the two Harvard astronomers, Bok
and McCuskey, put to such successful use in 1936.
They placed their prism in front of the telescope lens, as
described. And behind the lens, in front of the photographic
plate, they placed a thin glass cell containing a solution of
neodymium chloride. This liquid, although it is transparent
to most rays, has the faculty of absorbing certain wave
[62]
THE SHINING STARS
lengths of starlight, and the effect is to add a few dark lines
or bands to the star spectrum. These additions, because of
their stationary origin, show no shift. By this means there
is photographed with each stellar image the comparison
which tells whether the star is approaching or receding.
Already Bok and McCuskey have accumulated important
new records, and the program they have mapped out and
are now pursuing promises much valuable news of how the
stars move in our celestial whirlpool.
3
While astronomers are using these and other ways to
extend their data to more numerous and yet more distant
beacons, the physicists have applied another method of
testing the rotation. This newly discovered physical evi-
dence is the varying intensity of cosmic rays. There has
been considerable controversy among the experts as to
the nature of cosmic rays; but whatever the outcome of
that debate may finally be, there is hardly any difference
of opinion as to the general place of origin of the mysterious
radiation. All evidence points to a source outside the Milky
Way.
If the source is outside, and if our Milky Way is rotating,
then the bombardment should be more intense from the
direction toward which we are turning just as a man
running in a rain will get more raindrops in his face than on
his back. So reasoned Arthur H. Compton and I. A. Getting,
and they proceeded to look for evidence.
Our position in the Milky Way is such that as the Sun
sweeps along its course round the distant center, it seems to
move in the direction of the constellation Cygnus, the
Swan though, to be sure, Cygnus too is moving in the
same whirl. But Cygnus is in the northern skies; therefore
the direction of our rotational movement must be northerly.
This should mean that more cosmic rays beat upon the
northern hemisphere of the Earth than upon the southern,
THE ADVANCING FRONT OF SCIENCE
and observations recently published report that such is the
case.
But the Earth, as it is swung along the vast curving
race-track of stars in tow of the Sun, is also turning on its
axis, continually exposing a different area to Cygnus.
When we see Cygnus overhead we are looking toward the
direction of our galactic rotation, and at that moment the
cosmic radiation should beat into our faces with an inten-
sity greater than at any other time. Recent tests with super-
sensitive detectors indicate that this is the case. There is a
daily variation in the bombardment of cosmic rays, and
its intensity at any station in the northern hemisphere is
greatest when Cygnus is overhead, least when Cygnus is
on the opposite side of the Earth. South of the equator the
northern constellation is never directly overhead; but at
Capetown in South Africa it rises slightly above the hori-
zon, and measurements made there show that at this
moment when Cygnus is in view the cosmic-ray intensity
for that region is at its height. Not only has this difference
been measured, but it provides an additional index to the
velocity of the Milky Way rotation. This figures about
185 miles a second, from the cosmic-ray measurements
a value which is in fair agreement with the astronomers'
findings from the direct evidence of the stars themselves.
An additional argument for rotation is the fact that
there are outside systems, other swarms like our Milky
Way, and the spectroscope shows that the nearest of them
are in rotation. The light from the more distant ones is too
faint to give the effect, but the spiral and elliptical shapes
of these outside systems are such as to suggest rotation,
and many leading authorities are inclined to believe that
whirl is a normal and universal attribute of galaxies.
Planets rotate, stars rotate, galaxies rotate. Does the
Universe also rotate? Possibly. It may be that the whole
sphere of space-time, with its millions of included galaxies
and the invisible stuff between the galaxies, is itself the
THE SHINING STARS
supreme whirlpool. But of such motion, if it exists, we have
no evidence, and the suggestion remains a conjecture.
There is, however, an apparent motion of the galaxies
through the Universe, and certain observations have been
thought to point to a remarkable uniformity in the direction
of this motion. Let us turn to the evidence.
[65]
Chapter IV S K I E S ARE
REDDENI NG
Their red, it never dies.
HENRY AUSTIN DOBSON
PERHAPS the most publicized theory of the world as a
whole is that suggested by the picture of the expanding
Universe a phrase and an idea which have been broadcast
by public lectures, radio, newspapers, magazines, and books
to every nook and cranny of literate civilization.
Who has not heard of the famous red shift the curiously
unanimous trend of the light of the distant galaxies when
it is passed through a prism? The picture which the red
shift suggested was of the Universe in process of dispersal:
innumerable galaxies all rushing away, or being carried
away by the distension of the cosmic bubble. It was as
though the Universe were exploding, scattering itself out-
ward at a rate which increased with distance, doomed to an
ultimate acceleration at which its parts would be traveling
with the speed of light, each part thereafter invisible to all
the others. The most generally accepted theory of the ex-
panding Universe predicted this sort of end and still
predicts it.
But late in 1936 and early in 1937, astronomers of Mount
Wilson Observatory began to publish details of an analysis
of the evidence which casts doubt on the reality of the
[66]
SKIES ARE REDDENING
expansion, and makes it necessary to reconsider the whole
problem of the meaning of the red shift. This startling
announcement from the mountaintop in California has
come like a bombshell into the camp of the theorists and
is providing a major topic of conversation among astron-
omers, cosmologists, mathematicians, physicists, and other
universe explorers. Though it concerns the vastest subject
of which the mind can conceive, the nature and behavior
of the Whole, and though it makes use of the powerful and
highly specialized technique of mathematics to reach its
conclusions, this new critical attack is quite picturable. The
present chapter will attempt to outline in familiar terms
what the red shift has been thought to mean, and why the
accepted interpretation is now called into question.
That there is a red shift no one denies, for the evidence is
photographic, measured, and consistent throughout. Ex-
cept for a few galaxies in our immediate neighborhood,
which may constitute a local group or association of Milky
Ways with motions of their own, all the hundreds of others
from which it has been possible to obtain a spectrum show a
displacement of their lines toward the red. In studies of
individual stars, this shifting of spectral lines has been
accepted as evidence of motion of the stars. Thus, one
reason why we believe the Sun rotates is the fact that the
light from its western limb shifts toward the red, indicating
that the western edge of the Sun is turning away from the
observer, while the light from the eastern edge shows a
displacement toward the violet, indicating a motion of
approach. The other stars are too remote to show their
images as a rotating disk in even the largest telescope, but
from the displacements of their spectral light it has been
possible to detect the general motions of approach and
recession for thousands of stars. This interpretation of the
THE ADVANCING FRONT OF SCIENCE
effect is the basis of the method of Bok and McCuskey in
their current survey of the motions of distant stars of our
home system.
The reason why these shifts of light are accepted as
evidence of motion is simple. Just as a receding locomotive
tends to pull the vibrations of sound from its whistle into
longer waves, causing the departing whistle to howl with a
deeper bass note than the whistle gives when the locomotive
is standing still, so does a receding star tend to pull its
vibrations of light into longer waves. But a prism is less
able to bend long waves than short ones. Therefore, when
the light from a receding star is passed through a prism, its
characteristic lines of color and shadow are not bent so
obliquely as they would be if the star were stationary. In
practice, the astronomer selects certain spectral lines as
landmarks and centers his attention on them. There are
two bold lines generated by glowing calcium gas, known
as the H and K lines of calcium, which appear in the light
of practically all stars. Characteristically these lines fall in
certain places in the violet region of the spectrum, and when
the calcium light is generated in the laboratory or from some
other stationary source the H and K lines are always found
in these standard positions. But when a star which con-
tains calcium is moving away, outward bound, the waves
of its calcium rays are lengthened, the prism is less able to
bend them, and they fall upon the photographic plate to
the redward side of their accustomed positions on the scale.
The faster the star is receding, the more drastic is the
lengthening of its wave lengths, and the more redward is
the position of the photographed lines. By measuring the
amount of the shift, the astronomer is able to gauge the
velocity of recession of departing stars, such as Aldebaran,
Betelgeuse, and Capella. Similarly, by measuring the
extent of a violetward shift, the astronomer may deter-
mine the velocity of approach of oncoming stars like
Antares, Sirius, and Vega.
[68]
SKIES ARE REDDENING
In the catalogue of stars there are about as many violet
shifts as there are red shifts. Indeed, as I have said, the
individual stellar motions appear to be in every direction.
But in the roll call of the galaxies the vote is not divided;
it is practically unanimous. Except for a few members of
the local group, all of which lie within a million light-years
of the Earth, the reds have it. From the outer systems,
every single spectrum shows a shift toward the red.
It is this unanimity of the effect that caused many
astronomers to question the interpretation. Might it not
be that space has an influence on light, that light degener-
ates with age just as other things do, that reddening is a
consequence of something that happens to the rays in their
millions of years of flight through millions of millions of
miles of the void ?
Physicists, and particularly those physicists who concern
themselves with stars, have been reluctant to admit this
latter hypothesis. For if a flight of 100 million years affects
a ray of light in a certain way, is it not reasonable to think
that a flight of a million years would affect it perhaps a
hundredth as much, and a flight of 1000 years or 10 years
or 10 minutes would similarly affect it proportionately?
Such questions are disquieting, for our physical world
picture is based on the idea of the inviolability of light.
The ruggedness of rays, their ability to endure time and
perform motion without degeneration, is a cardinal prin-
ciple of physics. It is recognized, of course, that an en-
counter between a light ray and an atom or other particle
of matter may have violent consequences. Invariably, in
such collisions, the light is robbed of some of its energy,
and in extreme cases its quantum may be absorbed entirely
by the particle of matter. But assuming no collisions,
assuming that in traversing the void between the galaxies
and between the stars the light escapes these encounters,
science has held that a quantum could travel any distance
without internal deterioration. The theory of relativity is
[69]
THE ADVANCING FRONT OF SCIENCE
built on the idea of the constancy of the velocity of light.
And now to question the constancy of the energy of light,
to suggest that light may tire or grow decrepit with age,
seems to threaten the foundations. It seems to open the way
to a flock of doubts and uncertainties.
But science supremely is the art of entertaining doubts of
beliefs experimentally accepted. No truth is sacrosanct. No
belief is too generally approved, too well established by
experiment, to escape the challenge of doubt. And no
doubt is too radical to receive a hearing if it is seriously
proposed.
Quite early in the discovery of the red shift of light
from the distant galaxies, doubts such as these were ex-
pressed as to the meaning of the effect. The shifts were so
much more pronounced than those of individual stars, indi-
cating velocities of thousands and even tens of thousands of
miles per second, that there were several critics who said at
once that the red shift might mean something other than
motion. But the doubters were silenced by the retort of
the theorists who found that the reddening effect fitted in
quite neatly with their ideas of the behavior of the Universe.
For, according to the general theory of relativity, the
Universe cannot stand still. Given such and such condi-
tions, it must either expand or contract. Some of the
experts held that it would first expand and then contract, a
pulsating Universe. Others held that the expansion was an
irrevocable tendency, that the world bubble must con-
tinually blow up with a perpetual scattering of the gal-
axies. There were dozens of hypotheses, each distinguished
by some detail, but all grounded on the assumption that
the photographic record of the red shift was evidence of
the runaway motions which theory predicted.
In 1934 a practicing astronomer, Edwin Hubble of Mount
Wilson Observatory, and a theoretical physicist, Richard
C. Tolman of California Institute of Technology, collabo-
rated in a new attack on the problem. Up to that time, the
[70]
SKIES ARE REDDENING
only observational evidence cited in support of the expan-
sion was the red shift. Theory called for such a shift, and
the presence of the shift was accepted as a proof of the
theory. But theory also called for a uniform distribution of
the galaxies. It was only in a world where the star systems
were scattered with approximate regularity that they
could move in this systematic way. And so Hubble and
Tolman turned from the photographs of the spectra to the
photographs of the galaxies themselves, to see if the assump-
tion of uniform distribution was supported by the actual
counts. A preliminary announcement of this study was
published by the two investigators in 1935, and more de-
tailed and conclusive reports by Hubble in 1936 and 1937.
The findings may be summarized quite simply.
Five carefully calibrated surveys of the northern skies
have been made one at Lick Observatory with its 36-inch
Crossley reflecting telescope; the others at Mount Wilson
Observatory, two with its 6o-inch reflector, and two with
the loo-inch reflector. Each telescope has its limiting dis-
tance for the kind of photographic plate used and the
length of time of exposure, and the problem was to find
how the brightness of the galaxies dimmed with dis-
tance. There is a law of optics which tells how it ought to
dim, all other factors being equal, and thus by counting the
images and classifying them according to magnitude one
should be able to learn whether the spacing of galaxies
thinned with increase of distance, or became more crowded,
or remained uniform.
Altogether 888 satisfactory photographs were obtained,
each representing a sampling of the heavens in a particular
sector. Each photograph showed the images of many gal-
axies, ranging from the bright and comparatively near ones
to the faint and remote. In this way a total of 41,069
significant galaxies were recorded. These were plotted as a
[71]
THE ADVANCING FRONT OF SCIENCE
chart of diminishing magnitudes, or brightness, rated
according to distance.
But the raw records, as measured directly from the photo-
graphs, do not represent the actual state of affairs. For our
chart to approximate reality, certain corrections must be
made; specifically, two kinds of corrections.
1. There are inevitable instrumental limitations: those of
the atmosphere, those of the mirror and other optical parts
of the telescope, and those of the photographic plate. Each
has a distorting influence on the image as recorded. Thus,
in passing through the Earth's atmosphere, the light from
the distant worlds is subjected to a certain probability of
collision and scattering, and in these encounters the longer
waves of red light fare better than the shorter waves of
blue. It follows that since proportionately more long waves
get through to the telescope, the image received there is
less brilliant than it would be if the telescope were poised
in space above the atmosphere and so enabled to receive
all wave lengths equally. Then, too, there is a selective
effect in the mirrors and lenses of the telescope. Silver,
which until recently was used almost universally as a coat-
ing for telescope mirrors, reflects very poorly the rays at
the violet end of the spectrum. And while the new form of
surfacing, aluminum, is an improvement, still even here
there are certain lapses of reflection that must be measured
and accounted for in this painstaking appraisal of the
brightness of the remote galaxies. Not only the atmosphere
and the optical parts, but also the photographic plate
chooses certain wave lengths and rejects others a selective
sensitivity that no careful measurer can afford to ignore.
Each of these three instrumental limitations is tested
experimentally, calibrated by exact laboratory trials, and
then applied to rate the images at the brightness they
would show if instruments were perfect.
2. But even if instruments were perfect and trans-
mitted all light rays without distortion, there is still a cor-
[72]
SKIES ARE REDDENING
rection inherent in the light itself a correction that must
be made to care for the changed energy of the light. For,
although the longer wave lengths of red are more successful
in penetrating the atmosphere than are the shorter wave
lengths of blue, the redder light is actually endowed with
less radiant energy. Therefore, an image of an object pro-
jected with red light will appear not so bright as an image
of the same object projected with blue light. But we know
that the true image of a distant galaxy is bluer than that
which appears in our corrected photographs because the
H and K lines generated by its violet calcium light show
their redward shift, revealing that their rays arrive with
less energy than they carried at their start. It is clear from
this analysis that the images we receive are less brilliant
than they would be if there were no red shift. Therefore,
this energy effect must be reckoned for each galaxy and the
magnitude of its image changed accordingly.
All these minute details were very carefully investigated
and measured by Hubble and Tolman. And when they
were applied as corrections, the chart of magnitudes
assumed a form which declared the distribution to be uni-
form. Former discrepancies disappeared. The counts now
indicated that the galaxies dimmed at a rate that was
approximately constant, suggesting that these huge stellar
swarms are scattered fairly evenly through space. Here and
there clusterings are found, and in these clusters of galaxies
the density exceeds the average. But on the whole Hubble
reports that the Mount Wilson samplings, reaching to a
distance of about 400 million light-years, show a reassuring
uniformity, with the galaxies spaced on the average about
2 million light-years apart. All this agrees with our common-
sense idea of a harmonious, balanced Universe. Also it is
in accord with the relativists' idea of an expanding Universe.
But, hold a moment. If we are to assume an expanding
Universe, there turns out, say Hubble and Tolman, still
another correction that must be made. For if these distant
[73]
THE ADVANCING FRONT OF SCIENCE
objects which we see in our photographs as faint spots of
light are all running away from us, then their outward
motion must affect the quantity of light which reaches us
from them. The number of light units, or quanta, received
from a receding body in a second of time must be less than
the number from a stationary body. Therefore we revise
our ratings to care for this third correction:
3. The number effect. This effect may be computed from
the velocity of the object. One of the photographed gal-
axies has a red shift so considerable that its velocity of
recession figures about 25,000 miles a second assuming,
as we are here, that red shift is an effect of recession. This
velocity is more than an eighth the velocity of light, and it
is only a problem in computation to reckon the number of
quanta per second that would be subtracted from the
normal number by such a speed of withdrawal. There are
other galaxies with red shifts which indicate velocities of
15,000 miles a second, a speed of withdrawal which would
affect the number of arriving quanta by its proportionate
smaller amount. And so with galaxies of lesser shifts,
indicating lesser speeds of recession: each can be calculated,
the number effect arrived at quite exactly, and the correc-
tion applied.
Let us make sure that we understand why this latest cor-
rection is necessary. If a distant luminous body is broad-
casting 1000 million quanta from a certain unit area of its
surface each second, and if only 900 million quanta reach
us, it is inevitable that the photographic image which the
900 make will be fainter than the image which the full
1000 would have made. Thus, the image we receive is less
luminous than it should be to represent the actual bright-
ness of the galaxy. Since faintness is the criterion of dis-
tance, and since the extent of the red shift increases directly
with the distance of the object, it follows that we have been
rating the remote galaxies as more distant than they
really are. Assuredly, then, the correction for the number
[74]
SKIES ARE REDDENING
effect must be made. And so we accept it, altering the
brightness of our objects, and changing their distances
accordingly.
What follows is a shrinkage of our scale. The correction
draws the galaxies nearer to us, the more remote the object
the more considerable is the reduction of its distance, and
thus we attain a corrected density which assumes a dif-
ferent arrangement from the comfortable reassuring com-
mon-sense density of uniform distribution.
Thus corrected, our astronomical photographs disclose
a curiously unbalanced world. The distribution of matter
grows more dense with distance, the spacing between the
galaxies dwindles, the emptiness fills in, the star systems
increasingly gang closer and closer together a strange,
lawless, unaccountable Universe which no authority is
willing to accept.
3
Dr. Hubble points out that the fantastic picture may
be avoided, and the results interpreted within the theory of
the expanding Universe, if we assume that space is sharply
curved. The increased crowding of the galaxies with dis-
tance may then be explained as a relativity effect, the
curvature of space causing the galaxies to appear more
concentrated than they really are.
But such an assumption involves other considerations.
This idea of curved space is quite fundamental to the
theory of relativity; for relativity holds that space indeed
is curved by the gravitational influence of the matter which
it contains, and that the greater the mass of the matter
the greater is the curvature. If there were no matter,
there would be no curvature. The fact of curvature indi-
cates the presence of matter. And from the degree of
curvature the density of space, i.e. y its content of matter,
may be computed. Hubble calculates that if the total
matter of the Universe be assumed to average the one-
[75]
THE ADVANCING FRONT OF SCIENCE
hundred million million million millionth (io~ 26 ) part of a
gram to each cubic centimeter of space, then the curvature
would be such that the red shift would operate about as we
see it, the apparent increase of crowding with distance would
be resolved as an illusion and the distribution made uniform
again, and thus the strange picture would be reconciled.
Although Hubble's calculated density may seem to be a
very small fraction, it is really an enormous increase over
the densities previously assumed. For such a density to be
actual, it is necessary that the Universe contain vast
quantities of nonluminous material. Indeed, by his reckon-
ing, the invisible dark stuff must be a thousandfold more
than the luminous stuff of stars and nebulae which we see
as making up the galaxies. We know that there is non-
luminous material in the spaces between the stars. Several
years ago thin mists of sodium and calcium atoms were
detected floating through the interstellar wastes, and
recently Walter S. Adams and Theodore Dunham dis-
covered titanium atoms also among these diffuse wan-
derers. We know of yet denser clouds of nonluminous
material they have been sighted as a fog of dust obscur-
ing the central girdle of our Milky Way and appearing as
obscuring belts encircling some of the outside galaxies.
But this dark dust cannot account for the huge surplus of
mass that is needed to curve space according to the new
computation, for the dust very markedly obscures light.
Since the light from the distant galaxies gets through
without noticeable obscuration, the unknown material that
we seek in the darkness must be of such size and in such
condition that it does not absorb light. Conceivably the
nonluminous matter may exist in concentrated form, in
chunks or large fragments; and of course there are the
highly condensed black dwarf stars which we are just
beginning to recognize and which may exist in large
numbers. It is not impossible that the invisible contents
of space may outweigh the visible a thousandfold.
[76]
SKIES ARE REDDENING
All these assumptions might be acceptable to the expan-
sionists, but for one item. Hubble finds that the radius of
curvature of a world as dense as he has calculated would
be a matter of a mere 470 million light-years. And that is
almost inconceivably small. In 1934, guided by the actual
observations of the distribution of galaxies in representa-
tive samplings of space, Hubble estimated the radius to be
3000 million light-years. It is this sharp reduction of the
scale, this shrinkage to about a sixth its former value, that
makes the 1936 findings so astounding to all cosmologists
and so challenging to the relativists.
Does Hubble's small-scale model represent the real
structure of the Universe ? Not necessarily he has pro-
posed an alternative solution but if we accept the red
shift as a result of receding motion, it is the only model
that fits the conditions. To quote Dr. Hubble: "If red shifts
are velocity shifts, the model is closed, small, and dense.
It is rapidly expanding, but over a long period the rate of
expansion has been rapidly diminishing. Existing instru-
ments (the loo-inch telescope, for example) range through
a considerable fraction of past time since the expansion
began. "
In other words, if the red shift means expansion, the
Universe must be a very small system of which we have
already glimpsed a large part.
But suppose the red shift means something other than a
velocity. Suppose we abandon the idea that this curious
behavior of light, which tells so much of the motion of our
stars, is giving us the same sort of information regarding
the motions of outside galaxies. Grant that we have no
certain evidence of recession of these remote bodies. Then
that third correction the number effect, which caused all
this seeming nonsense becomes unnecessary. And the
uniform distribution which we found at the end of our first
two sets of corrections is restored. With no clue to the
reason for the red shift, we can no longer cite any observa-
[77]
THE ADVANCING FRONT OF SCIENCE
tional evidence for expansion, we can find no trace of cur-
vature, no limitation of space, no restriction of the time
scale. "The sample, it seems, is too small to indicate the
type of Universe we inhabit." For all we know, then, the
Universe may be infinite in extent, ageless in time, and
subject to "some unknown principle of nature " which
eternally shifts fossil light toward the red.
4
These two solutions have been proposed by Dr. Hubble
as alternatives. And while he is not committed to either of
them, he admits that in the present state of knowledge the
second solution seems the more promising approach to the
problem. The expanding model, with its small, dense, closed
Universe, involves many improbabilities and seems less
plausible than the suggestion of an unknown immensity
of which we have sounded only an insignificant sample and
in which there is yet to be discovered the "unknown prin-
ciple" which mysteriously reddens our skies.
Other authorities also indicate a tentative preference
for the second solution, but with a reasonable caution. In
the opinion of H. P. Robertson, as expressed in a report
to the Physical Colloquium at Princeton discussing Dr.
Bubble's preliminary announcement, the second alterna-
tive would seem easier to reconcile with the facts now
before us provided there were any experimental or theoretical
grounds for believing that light is subject to fatigue. The great
difficulty, of course, is that no such grounds are known.
But apart from this, and quite independent of what the red
shift may finally prove to mean, the general theory of
relativity stands established by many experimental tests.
As long as relativity is accepted as correct, and as long as
the evidence points to a sensibly uniform distribution of
matter in space, one is necessarily led to one model or an-
other of the several types of "expanding universes"
broached by Alexander Friedmann on theoretical considera-
[78]
SKIES ARE REDDENING
tions in 1922. This was before the strong evidence of the red
shift had accumulated; indeed, Friedmann arrived at his
conclusions without knowledge of the red shifts. We may
therefore say that a world picture which was derived from
sound theory in 1922, without the assistance of observa-
tional evidence, and later was supposedly confirmed by the
discovery of the evidence of the red shift, does not neces-
sarily fall when the assurance of the evidence is questioned.
One of the details found by Hubble in his first alternative
the small, dense, closed model, with the red shifts
accepted as measures of velocity is that the rate of ex-
pansion has been rapidly slowing down. From the data
given in Hubble's preliminary report to the National
Academy of Sciences, Robertson has derived a tentative
estimate that the present age of this small-scale Universe is
probably less than 1000 million years. This is a cramped
time-scale for a world in which the Earth is rated as thou-
sands of millions of years old and the stars as yet older.
If the smallness, youthfulness, and other anomalies of
this dense closed model compel us to abandon our cus-
tomary interpretation of the red shift, we have left at
present no way of choosing among the various proposed
types of expanding universes or even between them and
the static universe first suggested by Einstein in 1917. The
dilemma, therefore, is more complicated than appears at
first sight in Dr. Hubble's two alternatives. If we reject the
curiously small, youthful, closed model, with its remark-
ably high density of matter, to accept a postulate of tired
light, we have to accept also the idea that this light is
propagated in a Universe which may be expanding in any
one of several ways without our being able to test it by any
physical means now at our disposal.
But present limitations may be springboards for future
accomplishments. The 2OO-inch telescope mirror is in
process of being ground in Pasadena. Its massive metal
mounting and mechanism, precise and responsive to the
[79]
THE ADVANCING FRONT OF SCIENCE
hundredth of an inch, is in process of construction in
Philadelphia. Its foundations are already being prepared on
Mount Paloman The great mirror will have the light-
gathering power of 1,000,000 human eyes. It should pene-
trate more than 1000 million light-years. By 1940 it will
sweep the skies, surely to break through many barriers
possibly to push out into a vaster world than even our
imaginations dream or, it may be, to prove that the
small, dense, closed world is indeed the Whole.
Meanwhile, some penetrating thrust of theory, some
adroit mathematical countermarch, may resolve the diffi-
culty in advance of the instrument.
[so]
Chapter V-THE ENCIRCLING
DARKNESS
I feel and seek the light I cannot see.
- S. T. COLERIDGE, IL 2APOLYA
INSTRUMENTS such as the loo-inch telescope now on
Mount Wilson, or the 2OO-inch now under construction
for Mount Palomar, might prove to be rather embarrassing
"white elephants " were it not for the auxiliary equipment
which extends the reach of the telescopes and gives in-
creased effectiveness and permanency to their seeing. We
need more than telescopes for our ventures into the
darkness.
All that a telescope can do is to concentrate light. The
great mirrors spread a concave glass disk as a trap to catch
rays, and the curve of the mirror and the shape and
arrangement of the accessory optical parts are such as to
concentrate all the captured light into a very small area or
point. The eye of the astronomer then sees what it would
see if its pupil were as large as the mirror. It sees stars and
nebulae that were invisible to the naked eye. And it sees
them, not because the telescope has magnified them, but
because it has intercepted and collected and concentrated
a large enough quantity of their light. A certain minimum
number of quanta are necessary for seeing. The number
varies for each color or wave length, but even for the most
[81]
THE ADVANCING FRONT OF SCIENCE
energetic blue light the requirement is many thousands per
second. Until at least this number is being delivered to the
retina in each unit of time, there can be no sensible activa-
tion of the optic nerve, no image received by the brain, no
vision.
The most distant objects measured by Dr. Hubble and
his associates in their recent survey of the distribution of
outside star systems are faint galaxies rated as of the 2i>
magnitude. That is to say, each of these immense star
swarms shines with a brightness about equal to that of a
2iK-magnitude star. And the apparent luminosity of a
star of this magnitude is that of a candle viewed with
the unaided eye at a distance of 8575 miles. Hubble esti-
mates the distance to these galaxies as about $00 million
light-years. Their light is so scant that the entire surface of
the loo-inch mirror intercepts only about 500 of their quanta
per second. This is far below the minimum requirements of
human vision; many thousands per second would be neces-
sary for the optic nerve to catch even the beginning of an
image. So, even with the help of the largest telescope on
Earth, the eye of a man is unable to see an object of the
21^ magnitude.
It is by the aid of photography that these faint luminaries
have been made to show themselves, and then only by pro-
longed exposures. Seven years ago exposures of 40 hours
were common practice; a single photograph of a spectrum
would represent several nights of slow accretion of the
image on the plate. Today, with the more sensitive emul-
sions now available and with the added help of the more
reflective aluminum surfaces for mirrors and of other optical
aids, an exposure of 3 hours through the loo-inch telescope
is sufficient to reach these remote systems.
This ability of the photographic emulsion to record faint
images by a cumulative process is not the only reason why
the large telescopes have become primarily the apertures
and optical systems of powerful cameras and why the
[82]
THE ENCIRCLING DARKNESS
modern astronomer has become an expert photographer.
There are other reasons many advantages a permanent
photographic record has over a passing visual view. With
the introduction of motion-picture technique, such as that
already begun at the University of Michigan, photography
may attain a superiority over the eye even in the observa-
tion of rapidly changing features of the sky scene. But a
yet more fundamental and clinching argument is the fact
that photography is sensitive to invisible rays of which the
eye is not aware. The inanimate but responsive chemical
mechanisms of the photographic plate can "feel and seek
the light I cannot see."
That there is a light the human eye cannot see was
beautifully demonstrated at the Kodak Research Labora-
tories in Rochester one morning. A group of industrial
executives gathered from various cities had come here to
see some of the wonders of modern photography, and
were waiting in a little theater on the top floor of the six-
story laboratory building. This theater is in itself a unique
institution, completely equipped with ev$ry photographic
and lighting facility, a versatile projection room for sound-
movie films, an outpost and testing ground for photog-
raphy, a place where light is explored, experimented with,
put through its paces. The group of visitors were seated
here when a voice from the stage announced, "Hold
steady a moment, we are going to take your picture," and
the lights were switched off.
"In the dark?" A man held up his hand 2 feet from his
face and could not see the faintest outline of it.
There was a click, a second of midnight silence, then the
shutter gave another click and the lights were turned on
again. Twenty minutes later damp prints of the photograph
were being passed among the astonished visitors. Each
THE ADVANCING FRONT OF SCIENCE
saw himself as the invisible camera eye had spied him in
the blackness.
It was very strange, especially to those who had been
schooled from their earliest picture-taking days in the
necessity of good lighting for good photography. Here,
apparently, was a kind of photography that was able to
dispense with light.
The feat was no trick stunt of the magic theater, how-
ever; for a few weeks later Captain Albert W. Stevens,
photographer of the United States Army Air Corps, took
his aerial camera on a flight above California and showed
what could be done in the open. At a height of 23,000 feet
he pointed his lens due north, opened the shutter, and let
the camera register what it saw. Ordinarily one would
expect a blur, for the panorama was wrapped in haze, and
eyesight could penetrate only a few meager miles. But
when the plate was developed Captain Stevens found that
he had taken a picture of the snow-clad peak of Mount
Shasta 331 miles away.
What a contrast with that first portrait taken nearly a
century ago on the roof of New York University when
the " subject " was compelled to daub her face with white
powder and sit motionless several minutes in the bright
sunlight while the daguerreotype slowly built in its image!
To penetrate 25 feet of theatrical darkness or 331 miles
of atmospheric haze, the problem is essentially the same:
a problem in sensitivity. The noses of dogs are more
sensitive than the noses of men; they register smells which
are beyond human apprehension. Similarly with these
photographic plates; they are more receptive than the optic
nerve, and register light waves which are beyond human
perception.
So there were light waves in the dark theater ?
"Plenty of them," answered C. E. K. Mees, director of
the laboratories and master of this unique show. "But," he
quickly explained, "the light was of an invisible quality
THE ENCIRCLING DARKNESS
that is to say, of a wave length so long that it is beyond
human seeing/' All the photographers did was to coat the
photographic plate with a thin film of chemical emulsion
that is sensitive to these rays, and expose that in the
camera of the darkened theater. At the same time, certain
hidden electric lamps flooded the room with invisible heat
radiation. These rays are effective on this kind of sensi-
tized plate in much the same way that the visible rays of
sunlight are effective on ordinary photographic plates and
films.
To approach our problem systematically let us recall a
few familiar facts. When sunlight passes through a prism it
emerges in the banded rainbow pattern of the spectrum,
the well-known series of colors ranging from the deep blue
of violet to the deep red of glowing iron, together with
innumerable intermediate tints that shade from one
primary color into the next one. But this seemingly infinite
variety is really quite finite. Each color is the signal of a
certain wave length. Beyond the violet at one side of the
rainbow is a considerable series of other vibrations, each of
shorter wave length than its predecessor. Similarly, at the
other side, beyond the red, are other vibrations in a lengthy
sequence, each of longer and yet longer wave length. To
these shorter vibrations beyond the violet and these longer
ones beyond the red, the eye is stone-blind.
The wave length of deep blue light is about 15 millionths
of an inch. This is the measured distance from one wave
crest to the next of the kind of vibration that makes an
eye see what we call blue. The wave length of red light is
just about double that of the blue 30 millionths of an
inch.
A red-hot poker, the!}, is broadcasting on a wave length
of 30 millionths of an inch. But when it is heated more and
glows a deep blue, it is broadcasting on a wave length of
15 millionths of an inch. We are assuming an ideal poker
that does not melt, no matter how high you heat it. Be-
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THEADVANCING FRONT OF SCIENCE
tween the two wave lengths lies all the visibility of the
world.
Suppose we allow the red-hot poker to cool until it no
longer glows. In the dark we cannot see the poker, but it
has not ceased to broadcast radiant energy, for we still
feel its heat beating against us through space. It has
merely shifted to a longer wave length and is now radiating
a wave perhaps double that of the red. Presently, as it cools
more, it will shift to yet longer vibrations; and presumably
it will continue to radiate until its molecular motions
approach the inactive stage of absolute zero temperature.
The problem of seeing, therefore, essentially is one of
tuning in. If we could tune our eyes, as we do our radio
sets, to receive waves longer than 30 millionths of an inch,
we could see the infra-red. Then the cooling poker would
be clearly discernable in the dark, a desert would glow at
night in the "light" of its hot sands, midnight in any land
would be luminous with the infra-red rays of the warm
Earth.
There is no darkness in any absolute sense. The deepest
mine is aglow with the rays generated by its warm rocks
and metals if we could but see them. The blackness of
the abyss of interstellar space is shot through and through
from every direction with innumerable darts of radiation.
Man, so weak of eyesight that he can directly apprehend
only a sixtieth part of the range of radiant energy that we
now know, has yet discovered that wide range. By indirect
chemical and physical means he has contrived to capture
the unseen, and to convert its invisible motions into visible
messages which his eyes can see and at least, in part can
decode and understand. Photography and electronics are
two principal techniques of this advance.
Modern photography, like almost every other attain-
ment of science, is the result of a many-sided collaboration.
[86]
THE ENCIRCLING DARKNESS
Optical experts, physicists, mechanicians, and divers other
precisionists had a hand in the new development, but the
rapid advance in the photography of invisible radiation is
largely the work of chemists experimenting with new com-
binations of dyes.
The ordinary photographic plate or film is even more
limited in its color range than the human eye, for it can
"see" of the visible spectrum only violet, indigo, and blue
light. Objects of a green, yellow, orange, or red color affect
such photographic emulsions as though they were dark,
which means that they do not affect them at all. In 1873,
H. W. Vogel, a Berlin chemist, noticed that some dry
plates in his possession showed a sensitivity to green light.
He investigated, and found that a certain dye, which had
been mixed in the emulsion to prevent spreading of the
image by halation, was responsible for the added sensi-
tivity. Vogel tried other dyes and from them obtained
similar effects, and out of his pioneering came the dis-
covery that when a dye acts as a sensitizer, the color for
which it is effective is the color which the dye itself ab-
sorbs. For example, the dyes which sensitized the emulsion
for green light were each a substance that quite apart from
the photographic mixture was itself an absorber of green
light. "This fundamental relationship underlies all work on
sensitizing," points out Dr. Mees, "and it is worthy of
attention that Vogel grasped this truth immediately in
spite of the fact that his emulsions were very slow, his
dyes probably impure and, at best, weak sensitizers, and
his apparatus primitive."
Although the principle was discovered so early, more
than 30 years were to pass before photographic plates re-
sponsive to the entire range of visible light became avail-
able. By 1904 several isocyanine dyes had been found to
extend photographic sensitivity through the green, yellow,
and orange regions. In 1905 came the synthesis of a new
dye, pinacyanol, which carried the conquest of the chemist
THE ADVANCING FRONT OF SCIENCE
over the entire region of red and even a little beyond into
the invisible infra-red. Astronomers and physicists imme-
diately began to use the new tool.
But they yearned to photograph more than the visible.
It was known that the Sun broadcasts heat as well as light,
and the Sun explorers were eager to have a photographic
record of this heat spectrum for the news that it might
bring. Away back in the later years of the nineteenth
century the English investigator Abney had succeeded in
getting a few such records, but his plates were extremely
difficult to make and use. The first substantial approach
to the problem was provided by the pinacyanol dye, for,
as I have said, this German dye showed a sensitivity to a
few of the heat rays just beyond the deep red at which
visibility ends. In 1910 R. W. Wood at Johns Hopkins
University made good use of this opportunity. He photo-
graphed sunlit landscapes on plates sensitized with pina-
cyanoL Before exposing the plates he fitted a red glass
filter over the lens so that all the wave lengths of visible
light would be stopped and only those of the invisible
infra-red admitted. These early infra-red landscapes re-
semble our modern ones quite closely; they show the
same striking contrast of dark sky and light clouds, the
same brilliant " whiteness" of foliage. But there is this
significant difference between Dr. Wood's photographs
and our modern ones: he found it necessary to expose the
plate about 5 minutes in each instance, whereas the same
results are obtained today in a fiftieth of a second.
The modern advance is measured not only by the quicker
response of the new dyes, as indicated by the speeding up of
exposure time, but also by the wider range of invisible
wave lengths now subject to photography. I have spoken
of wave lengths in terms of fractions of an inch. But
measurements of these small-scale dimensions in fractions
of large-scale units is awkward, and many years ago the
physicists adopted a unit known as the angstrom so
[88]
THE ENCIRCLING DARKNESS
named in honor of A. J. Angstrom, the distinguished
Swedish spectroscopist. An angstrom is the one hundred-
millionth part of a centimeter. The shortest wave of visible
light (blue end of the spectrum) measures 4000 angstroms,
the longest wave of red measures 7000 angstroms. Dr.
Wood, with his plate sensitized by pinacyanol, was able to
photograph out to about 7100 angstroms. Since by the
filter he had cut out all vibrations shorter than 7000, his
photography in 1910 was confined to the narrow region of
vibrations between 7000 and 7100.
The first substantial advance came about a decade later.
E. Q. Adams and H. L. Haller, experimenting at the
Bureau of Chemistry in Washington in 1919, discovered
a new dye which sensitized very powerfully for infra-red
radiation out to 8000 angstroms. This synthetic com-
pound was named kryptocyanine. I should add, to make
the record clear, that an earlier dye known as dicyanine
had been discovered in Germany and found effective as" a
sensitizer for this same infra-red region, and even beyond.
But dicyanine was so unstable, so likely to break down
suddenly and fog the emulsions, that few scientists used it.
The new kryptocyanine, on the other hand, was quite
stable, easy to handle, and could be added to a photo-
graphic emulsion without danger of rapid deterioration. It
was so powerful that one part of the dye in half a million
parts of the emulsion was sufficient to give the maximum
sensitization.
By means of this new compound the chemical conquisi-
tadors of light pushed their photographic domain out to
cover an infra-red range ten times greater than that Dr.
Wood had photographed. But it was only a beginning of the
swift advance of the next decade. In 1925, H. T. Clarke
was preparing some kryptocyanine in the Kodak Research
Laboratories when he noticed that the condensation re-
sulted not only in the expected product, but also in a less
soluble dye which separated out. By further experiment
THE ADVANCING FRONT OF SCIENCE
Dr. Clarke prepared the new dye as the main product.
Tests showed that this neocyanine, as the discoverer
named his accidental find, was sensitive out to 9000 ang-
stroms. Later trials revealed that a still farther reach of
sensitivity can be given to neocyanine by treating it with
ammonia. Using plates so treated, H. D. Babcock at Mount
Wilson Observatory photographed the solar spectrum as
:ar as 11,634 angstroms.
But this is not our limit. In 1932 a new group of dyes
:>egan to issue from the laboratories of the molecule
Builders, refabricated compounds which were immediately
;ested by the photographic chemists and found to be un-
rommonly absorptive of heat rays. Some were absorptive
>f one band of wave lengths, some of another, and the one
vhich carried this absorptive quality to the farthest
extreme was the dye called xenocyanine. It was a very
lighty compound, could be prepared and used only at low
emperatures, and the emulsions were effective only if used
hortly after making. Despite these conditions, some help-
ul results were obtained with the use of this temperamental
:hemical. But research pushed on. Soon other compounds
yere found to possess the heat-absorptive quality, and
ately some have been obtained which are more stable than
:enocyanine. The photographic researchers have given up
rying to find descriptive names for the new dyes, and these
atest compounds are known as "class Z sensitizing." W. F.
Meggers and C. C. Kiess, at the National Bureau of
Standards, have used plates sensitized with this new
naterial to extend our standards beyond 12,000 angstroms
rave length. Babcock, again using the great solar spectro-
;raph at Mount Wilson, has found the new sensitizer use-
ul in carrying this survey of the Sun's spectrum out to
3,536 angstroms.
3
A characteristic of infra-red waves of radiation is their
bility to get through haze and other conglomerations of
[90]
THE ENCIRCLING DARKNESS
atmosphere. The shorter wave lengths are less successful,
and even in a clear sky some are stopped. Indeed the fact
that the sky looks blue is evidence that much of the blue
sunlight of short wave length is scattered. The blue waves
are scattered by reason of their collisions with air molecules
and invisible dust motes of the atmosphere, and the longer
the wave lengths the less susceptible are they to this
scattering effect. When the sky is thick with haze, caused
by dust motes afloat in the air, the Sun may appear red as
at sunset, an effect caused by the scattering of most of the
wave lengths shorter than red. As the haze thickens with
increased density of dust or increasing distance to be pene-
trated, or as moisture collects on the particles and deepens
the haze to a slight cloud or slight fog, even the reddest
wave lengths may be turned aside and scattered. Then the
Sun is no longer visible as an image, only the gray indis-
tinctness of neutral or scattered light remains. It is at this
stage that the infra-red waves become indispensable, if we
are curious about what lies beyond the haze. For the
infra-red vibrations, of slower frequency and longer wave
length, are large enough to spill over the atmospheric par-
ticles and pulse through the haze for long distances, and
write their invisible messages as photographic images on
our plates provided the plates are sensitized with the
right dyes.
It must not be inferred that infra-red photography is
effective through all densities of mist. The new dyes can be
used to increase visibility through haze, and even through
a light fog or cloud, but the infra-red rays that penetrate
ordinary fog densities are of wave lengths too long for our
present photographic stratagems. The reach that we have
won, however, is of very great practical importance.
When the first kryptocyanine plates were received at
Lick Observatory on Mount Hamilton, W. H. Wright there
thought he would try the new photography on a terrestrial
scene. He pointed his camera at the Yosemite Valley.
The valley lies 130 miles from Mount Hamilton, hidden
THE ADVANCING FRONT OF SCIENCE
behind the haze of that long stretch of air, vague and
fuzzy on even the clearest days. In the infra-red photo-
graphs the details came out with remarkable sharpness,
and at once it was recognized that here was a powerful
practical tool for penetrating atmospheric opacities.
If a distant scene could be photographed from a moun-
taintop, as Dr. Wright had demonstrated, why not from a
moving airplane? Captain Stevens was one of the first to
try that, and his photograph of Mount Shasta is only one of
a series of successful long-distance shots. His first major
attempt of this kind was directed at Mount Rainier. It is
said that on that flight his pilot was rather mystified by the
captain's actions. He could not understand why, long
after the mountain had disappeared from sight, the captain
pointed his camera in that direction apparently at
nothing. The pilot was even more astonished a few hours
later, when the negative was developed and printed, and
he saw the clear photograph of a wide stretch of moun-
tains and valleys, dotted with familiar peaks: the Three
Sisters, Three-fingered Jack, Mount Jefferson, Mount
Hood, and farthest of all, the white spire of Mount Rainier.
This last had been photographed through 227 miles.
Later, on a flight in South America, Captain Stevens
obtained a sharp photograph of Mount Aconcagua, in the
Andes, at a distance of 310 miles. This picture is remarkable
in many respects. It shows the line of haze over the South
American pampas as curved, corresponding to the curva-
ture of the Earth's surface. Subsequently, from the strato-
sphere balloon Explorer II, taking an oblique photograph
at a height of more than 13 miles, Stevens got an even
more impressive record of the curvature. These results sug-
gest that some day some higher flying aeronaut or rocketeer
may capture on a sensitive film the vast bend of our
planetary edge in yet more distant perspective and show
an appreciable segment of our globe. "There is no limit to
the distance over which objects can now be photographed,
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THE ENCIRCLING DARKNESS
except that imposed by their size and by the curvature of
the Earth," says Dr. Walter Clark.
Infra-red photographs appear weird in some of their
details, and this is because certain substances reflect and
transmit the invisible rays much more freely than they do
our familiar visible light. In an infra-red photograph of a
landscape, for example, the foliage shows an intense bril-
liancy as though it were powdered with snow. This ap-
pearance is explained by the presence of chlorophyll, the
green coloring matter of the leaves, which has a very
high reflectability for the infra-red. In an exposure of an
outdoor scene, more of the invisible light is reflected by the
leaves than by other objects, consequently more reaches
the photograph from the leaves than from other objects,
and their images are made to appear brighter by contrast.
It has been discovered that infra-red radiation pene-
trates the skin and some distance into the underlying
tissues of the human body. The network of skin and tissues
scatters the rays, and the photographed result is a white
effect on the infra-red print. If there is a blood vessel under
the skin, this different substance interferes with the
scattering, and the blood vessel photographs dark against
the lighter background of skin and tissues. Thus many
details of underlying blood vessels which are quite hidden
to the eye are brought to view by the penetrating rays.
Varicose veins, capillary congestions, and similar dis-
arrangements show up in infra-red prints, and the pos-
sibility of using this new photography as an aid to medical
diagnosis seems favorable. Already botanists have found
that certain diseases of plants may be detected in their
early stages by infra-red photography of the foliage.
There is a treasured copy of De Bry's Voyages in the
Huntington Library at San Marino, California, but the
book is sadly defaced. It seems that certain of its passages
offended an ecclesiastical censor back in 1632, and so he
blotted them out with thick layers of black ink. The
[93]
THE ADVANCING FRONT OF SCIENCE
Library authorities tried various means to circumvent
the censor without endangering the book, but all these
efforts were unsuccessful until they heard of the infra-
red photography that Mount Wilson astronomers were
using to get through the obscuring clouds of planets. Might
it not also penetrate the censor's ink? Dr. L. Bendikson
borrowed some of the infra-red plates from the observatory,
and was delighted to find that in photographs made with
the invisible light the hidden passages came clearly to view.
It was this quality of selective transparency that made
such a result possible; for if the two inks had responded
similarly to the infra-red, or even if the outer ink had
possessed less transparency than that of the printing, the
censor might still be triumphant.
Each of these practical uses of the new sensitivity sug-
gests other possibilities, and it seems likely that infra-red
photography may in time have as many and as different
applications as x-ray photography has attained in its 40
years. The astronomers have made more use of the tech-
nique than any other group but perhaps their results
would not meet the tests of "practicality" with which
some men, as Joseph Conrad has said, starve their imagina-
tions to feed their bodies. Have a care, though, how you
pronounce on futures in these realms. Some day some
rocketing real estate magnate, looking for other planets to
stake out and subdivide for development, may find it quite
important to know whether Venus has a better atmosphere
than Mars, and what sort of arrangements may be found in
Jupiter and Saturn. Already the astronomers have some
reliable data on these questions, acquired by means of
infra-red photography.
4
Most of the astronomical explorations with infra-red
have been made through the spectroscope. That is to say,
the direct image of the heavenly body is not photographed,
[94]
THE ENCIRCLING DARKNESS
but its light is passed through a prism or reflected from a
diffraction grating, and the resulting spectrum is photo-
graphed. Many of the lines in the spectrum are far out in
the invisible regions on either side of the rainbow, and for
some elements and compounds these lines of invisible light
are the only significant signals. If they are far out in the
ultra-violet, they are lost in the upper air where a high
layer of ozone absorbs all the ultra-violet except for a
narrow region near the visible. Thus, most of the ultra-
violet light is filtered out of the sunshine by this gaseous
layer and never reaches us. But if the signals are lines of
the infra-red, they are now an open book, thanks to the
facility of the new photography. The presence of phos-
phorus in the Sun was recently discovered in this way, by
the photographing of infra-red phosphorus lines in the
solar spectrum. And similarly astronomers have been
exploring the atmospheres of the planets.
Planets, of course, have no light of their own. Each shines
by reflected sunlight. But it so happens that when the
light of the Sun falls upon an envelope of gas, such as the
atmosphere surrounding a planet, the atoms and molecules
of the atmosphere absorb certain wave lengths of the sun-
light according to their peculiar affinities. The result of this
selective absorption is to add certain dark lines to the
spectrum, and these then show up by contrast with the
spectrum of direct sunlight. The dark absorption lines
added by the planetary atmosphere become clues to the
make-up of the atmosphere. In this way it was recently
discovered at Mount Wilson Observatory that the atmos-
phere of Venus is dense with carbon dioxide gas, its upper
layers containing 10,000 times as much carbon dioxide as
is in the whole atmosphere of the Earth, that the atmos-
pheres of Jupiter and Saturn contain ammonia, and that
the amount of oxygen in the atmosphere of Mars is not
more than Y of I per cent of the Earth's atmospheric
oxygen. Similar studies at Lowell Observatory have re-
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THE ADVANCING FRONT OF SCIENCE
vealed the presence of marsh gas (methane) in the atmos-
pheres of Jupiter and Saturn. These findings are not
encouraging to the hypothesis of life on the planets. We
know no form of animal life that can breathe ammonia and
methane, or that could get along on the meager oxygen
available on Mars. The presence of so much carbon dioxide
on Venus might argue an environment favorable to plant
life were it not for the fact that Venus is perpetually
shrouded in dense clouds. These completely blanket it
from the visible rays which on our Earth are necessary to
vegetation.
The presence of ammonia and methane in the atmos-
phere of the two largest planets, Jupiter and Saturn, raises
some nice speculations of chemical origins and evolution
which a chemist, Walter Clark, recently discussed. "Am-
monia," as Dr. Clark pointed out, "is a very reactive gas,
consisting of nitrogen saturated with hydrogen. Methane,
less reactive than ammonia, and familiar as 'marsh gas/
consists of carbon saturated with hydrogen. Both gases are
stable. It is possible that collisions of atoms in the atmos-
pheres of the planets have continued over vast periods of
time, until eventually these most stable constituents have
survived. It has been suggested that methane and ammonia
are just the gases which would be expected to form if a mass
of gas, having a composition like the atmosphere of the
Sun, were allowed to cool slowly to a very low tempera-
ture." The present temperature of Jupiter and Saturn is
rated at about 180 below zero Fahrenheit.
5
Thus far, our story of the new photography has empha-
sized attainments with infra-red. Ultra-violet radiation is
somewhat less useful to astronomers, because of the atmos-
pheric absorption mentioned on a foregoing page. But these
short waves beyond the violet have done wonders for the
physicist. They have brought news of the structure of
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THE ENCIRCLING DARKNESS
atoms and have provided tools for probing into the behavior
of atomic parts. Just as the temperature or energy state
determines whether the iron atoms of the poker shall broad-
cast blue light, or red light, or invisible infra-red, so does it
ordain the invisible radiations at the other side of the
spectrum. An atom excited to a certain energy state
vibrates visible light. Excited to a higher energy state,
it gives off ultra-violet. Still higher, its output is an x-ray.
And when the central citadel, the nucleus, is in a state of
agitation, its radiation comes forth in the yet shorter wave
known as a gamma ray. All these waves beyond the violet
are potent photographically. Indeed, it was the accidental
fogging of some plates in his laboratory that prompted
Rontgen to search for and find the x-rays. Similarly, it was
by means of photography that Becquerel discovered the
gamma rays.
The shortest wave of visible light measures, as we have
seen, about 4000 angstroms. Just beyond this extreme blue
end of the spectrum the ultra-violet begins, and its region
extends through shorter and yet shorter vibrations until a
wave length of about 100 angstroms is reached. The in-
visible regions overlap, there is no sharp boundary between
the shortest ultra-violet rays and the longest x-rays, nor
between x-rays and gamma rays. But in general it is
accepted that the sequence from about 100 angstroms to
about Moo angstrom is the realm of x-rays, and from
Moo angstrom down is that of gamma rays.
Most x-rays, and all gamma rays, are of such short wave
length that they can penetrate solid materials, like flesh,
or even sheets of metal, darting their way through the
relatively enormous open spaces between atoms and atomic
parts. Also, they are so packed with energy that in a
collision they are able to knock parts out of atoms. It is
plain to see that if we have a means of detecting the
mutilation of atoms we should thereby have a means of
detecting the presence of x-rays and gamma rays. Such
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THE ADVANCING FRONT OF SCIENCE
detectors have been made electroscopes and ionization
chambers are examples and with these electronic devices
it is quite possible to "see and feel" the invisible short-
wave light of x-rays and gamma rays even without a
photographic plate. Refinements of these devices have
enabled the investigator to measure the energy of the rays.
And since wave length is related to energy in a very definite
way the higher the energy, the shorter the wave length
it is possible from these measurements to ascertain the
energy and wave length of unknown rays; such unknowns,
for example, as cosmic rays, the mysterious bombardment
that continually beats upon our Earth and all its cargo.
The penetrating power of some of this cosmic bombard-
ment is so great, its load of energy is so tremendous, that
if the thing is a species of light its wave length must be
thousands of times shorter than any known gamma ray.
If the thing is a charged particle of matter, its velocity must
be enormously high. Science is still groping for knowledge
of the origin and nature of the bombardment, but the
story of its discovery and continued pursuit is one of the
most fascinating in the annals of modern research.
[98]
Chapter VI -THE COSMIC
BOM BARDMENT
I cannot tell you how it was;
But this I know: it came to pass.
CHRISTINA ROSSETTI, MAY
THE electroscopes began it. They would not behave
or they could not. It became necessary to find out what
was ailing them, whether an electroscope was really the
sober law-abiding trustee and holder of electricity it was
supposed to be, or something else quite different. Out of
such detective work a new presence was discovered, strange,
invisible, but superlatively active demons of energy
the ubiquitous cosmic rays.
Ubiquitous, says my dictionary, means "everywhere
present. " That describes cosmic rays. They beat upon the
Earth from every direction. Nothing is exempt from their
toll. No creature is immune to their prying darts. While
you have been reading these paragraphs several hundred
cosmic rays have plowed through your body.
Atoms of metals are hammered into excitation and erup-
tion by their impacts, and what may happen to the lighter
atoms of flesh and blood we can only conjecture. Cosmic
rays may be benefactors, the aiders and abettors of life,
or they may be destroyers, the insidious enemy of all that
breathe, or they may be of no biological consequence we
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THE ADVANCING FRONT OF SCIENCE
do not know. The speculation, however, gives to the
mysterious radiation a temptingly personal aspect. It pro-
vides for our table talk a new and tantalizing if. Instead
of blaming our tempers and other idiosyncrasies on the
heat or the humidity or the depression, we may find in the
cosmic rays a new alibi. Possibly evolution is hastened by
the incessant bombardment. The idiot may be the casualty
of some cosmic-ray collision with the living atoms of
heredity, and similarly the genius may be the accidental
outcome of a more fortunate mutilation.
You may wonder that this bombardment could go on for
untold ages, and only yesterday be discovered. Our knowl-
edge of cosmic rays is a thing of the twentieth century; it
dates back hardly 25 years; and, as I have said, the electro-
scopes began it.
A cat's back is a familiar form of electroscope. Stroke
its fur and you charge it with electricity. The hairs of the
fur stand on end with the charge, but bring the tip of your
finger near, there is a sudden crackling and the flash of a
spark as the load passes off and is dissipated, while the
erect hairs settle down. But cats are temperamental, and
for reliable laboratory service the pioneer electricians
invented the gold-leaf electroscope. Here a thin strip of
gold-foil substitutes for the fur and when charged stands
out from its insulated support, erect and bristling with
electrical potential.
It was this gold-leaf electroscope that the early explorers
of radium turned to as an aid to their researches. Radium is
continually shooting out its gamma rays; these rays smash
the air particles they collide with, thus electrifying the
particles and causing them to flow to the gold leaf and dis-
charge it. The radiologists found that the time required
for the gold leaf to settle down was an index to the intensity
of the radium rays.
[100]
THE COSMIC BOMBARDMENT
But was it a precise indicator ? If they could be sure that
the discharge was caused solely by the electrified particles
actuated by the radium, and that no other influence was
affecting the apparatus, then they could rate the intensity
of the gamma rays directly in terms of the behavior of the
gold leaf.
So tests were made. An electroscope was completely insu-
lated, and isolated from all known sources of electrification.
Then it was charged. Theoretically, it ought to hold that
charge indefinitely. But after a few hours the gold leaf
began to droop, and eventually its charge had disappeared.
Trial after trial demonstrated that no amount of insula-
tion or isolation would stop this strange loss. It was called
"the natural leakage," and physicists were able to compute
its magnitude and allow for it. But computing an unknown
does not explain it, and many were the speculations on this
odd behavior.
A favorite theory attributed the natural leakage to the
natural radioactivity of the Earth. The rocks and soil
possess their small quota of radium and other radioactive
metals, even the air carries finely attenuated amounts of
radon gas, and the radiations given off by the exploding
atoms of these elements might account for the leak. But
3 inches of lead will stop the most powerful known gamma
ray; so an electroscope was sheathed in leaden plates several
inches thick, in addition to the protection of its insulation.
The leakage was slowed down somewhat, but it continued
as before. A group of Canadian experimenters sledded an
electroscope far out onto the frozen surface of Lake Ontario.
Six feet of water will stop all radium rays; here the thick-
ness of water and ice between the instrument and the rocks
of the Earth was several hundred feet, but this unusual
protection did not avail. The charged gold leaf slowly
settled down.
How high up in the air would this strange influence reach ?
Father Theodore Wulf, a Jesuit priest in Paris, carried an
[101]
THE ADVANCING FRONT OF SCIENCE
electroscope to the top of the Eiffel Tower and found that it
continued to discharge at that height, 984 feet. Then, in
Switzerland, A. Gockel loaded an electroscope into the
basket of a balloon and found that at the 3-mile level the
gold leaf still leaked. Certain observations prompted him to
suggest that the effect might be expected to increase with
altitude.
Stimulated by these experiments, the German physicist
V. F. Hess engaged a larger balloon and attained a higher
altitude. And Hess came down with an amazing report of
fulfillment of Gockel's prediction. Not only did the elec-
troscope continue to discharge at the ceiling of his flight,
but the discharge steadily increased as he went up. Hess
concluded that the invisible influence " enters our atmos-
phere from above/'
These reports were disquieting to the custodians of
knowledge. Many doubted the accuracy of the experiments.
Another German, W. Kolhorster, determined to make a
definitive test. He procured a very large balloon, installed
an extremely sensitive electroscope, and ascended to a
height of nearly 6 miles. Kolhorster's more precise measure-
ment over a much longer range of altitude completely con-
firmed Hess's result. There could be no doubt about it:
the higher the balloon rose, the more rapidly did the charge
on the electroscope ooze away.
The World War arrived shortly after these events, and
further investigation was set aside by the more insistent
demands of the Great Madness. Perhaps if any of the
military minds had been aware of the tremendous energies
resident in cosmic rays, they might have been captivated
by the thought of possibly harnessing the rays for war
purposes, and research might have advanced still farther.
For while the total amount of heat brought to the Earth
by cosmic rays is less than that of starlight, the energy of
the individual ray is unbelievably great. Thus, when a
cannon ball is moving at its greatest velocity, the energy
[102]
THE COSMIC BOMBARDMENT
of its motion averages less than one electron-volt per
atom but cosmic-ray encounters recently photographed
show that some of the rays are endowed with energies of
20,000 million electron-volts and more. Imagine cosmic
rays concentrated into a beam!
However, the war lords knew nothing of this in 1914 to
1918, and it was not until about 1926 that the lay public
became aware of cosmic rays.
Robert A. Millikan and his associates at California
Institute of Technology had taken up the subject in
America, and Kolhorster with his coworkers had resumed
the researches in Europe; and presently exciting stories
began to appear in the press in report of the findings of
these and other groups of investigators. Electroscopes had
been sheathed in lead containers, and lowered into crevasses
in the Swiss Alps under the overhanging ledges of glaciers.
But the ice shield was no effective obstacle to a radiation
that seemed all-pervasive. Other electroscopes were encased
in waterproof boxes and lowered to the bottoms of glacial
lakes on Californian mountaintops. But the hundreds of
feet of water were not sufficient to absorb all the radiation
from above, and the protected electroscopes gradually
leaked their charges away, and at specific rates which cor-
related with one another. In other experiments, the detec-
tors were carried into basement vaults, tunnels, and
mines; but somehow the irresistible rays bored through soil
and rock and concrete and steel, and had their usual way
with the electroscopes.
It was out of such experiments that the first estimates of
the energies of the rays were derived from observations of
their penetrating power.
2
But in 1932 a more exact method of measurement was
attained by Carl D. Anderson, one of Millikan's associates
in California, and with it came a memorable discovery.
[103]
THE ADVANCING FRONT OF SCIENCE
Anderson made use of an English invention, a device
known as the Wilson cloud chamber from its creator C. T.
R. Wilson. In the moisture-laden air of the chamber micro-
scopic droplets of water vapor are caused to cluster round
invisible speeding electrified particles. The path of each
moving mote is thereby rendered visible as a streak of
cloud, and may be photographed. Anderson placed his
cloud chamber between the poles of a powerful electro-
magnet, and in this magnetic field the particle was swerved
one way if it carried a positive electric charge and another
way if its charge was negative. In either case, the higher
the energy of the particle, the swifter was its speed and the
greater its ability to resist the pull of the magnet. There-
fore, the degree of curvature described by the streak was a
direct index to the energy.
When this powerful combination of apparatus was set
in operation, Anderson found that particles were darting
out of the metal frame of the cloud chamber at velocities
greater than 100,000 miles a second. They were fragments
of atoms blasted out of the metal by the accidental impact
of cosmic rays.
The cloud tracks of these particles were so nearly straight
lines that it was impossible to tell from which side of the
chamber they originated. The powerful magnet was not
strong enough to deflect them perceptibly, but Anderson
hit on the maneuver of inserting a plate of lead in the
center of the chamber. Thereafter the ejected particles had
to pass through this barrier, and in doing so some of their
energy was absorbed; consequently they emerged from the
lead with lessened speed, and during the remainder of
their journey the magnet was able to deflect them more
noticeably. By these means Anderson could identify the
direction of travel of the particle. He photographed cloud
tracks whose curves indicated energies of thousands of
millions of electron-volts, and measured for the first time
the energy values of the activating rays.
[104]
THE COSMIC BOMBARDMENT
On the afternoon of August 2, 1932, this apparatus pro-
duced a photograph that is now part of the history of
science. Even while Anderson was in the photographic
darkroom developing the negative, he recognized that he
had made an extraordinary find. The image was that of a
cloud track bent to the left under the measured force of the
electromagnet therefore he knew it must be the path of a
positively charged particle, since only positives could
move through the magnetic field in that direction. But this
was a new kind of positive. Protons, the massive kernels of
hydrogen atoms, are single charges of positive electricity
and were the only simple units with this sign. But here in
Anderson's photograph was a cloud track which said that it
was made by a positive particle nearly 2000 times lighter
than the proton. A bantamweight positive! Anderson and
his coworker, Seth Neddermeyer, spent the whole of that
night at the laboratory trying to figure the event out. It was
for this discovery of the positron that Anderson was sum-
monsed to Stockholm in 1936 to receive the Nobel Prize in
Physics jointly with V. F. Hess. It was Hess, you remem-
ber, who was first to discover that the cosmic radiation
increased in intensity the higher he arose in his balloon,
and who proposed the idea that the strange penetration
"enters our atmosphere from above." Anderson was the
first to trap a cosmic ray in a cloud chamber and definitely
measure its energy under the calibrated pull of magnetism,
and first to distinguish among the cosmic-ray wreckage the
peculiar wake of the positron. So the 1936 Nobel Prize in
Physics was made a cosmic-ray award to be shared be-
tween these two discoverers.
After the initial spotting of positrons among the cosmic-
ray smashings, various experimenters tried other radia-
tions. It was shown that radium rays and other high-energy
bombardments also may crash positrons out of matter, and
today the physicists are invoking veritable showers of the
new-found particles. But do not forget that it was by the
[105]
THE ADVANCING FRONT OF SCIENCE
accidental blow of a cosmic ray that the great detection
was made. In consequence we may claim a certain utility
for the mysterious radiation. It has become a tool of
science. While we cannot say that we have harnessed it, we
have successfully used it to peep a little closer into the
keyhole of the unknown.
3
Meanwhile, the nature of the cosmic radiation remains
a tantalizing part of the unknown. At first it was believed
that the rays were a form of radiant energy like x-rays,
only of extremely shorter wave length and higher frequency
of vibration. Such rays are electrically neutral, they travel
in straight lines, and they are indifferent to the pull of the
magnetic field. But a few years ago Kolhorster and his
colleague Bothe, in Germany, found evidence that some
cosmic rays behaved, not like light rays, but more like
charged particles. And this raised a bold question mark.
It was pointed out that, if cosmic rays are charged par-
ticles, they should bend to the influence of magnetism; and
if this be true, the Earth's magnetism should affect them
and distort their paths of penetration into the atmosphere.
Our planet is a whirling magnet, with one magnetic pole in
northern Canada and the other in Antarctica, and the lines
of magnetic force quivering out from these poles reach into
space for many thousands of miles. Any charged particle
headed earthward would be deflected by this vast planetary
field of magnetism, just as the electrified particles smashed
out of metals were swerved in the cloud chamber between
the poles of Anderson's magnet. And so the cosmic-ray
searchers began to look for a latitude effect.
First to find it was J. Clay, an Amsterdam physicist who
was making an ocean survey for the Dutch government.
Indeed, Clay discovered the effect some months before
Kolhorster and Bothe published their question. As he
traveled away from the equator, he noticed a slight differ-
[106]
THE COSMIC BOMBARDMENT
ence in the intensity of the bombardment. Others con-
firmed this. A survey directed by A. H. Compton showed
that these variations followed the Earth's magnetic latitude
rather than the geographic latitude, an important distinc-
tion. Various types of cosmic-ray detectors were installed on
steamships and by their automatic mechanisms were
enabled to write a continuous record of the intensity of the
bombardment as their voyages carried them across oceans,
north and south to widely separated regions of the Earth.
From these studies it has been possible to plot the zones of
intensity on the map. All authorities agree that there is a
latitude effect.
There is also a longitude effect, discovered independently
by Clay and Millikan, and further investigation by other
observers in many parts of the world has confirmed this.
For example, Lima, Peru, and Singapore in the Malay
Peninsula are both close to the magnetic equator, but are
separated in longitude by half the circumference of the
Earth, about 12,000 miles. The equatorial belt is a zone of
low intensity for the rays, but apparently lowness in the
Western Hemisphere does not mean the same as lowness in
the Eastern. For the measurements show that the cosmic
bombardment at Lima is 4 per cent more intense than that
at Singapore. These variations are explained by the eccen-
tric positions of the magnetic poles, for the North Magnetic
Pole in the Boothia Peninsula of Canada is not exactly
opposite the South Magnetic Pole in South Victoria Land of
Antarctica. A line joining the two magnetic poles misses the
Earth's center by about 300 miles. It is this lopsided shape
of our terrestrial magnetic structure that makes the cosmic-
ray intensity vary with longitude.
Still another kind of variation was discovered in 1933 by
two scientists from the United States working independ-
ently in Mexico City. There was an idea that the particles
might show some preferential direction in entering the
Earth's atmosphere. Mexico City perched among its
[ 107 ]
THE ADVANCING FRONT OF SCIENCE
mountains, high above sea level, is in the latitude of most
rapid change of cosmic-ray intensity, and it was selected
as a favorable site for the directional test. Luis Alvarez,
then of the University of Chicago, and T. H. Johnson, of
the Franklin Institute's Bartol Research Foundation in
Philadelphia, were the researchers. Both men used the
well-known scheme of mounting two or three cosmic-ray
detectors in vertical series, one on top of the other in per-
pendicular arrangement. The wired connections were such
that only when a ray passed through all two (or three)
units would it make any record. Thus, by pointing the
apparatus in different directions, it was possible to tell
whether the intensity of the rays was greater from one
point of the sky than another. Both men reported their dis-
covery separately to their collaborator, M. S. Vallarta at
the Massachusetts Institute of Technology. And the dis-
covery was this: the bombardment from the west was
fully 10 per cent more intense than that from the east.
Later studies have detected this west-to-east effect in other
latitudes and altitudes. In the United States it is about
2 per cent.
This preponderance of the bombardment from the west
had been predicted on theoretical grounds, assuming that a
certain percentage of the radiation was in the form of
positively charged particles. Positive charges entering the
Earth's atmosphere from outside should be swerved by our
magnetic field in such a way as to appear to slant in from
the west. Hence the discovery by Johnson and Alvarez
added further evidence in support of the particle hypothe-
sis, and also indicated that at least some of the particles
were positively charged.
An obvious difficulty in all these researches is the sifting
of the observed effects back to the primary causes, and
determining from the secondaries which we detect the
primaries which actuated them. For it is not cosmic rays
that we record in our electroscopes, ionization chambers,
[108]
THE COSMIC BOMBARDMENT
counters, and cloud tracks, but the fragments of atoms
that have been smashed by an invisible something. Is that
immediately causative something a cosmic ray, or some
particle that earlier had been activated by a cosmic ray?
This is the nub of the controversy over the nature of cosmic
rays, the difficulty that our scientists find in identifying
the primaries amid all the medley of mutilations that are
continually occurring in our atmosphere, in our scientific
instruments, perhaps in the bodies, the eyes, the brains of
the observers themselves. It is pretty generally accepted
by all authorities today that some of the cosmic radiation
is in the form of high-speed charged particles, probably
electrons and positrons. Millikan favors this view, but
holds that the charged particles are only a minority group
in the bombardment that actually gets down to sea level,
the greater number of the missiles being in the form of a
high-energy radiation. Compton takes a different view,
regarding the bombardment as composed mainly of charged
particles.
Both Millikan and Compton base their conclusions on
experimental studies which represent perhaps the most
far-ranging survey of a physical phenomenon that has
ever been made within an equal period of time. Dr. Millikan
uses a sensitive electroscope which includes an automatic
recording device. All that is necessary is to keep the thing
wound up, like a clock; then the automatic mechanism
charges and recharges the electroscope at fixed intervals,
and meanwhile photographs a record of the rate at which
the apparatus discharges. Electroscopes of this type have
been sent all over the world, carried high into the stratos-
phere by balloons, buried in mines and under water. Dr.
Compton uses a sensitive ionization chamber, a device
which measures the flow of currents of ions originated by
cosmic rays, and it too has an automatic recording device
which continually keeps tabs on any increase or decrease in
the rate of ionization. This apparatus has been installed on
[109]
THE ADVANCING FRONT OF SCIENCE
ships and carried on trips from Vancouver Island in Canada
to Australia and between other widely separated places. It
has made its record on mountaintops and from ascending
balloons.
Early in 1937 scientists at the Department of Terrestrial
Magnetism of the Carnegie Institution in Washington were
experimenting with a new type of extremely light apparatus
for measuring and reporting cosmic-ray intensities in the
atmosphere. Previously, in the fall of 1936, Dr. Johnson at
Philadelphia had sent up a balloon carrying a box equipped
with a cosmic-ray detector wired to a radio transmitter.
As the balloon rose from the ground to its ceiling 14 miles
up, the automatic apparatus faithfully relayed by radio the
signal of each cosmic-ray encounter. Even earlier, in experi-
ments in India in 1934, J. M. Benade of the University of
Punjab demonstrated a cosmic-ray meter transmitting its
readings automatically by radio from balloon to ground.
The new mechanism developed in Washington in 1937, by
S. A. Korff, is extremely light it weighs only 5 pounds
and it is cheap, so inexpensive, in fact, that no precautions
are taken to recover the apparatus after it has completed
its flight. The thing radios its report as it goes up, a receiver
in the laboratory down on the ground picks up these signals
and records them on a moving tape, and what becomes of
the floating apparatus after it has completed its report is
immaterial to the investigators. It may drift to sea or drop
in a jungle without any serious loss. In former cosmic-ray
surveys of the stratosphere the recovery of the apparatus
with its contained record has been one of the chief anxieties,
and in several instances coveted records have been lost
with their fallen apparatus.
Doubtless many ingenuities must be resorted to before
we unveil the complete story of the cosmic bombardment,
and know to a certainty of what and how it is composed.
There is no reason to expect the phenomenon to be one
simple effect. Various factors may collaborate; the forces
[no]
THE COSMIC BOMBARDMENT
that bombard us may be many, and not necessarily one.
Similarly with the origin of the rays. Some may come from
one source, some from another; some born of one process,
some of another. The Universe is not simple and " nature
loves to hide."
4
Whatever the cause of the bombardment, there is no
question of the tremendous energies carried by its missiles.
These values can be rated rather reliably from the resulting
wreckage. Several years ago Dr. Millikan undertook to
reckon the density of cosmic radiation reaching the Earth.
He found that it averages about 0.0032 erg per second for
each square centimeter of our surface. Since an erg itself
is a very small unit the energy required to raise one pound
to a height of one foot against gravity being 13,500,000
ergs this fraction may seem to be a very small quantity.
And yet, according to a recent computation by Dr. Korff,
the whole energy of the Universe, the torrent of radiation
thrown into space by the thousands of millions of stars of
our Galaxy and by the stars of the millions of outside
galaxies, totals a density of around 0.0069, on ^Y about
double that of cosmic rays. So far as starlight is concerned,
we are in a particular bright spot, surrounded as the Solar
System is by the Milky Way; and because of our relative
nearness to stars more of their radiation reaches us than
reaches most places outside the galaxies. Indeed, most of
the Universe is empty space, and Korff figures that Out
There at a distance of a million light years from the nearest
galaxy, the density of radiation from all the galaxies
reaching that point would be only 0.000205. This is less
than the thirty-fourth part of the energy density in our
part of the stellar Universe. But cosmic rays are equally
dense everywhere, so say our present hypotheses. From
these considerations we are led to conclude that most of
the energy flooding the vast wastes between the galaxies
THE ADVANCING FRONT OF SCIENCE
is in the form of cosmic radiation, and that this is by a wide
margin the preponderant energy of the Universe.
How strange! No theory predicted this, and no theory
today can account satisfactorily for all its observed effects
yet experiment speaks unequivocally of the existence of
the unpredicted unaccountable radiation. "This I know:
it came to pass."
We are brought to a picture of reality in which most of
the energy that activates the physical world is of a highly
concentrated type, with millions of millenia ahead before
it can reasonably be expected to degenerate to heat, or
even to light.
The Universe, it would seem, is still very young. We are
here, haply in this luminous neighborhood of space-time,
in the childhood of the cosmos, and uncounted aeons await
the adventuring pertinacity of restless questioning man.
The fire snatcher need not fear a shortage of time, nor is
there any threat of a shortage of problems to engage his
time.
Every hour the semen of centuries, and still of centuries.
I must follow up these continual lessons of the air,
water, earth,
I perceive I have no time to lose.
Chapter VII - DEEPER INTO
THE ATOM
Force, Force, everywhere Force; we ourselves a mysterious
Force in the center of that. There is not a leaf rotting on
the highway but has Force in it.
THOMAS CARLYLE
WHEN the full story of our times is critically appraised,
perhaps a century hence, many occurrences will
assume an order of importance quite different from that
assigned by our contemporary historians. Just as the
obscure invention of gunpowder was an event more momen-
tous than the widely heralded Battle of Waterloo, so there
are little-known happenings of today that the sifting of the
years will bring to the fore. They will become less obscure
as time advances and their fundamental nature is more
generally understood and their uses become manifest. For
they mark permanent gains in man's ceaseless march and
countermarch. Whatever the future of governments and
individuals may be, the victories of the laboratories will
stand as lasting assets of the race.
Among the recent victories is a discovery made in 1936
at Washington, D.C., at the high-voltage laboratory of the
Carnegie Institution's Department of Research in Ter-
restrial Magnetism. It brought to knowledge an unknown
force of the Universe, subjected the force to tests of meas-
THE ADVANCING FRONT OF SCIENCE
urement and analysis, and defined the law by which the
force operates.
For an approximate analogy, to suggest the significance
of this American discovery, one must go back to the seven-
teenth century contribution of Isaac Newton his discovery
of the law of gravitation. As the Newtonian discovery
brought a new and clarifying interpretation to certain
mysterious behavior of planets that seemed to violate
Galileo's rules of motion, so does this American discovery
brilliantly illuminate certain perverse behavior of atoms
that seemed to violate the established rules of electricity.
The former discovery provided a force and a law that gave
scientific meaning to celestial mechanics; the latter has
provided a force and a law that give scientific meaning to
atomic mechanics. Since it seems certain that in atomic
mechanics are the sources and repositories of the world's
energy, the consequences of this recent discovery appear to
be of the highest promise to mankind.
If the world is built of atoms, as we believe, we must know
atoms before we can expect to comprehend the physical
reality. Nothing seems nearer, more conveniently at hand
for investigation, than atoms. They are the air we breathe,
the water we drink, the soil and rocks and trees and leaves;
they are our physical bodies. And yet, perhaps nothing else
is so hidden, so alien to our accustomed techniques, so
beyond our reach. Instead of being the round hard solid
particle that our fathers imagined, the atom is an abyss.
Its depths are more remote in our scale of dimensions than
the dim galaxies. The darkness beyond the faintest nebula
is not more tantalizing to our limited organs of vision than
is the blackness of the chasm within the atom.
In these atomic depths, energy breeds other energy.
Here the strange eruptions of radium are initiated and con-
trolled. There is a suspicion that here cosmic rays are born.
The nature of substances, that which makes oxygen grega-
rious and helium a hermit, which gives iron sensitivity to
DEEPER INTO THE ATOM
magnetism and caesium a responsiveness to light, which im-
plants in the carbon atom such capacities as a "joiner"
that the huge molecules of living substances are enabled to
form and to hold together all these and other distin-
guishing properties of elements, although apparently "ex-
ternal" attributes, are determined here in the innermost
depths. In the atomic nucleus and not in some far-
off center of galactic rotation is the power house of
the Universe, multiplied endlessly, repeated in each of the
innumerable hidden microcosmic systems. Are they the
"mills of the gods" ? the "looms of destiny" ? the "mighty
workings" that somehow spin our mortality? Physicists, as
scientists, can not answer, though some in their more
metaphysical moods may risk to pronounce on such ques-
tions. As scientists they believe that in the nucleus is the
mechanism of matter stripped to its prime mover; hence the
preoccupation of experimental physics today with this field.
The nucleus is the battlefront for a score of brilliant
strategists in America, Europe, and Asia. Against it the
artillerylike discharge tubes, the mighty cyclotrons, and
other atom-smashing devices are aimed. And it was along
this front that the Washington experimenters won their
1936 victory.
The story of the discovery can be simply told. And I shall
make the telling very simple, beginning with familiar con-
cepts, recalling elementary features that are common
knowledge, ignoring complications such as "wave behavior"
and other items of quantum theory that are so important
and indeed indispensable to the technician but not neces-
sary to the present resume, and shall focus attention only
on features primary to our picture. Admit that we are
imagists. All word pictures of atoms must necessarily be in
the nature of parables, of moral tales, with the whites all
white, and the blacks completely black. We understand
among ourselves, of course, that white shades into black
along gray no-man's lands; but these defy precise picturiza-
THE ADVANCING FRONT OF SCIENCE
tion, and attempts to include all details in one parable
result only in confusion. So let us be realistic and, there-
fore, imaginative. Our parable is frankly an approximation
devised to illumine one facet of truth. If it does that it will
have performed its intended function, and proved itself a
useful parable.
A drop of water contains about 200 million million mil-
lion molecues. No one has made an actual count, of course
there are not enough years in which to count that number
of objects but we know how much a drop of water weighs,
we know how much a molecule of water weighs, and the
rest is simple division. I mention the number to suggest the
smallness of the scale of dimensions that we must accept in
approaching the realm of the elementary particles. A drop
of ordinary water weighs about 3600,000,000,000,000,-
000,000 atomic units. A molecule of water weighs about
18 units. The molecule is far beyond the limit of visibility
even with the ultramicroscope, but we have chemical and
physical ways of isolating it, measuring it, dealing with it
quite objectively. Let us enter this molecular world.
Send a current of electricity through the water. The
molecules begin to break up into three pieces each: one piece
of oxygen and two pieces of hydrogen. These are the atoms.
And by further manipulation with electricity we can break
the atoms into yet more fundamental units hydrogen into
a certain number and arrangement of particles, oxygen into
a different number and arrangement.
This hydrogen is highly interesting. Apparently it is the
most abundant element in the Universe. Its atom is the
simplest material system we know an arrangement of two
charged particles, one massive and electrically positive,
the other lighter and more, diffuse and electrically negative.
The negative charge is the electron, and it revolves as a
swiftly moving satellite round the positive charge, the proton.
[n6]
DEEPER INTO THE ATOM
And now we have reached the solid land we seek, the
nucleus. For the proton is the hydrogen nucleus. If we could
magnify the hydrogen atom so that its proton became just
barely visible, the encircling path of the spinning electron
would be about 6 feet from that center. Both particles
barely large enough to be seen, and yet the revolving system
outlines a sphere 12 feet in diameter? You can see why we
think of the atom as an abyss, mostly empty space, its
members relatively farther apart than the Earth is from
the Sun.
The proton is the simplest nucleus now known. Appar-
ently it is a single particle. Physicists find no difficulty in
breaking hydrogen atoms, stripping off of each its revolving
electron, and leaving the proton naked. Then they subject
this unprotected proton to concentrated bombardments,
using projectiles even more massive than the target, and
shooting them at velocities of thousands of miles a second.
But somehow the proton holds together. No one yet has
been able to break one at least, we have no clear evidence
of such breakage. And so we assume that the proton is an
indivisible unit. It is extremely massive. If you could lay
a single proton in one pan of the scales of an infinitesimal
balance, you would need to pile 1835 electrons in the
opposite pan to bring the weight to equilibrium. Protons
represent a tremendous amount of matter concentrated in
small space. And the stuff of this matter appears to be
electricity.
Apparently the proton is nothing but electricity elec-
tricity of a peculiar behavior which we label positive.
Similarly, the electron is pure electricity, but negative. A
curious unexplained fact of nature is that the two particles
exactly balance each other in electrical characteristics.
That is to say, a piece of positive electricity, which is equal
to 1835 pieces of negative electricity in quantity of mass,
is equal to only I negative in quantity of charge. And so we
find that despite its relatively enormous weight, the
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THE ADVANCING FRONT OF SCIENCE
proton is never attended by more than one electron. You
may surround the atom with electrons, penetrate its depths
with speeding electrons, but none of them will stick.
Sometimes we find a hydrogen atom of double weight.
But the extra weight is entirely within the nucleus, for only
a single revolving electron is found in these as in all other
hydrogen atoms. Examine the double-weight nucleus and
we see why this is so: it is a two-particle affair, made of one
proton and one neutron. The proton is our familiar posi-
tively charged particle. But the neutron is a curiously
neutral thing; for it has no charge, and, although its mass
is about the same as that of the proton, it shows no elec-
trical characteristics, neither attracts electrons nor repels
them. More recently the atomic explorers have turned up
hydrogens of triple weight; the nucleus here contains one
proton and two neutrons, but even these swing only the
single orbital electron. Apparently a nucleus, no matter
how massive it is, can control only one electron with one
proton.
With more protons, however, it can control more elec-
trons. This we may demonstrate by examining that other
partner in the water molecule, the atom of oxygen. Its
nucleus is a complex of protons and neutrons. Some oxygens
contain eight neutrons, a few contain nine, and a still
smaller proportion of the world's oxygen contains ten
neutrons; but every last one of them contains eight protons,
and only eight. Also, every last one of the oxygen atoms
swings eight orbital electrons, and only eight. This arrange-
ment of matching one orbital electron against each nuclear
proton appears to be one of nature's immutable principles of
architecture; for as we go up the scale of atoms, the rule
holds without an exception.
There is another rule of electrical behavior that we sup-
posed held imperiously. This is the rule that if a body is
positively charged and another body is negatively charged,
they will mutually attract each other; but contrarily, two
l8.J
DEEPER INTO THE ATOM
bodies carrying the same kind of charge will be mutually
repellent. Just before the upheaval of the French Revolu-
tion the Parisian scientist Charles Augustin Coulomb made
very careful measurements of these electrical forces of
attraction and repulsion, and discovered the law by which
they operate. The nearer together the bodies are, the
stronger are the forces; and the forces increase inversely
with the square of the distance, just as gravitation does.
This is Coulomb's law.
To illustrate its operation by a very obvious example,
recall our enlarged model of the hydrogen atom with the
proton just visible at the center and the electron revolving
round it at a radius of 6 feet. Suppose we measure the
electrostatic force of attraction between proton and elec-
tron at that distance. Then, if we bring the electron
nearer, so that it is only half as far, or 3 feet, the force of
attraction will not be two times; it will be the square of
two, or four times as great. If we bring the electron still
nearer, so that it is only a third of the original distance,
the attraction will be magnified by the square of three, or
nine times. It is easy to see from this why electrons in orbits
closer to the nucleus move more rapidly. Just as the
velocity of the Earth in its circuit generates centrifugal
force to counterbalance the gravitational influence of the
Sun, so does the velocity of the electron in its curving path
engender such an effect to offset the attraction of the
nucleus. Hydrogen atoms would collapse were it not that
the electron moves so swiftly. A velocity of 1350 miles a
second has been calculated for the innermost orbit of
ordinary hydrogen.
These mutual relations between the positively charged
nucleus and the negatively charged satellite appear to con-
form strictly to Coulomb's law. This is true not only for
the simple hydrogen atom; it has been observed also in the
behavior of more complicated atoms. The eight electrons of
the oxygen atom, for example, move in their orbits at
THE ADVANCING FRONT OF SCIENCE
velocities proportional to their distances from the eight
protons in the oxygen nucleus.
Eight protons in a nucleus ? The reader who has followed
the parable thus far may reasonably object. How can the
oxygen nucleus hold together?
This indeed is our dilemma. The nucleus of oxygen is
very small, not much larger than the nucleus of hydrogen.
But the primary objection is not that so many particles
should exist in a space not much larger than one of them,
but that the particles of positive electricity should stay
together at all.
Coulomb's law insists that positive particles repel one
another in the same degree that they attract negative par-
ticles. Abundant experience confirms the law. There are
electric motors activated by this force of repulsion; it
operates in telephone and telegraph circuits; it is used in
other industrial applications. No behavior of electricity is
better known among the large-scale phenomena of elec-
trical engineering. Engineers only occasionally deal with
pure charges of electricity; most of their work is with gross
bodies carrying charges. But the chemist Frederick Soddy,
after measuring the force of repulsion that exists between
two free protons, made an interesting calculation.
A gram is a small quantity in our everyday world; it
rates about the twenty-eighth part of an ounce. But Dr.
Soddy's figures show that if it were possible to accumulate
a gram of protons at one pole on the Earth's surface and
another gram at the opposite pole on the other side of our
globe, the mutually repellent force of these two small
quantities of positive electricity would be equivalent to the
pressure of 26 tons, even at that distance of about 8000
miles. Try to imagine, then, what should be the repulsion
of proton against proton within the narrow zone of the
atomic nucleus, where dimensions are reckoned in tenths
of million millionths of an inch.
On the logic of Coulomb's law one could expect to find
no atoms in the Universe except those of hydrogen, since
[ 120]
DEEPER INTO THE ATOM
it should be impossible for more than one proton to occupy
a nucleus. And if by chance two or more high-speed protons
collide and find themselves accidentally associated in close
quarters, Coulomb's law required that they instantly fly
apart at terrific speeds of repulsion. Instead of this, the
searchers found that the physical world includes a com-
plete sequence of "impossible" structures the helium
atom with 2 protons in its nucleus, the lithium with 3,
beryllium with 4, boron with 5, carbon with 6, and so on
up the scale to the heaviest, uranium, with its gigantic
family of 92 protons housed with 146 neutrons in the
diminutive confines of nuclear space.
This uranium atom, to be sure, is a wobbly structure.
Every now and then one ejects a cluster of protons and
neutrons from its center, to leave a less crowded residue.
This residue we call radium, and its nucleus in turn also
explodes with a series of ejections, breaking down to form
the simpler polonium. Finally polonium, after ridding itself
of a cluster oi 2 protons and 2 neutrons, settles into the
stable structure we call lead. But why should lead be
stable ? Its nucleus, even after the successive explosions,
still contains 82 protons, and each of them should waste
no time in getting away from the hated presence of its
fellows.
Such is the anomaly that for more than 20 years defied
explanation. 1 Coulomb's law, which ruled precisely in the
atomic environs and within the spaces between nucleus
and orbits, did not apply to bodies in the central core. Why
1 Until the discovery of the neutron (1932) atomic nuclei were thought to
contain protons and a smaller number of electrons, but the nature and binding
forces of such a structure were a complete puzzle, outside all conception of
theory. The neutron helped the situation but little, although it conceivably
could act as the intermediary for binding protons together in spite of their
repulsive forces. In fact, a whole theory of nuclear structure, now abandoned,
was built up on this hypothesis as soon as specific forces, assumed to be attrac-
tive, were demonstrated by neutron-scattering experiments to exist between
neutrons and protons. These forces, it is now known, assist the proton-proton
and neutron-neutron forces in binding the nuclear particles together.
[121]
THE ADVANCING FRONT OF SCIENCE
was it flouted there ? By what supreme court, by what more
powerful ordinance, was it overruled ?
The Washington experiments of 1936 brought the first
satisfactory answer to that question. They penetrated the
inner fortress to demonstrate directly the existence of a
mighty force which is operative only within the small
dimensions of the nuclear zone a force more powerful
than the Coulomb force of repulsion, more attractive than
the Newtonian force of gravitation: a sort of central traffic
control which dominates and directs the other material
forces. Apparently it is responsible for the wide variety
of atomic forms that matter may assume. Also we are to
think of it as a unifying agency which underlies all physical
reality. Without it there could be no metal, no carbon, no
living cell, no Earth, no Sun, no Galaxy, no manifold Uni-
verse there could be nothing more complex than hydrogen,
and the Whole would be only a vast cloud of diffuse
hydrogen gas interspersed or combined with free neutrons.
At least, such is the picture we infer from the facts we
know. Our new-found force is the medium that holds the
world together. It is the invisible tie that binds.
Many of the great discoveries of science were accidental
finds, but this binding force of the nucleus was not chanced
upon by accident. Its detection is the culmination of 10
years of experiments aimed directly at this mystery.
When the Carnegie Institution of Washington estab-
lished a Department of Research in Terrestrial Magnetism
in 1904, the specialists in charge realized that their studies
must lead eventually to atomic physics. At that time no
one dreamed of massive central nuclei surrounded by
revolving electrons. But no one doubted that the secret of
the Earth's magnetism, of whose reality the quivering
compass needle is perpetual witness, must be sought not
only in the Earth and its atmosphere but also in the in-
[122]
DEEPER INTO THE ATOM
visible molecules and atoms of the needle itself. Matter
must be minutely explored for the magnetic mechanism
within it. The early studies were directed at large-scale
phenomena, magnetic surveys of the continents and seas,
and mapping; but in 1926 a definite program of subatomic
research was initiated. By this time considerable data on
the intimate behavior of subatomic parts had been accumu-
lated by laboratories in Europe, Canada, and the United
States. Conspicuous among the anomalies thus brought to
view was this curious inexplicable behavior of protons
within the nucleus. The Coulomb forces are so fundamental
to our idea of the response of the compass needle that any
variation or suspension of their action in any region of the
Universe must be a cause of concern to explorers of mag-
netism. And so, among the problems outlined for inve's-
tigation by the department was that of the nature of the
nuclear mechanism. A special laboratory was built to house
the research. Special apparatus was designed and installed:
first a high-voltage discharge tube capable of delivering
momentary blows with a pressure of about 1,000,000 volts;
then an electrostatic machine and tube continuously ener-
gized by 500,000 volts; and finally the present towering
atom smasher of 1,200,000 volts capacity, with which the
great detection was achieved.
The detectives in this search were led by Merle A. Tuve,
and the group included L. R. Hafstad, O. Dahl, and N. P.
Heydenburg, physicists all. At various times during the
10 years other men were on the staff, and each contributed
some spark of illumination to the slow plugging through
the darkness. But I am naming above the fortunate four
who were working with the big atom gun that cold January
day early in 1936 when the first rumors of the new result
began to trickle in. Months were to pass before the dis-
coverers made any public announcement of what they had
done for an effect so apparently exaggerated must be
tested, checked and rechecked, and submitted to the
THE ADVANCING FRONT OF SCIENCE
penetrating eye of mathematical analysis before it could
be announced as a certainty. Indeed, nearly as important
as the observations themselves, which by direct inspection
only showed the failure of the Coulomb law, was this
mathematical analysis of the observations in terms of the
"wave mechanics," a service performed by Gregory Breit
and two associates. All these tests and calculations, the
checkings and recheckings, were concluded successfully,
and the full story of the discovery was reported to the inter-
national group of scientists assembled at Cambridge in Sep-
tember of 1936 for the Harvard Tercentenary Conference.
The thing sought in the experiments was a definite
measurement. We may outline the logic of the campaign
in three steps. Observation had shown (i) that protons
dwell together within a nucleus, and (2) that protons out-
side a nucleus are repelled; therefore, reasoned Tuve and
Breit and their associates, there must be (3) a critical dis-
tance at which the force of repulsion is overcome and within
which the protons become reconciled to one another's
presence. To find that critical distance became the first
objective.
The means used were those of bombardment. Suppose
you have a vessel full of pure hydrogen gas of a measured
density. And suppose you fire a stream of protons into this
atmosphere of hydrogen. Each hydrogen atom, remember,
has a proton in its core; so what you are doing is a bom-
bardment of protons with protons. Some of the bombarding
protons will approach the nuclear protons head on, others
may pass close by on either side, and in every case the
mutual forces of repulsion will act to rebuff the particles.
They will never touch; the collisions will be only approaches
and the nearer the approach the more powerful will be the
repulsion. Since targets and projectiles are of equal mass,
the effect will be a scattering. But the scattering will not
be heterogeneous; it will be quite systematic in its direc-
tions. Just as it is possible to predict the behavior of
DEEPER INTO THE ATOM
billiard balls from the angle at which the projectile ball
strikes the target ball, so it is possible to predict the
behavior of the protons. Some years ago the British
physicist N. F. Mott made a careful mathematical study
of this phenomenon, and predicted the relative number of
protons that would be scattered from each angle of ap-
proach in obedience to Coulomb's law.
All these data of the ratios and numbers of particles that
would be turned back at each angle were available for
Dr. Tuve and his laboratory crew. They provided a sort of
bench mark, a measurement of the norm of behavior to be
expected of protons acting according to Coulomb's law of
repulsion. Any departures from this norm might be regarded
as evidence of the breakdown of the law. And what the
Washington experimenters proposed was to bombard
hydrogen gas with faster and still faster protons until they
got a scattering different from that predicted by Mott's
calculations. The greater the velocity of the protons, the
greater would be their momentum, and therefore the
greater would be their ability to overcome the repulsion
and approach closer to the nucleus.
This game of aerial billiards with ultrascopic particles
seems very simple in principle, but it proved almost in-
finitely difficult in execution. The measurement of the
angles could mean nothing specific unless there were an
equally accurate measurement of the purity of the particles,
of the density of the particles in the hydrogen at the target
end of the apparatus, and of the velocity of the stream of
projectiles. Very precise control was required in each of
these items. Without going into details of the successive
steps, I can say that many expedients, many variations,
many skills were tried before the actual scattering experi-
ment was even attempted, and before the present apparatus
with its marvelously exact control was attained.
The atomic artillery piece looks its part a sort of super
machine gun mounted on its sprawling tripod, towering 20
THE ADVANCING FRONT OF SCIENCE
feet above the floor, with its muzzle pointing straight down
and passing through the floor into the basement room be-
low. At its top is an aluminum sphere of 6 feet diameter,
the loading device. Descending from the sphere is a vacuum
tube of sturdy glass, the aforesaid muzzle. Charges of
positive electricity from a generator are fed by a traveling
belt to the aluminum sphere, and these are allowed to
accumulate on the metal surface to build up a pressure as
high as 1,200,000 volts, under conditions of accurate
control and precise measurement. This pressure discharges
steadily through the long vacuum tube; and by releasing
protons into the tube at the top, the gunner provides pro-
jectiles for the voltage to work on. The protons may be
speeded to any desired velocity, depending on the voltage
applied; and, what is equally important, the installation
includes clever focusing devices to concentrate the stream,
and an analyzing magnet at the bottom to pull out stray
particles, unwanted molecules, and stragglers along the
fringes of the stream. Thus the instrument is able to deliver
to the target chamber at the bottom of the tube a finely
focused stream of homogeneous protons all moving in paral-
lel lines and at the same velocity.
In effect, it is as though you had generated a continuous
lightning bolt, had harnessed it within the confines of the
vacuum, had sifted out all heterogeneous and diffuse ele-
ments, and concentrated its missiles into a steady beam
narrowed for a measured attack on anything you choose to
place as a target in its path.
The target chamber in which the scattering takes place is
in the basement room, at the focus of the tube. This
chamber is a small cylindrical compartment about 6 inches
in diameter, into which highly purified hydrogen gas is
released. And built into the compartment is an ion detector
mounted on an axis so that it may be pointed toward the
incoming stream of projectiles at any angle, ranging from
zero to ninety degrees. Here is the final link in the chain of
[126]
DEEPER INTO THE ATOM
stratagems. For, by knowing precisely the original number
of particles in the beam, and the number of particles
(hydrogen gas) in the chamber, and then by counting the
actual number of rebounding or swerving particles which
smash into this detector at each of its angular positions,
you can tell whether or not the projectiles are being scat-
tered according to Mott's calculations i.e., according to
Coulomb's law.
When the thing is operating there is an awesome hum, the
drone of the generating mechanism. Occasionally, when
affairs are not well adjusted, a spark will flash with a lively
crackling from the charged belt to the ceiling above the
sphere. And to stand on the floor of this room is to place
oneself in the presence of invisible influences which curve
through space along the mysterious lines of force which
radiate from charged bodies. Indeed, one becomes a charged
body. My finger put out toward another person sprayed
sparks.
But the workers spend most of their time in the base-
ment room where the targets are manipulated. Lead salts
fused in the glass of the tube protects them from random
x-rays and other stray radiations that might be generated
by chance collisions of the protron stream passing down the
tube. Very accurate is the detector device which measures
the number of protons scattered at each angle. Each of the
bounced protons gives a signal, the signal is amplified by a
powerful device, and thereby these infinitely small move-
ments of infinitely small objects are brought within the
range of man's perception.
Tuve and his associates began the bombardment with a
stream energized by a pressure of 600,000 volts, which
means that the protons had velocities of 6720 miles a
second. The detector registered the scattering for each
angle, and found that Mott's calculations held, that
Coulomb's law of repulsion was operating quite normally.
Then the bombarders increased their artillery fire; the
[127]
THE ADVANCING FRONT OF SCIENCE
pressure was increased to 700,000 volts, speeding the
particles to 7200 miles a second and Coulomb's law still
held. They quickened the attack to 800,000 volts, produc-
ing velocities of 7700 miles a second and the ancient law
began to show evidence of failure. Then the electrical poten-
tial was raised on up to 900,000 volts, the stream of protons
moved with the momentum imparted by velocities of 8200
miles a second, and now something new began to happen !
Instead of recoiling or swerving as before, the projectiles
moved in toward their nuclear targets. The change in the
number of scatterings from certain significant angles said
so, and spoke unmistakably. The inertia of the fast-moving
protons carried them headlong through the zone of rapidly
increasing force of repulsion until at last the critical dis-
tance had been attained by sheer brute momentum, the
long steeply ascending barrier of the nucleus had been
mounted, and the invading proton was admitted to the
citadel.
Hundreds of experiments of this kind were performed.
There could be no doubt that the Coulomb law had failed
but why ?
The records of all the observations were forwarded to
Gregory Breit for further analysis. Dr. Breit is a mathe-
matical physicist, was long on the staff of the Department
of Research in Terrestrial Magnetism indeed he was the
leader of this atom-smashing crew at the beginning of the
campaign back in 1926 and is still connected with the
Washington laboratory as a research associate. But he is
now professor at the University of Wisconsin, and in the
winter of 1936, when this body of observational data
reached him, chanced to be in Princeton attending the
Institute for Advanced Study. Right in the neighborhood,
across the corridor in Palmer Physical Laboratory, was
Edward U. Condon, whose mathematical explorations of
atomic behavior have given him wide experience with
these technicalities. Dr. Breit called Dr. Condon into con-
sultation, and together they began to dissect the batch of
[1281
DEEPER INTO THE ATOM
plotted curves and numerical tabulations. Certain details
of the problem made it expedient to consult another expert,
and R. D. Present of Purdue University made the third
member of this mathematical team. By applying the highly
complex calculations of "wave mechanics" to the experi-
mental observations, Breit and his associates showed that
beyond all doubt the observed failure was not attributable
to a possible added repulsion (for a sudden sharp increase
here might also distort the predicted scattering), but was
actually a result of encountering for the first time the long-
suspected attractive force which binds particle to particle
within the nucleus.
The outcome of the mathematical analysis of these experi-
ments may be conveniently summarized as four findings.
1. The critical distance at which the Coulomb force of
repulsion between protons breaks down is about 1/12,000,-
000,000,000 of an inch. ,
2. The sudden change which occurs in the relations
between two protons separated by this critical distance
can be explained if we assume the existence of a superior
force of attraction which at that and lesser distances
dominates the two particles.
3. The binding power of this force, as it operates be-
tween two protons at the critical distance, is approximately
io 86 times greater than the Newtonian force of gravitation
between the two protons.
4. Not only protons but also neutrons are subject to this
powerful force. The attractive force between a proton and
a neutron or between two neutrons is the same as that
between two protons, except for the absence of the Coulomb
repulsion when the chargeless neutrons are involved. These
conclusions regarding neutrons are derived indirectly from
other data, but the evidence seems to indicate that the
nuclear force of attraction is somehow intimately asso-
ciated with the mass of these primary particles, and de-
pends little, if at all, on whether or not they are electrically
charged.
[129]
THE ADVANCING FRONT OF SCIENCE
To grasp some concrete idea of the enormity of this
force we must resort to a comparison. Remember that the
proton is inconceivably small. Its weight is less than this
almost infinitesimal fraction of a gram:
600,000,000,000,000,000,000,000
And a gram is ^54 of a pound.
Now the measurements show that the pull of proton for
proton within the region of the nucleus is so great that the
two tiny particles move toward one another as though im-
pelled by a pressure of from 10 to 50 pounds. If the New-
tonian force of gravitation operated on the same scale, a
feather on the Earth's surface would weigh billions of tons.
When free protons or neutrons are captured and incor-
porated into a nucleus, a certain proportion of the original
mass of the particles is converted into energy. The nuclear
force, by its bringing of the particles together, seems to
take a toll out of their substance, and the wnole nucleus
becomes lighter than the sum of its separate parts. Thus, if
we weigh a single proton the scales show a mass of 1.0081;
if we weigh a single neutron, 1.0091. The total weight of
the two particles therefore is 2.0172. But when they unite
to form the nucleus of a heavy hydrogen atom, the mass
of the resulting nucleus is only 2.0147 in weight. The dif-
ference, .0025, represents the energy of the binding force
which holds the two particles together. By computation we
find that .0025 of mass is equivalent to 2,200,000 volts of
energy. And experiment shows that to crack a heavy hydro-
gen nucleus and separate its neutron from its proton
requires the blow of a projectile moving with an energy
exceeding 2,200,000 volts.
3
By these means, and in other ways as well, the new-
found phenomena check. There dwells within the centers of
[ 130]
DEEPER INTO THE ATOM
atoms atoms of the rocks, atoms of the air, atoms of flesh
and blood this titan of forces, this indefinable dryad, if
you will, which pulls masses together, expends tremendous
energy to bind them into nuclear systems, and in the
process makes the masses less massive.
Various names have been proposed for the new entity.
One suggestion is that it be called the force of "-levity,"
since the effect is to reduce the masses of the bound par-
ticles and therefore to make them lighter; but surely levity
is not the most fundamental aspect of this tie that binds.
Another suggestion is "supergravitation"; but the new-
found force is so superlatively super that this title sounds
makeshift. The thing has also been referred to as the force
of " nucleation," suggesting its effect in causing elementary
particles to consolidate their influences, to nucleate into
atomic cores. Since the force manifests itself as the central
force of all physical nature, it deserves an unequivocal
name.
We may surmise that gravitation, magnetism, and the
electrical properties of attraction and repulsion are only
special cases, or conditioned reflections, reactions, or inter-
actions, of this mighty central Something that holds the
world together.
And what shall we say of atomic power that dream of
the modern alchemists who have said that energy sufficient
to propel an ocean liner across the Atlantic is locked within
a teaspoon of water? Surely its secret lies here. Reckon the
billions of billions of protons and neutrons contained in
water, remember that each is bound to its neighbor with a
force of millions of electron-volts, that proton is linked to
proton as if with a pressure of many pounds, and sum up the
total. If it were possible to treat a teaspoon of water
expeditiously, to cause the protons of its hydrogen atoms
to combine into more complex nuclear patterns and thus
form atoms of heavier elements, the energy released in
binding these interior particles together would total several
[131]
THE ADVANCING FRONT OF SCIENCE
hundred thousand kilowatt-hours quite sufficient, if har-
nessed, to drive a steamship from New York to Havre. But
we must admit that we know no. means of harnessing the
forces even if we were able to release them economically;
and the plain fact is that our present methods of separating
and synthesizing nuclear structures require more energy
in the bombardment than we get back from the trans-
mutations. The utilization of atomic energy is a goal for
the future as far as we can see today, for the very distant
future but a beginning has .been made in the Washington
experiments. The discovery and measurements of the
forces provide a firmer basis for our dreamers and, let us
hope, for our future engineers.
Dr. Tuve and his associates are planning deeper forays.
In 1937 they began the construction of a new electrostatic
generator and discharge tube designed to operate at
potentials above 5 million volts. Protons accelerated by
this electrical pressure will hit the target witii a velocity
of 19,300 miles a second. The resulting momentum should
carry the projectiles into the nuclear zones of massive
atoms, such as those of the metals, whose inner cores present
complexities in striking contrast with the simplicity of
hydrogen. The problem is a peculiarly enticing one,
and various laboratories in Europe and America are now
engaged in a strong attack upon it. The frontiers have
been crossed, but a vast hiddenness still awaits explora-
tion. The nature of the internal structure, how the interior
particles move and interact within their narrowly bounded
zone, their degrees of freedom and compulsion such ques-
tions beg for answers. There are inklings of news from
within, fragmentary flashes of this and that, and theorists
are never idle with their charming mathematical symbolism.
But the ultimate battle must be won by the experimentalist.
Theory must be tested and proved by experience, before
we can go in and possess the new land.
Chapter VIII -THE NEW
SCIENCE OF SOUND
Hear ye not the hum
Of mighty workings ?
JOHN KEATS, SONNET XtV
IT is not only in the microcosmic realm of atomic trans-
mutations and mysterious nuclear forces that the world
of physics has become new again, and exciting. Even so
ancient and familiar a technology as acoustics, which dates
from the time of Pythagoras, has inhaled new life and re-
ceived new illumination from the recent applications of
electronics. Indeed, our modern engineering of sound
waves is a thing of the telephone era. And in the last decade,
with the swift rise of the radio and the talkies and their
insistent demands upon the laboratories, so much that is
new has been discovered and so much that was old has
been rescued from guesswork that acoustics today may be
rated among the youngest of the sciences. Recent experi-
mental findings overturn many of the classical formulae.
Physicists are beginning to use sound waves as probes for
inquiring into the intimate behavior of gaseous matter.
Chemists are learning that there is a chemistry of sound.
Engineers are putting the more precise knowledge to work
in new musical instruments, in new arrangements for en-
hancing the auditory characteristics of rooms, and in
clever schemes for reducing the noise nuisance.
[133]
THE ADVANCING FRONT OF SCIENCE
Many devices enter into the equipment of the new
acoustics, but two may be regarded as the lever and ful-
crum of our advance: the microphone, and the thermionic
vacuum tube.
The microphone is the electric ear which picks up waves
of sound and converts them into a faithful counterpart of
waves of electricity. By transforming sound patterns into
electrical patterns we reduce them to more manageable
phenomena, and on this facility hinges the whole rapid
development.
The vacuum tube is so versatile that a full list of its
services would be a lengthy catalogue. In general one may
say that the vacuum tube makes possible the amplifier
which is indispensable in long-distance telephony, in radio
transmission and reception, in the acoustical performance
of sound pictures, and in many other applications.
Both microphone and vacuum tube are essential parts
of the new instruments of measurement the s^und meters,
frequency analyzers, and other mechanisms for the exact
determination of the characteristics of vibration. It is these
sensitive gauges that have given a new precision and an
unaccustomed control to acoustics. They have substituted
for the judgment of the ear, with its variable sensitivity and
its liability to psychological bias, the impersonal verdict
of the pointer reading. Even in those fields in which human
judgment must be the final arbiter the electrical measuring
devices have enabled us to make more accurate tests of
what the ear hears. They have revealed much that was
unknown and corrected much that was wrongly believed.
It has long been believed, for example, that each of the
three recognizable characteristics of a musical tone is deter-
mined by a single physical characteristic of the sound
wave. Pick up any standard textbook of physics and you
[134)
THE NEW SCIENCE OF SOUND
will doubtless find some such pronouncement as this: The
pitch of a sound depends upon the frequency of its vibra-
tion, the loudness on the amplitude of its wave, and the
timbre on the shape of its wave. This generalization reduces
the subject to a neat formula, pigeonholing each char-
acteristic with a single determining cause but recent re-
search shows that it does not tell the whole story.
Experiments conducted by Harvey Fletcher and his
associates at the Bell Telephone Laboratories demonstrate
that a variation in any one of the three factors may affect
each of the tonal characteristics. They prove that pitch
may be changed by altering the amplitude or the wave form
as well as by altering the frequency; and similarly that
loudness and timbre may respond to changes in frequency
or amplitude or wave form.
In the case of pitch, for example, tones that have fre-
quencies of about 200 cycles (or vibrations a second)
appear to be very sensitive to changes in loudness. This is
the pitch that approximates that of middle A on the piano,
and is well within the range of most human voices. Dr.
Fletcher has found that if a tone of 200 cycles at a certain
loudness is amplified a hundredfold, its pitch may be heard
as a semitone lower. With still increased loudness the lower-
ing of pitch is yet more pronounced. Thus as the sound is
intensified in volume its pitch tends to shift from the
soprano toward the bass end of the scale.
The relation of loudness to changes of pitch is also experi-
mentally proved. For example, Fletcher finds that if a tone
of loo-cycles frequency is sounded with an intensity cor-
responding to 35 decibels above its threshold of audibility,
the tone gives a sensation of loudness equal to that of a
zooo-cycle tone at 60 decibels. Thus, as a low-pitched tone is
raised above its threshold intensity it increases in loudness
much faster than does a high-pitched tone. It covers as
long a range of loudness in going up 35 decibels as the
high-pitched tone does in rising 60 decibels.
[135]
THE ADVANCING FRONT OF SCIENCE
In the shaping of timbre and by timbre is meant the
quality which enables the ear to recognize one sound of a
given pitch as violin music and another sound of the same
pitch as vocal or piano music equally complicated factors
enter. This may be demonstrated when violin music is
reproduced over high-quality electrical system which
permits the sounds to be amplified to any degree of loud-
ness. By the use of electrical filters or other analyzing
devices it is possible to show that, no matter what amplifi-
cation is used, the wave form remains the same, with all its
overtone structures preserved intact and we used to think
that these structures alone determined the timbre. But if
the violin vibrations thus unaltered in wave form are
amplified to a loudness 10 to 100 times that of the sound
coming directly from the violin, they lose their violin
quality and are no longer recognizable. Other experiments
show that the timbre may be changed by varying the pitch.
All these discoveries have come to a focus since 1930.
And while the research cannot by any means be said to be
complete, the results are sufficiently representative to give
composers, singers, orchestra directors, and others an
obvious hint. Glorious as is its past, music may have a
still more distinguished future when these new relations of
its physical components are made use of by its creative
artists when acoustical art builds its beauty anew on the
realities of acoustical science.
The sounds we hear are only a fraction of the sounds that
exist. Indeed, it seems likely that the silent waves are more
numerous than the audible pulsations which make up our
speech, our music, and our noise.
Some sounds are inaudible because their vibrations are
of a frequency beyond the ability of the nervous system to
register. They are comparable to the ultra-violet light, whose
waves oscillate with a rapidity so great that the eye is in-
THE NEW SCIENCE OF SOUND
sensitive to their vibrations. It is only by means of instru-
ments that we are able to detect these invisible radiations,
and similarly it is only by ingenious devices of apparatus
that we are able to prove the presence of silent sounds. Of
course their existence has long been suspected. We hear a
hummingbird sing; his notes soar higher and higher until
finally nothing is heard. And yet his mouth is open, his
throat is pulsing, there is visual evidence that he is still
singing. Certain crickets also shrill their calls at a very
high pitch.
Recently, at the Research Laboratory of Physics at
Harvard, George W. Pierce and his associates set a trap to
catch these unheard melodies. They made use of certain
characteristics of crystals by which it has been found pos-
sible to control the vibrations of electrical devices. Crystals
cut of Rochelle salt, for example, have a wide range of
response and will vibrate in phase with sound waves that
strike them.
Dr. Pierce and his coworkers installed a Rochelle crystal
in a parabolic horn, and made this the receiving end of a
very sensitive sound detector. The apparatus is so respon-
sive that it can pick up the sound of a cricket at a distance of
900 feet. When the sound waves gathered by the horn strike
the crystal, the crystal responds at their frequency and by
its vibrations gives rise to a varying voltage. The sound
waves of the cricket's notes are thereby converted into
electrical vibrations, and these weak electrical waves are
amplified with the aid of vacuum tubes and other appa-
ratus. The result is a pattern of electrical vibrations cor-
responding precisely in frequency to the pattern of sound
waves. But how to detect that inaudible frequency? Dr.
Pierce reasoned that if he combined with the unknown
vibration another vibration of a known frequency that
from an electric oscillator, for example and applied the
two superimposed vibrations to a vacuum-tube detector,
certain coincidences of the two sets of waves should occur.
[137]
THE ADVANCING FRONT OF SCIENCE
And these coincidences or beats should make an audible
vibration in the loud-speaker. By analyzing the frequency
of this audible vibration, and knowing the frequency of
the super-imposed vibration from the electric oscillator,
one should be able to determine the frequency of the original
sound which actuated the Rochelle crystal.
The plan worked. A small brown field cricket (Nemobius
asciatus, by name) is shown by this apparatus to give off
a variety of high-frequency sounds. The main pitch of his
song was recorded as about 8000 vibrations a second, with
other notes strongly registered as 16,000, 24,000, and
32,000 cycles. Nor is this the limit. In their laboratory the
Harvard scientists have produced and detected sounds
having frequencies up to 2,000,000 cycles, and have demon-
strated the existence in nature of sounds as high-pitched as
40,000 cycles.
This is far beyond the range of human hearing. Few ears
can discern sounds of frequencies above 20,000 cycles, and
for most adult ears the limit is nearer 18,000. The higher
the frequency of a sound, the shorter is its wave length;
and there can no longer be any doubt that waves of ex-
ceedingly short length and very high frequency are con-
tinually agitating the air. Not only the crickets and other
insects, but scores of frictional encounters in nature, the
rubbing together of the hands, the blaze of an igniting
match, the vibration of leaves stirred by the wind, the
friction of clothing, are shown by these experiments to
produce, in addition to audible noises, many sounds of
pitch too high for human hearing. In the ticking of a watch
certain sounds of 30,000 cycles were detected at a distance
of 30 feet.
In addition to this unheard symphony of supersonics
which surrounds us there is a medley of audible noises
perpetually present but rarely if ever recognized because
of the competition of more energetic air vibrations. For
example, the beating of the heart makes a sound, and some
[138]
THE NEW SCIENCE OF SOUND
of this sound would be heard if our hearing were not already
monopolized by the continual agitation of louder sounds.
These latter have a masking effect like that of a passing
trolley's clanging when the listener is trying to give ear to
a delicate piano melody. When the masking noises are
shielded off, the weaker audibilities become perceptible.
In a perfectly soundproof room (an acoustical Utopia that
does not exist) the listener would be able to hear the minute
sounds made by his own pulse, the flow of blood through
arteries and veins, the pumping of the lungs, the inflow
and outflow of breathing faint audible sounds which
actually have been measured.
To measure sounds of low intensity it is necessary to
isolate them. An example of how this may be done was
demonstrated in a New York University classroom. E. E.
Free and his associate C. A. Johnson fitted up a cup with a
sensitive microphone as its bottom, connected this electric
ear with a powerful amplifying system, and closed the
circuit through a loud-speaker. When the cup was filled
with a handful of wheat grains, violent noises issued from
the loudspeaker crunchings and grindings so raucous that
professors in classrooms down the hall found it necessary to
protest against the disturbance. What was it? Dr. Free
searched through the wheat and found here and there a
grain with a tiny puncture. When these defective grains
were cut open each was found to contain a worm, the larva
of a weevil. It was the twistings and munchings of these
creatures within the granules of wheat that made the
noise. The microphone picked up the weak sound waves
and isolated them as waves of electricity, the amplifying
system magnified the waves to the appointed level of in-
tensity, and the loud-speaker converted back into sound
these magnified vibrations.
The apparatus operated as a sound microscope. The main
problem in its design was the amplifying system. For the
amplifier must be powerful enough to give audibility to the
[139]
THE ADVANCING FRONT OF SCIENCE
vibrations generated by the insects without unduly mag-
nifying the noise of the electrons flowing at thousands of
miles a second through the vacuum tubes of the delicate
apparatus itself. Calculation shows that these electronic
sounds measure only a little below zero on the decibel scale
of loudness, and experiment demonstrates that with
amplifications running into the billions, these electronic
vibrations become audible. So, to avoid imposing the zoom
of the atomic particles upon the noise of the squirming
insects, Free and Johnson designed their amplifier to oper-
ate at a mere ten million million fold magnification. That
was sufficient, however, to make it possible for the turning
of a worm to outshout a professor. If an ordinary whisper
were magnified by the same factor and released to the air
in New York, I am told that it should be heard in San
Francisco a blast of sound equivalent to that of the
explosion of a major volcano.
The amplified whisper would take on such^huge propor-
tions because it begins so much higher up the scale of
loudness. A whisper measures about 25 decibels, whereas
the insect noise may be zero or below. The decibel gets its
name from an earlier unit chosen some years ago by tele-
phone engineers to measure the rate of fading of telephone
signals sent over a wire. They called their unit the bel,
after Alexander Graham Bell, and defined I bel as an in-
tensity 10 times that of the zero level, 2 bels as 100 times
that of zero, 3 bels 1000 times, and so on each added bel
multiplying the magnitude by 10. Even before this scale
was adapted by acousticians to the measurement of sound
intensity, it appeared that the bel was too large a unit. So
each bel was divided into tenths, decibels. In general we may
say that a decibel represents about the smallest difference
that an average ear can distinguish. In the laboratory the
unit is defined in million millionths of a watt; but perhaps
its meaning may be suggested more graphically by mention-
ing the decibel equivalence of a few familiar sounds.
THE NEW SCIENCE OF SOUND
The noise of ordinary breathing measured at a distance of
1 foot registers about 10 decibels. It is one full bel ; therefore
is 10 times louder than a noise of zero magnitude on the scale.
The rustle of leaves in a breeze rates about 20 decibels
2 bels, 10 times louder than the level of breathing, or 100
times the zero level.
The noise made by turning the pages of a newspaper
approximates 30 decibels. The average intensity of con-
versation is 65 decibels. That of piano practice is 75. Five
units higher up than that of the piano thumping, at 80
decibels, is the noise of a passing motor truck. A lion's roar
has been metered at 95 decibels and this is also the loud-
ness of the river falling on the rocks below Niagara, and
that of a passing elevated train in New York. The clatter
of a steel riveter mounts to 105 decibels. Beyond this the
nerve response becomes pathological, and at somewhere
near 130 decibels ten million million times the zero point
of intensity sound is painful in the literal sense.
In using the term zero point it is not to be understood
that the sound at that level is of no value. Zero decibels is
the reference level on our scale of loudness, just as zero
degrees is the reference level on the centigrade scale of
temperature. In general zero is thought of as approxi-
mately the threshold of hearing, but this is true only for
vibrations of certain frequencies. For those of other fre-
quencies the threshold may extend below the zero mark;
while for an even wider range, both at the bass and at the
treble end of the sound spectrum, the threshold of hearing
is above zero.
Similarly, the threshold of painful sounds must be charted
as a curved line. While it is near or beyond 130 decibels for
a limited number of low frequencies and a limited number
of high frequencies, it does not rise even to 120 decibels for
certain sounds intermediate between these extremes.
The thermometer again provides a simple analogue. Just
as the freezing point of water is at one temperature and that
THE ADVANCING FRONT OF SCIENCE
of mercury at quite a different temperature, so is the
threshold of hearing for a deep bass note quite different
from that of a piccolo's high treble. A high C on the piccolo,
vibrating 4096 cycles a second, may be caught by some
ears when its loudness is a few decibels below zero, whereas
a low C on the organ, vibrating 32 cycles, must be sounded
with an intensity of at least 60 decibels to be heard at all.
The threshold of hearing for this organ tone thus requires
an intensity level more than a million times louder than
that of the piccolo tone.
A similar relativity between pitch and loudness exists at
the other extreme. The threshold of painful sound, the
boiling point on our noise thermometer, is close to 130
decibels for the low C of the organ; but for the high C of the
piccolo it may begin to be felt at about 118 decibels.
Quicksilver can stand more heat than water can before it
boils, and so is the ear able to endure a louder bass sound
than it can a sound of high soprano. ^
3
When the sound meters, filters, analyzers, and other
devices have done their jobs have isolated the frequencies
that are giving offense as noisemakers, and have rated the
magnitude of their offense in decibels the acoustical doc-
tor is provided with the basis for a diagnosis.
Sometimes a noise detector is used as a spy to keep watch
on the mechanical condition of a machine. The huge
2O,ooo-kilowatt turbines of the mercury vapor power plant
at Schenectady were lately equipped with a device which
records the noises generated when their steel vanes are
spinning under the blast from boiling quicksilver. The
clearance between rotating parts and stationary casing is a
matter of only a few hairbreadths, and any undue expan-
sion of the rotor or sagging of its shaft might damage the
costly machine. So the listening device is installed (along
with other electrical watchmen) to keep an ear on the
THE NEW SCIENCE OF SOUND
noises and give prompt warning if any unusual sound
develops amid the normal bedlam.
A more common use of the sound meter is that to which
it is put by the manufacturer of mechanical products, as
an aid to "silent" designs. Today's electric fans operate
with only a third of the noise which was normal to fans of
20 years ago; and electric refrigerators, washing machines,
vacuum cleaners, and other appliances have lately suffered
the loss of some of their customary operating noises. The
tick of the bedroom clock has been softened. Air pas-
sengers of the 1920*8 were accustomed to stuff their ears
with cotton before entering a plane for a flight; such
insulation is no longer necessary, and noise meters report
that the new " soundproof" cabins of the modern air-
planes are not more noisy than an ordinary Pullman car.
The airplane cabin, however, can hardly be called a
machine; its improvement in noise abatement cannot be
credited to redesign of motors or propellers, but is primarily
a matter of architectural acoustics. In particular it is the
result of "treatment," by which is meant the use of sound-
absorbing material in the construction of the walls, ceiling,
and floor of the cabin. The same practice has been applied
in the design or adaptation of larger rooms, and especially
in the attainment of suitable auditoriums where the prob-
lem is not merely to exclude outside noises, but also to
insure the most suitable interior conditions for the hearing
of speech and music.
The foundations of architectural acoustics were laid 40
years ago by Wallace C. Sabine, as the solution of a prac-
tical problem referred to him. Dr. Sabine was Hollis Pro-
fessor of Mathematics and Natural Philosophy at Harvard,
and there had lately been added to the university's plant
the Fogg Art Museum, which included among its rooms a
large lecture hall. The hall was intended for use not only by
art classes, but also by other groups that required a sizable
room but the very first speaker to lecture in the place
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THE ADVANCING FRONT OF SCIENCE
found the task almost insupportable. Let a sentence be
spoken from the rostrum, and its syllables reverberated re-
peatedly. Sounds became a jumble; hearing was almost
impossible. The problem of disentangling the waves seemed
one for a mathematician and a natural philosopher, so
President Eliot turned to Professor Sabine and asked him
what could be done.
Broadly speaking, there are only two variables affecting
the internal acoustics of a room: its shape (including size),
and its materials (including furnishings). Dr. Sabine dis-
missed consideration of the first, for it was not practicable
to alter the room's shape or size. But the materials of its
surface might be changed, and so he began a series of
experiments in that direction.
Three consequences may befall sound as a result of its
collision with walls or other surfaces. The surfaces may
reflect the waves, in which case there is reverberation. Or
they may transmit the waves, and then the soynd is heard
in adjoining rooms. Or they may absorb the energy of the
waves, and thereby swallow up the sound. Dr. Sabine found
that the smooth hard surfaces of the plastered masonry walls
and of the ceiling, floor, and varnished seats of the lecture
room absorbed very little; they transmitted practically none,
but they were very effective reflectors. When a word was
spoken in an ordinary tone, the sound continued to be heard
for more than 5 seconds while it reverberated between op-
posite surfaces. Even a slow speaker would have uttered a
dozen or more syllables in those 5 seconds, and it was easy
to understand that the ensuing mixture of primary waves
with a succession of reflected waves would jumble to make
hearing difficult.
The professor set up an organ pipe as a sound source of
constant pitch and loudness, and installed a suitable
chronograph for recording duration. When the pipe was
intoned in the empty lecture room and suddenly stopped,
the chronograph showed that 5.6 seconds elapsed before the
1144]
THE NEW SCIENCE OF SOUND
sound faded to a millionth of its original strength the point
at which sound is rated inaudible. This period he defined
as "time of reverberation." Could it be shortened by the
simple expedient of covering some of the hard surfaces
with softer, more pliable material ?
As the material for his experiment Dr. Sabine borrowed
all the cushions from the seats of near-by Sanders Theatre.
Some of these were brought into the lecture room and placed
on its seats until a stretch of about 27 feet was cushioned;
then the organ note was sounded, and in 5.3 seconds it had
diminished to inaudibility. More cushions were added,
enough to double the area of covered seats; and now the
sound of the pipe died yet more rapidly, in 4.9 seconds.
Additional cushions were placed until every one of the 436
seats was covered and then the sound was audible only
a small fraction beyond 2 seconds. Obviously he was on the
right track.
More than a thousand cushions were waiting unused, and
Sabine was determined to test their full effect. He carpeted
the aisles with them, covered the platform, draped them on
a scaffolding, cushioned the rear wall from floor to ceiling.
When all were spread, absorption was so considerable that
the sound lasted only i.i seconds.
Many of the tests were made in the quiet of night. They
continued two years, and Dr. Sabine tried a variety of
materials. The final outcome was a recommendation for
resurfacing certain wall areas with felt. When this was
done, as the professor modestly records the verdict in his
final report, "the room was rendered not excellent, but
entirely serviceable." It is still used; and while Harvard
has built a new Fogg Art Museum and removed its ex-
hibits and art quarters to the new and larger structure, one
hopes that the old lecture hall may long be allowed to
stand, for historical reasons if for no other.
Later investigators, with more sensitive and more exact
tools of exploration, have added important refinements to
ins)
THE ADVANCING FRONT OF SCIENCE
Sabine's work; but all modern achievements in the improve-
ment of room acoustics rest on the foundations laid in the
first Fogg lecture room. Reverberation time is recognized
as a direct index to the acoustical quality of a room. And
since the optimum time varies with the size of the room and
the purpose for which it is to be used (music halls requiring,
in general, a longer reverberation time than speech halls),
the acoustical engineer has become an important ally of the
architect. Too often he is not called into consultation until
after the hall is built, but his art is such that by the use of
" treatment " he may transform reflecting surfaces into
absorbent ones, and by skillful placing of surfaces delete
echoes, touch up dead spots, add resonance, and pretty well
refashion a room into whatever acoustical pattern is
desired.
The new Madison Square Garden, Radio City Music
Hall, and Center Theatre in New York are examples of
recent architecture whose acoustics were improved by the
adept use of treatment. And for treatment the acoustician
is no longer dependent on improvisations with cushions,
felts, and other adapted fabrics. There has sprung up a
whole new industry devoted to the manufacture of sound
absorbents, and treatment may be bought in convenient
slabs and blankets. The material must be porous or resilient,
preferably both. And various ways of giving these qualities
to a surface have been developed. One practice uses a hard
smooth surface (of steel, plaster, or composition board) per-
forated with numerous small holes, and lays this over a
blanket of rock wool or other soft fibrous material. The per-
forations in the hard outer surface provide pores to admit
sound to the fibrous inner material whose resiliency and
porosity are such as to absorb the waves.
Perhaps the most exacting practitioners of the new
acoustical techniques are sound-picture recorders and radio
broadcasters. In a studio of the Columbia Broadcasting
System which I visited in New York half the room is
THE NEW SCIENCE OF SOUND
treated to provide sound absorption, and the other half is
differently treated to provide a desired echo. The dead
end, where absorption is 90 per cent, is the zone of hearing.
Here the microphones are stationed. Here the floor is
thickly carpeted, and walls and ceiling are lined with
4 inches of rock wool covered with perforated metal. This
treatment was carefully planned to absorb all frequencies
equally an important desideratum, for some absorbents
are selective, accepting high frequencies and reflecting the
lows. The live end of the room is paneled in wood, and the
panels are fastened only by their edges and so are free to
vibrate. The absorptive and reflective areas of the studio
are so proportioned and so placed with respect to one
another that the sound waves striking the live end are
thrown back to the microphone zone with a single reflection,
and the vibrant quality of the wood seems to add richness
and sonority to the reflected tones. The total effect is to
increase the brilliance of music and speech. The designer
explains this on the theory that the panels seem to act
selectively as absorbers of confused sounds and as resona-
tors of musically desirable sounds damping those waves
which are out of phase and reinforcing those that are in
phase. Certain of the panels are set at slight angles to the
vertical plane, care is taken that an absorptive surface
faces each reflective surface and by such ingenious use of
treatment an excellent medium-sized room for orchestral
broadcasts has been attained.
4
Sound absorption has been described as a surface effect,
and until the present decade it was regarded as almost
wholly that. But in 1930 Vern O. Knudsen, a physicist at
the University of California at Los Angeles, was trying to
calibrate a new sound laboratory there and chanced upon
a strange behavior. He noticed that the acoustical proper-
ties of the room followed the vagaries of the weather. On
[147]
THE ADVANCING FRONT OF SCIENCE
days when the wind blew from the Pacific, filling the
laboratory with moist air, certain high-pitched sounds
would reverberate 4 or 5 seconds. On other days, when the
wind from another direction brought the air from the
Mojave desert, the same kinds of sounds would reverberate
only 2 or 3 seconds. It was the same room, the same sur-
faces, the same vibrations only the air had changed. How
could it make a difference?
Thereafter Professor Knudsen spent much of his time in
pursuit of that question. First he considered the possibility
that the atmospheric changes might affect room surfaces
and so cause them to reflect more, or less, of the sound. To
test this idea he applied successive coats of paint and var-
nish to the walls, ceiling, and floor, to make them imper-
vious to moisture. But this surfacing made no difference
the weather continued to call the time. On a trip abroad
Knudsen discussed his problem with European physicists.
A German authority advised him to line tl^p room with
bathroom tile; then the anomaly would disappear, he said.
Before spending $2000 on this tile treatment the Cali-
fornian professor thought he would try another experiment
that might explore the difficulty less expensively. It
chanced that the university possessed a smaller room,
made, like the new laboratory, of concrete, and surfaced in
exactly the same way the only difference being that it
was less than half the size of the new laboratory. From the
dimensions Knudsen calculated that in the small room the
sound waves would be reflected back and forth approxi-
mately 200 times a second, whereas in traveling the wider
spaces of the large room only 93 reflections occurred. Thus,
in I second a wave would be in contact with the surface of
the small room more than twice as often as in the large
room; and if absorption were only a surface affair it should
proceed at a rate proportionate to the number of surface
encounters and, therefore, should occur more rapidly in
the smaller chamber. He was able to derive formulae for
THE NEW SCIENCE OF SOUND
the rates of sound decay in the two rooms; but when the
test was made glaring discrepancies between theory and
fact showed up. Experiment proved that the absorption
of sound at the surfaces was in no wise affected by the
humidity of the air, and indicated that the variations which
had been observed were due to the absorption of sound by
the air itself that dry air took in certain sounds of high
pitch, sucked them up as it were, while very moist air was
far less absorptive and therefore would conduct the sound
for greater distances.
All this was startling to the acoustical expert of 1930,
whose science rested on the theoretical structure erected in
the nineteenth century by Lord Rayleigh and his colleagues.
According to their teaching the condition of the air should
have very little effect on its conduction of sound. At that
time Rayleigh worked out a set of equations to account for
the behavior of sound, assuming it to be a wave form mov-
ing through a uniform continuous medium. Of course all
knew that the air is no such isotropic jellylike stuff. Ob-
viously it is a conglomeration of particles of different sizes
and weights, the molecules of nitrogen, oxygen, and other
gases. But, as Lord Rayleigh pointed out, the analysis of
sound phenomena on the basis of particle collisions involved
mathematical difficulties and, moreover, was not necessary.
It was not necessary, he reasoned, because the departures
of sound behavior in fact from the behavior pictured by
theory were so slight that for all practical purposes they
were negligible. The revolutionary effect of Knudsen's dis-
covery is to show that for certain high frequencies the de-
partures are not negligible, the actual air absorption in
some cases being 100 times greater than that predicted by
Rayleigh.
The California experiments demonstrated that both
humidity and temperature affect sound absorption. The
influence of temperature is steadily progressive. Cold sub-
zero air is practically transparent to sound, but with heat
I H9 1
THE ADVANCING FRONT OF SCIENCE
the air becomes increasingly absorptive until at high
temperatures it is so opaque to high-pitched sounds as to
make the latter inaudible at a distance of a few feet. In the
case of humidity this progressive relationship does not hold.
Perfectly dry air is the most transparent acoustically, air
containing a pinch of moisture (about 10 to 20 per cent
relative humidity) is the most opaque, and thereafter with
added moisture the ratio of absorption decreases until at
92 per cent relative humidity the transparency to sound is
almost back to the maximum. This latter condition cor-
responds to the moist fog-laden air of the ocean, while air
which is only 20 per cent humid approximates that of the
desert.
Many phenomena of nature are illuminated by this dis-
covery of the influence of atmospheric conditions on sound.
In the Arctic it is not uncommon for two men conversing
in the open to be heard over the icy wastes for distances of
4 miles, and the barking of dogs has been he^rd 15 miles.
It was the custom to explain these long-distance sounds as
a consequence of the reflection of sound waves back to the
ground by certain upper-air strata, but it seems likely now
that the Knudsen effect provides at least part of the ex-
planation. Desert travelers are familiar with the sound
blanketing of hot, almost moistureless air.
Nor are these findings only of academic interest. Dr.
Knudsen points out that in a large hall the reverberations
of high frequencies of speech and music may be affected
more by the conditions of the air than by the nature of the
surface materials. Consider, for example, sound at a pitch
of 10,000 cycles, a frequency within the range necessary for
high-quality music. If the air of an auditorium were at 7OF.
and of only 18 per cent relative humidity, sounds of that
pitch would be absorbed by the air so rapidly that, even
with totally reflective walls, ceiling, and floor, the sounds
would decay in % seconds. The inherent absorption by the
room boundaries, including the audience, would reduce
[150]
THE NEW SCIENCE OF SOUND
the time of reverberation to less than % second. Admittedly
this air is drier than is customary, but even with a relative
humidity of 50 per cent the reverberation time would be
less than a second a duration too brief for good musical
effect. Not only surface treatment but also humidity and
temperature control may be important considerations in
the acoustical engineering of the next 10 years. Designers of
sound-reproducing equipment for use in large theaters and
out of doors may need to take into account the absorptive
characteristics of air, and also those who plan to use sound
in distant signaling, in altimeters for aircraft, and in fog
warnings.
From his discovery of this curious effect of moisture and
temperature on the acoustical properties of the air, Knud-
sen was led to dissect the air into its gases and investigate
these separately. He found that when a small pinch of
moisture is introduced into an atmosphere of pure oxygen,
the ratio of sound absorption is five times greater than that
of air containing an equal proportion of moisture. But when
the same amount of moisture was introduced into pure
nitrogen there was no increase in the sound absorption.
So it is the oxygen in our air, and not the nitrogen, that
is responsible for the greater part of the sound absorption.
If our atmosphere contained no nitrogen, but were made up
wholly of oxygen with such admixtures of water vapor as
are common, it would be difficult to hear a message across
the street. The high-frequency components of speech such
consonant sounds as M, J, and m would be swallowed up
within 50 or 70 feet. Knudsen's later studies of other gases
show that carbon dioxide is even more absorbent than
oxygen. Conversation in an atmosphere of carbon dioxide
would require the voice of Stentor, for the high-frequency
consonants would be absorbed within a few feet.
The explanation of these newly discovered acoustical
qualities of gases seems to lie in the varying characteristics
of collisions between the gas molecules. The progress of a
[151]
THE ADVANCING FRONT OF SCIENCE
sound wave shakes the air into a succession of contractions
and expansions, molecule is bumped against molecule, and
into the thermal movement of particles which is char-
acteristic of the gas there is injected this additional periodic
agitation. We used to think that the colliding molecules
would behave approximately alike so far as their influence
on sound is concerned, but Knudsen's work shows that uni-
formity does not exist. Roughly, it is as though a billiard
player who has been pursuing his game on the theory that
all the balls are of hard ivory should suddenly discover that
some of the balls are of soft rubber. A rubber ball takes the
energy of a collision differently from an ivory ball, and
similarly the interaction of an oxygen molecule in collision
with a molecule of water vapor produces a result different
from that of nitrogen colliding with water vapor. Still
different is the effect of carbon dioxide collisions. What we
are dealing with in these collisions is a chemical phenome-
non, for it appears that certain gases have preferential
affinities, and in the bouncing of molecule against molecule
temporary combinations are formed whose duration is dif-
ferent for different gases. These temporary compounds, of
oxygen and water vapor, for example, or of carbon dioxide
and water vapor, may endure for only a small fraction of a
second and then break apart into their constituent mole-
cules, but their temporary linkings are sufficiently potent
to take up some of the energy of the sound waves and
thereby to absorb or diminish vibrations.
Several scientists have made important contributions to
the theory of this new-found behavior. Among others H. O.
Kneser, of the University of Marburg, has worked out a
mathematical analysis. Professor Kneser shows that the
energy transitions which occur during these collisions and
partnerships must be reckoned in terms of Planck's con-
stant h y the immutable constant of action which figures in
the quantum mechanics of the atom. Sound-absorption
measurements thus provide a means of determining the
[152]
THE NEW SCIENCE OF SOUND
reaction constants of gases, and these give important in-
formation regarding the nature of molecular collisions. Thus
the research scientist finds in the Knudsen effect a new tool
of exploration, a means of prying into the minute mechanics
of gases.
So important is this discovery, so fundamental to the
advancing front of physical knowledge, that at its Christ-
mas week meetings of 1934 the American Association for
the Advancement of Science awarded its $1000 prize for
the year to Professor Knudsen. He is continuing his re-
searches at the laboratory in Los Angeles, where he has
fitted up a 2-foot cubical steel box as his reverberation
chamber. With that more compact and convenient appa-
ratus he is pursuing fresh explorations into this novel
borderland where physics merges with a new chemistry.
[153]
Chapter IX - CHEMISTRY
ADVANCING
Chemistry is not merely a great science among other
sciences, but a science which pervades the whole of life.
ARTHUR JAMES BALFOUR
T
IEN thousand chemists gathered in New York in 1935
to celebrate the three-hundredth anniversary of the
establishment of chemical industries on the American con-
tinent. It was, so statisticians said, the largest gathering of
scientific workers ever assembled in the United States
and appropriately so, for chemistry is basic to our industrial
civilization and the chemists constitute our largest group of
technicians.
They are more than technicians. They are what some
of us, more apt in phrase making than in quantitative
analysis, are inclined to call doers of the impossible. For it
is of the practical applications of chemistry, rather than of
its theoretical principles and fundamental discoveries,
that our thoughts first turn. We are still of a mind akin to
that of old John Adams, in his address to practitioners of
his day: "Chymists! Pursue your experiments with inde-
fatigable ardour and perseverence. Give us the best possible
Bread, Butter, and Cheese, Wine, Beer, and Cider, Houses,
Ships and Steamboats, Gardens, Orchards, Fields, not to
mention clothiers or cooks. If your investigations lead
[154]
CHEMISTRY ADVANCING
accidentally to any deep discovery, rejoice and cry
'Eureka !' But never institute any experiment with a view
or hope of discovering the first and smallest particles of
matter." One cannot say that the chemists have taken
President Adams's oracular warning seriously. For while it
is true that many of their deep discoveries have been hit
upon by accident, it is also true that many more, and
perhaps the most important discoveries, have been the
rewards of planned expeditions into the realm of the first
and smallest particles of matter. The three American scien-
tists whose work has been recognized with a Nobel Prize in
Chemistry each deliberately blazed a trail into the micro-
cosmos: Theodore W. Richards, by his careful atomic
weighing of elements; Irving Langmuir, by his exploration
of the invisible flatland of monomolecular films; and
Harold C. Urey, by his discovery of the double-weight
hydrogen atom. Even so, it is the mundane tendency of
the lay mind to evaluate the chemists for their practical
achievements. We too subconsciously bracket them with
clothiers and cooks. And also we are inclined to rate their
bread, butter, and cheese above their protons, neutrons,
and deuterons.
Perhaps this utilitarian attitude is the most instinctive
approach to modern chemistry, even to its borderlands. The
alchemy which fathered our science was a very utilitarian
pursuit of two practical desires of mankind: first, the
almagest, by which wealth might be attained from baser
materials; and second, the elixir of life, by which age and
death might be defeated. In a certain sense these two pur-
suits are still dominant objectives of chemistry. In later
chapters mention will be made of current work of the
biochemists, and some accounting given of the modern
search of the mystery of life, of aging, and of death. Here
we shall dwell more particularly on the wealth winners:
such realists as those who have snatched unwilling nitrogen
out of the air to fertilize agricultural fields, those who have
THE ADVANCING FRONT OF SCIENCE
spun forests into fabrics finer than silk, those who have
made rubber in a test tube without benefit of Brazil or the
East Indies to mention but three of the long roster of
alchemical retrievers.
There is, for example, the incident of the floating labora-
tory. This was an old ship equipped with the necessary
apparatus, manned with a staff of chemical engineers, and
sent to prospect the ocean. For months at a time it was out
there, pumping water through an ingenious chemical sieve,
picking off certain preferred molecules from each gallon,
and pouring the residue back into the ocean. At the end of
their prospecting the sea miners had extracted a few
hundred pounds of bromine at a cost of $500,000 which
would seem to imply that bromine might be rated as a new
substitute for gold.
But not so. Bromine is indispensable to the manufacture
and use of no-knock gasoline; and because of the mounting
demand of motorists for the improved fuel, it was neces-
sary to look for new sources of supply. The old brine wells
were failing, new ones were not being discovered, and in
this dilemma the industrialists turned to that universal
treasure trove, the sea, which contains all things in solution.
Analysis shows that about seven millionths of each drop of
sea water is bromine. But was chemistry able to extract
so minute a fraction at a reasonable cost ?
The floating laboratory and its prolonged experiment
answered that question. Today a commercial plant for
extracting bromine from the Atlantic Ocean is in opera-
tion on the North Carolina coast. It is turning out thou-
sands of pounds a day. And since each cubic mile of sea
water contains some 600,000 tons of the element, there is
no danger of the factory ever being short of raw material.
This success suggests another question. Since the sea
contains all things in solution, why not mine other sub-
CHEMISTRY ADVANCING
stances too? Gold, for example, is selling for #35 an ounce,
whereas bromine is quoted at less than 2 cents an ounce.
Is there any gold in the sea ?
Yes, and this North Carolina bromine plant has already
extracted minute quantities of it and other precious metals.
At a recent meeting of the American Chemical Society one
of the engineers exhibited particles of pure gold and pure
silver which had been taken from the flood of Atlantic water
sluicing through the bromine extractors. The sea gold is
dilute. A gallon of Atlantic water contains only one thirty-
thousandth as much gold as it contains bromine, and of
course the gold did not drop out of the water obligingly.
It had to be captured by delicate processes which cost
ten times the present market value of the gold. But the
point is that the thing has been done and what is done
at great effort and expense now may be accomplished more
easily and economically next time. Indeed, the chemist
who attained this sea gold predicts that within our century
we shall be mining the ocean for it on a commercial scale.
Getting a scarce product from a difficult source is one
thing. Improving the product or making an entirely new one
is another and these doers of the impossible are versatile.
Take glass, for example. The very first characteristic
of glass that occurs to you is its fragility. It is, traditionally,
something to be handled with care. But in a research
laboratory I saw a man tossing a glass lens into the air and
allowing it to fall on a concrete floor. Indeed, the per-
formance seemed to be a game to see how hard he could
drop the glass. Repeatedly the lens fell from a height of
10 feet without even chipping. And this lens was not
fabricated of thin laminated sections like an automobile
windshield; nor was it reinforced by wires or any other
mechanical aids. It was a solid piece of clear optical glass
tough glass that can be broken if you insist on it, but your
[157]
THE ADVANCING FRONT OF SCIENCE
blow must be thirteen times as great as that required to
break a similar lens of ordinary glass.
The chemists make this tough glass by violating a long
established rule of factory practice. The conventional idea
is that after a piece of glass is poured or cast, it must be
cooled slowly. But this tough glass gets no such babying.
It is plunged from a heat of 1500 into a bath of oil at 400,
and by that sudden change of temperature the toughness is
imparted. The exterior layer solidifies before the interior
does; and in the slow contraction of the interior, tensions
are set up which oppose and counterbalance exterior blows.
By another new process, glass is being spun into fibers
soft as eider down. " Glass wool" is an old story, and has
been used for many years as a packing for heat insulation
and even woven into fabrics for hats, dresses, and scarfs;
but this new fiber is glass in a new physical form, so fine
that it is almost all surface, and yet so strong that it pos-
sesses a tensile strength approaching that <jf steel. The
fibers are obtained by a process somewhat similar to that
used in rayon manufacture the molten glass is forced
from tanks in fine filaments, the pressure being so great
that the glass spurts out at a speed comparable to that of a
rifle bullet. In addition to the customary uses of glass wool,
many novel and indeed amazing applications of the new
fiber are in process of development. It gives every promise
of being a material with a future.
Glass suggests building materials. Glass brick and glass
paneling and glass columns are now on the market, and
houses with a wall or a roof of glass have been constructed.
Chemists have added to glass the ability to filter the solar
heat rays and transmit only the rays of light; so a glass
house may be cool. And it may be proof against the stone
thrower too, for toughness is not confined to optical glass.
As a test a 3 -ton truck was driven upon a I -inch-thick sheet
of this glass, a cable was passed about both, and the whole
lifted high by a crane. The glass bent, but did not break.
[158]
CHEMISTRY ADVANCING
3
Also just out of the laboratory are artificial stones and
artificial woods made of waste, stainless metals made of
new alloys, synthetic resins fashioned out of new chemical
combinations. A typical example of the last named, and
also of the skill of modern synthetic chemistry, is vinylite,
developed at the Mellon Institute in Pittsburgh.
Visitors to the Century of Progress Exposition will re-
member the three-room apartment molded entirely of this
new stuff out of a test tube : the floors of vinylite tiles, the
walls of vinylite panels, the baseboards, sills, ceiling, all of
the same; each door a single piece of vinylite, cast and
pressed into shape; even the windows a translucent vinylite.
More recently the applications of this material have been
widely extended. It is possible to have whole tables, desks,
chairs, chests, and other articles of furniture molded of
one piece. And there are other plastics some remarkably
transparent like glass. The transparency of the new lucite,
reports a chemist, "puts it on the same plane as quartz or
the finest crystal." Some of these clear unbreakable glass-
like plastics are lightweight, suggesting their adaptability
for airplanes, automobiles, railway coaches, and other
places where ruggedness and light weight are esteemed.
One of the objectives of modern chemical research is a
cheap method of processing common clay for aluminum.
Our present source of supply for this metal is bauxite ore,
the deposits of which are closely held. But aluminum is one
of the most abundant elements in the Earth; it is found in
ordinary clay, which is widely distributed; and the unlock-
ing of that plenteous source should make the metal cheaper.
Then we may expect a rapid multiplication of its uses, which
already are legion.
Aluminum of itself is relatively soft, but when alloyed
with small proportions of other metals it becomes extremely
hard and durable. These alloys, which received their first
[159]
THE ADVANCING FRONT OF SCIENCE
substantial encouragement from the aeronautical designers,
are now stepping over the lines into all sorts of industries.
Factories have discovered that the heavier a crane is in
proportion to its strength, the less load it can carry so
they are making giant cranes of aluminum alloy. And
those swift streamlined passenger trains! They can be
credited to the chemist's crucible quite as much as to the
engineer's slide rule, for there is hardly a material in the
new trains which did not come out of recent research.
Locomotive parts are being built of lightweight alloys.
One train of three cars weighs no more than a single Pull-
man car of the old all-steel construction.
Alloys in bewildering variety are on the horizon, and
metals that were laboratory curiosities a few years ago are
rapidly coming into useful service. Cadmium is threatening
the supremacy of zinc. And also titanium its pigments are
taking the place of the familiar zinc in paints and rubber.
The little known metal indium is substituting pr silver as
a mirror material. Tantalum, gallium, and germanium are
making important beginnings in industrial applications, and
in another 10 years these rarities will be commonplaces.
The metal sodium (an ingredient of common salt) is a
better conductor of electricity than copper and the
electrochemists are playing with that fact in researches
that may prove revolutionary. Recent discoveries of the
properties of skins of metals have given the chemist new
and powerful means of adding durability, protecting against
corrosion, and testing for invisible flaws. Surface effects of
magnetism, x-ray reflections, and spectroscopic analysis have
become tools of the metallurgist in applying the chemistry of
metals to the multiplying uses of our age of speed.
But our age of speed glides forward not only on the new
alloys, but also on the new fuels which chemists are obtain-
ing from coal, petroleum, and wood. The process of crack-
ing the heavy oils and other residue of petroleum, after the
normal stores of gas and gasoline are extracted, is adding
[160]
CHEMISTRY ADVANCING
many millions of barrels of fuel to our use. In the cracking
stills, the heavy residue (material that in other days had
to be disposed of as waste) is subjected to high tempera-
ture and enormous pressure. The combined effect is to
" crack " the large molecules into smaller ones, and some of
the small molecules turn out to be gasoline, others to be a
fine grade of furnace oil, others to be gas. By distillation
each of these products is separated out, including not only
fuels but other molecular structures which form the raw
material for synthetic processes of making alcohol, lacquers,
plastics, and rubber substitutes.
By another process or series of processes, which the
chemists call polymerization, combustible gases are caused
to combine into molecules of gasoline. And this synthetic
gasoline is so uniform chemically, its molecules are so
nearly the same throughout in structure and energy con-
tent, that the control of combustion in engine cylinders is
greatly enhanced over that of the old natural gasolines.
This enhanced control makes possible important improve-
ments in power output and fuel economy. Since the raw
materials of the polymerization processes are the gases
which are yielded up as by-products of the cracking process
and the dissolved gases derived from crude oil, natural
gasoline, and natural gas industries, the new techniques of
the polymerizers are powerful factors in getting more and
more gasoline from our present raw materials. Recent esti-
mates by Gustav Egloff suggest that 9000 million additional
gallons of American gasoline can be obtained annually
through these means. Therefore the new techniques are to
be hailed as agencies of conservation.
The transformation of coal into gasoline a process which
is now operated on an industrial basis in Germany was
demonstrated in the United States in 1936 at the Bureau of
Mines in Pittsburgh. Here, in a small experimental plant,
powdered coal is treated to high pressures and high tem-
peratures and exposed to hydrogen gas. In the mauling and
[161]
THE ADVANCING FRONT OF SCIENCE
mixing of the molecules some of the hydrogen atoms com-
bine with the hydrocarbons of the coal to form the larger
molecules of fuel oil, gasoline, or gas for it is possible by
varying the treatment to transmute the coal into any
selected one or more of several products. Hydrogenation, as
the process is called, is more costly than our present
processes of refining crude oil and cracking its residues;
and there is no call for coal hydrogenation in the present
stage of American economy. But the Bureau of Mines
looks ahead to the approaching exhaustion of the petroleum
reserves. Some authorities estimate that by the early 1950*5
the underground pools, which made North America the
greatest petroleum producer, will have been exploited to the
limit of economical extraction. Then the automobiles, air-
planes, and other vehicles and utilities powered by explosive
motors will have to look to other sources for fuel. The coal
fields of the United States are many times more prolific
than the petroleum fields. A. C. Fielder recer*ly computed
that if all the present proved petroleum supplies of the
United States were spread over the state of Ohio they would
cover its 41,000 square miles to a depth of % inch; but if
all the coal deposits were similarly distributed over the
same area they would make a layer 76 feet deep. There is
fuel here for hundreds of years of accelerating industrialism.
Frederich Bergius, the German chemist who developed
the hydrogenation process of converting coal into oil, is
also author of a process of converting wood into food. Dr.
Bergius's method rests on an earlier discovery by two other
German experimenters, Willstatter and Zechmeister, who
found that the cellulose extracted from wood will com-
pletely dissolve if submerged in a strong solution of hydro-
chloric acid, and that while in this solution the cellulose
"transforms" 100 per cent into glucose sugar. What
happens in the fluid is the merging of one molecule of
water with one molecule of cellulose, the sum of the two
being sugar; and because of this the process is called wood
[162]
CHEMISTRY ADVANCING
hydrolysis. But cellulose is only one ingredient of wood,
and to separate it from the hemicelluloses, lignin, and other
constituents of raw timber involves a costly preliminary
process. The great achievement of Bergius is the applica-
tion of the process to raw timber. The log ends and other
refuse of logging, the sawdust, slabs, shavings, and other
wastes of the lumber mill, whole trees or parts of trees as
may be available, all are grist for Bergius's chemical mill.
It converts the wood into digestible carbohydrates of the
sugar type, to the extent of from 60 to 65 per cent, and even
the fibrous residue is material for charcoal, wallboard, and
other by-products. But the food derivatives are the prime
objective, of course, and from the simple sugarlike products
other foodstuffs may be obtained.
Thus, "the carbohydrates consumed by pigs will form
fat," points out Dr. Bergius. "With a suitable yeast, pro-
tein can be produced from hydrolized wood solution.
Crystallized glucose produced from the wood can supply a
considerable amount of edible carbohydrates necessary for
nutrition. In other words, it is possible to produce prac-
tically all the fundamental elements of nutrition from
waste wood. This can be done without reducing the forest
reserves, because the waste of the lumber production can
supply enormous quantities of raw material for wood
hydrolization. The process is not only suited to supply food-
stuffs to countries lacking such, but also gives an opportunity
to turn a waste product into something useful. 5 '
Here is an even more adept chemistry than that of the
Brobdingnagians who made two blades of grass to grow
where only one grew before. Nor is it only a project, a
prospectus of possibilities: it has been done, and is in
practical use today.
4
The achievements in fundamental chemical research are
not so obvious as are the applications wrought in the indus-
THE ADVANCING FRONT OF SCIENCE
trial laboratories ; they are not expressible in terms of added
conveniences or lowered costs or utilized wastes, but I
assure you they are preeminently important to the future of
mankind that is, if we may judge the future by the past.
The very foundations of thought are in process of change.
America is contributing to this revolution. The fact that
twice within the 1930*5 the Nobel Prize in Chemistry has
been awarded to a citizen of the United States is fairly cir-
cumstantial evidence that the science is alive and fructify-
ing on these shores. Science is international, and planetary
rather than continental, and I would not inject into this
account any specious parochialism. But too long the
chemical researchers within the United States have ap-
peared to be preoccupied with profitable applications, and
it is worth noting that fundamental discoveries are now
increasingly rewarding seekers who "have no time to make
money." Nor do the fundamental finds remain merely in-
teresting curiosities very long. A recent Industrial Bulletin
of Arthur D. Little, Inc., calls attention to the fact that
heavy hydrogen, a discovery of 1931, has already shown a
quality foreshadowing important industrial uses. The
energy density of this rare variety of hydrogen, it seems, is
enormously great. With this gas, jets of such high velocity
are produced that the energy available in I pound of
heavy hydrogen, and attributable to the speed alone, is
equal to that obtainable from the combustion of 5 million
pounds of coal.
Heavy hydrogen and its consequence, heavy water, are
only the headliners among a horde of isotopes and com-
pounds recently turned up in the pursuit of knowledge for
its own sake. And these pioneering chemists many of
them mere youths in their twenties and thirties are press-
ing the merger of physics and chemistry closer and ever
closer with their applications of the new-found principles
to chemical practice. We are coming into a new technique,
the so-called quantum chemistry. Here chemistry emerges
CHEMISTRY ADVANCING
from the hit-or-miss of an empirical science to the attain-
ment of a reasoned logic in which properties and behaviors
are calculated and predicted. This new chemical com-
petence rests on the surer knowledge of atomic structures
and forces which recent research has brought, enabling the
chemist to foresee not only the possible combinations, but
also the speed and order with which the reactions will occur.
Let us consider the item of speed. Life itself is one phase
of this engaging question, as the Princeton chemist Henry
Eyring has pointed out, and I am quoting from a recent
paper of his to illuminate our curiosity about chemical
speed. "For molecules to combime to form new ones, they
must collide with catastrophic violence/' says Dr. Eyring.
"The atoms in the two colliding molecules must approach
so closely that they no longer know whether they are bound
to the new or the old atoms. For convenience, this is known
as the activated state. If these violent encounters occur once
in every million million collisions, the reaction goes mod-
erately fast. But if they go faster, say once in every thou-
sand million collisions, an experimental chemist will be
unable to distinguish between this rate and reaction on
every collision. He will simply say in either case that the
reaction goes immeasurably fast. By cooling his vessel he
slows down all the molecules and can so cut down his rate
to something measurable. Thus, simply by observing how
a chemical reaction changes with temperature, he can tell
you how violent a collision must be in a particular case to
cause reaction; but, until the last 3 or 4 years, he could not
even guess how violent a new type of collision must be to
bring about a reaction. This the quantum mechanics has
completely changed. He can now calculate, as accurately
as he pleases, how energetic a collision must be to cause
chemical change, and, therefore, at what temperature it
has a measurable rate. Moreover, approximate calculations,
which are simply made, frequently tell him which of two
reactions will go the faster. This is a type of question which
[165]
THE ADVANCING FRONT OF SCIENCE
to answer experimentally frequently requires a great
amount of time and great expenditures of money. For the
exact calculations one needs no other data than the laws of
quantum mechanics and the fact that one is dealing with a
certain set of charged particles, and all the physical and
chemical properties emerge as a matter of course."
This new precision seems very far removed from the
chemical pioneering of 300 years ago. It was in 1635 that
the science obtained its first foothold in the New World. In
that year John Winthrop, Jr., a young alchemist of the
Massachusetts Bay Colony, visited England and obtained
from the Crown a commission to develop certain native
mineral resources. He was interested in the production of
copper, glass, iron, lead, tar, and other "chymicals" in-
cluding medicines no mere dreamer, this alchemist! The
Royal Society later asked him to see if the grain, Ameri-
can maize, would produce beer. Winthrop tried it and
brewed a "pale, well-tasted middle beer." H^even did re-
search on cornstalks and found that they yielded "syrup
sweet as sugar" a foretaste of the extensive corn-syrup
industry of today.
Winthrop's projects were primitive, his incentives appear
to have been wholly commercial, his research strictly indus-
trial. There was, in the year of his commission, not a college
or university, not a laboratory or other scientific institution
of any kind, in the Colonies, and indeed only the most
fragmentary approaches to science in Europe. But out of
these practical seekings chemistry grew, in knowledge and
stature and wealth. It is interesting to reflect that the two
American fortunes which have contributed most largely
to the equipment and support of scientific research are
founded on chemical industries the Carnegie fortune on
the steel industry, which received its greatest acceleration
from Bessemer's process of promoting the chemisms of
steelmaking, and the Rockefeller fortune on the petroleum
industry, which is so directly indebted to Willard Gibbs's
[166]
CHEMISTRY ADVANCING
discovery of the phase rule as the foundation of physical
chemistry. The Mellon fortune derived much from Charles
M. Hairs application of electrochemistry to the extraction
of aluminum, and in turn it has fostered many industrial
researches to useful and successful fruition. Chemistry
has been described as creative, but more aptly it may be
characterized as a catalytic agency, activating industry,
wealth, the other sciences civilization.
[167]
Chapter X A CHEMIST ON
VACATION
The chymists are a strange class of mortals impelled by an
almost insane impulse to seek their pleasure among smoke
and vapor, soot and flame, poisons and poverty, yet
among all these evils I seem to live so sweetly that may I
die if I would change places with the Persian king.
AN OLD ALCHEMIST
THE story of chemistry is not only the record of man's
measurement and manipulation of the ninety-two
chemical elements, and of their combination, activation,
and other manifestations. There is also a subjective side
to this discipline, an aspect of science as human endeavor.
Man the measurer is also a living soul, with hopes and
incentives, touched by inscrutable intuitions, moved by
thoughts that in other times or other personalities attune
the spirit to poetry or music or worship, " thoughts that do
often lie too deep for tears;" and the "dear delight " of dis-
covery invariably outweighs its richest fruits. There is
indeed an aesthetic element in the pursuit of science that
only its intimates know. Nietzsche held that the scientific
man is the finest development of the artistic man. Leonardo
da Vinci esteemed his scientific accomplishments above his
paintings and other art. "If Shelley had been born a
hundred years later, the twentieth century would have
[168]
A CHEMIST ON VACATION
seen a Newton among chemists/' says A. N. Whitehead.
Indeed it is poets and artists and dreamers that we ap-
proach when we visit the laboratories, with the added
distinction that these visionaries so often are able to see
their poems and art and dreams come true.
Some of the dreamers astronomers, cosmologists, world
builders take the Universe as their province, and seek to
comprehend the all in one inclusive system. Others and
perhaps they are the more ambitious look closer. They
probe among the invisible molecules, break these chemical
structures into their atoms, blast the atoms down to their
invisible parts, and try to read in the microcosm the
eternal riddle of a world and a life and an intelligence.
Irving Langmuir is of this latter group. He chose a trail
into the infinitely little as his way of satisfying the great
curiosity, and out of that highly specialized pursuit has
come new light on familiar mysteries, a new understanding
of fundamental phenomena, a whole new branch of science.
New industries, new factories, new products, new con-
veniences, as well as new ideas, emerged from his findings
yet he had no practical end in view when he entered upon
the search.
Indeed, the whole remarkable venture began as a
summer vacation. Langmuir was a teacher of chemistry
who varied the monotony of pedagogical tasks with sum-
mers of mountain climbing. In 1909, however, an oppor-
tunity opened to spend July and August in a research
laboratory. The vacation then begun has continued more
than a quarter century, for he never went back to his
classroom, but stayed on in the laboratory, fascinated by an
experiment. It led to other experiments, and discovery fol-
lowed discovery as he brilliantly pioneered new frontiers of
knowledge, blazing "paths where highways never ran,"
often a solitary figure, exploring, experiencing, satisfying his
soul. From such preoccupations he was called to Stockholm
in 1932 to receive the Nobel Prize in Chemistry.
[169]
THE ADVANCING FRONT OF SCIENCE
A search of the Langmuir pedigree reveals no scientific
forebears, unless we count a maternal grandfather who was
a New England physician. Irving Langmuir's father was a
businessman, self-made in the sense that he hired out as a
clerk at the age of fourteen and by the time he was thirty-
five had accumulated a comfortable fortune. Then, soon
after the birth of his fourth son, he lost it all and more in
a mining venture, and much of the remainder of his life
was a period of financial struggle. During his last 6 years
he was agency director for Europe of the New York Life
Insurance Company; the European post gave the family
advantages of travel and of cosmopolitan contacts; but the
four boys grew up in this atmosphere of struggle, and it
colored their life with a sense of serious purpose. There
was Dean, the youngest; Irving, 6 years older; next,
Charles Herbert, who was 5 years older than Irving; and
the eldest, Arthur, whose preoccupation wilfh chemistry
was to turn Irving's interest in that direction.
Perhaps the most definite tendency of science in the
household was the disposition to record accurately and
systematically whatever went on within the domain of the
family. Charles Langmuir, the father, began a diary in his
early manhood. He also kept a cashbook recording in
double entry every day's financial transactions, even to the
purchase of a penny newspaper or the payment of a boot-
black. He kept a separate record of his travels, the itin-
erary, the hotels visited, the number of the room he
occupied in each. Sadie Comings Langmuir, the mother,
was almost as keen as her husband for record keeping. She
too treasured the day's events in a diary, and instilled the
habit in her sons. She encouraged them to write detailed
accounts of their travels, experiences, and observations.
When he was eleven years old, living with an aunt in his
native Brooklyn, Irving Langmuir wrote his mother, in
[170]
A CHEMIST ON VACATION
Paris, of a project that was engaging his attention. The
definiteness of the detail is characteristic.
"I am building a windmill which is going to be about
3 feet high and I foot wide at the bottom and 6 inches
wide at the top. The wheel is going to be like this. [The
letter contains a sketch.] The wheel's axil is going to be
made of wood with pieces of tin this shape [another sketch],
each one being about 3^ inches long. The whole wheel's
diameter will be about 8 inches. I have two sides all done
and the other two sides half done of the tower part."
Within a year the family were settled in Paris the in-
surance company's headquarters were there and soon
after Irving's thirteenth birthday Mrs. Langmuir was
writing to a friend in America: "Irving's brain is working
like an engine all the time, and it is wonderful to hear him
talk with Herbert on scientific subjects. Herbert says he
fairly has to shun electricity, for the child gets beside him-
self with enthusiasm, and shows such intelligence on the
subject that it fairly scares him."
A tireless stoker of this scientific flame was Arthur, who
by now had completed undergraduate studies at Columbia
and was entering Heidelberg for a postgraduate course in
chemistry. There were many letters back and forth between
the two. Irving, eager to try the experiments which his
brother outlined, was delighted to have access to the
laboratory of a small boarding school in a Paris suburb
where he had been entered. One of the teachers encouraged
the thirteen-year-old to use logarithms and to solve prob-
lems in trigonometry. He delighted in these extracurricular
activities. But most of his time in the French school was
spiritual torture to the sensitive boy. The absurbly rigorous
discipline and the inflexible system of learning by rote stifled
him. Until he was fourteen he " hated school, and did poorly
at it," to quote his own recent estimate of that period.
In his fifteenth year he returned to America and entered
school in Philadelphia. The following year Arthur, who was
[171]
THE ADVANCING FRONT OF SCIENCE
now starting out as an industrial chemist, married, and
Irving came to live in his brother's home while attending
high school in Brooklyn. Here the boy taught himself the
calculus. He knew so much chemistry that the school
excused him from attending classes in the subject. He fitted
up a laboratory at home and learned qualitative analysis
under Arthur's tutelage.
When Irving Langmuir enrolled in Columbia University,
it was to become a candidate for the degree of metallurgical
engineer, in its School of Mines, though he had no intention
of practicing metallurgy or mining. "But the course was
strong in chemistry," he explains, "it had more physics
than the chemical course, and more mathematics than the
course in physics and I wanted all three."
Judged on usual collegiate standards, Langmuir's four
years at Columbia would be rated a failure. He "made" no
clubs or teams, took no part in athletics, never "went out"
for one of the university papers, was not inv^ed to join a
social fraternity or to serve on a class committee. Outside
classrooms and laboratories, the teeming university seem-
ingly was unaware of his existence.
The professors showed little intuitional ability to spot a
future Nobel laureate. The intense, eager youth was never
invited to any of the professorial homes for an evening's
chat. Dr. R. S. Woodward, professor of mechanics, one
day posed this question to the class: "If you could do what
you want most to do, what career would you choose?"
When the question came to young Langmuir he answered,
"I'd like to be situated like Lord Kelvin free to do re-
search as I wish." This touched some resonant chord in the
professor. He encouraged the ambitious junior to consult
him, and occasionally there were long talks between the
two after class. "Professor Woodward suggested many in-
teresting problems," recalls Langmuir, "which I loved to
work out for the fun of it." He was graduated in June,
1903, with an average grade of 94 per cent.
[172]
A CHEMIST ON VACATION
The following autumn the "metallurgical engineer" en-
rolled at Gottingen for advanced studies in physical chem-
istry under Walther Nernst. During the three ensuing
postgraduate years in Germany there was considerable
debate in the young scientist's mind, and by letter between
him and his brothers, as to his future. Should he go into
chemistry commercially, or should he aim for the more
rarefied heights of scientific research? I am privileged to
quote a letter he received at this time from his brother,
Charles Herbert:
"The whole matter resolves itself into the question
whether you have, or have not, exceptional ability in pure
science research. If you simply have a well-grounded
knowledge and a thorough efficiency, you should certainly
go right into the business of chemistry, where you can be of
most use to yourself and everybody else. But if you are the
exceptional man, it is, in my opinion, your duty to be one
of the pioneer scholars in America. . . . The time has come
when this country must have her distinctive scholars. If
they do not get great honor now, they surely will by the
time you have done anything particularly worthy. Mean-
while, you will have the incalculable advantage of a great
aim with all that it contributes to happiness and the full
life. . . .
"There is a great deal that is noble and inspiring in
business, and business can always be conducted in the
better way, but it is a lower thing for some men than re-
search and scholarship. Most of us are suited to nothing
else but business, not being finely enough organized
mentally to spend our careers in other than active work.
But perhaps you are one of the few with creative brains.
If you are (and don't decide so unless you have good
authority) you will betray your true self if you devote your
life selfishly to private enterprises and personal acquisition.
And the minute you allow yourself to deviate from the path
of pure science, you will lose something in character, and
[173]
THE ADVANCING FRONT OF SCIENCE
more still in the power to aspire and the possibility to be
truly happy."
This was in 1904. At that time no Nobel prize had come
to any American, though in Europe more than a dozen
scientists had received this supreme accolade. Just that
year Lord Rayleigh had been named as the prize man in
physics and Sir William Ramsey in chemistry, a double
recognition of their joint discovery of argon that strange
rare gas which Langmuir was destined to harness to the
purposes of man. Whether there entered the mind of the
young American in Gottingen any thought of his own
future in possible association with a Nobel prize, I do not
know. But when he came home in 1906 he had decided to
risk a career in scholarship, and had accepted appointment
as instructor in chemistry at Stevens Institute of Tech-
nology in Hoboken, New Jersey.
It is interesting to speculate on the "ifs" of the past.
What might have been this man's life if Columbia had dis-
cerned his latent powers, and had installed her brilliant
unknown in line for one of her chairs in science ? Or if
Stevens had recognized the genius of research who was
pacing away his hours trying to teach sophomore engineers
the rudiments of chemistry ? He had a difficult time there.
Teaching, with its demand for a disciplinarian and its inter-
minable piles of papers to be graded, was a chore. One
remembers Whistler serving as draftsman in the Coast
Survey office, and Charles Lamb poring over the ledgers of
the London accountant.
With his brother Dean, Irving used to take long walks
along the Palisades and into the highlands of the Hudson,
and the talks that enlivened these jaunts are forever
memorable to the younger man. Usually the theme was
some subject of science, frequently an interpretation of
familiar phenomena. A rainbow, a raindrop, an oil film on a
pond these are worlds of beauty and orderliness and mean-
ing to Irving Langmuir. I have seen him poise a soap bubble
[174]
A CHEMIST ON VACATION
to point out its dark monomolecular area that exists for an
instant just before the bubble bursts. How resonant his
voice, how vibrant as he rises to some peak of exposition,
like a mountain climber who has guided you up his favorite
height to point out his favorite view.
He might have gone mountaineering again that summer
of 1909 but for a meeting of a scientific society in Sche-
nectady the previous autumn. Langmuir attended the
meeting, and while there renewed his acquaintance with a
classmate of Columbia days, Dr. Colin G. Fink, who was
then on the staff of the General Electric Research Labora-
tory in Schenectady. Industrial research was compara-
tively new in America; most scientists associated it with
such pedestrian pursuits as tests and analyses; but as Dr.
Fink conducted his friend through this laboratory, intro-
duced him to members of the staff and to their work, the
visitor was enormously impressed and interested. Here was
an authentic atmosphere of research, and every facility to
delight the heart of an experimenter. When, a few months
later, the suggestion came that he spend his vacation in the
laboratory at Schenectady, it was not difficult for Lang-
muir to accept.
Among the problems under scrutiny was one which we
may call "the mystery of the lamp." The laboratory had
been trying to improve the incandescent electric lamp, and
had been blocked by a certain "offsetting" effect of the
wire filament. Tungsten, which will endure more heat than
any other solid, had been substituted for the earlier car-
bon and tantalum filaments, and the bulb had been
exhausted of its air to an extent attained in no other
laboratory; yet, after a few hundred hours of use, the
tungsten became brittle, the filament crumbled, the lamp
failed and nobody knew why. Accidentally, three tung-
[175]
THE ADVANCING FRONT OF SCIENCE
sten wires had been produced which gave fairly satisfactory
results but again, nobody knew why.
It occurred to Langmuir that there might be an impurity
in the tungsten. Perhaps it had absorbed some gas, and pos-
sibly this foreign inclusion was responsible for its un-
accountable behavior. As his summer's research Langmuir
proposed to heat various samples of tungsten wire in high
vacuum, and if any gases came off he would measure them.
He set up his apparatus, obtained specimens of wire, in-
stalled one in a lamp, and attached a vacuum pump.
He got gas, plenty of it, and kept heating the wire and
pumping the bulb until he had obtained an amount of gas
equal to seven thousand times the volume of the filament.
He was astonished. It was preposterous to assume that all
this had been hidden within the hairlike strand of tungsten.
Where did it come from ? Langmuir spent all that summer
trailing the gases to their sources, and never did get back to
his original project of investigating the sanaples of wire.
"How much more logical it would have been," he remarked
later, in reminiscence, "if I had dropped the work as soon
as it was evident that the method employed was not going
to solve the problem of the brittleness of the wire."
Curiosity led him on. "Frankly, I was not so much in-
terested in trying to improve the lamps as in finding out the
scientific principles underlying these peculiar effects."
September arrived. The classroom in Hoboken was
waiting, and here was its chemistry instructor in the midst
of an engrossing experiment. The director of the laboratory,
Dr. W. R. Whitney, asked if he would care to stay. Lang-
muir was eager to stay, but his Scotch conscience made him
protest that he could not foresee any practical issue from
his studies. "I am merely curious about the mysterious
phenomena that occur in these lamps." The discerning Dr.
Whitney recognized the temperament. "Go ahead; follow
any line of inquiry you like; find out all you can of what
goes on in a lamp."
[176]
A CHEMIST ON VACATION
And Langmuir did. The work absorbed him. He was
given first one assistant, than others, and thousands of
dollars were made available to provide the wherewithal for
his flights into the vacuum. He continued to track down
the ubiquitous gases to their lairs, and found that they came
for the most part from the glass bulb. He continued to
discover and record their varied behavior. He began to intro-
duce other gases into the lamp, purposely to spoil the vac-
uum, to see what would happen. He worked in these ways
nearly three years before any practical application was
made of any of his results.
But in the course of these studies he became intimately
acquainted with the invisible world of colliding molecules
and curiously individualistic atoms. A trace of nitrogen
introduced into the vacuum behaved very differently from
its usual inert self. Pure oxygen had its own atomic antics.
And so with each gas. Hydrogen was the most fascinating
actor of all, and presently Langmuir was concentrating all
his experiments on hydrogen. It lured him, as the North
Pole had lured Peary, and nights and days he could think
of nothing but the queer ways of hydrogen in a vacuum.
3
He found, for example, that the presence of any gas in the
lamp accelerated the loss of heat from the incandescent
filament. This was expected, for the gas molecules coming in
contact with the hot wire take up some of its energy, which
quickens their motion, and they fly off at higher velocities
to bang into other molecules or against the inner surface of
the bulb. Langmuir was familiar with this thermal conduc-
tion of gases. It was a subject he had studied at Gottingen
under Nernst; he had worked out curves to picture the in-
crease of conduction with temperature. But earlier experi-
ments had been with filaments of platinum, which melts
at 32OOF., and there were no data on performances at
temperatures above 2OOOF. Now he was working with the
[177]
THE ADVANCING FRONT OF SCIENCE
most refractory of all the elements, tungsten, which must be
heated to 62OOF. before it melts, and the experimenter was
eager to see what would happen in the higher range thus
opened up. He found that the ascending order of his curves
continued with fair consistency for all gases except
hydrogen.
When hydrogen was introduced, and the electric current
turned on, the rate of heat loss increased steadily until the
glowing filament reached a temperature of 36ooF. Then
the curve rose rapidly to a height five times as great as
would be expected. Evidently, at these higher temperatures,
something happened to hydrogen to make it a glutton for
heat.
The hydrogen also staged a mysterious disappearing act.
When a measured quantity of the gas was introduced into
the lamp bulb, the pressure rose exactly as one would
expect. But if you then turned the electric switch and
lighted the lamp, the pressure slowly dropped to zero. The
hydrogen had disappeared! More was introduced, and under
like conditions it too disappeared, until finally a stage was
reached when the pressure remained constant.
But where had the earlier hydrogen gone ? The filament
was suspect, but experiment soon exonerated it. The only
hiding place left was the inner surface of the glass bulb.
Langmuir put the lamp in an electric furnace and baked it,
heated the thing until its glass was near melting. Then, at
last, the lost hydrogen began to reappear. Like a swarm of
leeches, its particles had attached themselves to the glass;
and only the most drastic heat treatment could make them
budge.
One more experiment, and the mystery was unmasked.
Langmuir had introduced hydrogen into the bulb, had
lighted the filament to incandescence, and the hydrogen
had disappeared. His new experiment was to turn off the
current, allow the filament to cool, and then to introduce a
measured quantity of oxygen. Instantly the oxygen dis-
[178]
A CHEMIST ON VACATION
appeared. Other additions of oxygen vanished too, until a
point of saturation was reached. It was noticed that the
amount of oxygen taken up was exactly the quantity re-
quired by the hydrogen to combine in the proportions of
H 2 0.
Everyone knows that two parts of hydrogen join with one
part of oxygen to form water, but only the chemist knows
what tremendous activation is required to effect this union.
You might mix the two gases till doomsday, and nothing
would happen until you gave the mixture some violent
molecular blow, as by an electric spark, a ray of ultra-
light, or some other packed quantum of energy.
But here in Langmuir's experiment the union occurred
spontaneously, in a cold lamp bulb, without any outside
stimulus. Obviously the experience that had made the
hydrogen such a glutton for heat, that had caused it to
swarm to the inner surface of the glass, had also endowed it
with extraordinary affinity for oxygen. It could no longer
be regarded as the familiar hydrogen of ordinary usage, a
gas which exists in compact molecules of two atoms each.
It must be different. It was different. And now Langmuir
knew precisely what it was, and saw how it came to be.
The tumultuous heat of incandescent tungsten had split
the hydrogen molecule in two.
The bursting of these bonds had drained enormous
energy from the tungsten, as was indicated by the extra-
ordinary heat loss.
These sundered halves of the hydrogen molecule, these
two separated hydrogen atoms, with their natural affinities
now loose and unsatisfied, were eager for any kind of union
with oxygen, if oxygen was to be had; if not, with the
glass surface of the bulb.
Theory had predicted that, if hydrogen existed free in
its atomic form, it should have these characteristics. And
now Langmuir had discovered it. The demon within the
lamp was atomic hydrogen!
[179]
THE ADVANCING FRONT OF SCIENCE
4
I have sketched this pioneer research in some detail,
because it is one of the fundamental explorations of the new
chemicophysics, now our basic science. Fifty years from now
men will look back to it as to a lofty landmark in the march
of discovery, just as today we rate Faraday's work with
electromagnetism as epochal. Mr. Gladstone, attending an
early demonstration of the dynamo, was prompted to ask
Faraday, "But what use is it?" a question which I believe
Langmuir's discovery was never challenged to answer. No,
the practical engineers at Schenectady knew what they were
after all the time, and were wise enough to see that this
quiet searcher in the laboratory, who was "merely curious
about the mysterious phenomena that occur in these
lamps," was getting somewhere though they did not
dream of the wealth of applications that would trail off
from his indulgence of his scientific curiosity. Four prac-
tical results are outstanding:
1. First, better lamps. From his studies of the behavior
of gases in the bulb, Langmuir learned that the vacuum
was not the secret of lamp efficiency. The main effort of
lamp makers up to this time had been concentrated on
attaining higher vacua within the bulb, but Langmuir
showed that the presence of gas was an advantage, pro-
vided it was the right sort of gas. For when the filament
was coiled in a certain way and the bulb filled with the
inert gas argon, the fatal crumbling away of the tungsten
did not occur. The argon, by its gaseous pressure, pre-
vented the filament from evaporating. By these and other
innovations Langmuir halved the lamp's consumption of
electric current. According to statisticians who keep tabs
on such minutiae, this improvement is yielding the Ameri-
can public an average nightly saving of $1,000,000 on its
electric-light bill.
2. His study of lamps led Langmuir to new methods of
pumping vacua, and resulted in his invention of the
[180]
A CHEMIST ON VACATION
mercury condensation pump. By means of a blast of hot
mercury vapor, this Langmuir pump siphons air out of a
container so rapidly that in 5 seconds a quart bulb is
emptied to a hundred millionth of an atmosphere. This
means that in those 5 seconds the harnessed tornado of
mercury jerks some 24,999,999 million million air mole-
cules out of the bulb.
3. With this powerful pump Langmuir was able to attain
degrees of emptiness far beyond any previously known, and
these equipped him to penetrate still deeper into that world
of the vacuum where radio communication has its home. He
discovered the "space charge/' now recognized as a fun-
damental principle of electronics. He found that an infini-
tesimal pinch of thorium added to the tungsten filament
would speed up its flow of current a hundred thousand fold.
By the summer of 1933, more than sixty patents had re-
sulted from Langmuir's studies, about half his patents
being in the field of radio engineering.
4. One of the more spectacular inventions in this list of
patented results is the atomic hydrogen torch. The idea
for this industrial application came as a hunch. Dr. Lang-
muir was with a laboratory colleague discussing some
related matter, when suddenly it flashed in his mind that
atomic hydrogen might be used to produce an intense flame.
For, he reasoned, if the temperature of incandescent tung-
sten is required to tear the halves of the molecules apart,
would not the broken molecules i.e., the separated atoms
if allowed to reunite, give up enormous heat in the proc-
ess ? The hunch was tried out, and it worked. Today the
highest steady temperature that man has been able to
generate and control is that of the atomic hydrogen torch.
Above 68ooF. has been registered. The torch is used in
welding the fine parts of machines and other metal con-
structions.
But these practicalities are only the fringes of his
achievement. The really significant outcome that resulted
[181]
THE ADVANCING FRONT OF SCIENCE
from the discovery of half a hydrogen molecule is its turn-
ing of attention to the chemical behavior of surfaces. The
Swedish Academy of Sciences, in its citation, declares that
the Nobel prize is awarded to Irving Langmuir "for
pioneer work in surface chemistry." And here we are down
to fundamentals. Surface chemistry represents a new and
strategic attack on the hidden mechanism of nature.
5
Forty years ago Lord Rayleigh was enticed by the
iridescent films which oil makes on water, and began impor-
tant studies of these familiar phenomena. Our own Willard
Gibbs interested himself in soap bubbles, was led to con-
sider what soap does to the surface of water, and from
these inquiries worked out a mathematical formula ac-
counting for the surface tension of liquids. Later Sir James
Dewar investigated the tendency of certain gases to attach
themselves to the surfaces of charcoal knowledge that
was put to practical use during the Worlcf War in the
manufacture of gas masks. Dr. Langmuir, in his pursuit of
the energetic hydrogen in the lamp, found that the gas
attached itself to the inner surface of the glass bulb in a
single layer of atoms.
This discovery of the monatomic film was a revolutionary
finding, though Langmuir was looking for just such an
arrangement as the most logical outcome of his theory.
Prior to this the generally accepted idea among chemists
was that when atoms or molecules were adsorbed, or
attached to a surface, the concentration was densest at the
surface, and gradually thinned out with distance above the
surface, like a miniature atmosphere. But here, in the case
of hydrogen on glass, there was no hovering atmosphere
just one tightly held layer of atoms, and above that little
attraction.
Langmuir explored other adsorbed films, and in every
instance the film was one layer deep. In the case of carbon
A CHEMIST ON VACATION
monoxide (a compound of one carbon atom combined with
one oxygen) the film was a single molecule thick and here
an interesting new detail showed itself: all the molecules
attached themselves to the surface with the carbon atoms
down. It was as though the carbon end were the head, and
alone had the power to bite into and hold on to the surface.
Oil films on water showed the same orientation. The
oil spread in a layer exactly one molecule thick, and each
molecule clung to the water in a uniform way. These oil
molecules are large. Predominantly they are groups of
hydrogen and carbon atoms, some being chains of fifteen
to twenty-nine of these groups linked together. All are alike
in one peculiarity: they have at the end of the chain an atom
of oxygen coupled with an atom of hydrogen. In every oil
film of his experiments, Langmuir found, it was this
OH end that attached the molecule to the water. It was
the head. It was able to satisfy its own affinity for the water
molecules, but was not strong enough to drag the long
hydrocarbon chain down into the water.
In molecules of short structure it is able to do this;
therefore such substances dissolve readily in water. Alcohol
is an example. Its hydrocarbon chain is only two atoms long,
and the eager oxygen-hydrogen head is able to pull the
whole molecule under.
All the soluble carbohydrates are strong in the OH group.
Sugar, for example, may be called hydra-headed, since in
every molecule there are several OH groups eleven in the
familiar cane sugar that dissolves so readily in our coffee
and tea.
In contrast with these mixers is a class of oils which
will have nothing to do with water. Pure mineral oil is an
example; it will neither dissolve nor form a monomolecular
film. Examine the make-up of its molecule and you find it
different from the others in one particular; it has no OH
group. Bereft of a head, the molecules are neutral to sur-
faces, and so hold themselves apart in inhospitable globules.
[183]
THE ADVANCING FRONT OF SCIENCE
These peculiarities of the infinitely little absorbed Lang-
muir. For months his laboratory was cluttered up with
trays of water alive with invisible oil films. He began to
measure the molecules. In the cases of stearic acid, a prin-
cipal ingredient of candle tallow, he found that the length
of the molecule is about one ten-millionth of an inch, its
width about one-fifth as much. Other oils showed slenderer
units. He visualized the oil film as made up of billions of
long waving molecules, like eelgrass in a swamp, each a
snakelike structure of linked atoms attached to the water
by its active head.
As oil after oil was studied, various shapes showed up.
The molecule of olive oil measured about the same in length
as in thickness. A surface film of olive oil suggests more the
appearance of a field of cabbages than of eelgrass. The
castor-oil molecule showed an even more striking departure,
for its height above the surface is only about a third of its
diameter, giving the molecule the appearanc^ of a disk.
This is explained as an effect of its abundance of heads, for
each molecule has not only three active OH groups at one
end, but six additional ones on its sides; the affinity of the
nine groups for water causes the molecule to lie flat rather
than stand erect. As a result, the castor-oil film is exceed-
ingly thin. It measures only one hundred-millionth of an
inch.
6
These studies led Langmuir into a curious flatland. The
adsorbed molecules could move about on the surface, but
were unable to rise above or dive beneath it. Their actions
constituted a chemistry confined to two dimensions. One
day, in his laboratory, I watched him fill a tray with water
and then touch the water surface with the tip of a needle
that had been dipped in an oil (myristic acid). The oil
instantly spread over the water as a film. Tests showed that
its particles were in continual agitation, like the colliding
A CHEMIST ON VACATION
molecule of a gas. Indeed, the oil film was a two-dimen-
sional gas which could move about freely in flatland, but
apparently was unaware of the third dimension.
Langmuir demonstrated this. He laid a strip of paper
across the water surface, and by gently pushing the strip
forced the oil to one end of the tray. If the agitated par-
ticles had possessed any freedom to leave the surface, they
surely would have used it to escape the crowding. Instead,
under the pressure of the paper barrier which acted as a two-
dimensional piston, the film condensed into a two-dimen-
sional liquid. Further pressure converted this liquid film
into a two-dimensional solid. The thin crust, measuring
only one twenty-millionth of an inch in thickness, was
invisible, but by blowing on it one could prove its rigidity.
On the release of the barrier the pressure dropped, and
instantly the two-dimensional solid melted into a two-
dimensional liquid, which in turn evaporated into a two-
dimensional gas and diffused over the surface as the freed
molecules darted about, collided, and rebounded, in wild
abandon. Why they had allowed themselves to be squeezed
into solidity seems an amazing bit of chemical perversity
until one knows the eagerness of the molecular head for
water. The OH group has an affinity.
This affinity is responsible for many characteristics of
water itself. For not only does the OH head of the oil mole-
cule have a liking for water, but the OH head of the water
molecule has an enormous fondness for the oil. The three
atoms of the water molecule H 2 O are arranged in the
sequence : H H. Thus both ends of the water molecule
are heads; on either side it presents an active group to its
fellows. The mutual attraction of these molecular heads
makes water molecules attract one another and gives to
the liquid surface of water a strong "skin." It is this surface
tension which enables insects to walk on water, causes par-
ticles of water to gang together into large drops, and endows
the fluid with a high boiling point which distillers and other
[185]
THE ADVANCING FRONT OF SCIENCE
commercial chemists find useful. These and other char-
acteristics of water are accounted for by the predominating
influence of the OH group.
To test this, destroy the OH group. It can be done by
removing the oxygen atom from the water molecule. What
is left is two hydrogen atoms, HH, which pair off as a single
molecule of hydrogen. Normally the stuff is a gas, but by
sufficiently lowering the temperature the gas can be reduced
to liquid, and then liquid hydrogen may be compared, quality
for quality, with liquid water. Striking results show up.
rr * ( boils at 423 below zero F.
H H** 1 ) ^ as "* un * ts f sur f ace energy
( occupies 47 units of volume
w ( boils at 212 above zero F.
~j ~ TJ < has 118 units of surface energy
( occupies 30 units of volume
Note that hydrogen has very little surface energy. This
means that its surface tension is slight; therefore it has a
weak "skin." When liquid hydrogen is poured or spilled, it
forms very minute drops. Attraction between its molecules
is so feeble that at a temperature of 423 F. below zero, the
molecules dart away from one another i.e., the hydrogen
boils. This behavior is at the opposite extreme from that
of water and yet, the only fundamental difference be-
tween a hydrogen molecule and a water molecule is the
absence of one oxygen from the hydrogen. By adding an O
to the HH we make it possible for the molecule to develop
an OH complex. The influence of that masterful combine
gives the water molecule such compactness that its volume
shrinks to about two thirds that of the hydrogen molecule.
And it gives to all the water molecules such affinity for one
another that the surface energy is increased above that of
liquid hydrogen twenty-three-fold, and the boiling point is
raised by 635 degrees.
This tenacity crops up all through nature. It explains
many curious contrasts. For example, ethane, one of the
[186]
A CHEMIST ON VACATION
constituents of illuminating gas, differs in structure from
alcohol by the trifle of a single atom. Ethane is C 2 He,
alcohol is C 2 H 6 O, but what a difference in characteristics
the presence or absence of that single oxygen makes !
Ethane
H H
I I
H C C H
H H
Alcohol
H H
I I
H C C O H
I I
H H
boils at 120 below zero F.
boils at 173 above zero F.
Ethane presents to the world an unbroken shell of hydro-
gen atoms, and it behaves much as hydrogen does. But add
a single oxygen atom, and the upset is enormous. The
effect is to break through the hydrogen and provide the
molecule with an OH head. Ethane by this addition of
oxygen is changed to alcohol, the boiling point is raised
from minus I2OF. to plus I73F. and the tenacious OH
group is the little giant that does it.
From such minute behavior Langmuir was led to formu-
late his Principle of Independent Surface Action, now
recognized as a primary law of the new chemistry. It sees
the compound molecule as a piece of architecture. Each
group of atoms within the molecule has its individual sur-
face characteristics. An OH surface is different from an H
surface, just as a sun porch is different from a basement
cell; and so with other groups. Dr. Langmuir found that he
could predict molecular behavior by this principle. Also, by
the same rule, from a study of behavior he could forecast
structure.
Surface chemistry thus assumes a primary role in
science. In the facades and other architectural peculiarities
[187]
THE ADVANCING FRONT OF SCIENCE
of the invisible particles lies an explanation of the strange
affinities and lack of affinities which bind and loose the
physical world. Through knowledge of molecular surface
differences has come increased ability to manage many
phenomena to man's advantage. Not only better lamps,
more sensitive radio tubes, and more absorbent gas masks,
but also such varied practicalities as tough-skinned lubri-
cants for airplane motors and other machines, improved
flotation methods of extracting ores, the production of
artificial fertilizers for agriculture, even a better under-
standing of the functioning of antitoxins and other serums
in the human body, are derived from knowledge of this
propensity of certain particles to arrange themselves on
surfaces in single-layer films.
Soon after Langmuir published reports of his early dis-
coveries in these chemical flatlands, he began to receive
letters from cytologists, cancer specialists, and other medi-
cal researchers. They had been seeking to learn the "go"
of the living cell, and were finding it increasingly a problem
of surface behavior. At the thin wall which divides the living
substance within from the multiplex world without, cer-
tain processes seem to act selectively. Just as the relations
between oil and water are selective, binding some oils to
water surfaces in a tenacious layer, and in other cases being
so different as to drive the oil apart into unsocial droplets,
so the interchanges between the internal protoplasm and
the external nutrients and poisons seemed to suggest a
monomolecular relationship. The biologists submitted some
of their observations to the chemist for elucidation; and
soon he was finding in their experiments new and tempting
trails into surface chemistry. Could the curious actions of
oil films throw a gleam on the mystery of life? He who in
his youth had the longing to be "free to do research as I
[188]
A CHEMIST ON VACATION
wish" turned to that problem. He was not a biologist; he
did not propose to dissect cells and test their behavior. But
he was a chemist, and could go as far as he liked with his
films, his interfaces, his two-dimensional gases, liquids, and
solids.
The first account of the new studies in this biological
direction was published in an address at Williams College
in the autumn of 1936, when the hundredth anniversary
of Mark Hopkins was celebrated there by a conference of
scholars. Langmuir reported what happened to his oil films
under changed conditions of acidity, alkalinity, and in the
presence of certain familiar metallic salts. As the film mate-
rial for these experiments he used a mixture of two fatty
substances: the mineral oil petrolatum, and the tallow's
stearic acid. The mineral oil has no OH group; therefore it
has no molecular head to bite into the surface, and will
not spread; it remains on the water as a bulging drop or
spatter of isolated droplets. But the stearic acid has its
OH group, and because of this active molecular head it
quickly distributes itself over the water surface. When a
small proportion of this gregarious stearic acid was mixed
with the individualistic petrolatum, the mixture acquired
an avidity for water and promptly spread into a surface
film one molecule deep. The techniques of these experiments
were developed by Katherine R. Blodgett, and also asso-
ciated in the study was C. N. Moore; Dr. Langmuir re-
ports the findings as the joint result of a collaboration
between himself and these two associates of his laboratory.
As a starting point for the search, the investigators chose
a water solution approximating that of sea water. Life
thrives in the sea; evolutionists believe that it first appeared
in the sea; in the animal body life requires a blood plasma
of approximately the same slight alkalinity as sea water:
therefore such a solution would appear to be normal to the
living membrane of the cell. How would it affect the non-
living membrane of the oil film ?
[189]
THE ADVANCING FRONT OF SCIENCE
Well, when a drop of the oil mixture was placed on this
slightly alkaline water (and the same proved true of pure
water), the oil film quickly spread into a monomolecular
film. And tests showed that the film was in the liquid state.
That is to say, the oil molecules distributed themselves
over the water surface with a density not so rigid as that
of a solid and yet not so diffuse as that of a gas they were
a two-dimensional liquid.
When this water was made acid, marked changes occurred.
Immediately the film expanded, the molecules moved far-
ther away from one another, their agitation became greater
the two-dimensional liquid had evaporated into a two-
dimensional gas. Further experiments showed that this
response to changes in acidity and alkalinity was extremely
sensitive. Even the slight acidity caused by the carbon
dioxide of the air (which amounts to only a few hundredths
of I per cent) transformed the oil film from the liquid to
the gaseous state within a few minutes. *
Then the experimenters tried a new tack. It is well known
that salts of the alkali metals sodium and potassium are in
solution in cell fluids and body plasma. Also those other
kindred metals, calcium and magnesium, are in living tis-
sues and fluids. How would these substances affect the
nonliving film of oil ? Very markedly, as the tests soon
demonstrated. The addition to the water of a little soluble
sodium salt or a slight pinch of potassium salt caused the
film of two-dimensional liquid to change to a gaseous phase;
the effect was similar to that of an acid. But calcium and
magnesium operated quite differently; under the influence
of salts of either of these metals the diffuse film of oil con-
tracted, shrunk to a smaller area, and presently it had
congealed into a two-dimensional solid. Thus the two pairs
of metals have antagonistic effects. Calcium and magnesium
cause the film to become more dense and less pervious;
sodium and potassium open it up into a more diffuse and
permeable structure.
[190]
A CHEMIST ON VACATION
These findings seem to have a bearing on the chemistry
of life. Biologists long have known that the permeability
of cell walls and other properties of cell material may be
affected drastically by slight changes in the ratio of calcium
and sodium salts dissolved in the surrounding medium. By
changing the calcium content of the blood only a minute
fraction it is possible to bring on biological disorders such
as tetany. All activities of the living organism sift down at
last to cell behavior; and if the interchanges by which a
cell selectively absorbs nutrients from without and selec-
tively discharges wastes from within are controlled by
molecular forces at the cell wall, we have in these experi-
ments with oil films a new and promising approach to
fundamental problems of biology. In such studies we have
an advantage over the usual techniques of the cell specialist
with his microscope, for here we can observe the phenomena
in the large. "We can make the artificial cell wall cover a
square foot if desired," points out Dr. Langmuir, "and we
can study in detail properties which would be very diffi-
cult to measure on a living cell. By quantitive studies we
can derive fundamental laws that govern these changes in
properties. We hope, by following up this work, we shall
be able to establish some principles that will be of great use
to the biologist in understanding the complicated depend-
ence of living cells upon the composition of the surrounding
medium. "
But the structure of cell walls is more complex than any
that can be represented by oil or other hydrocarbons. The
molecules of the living membrane are larger, they have the
added ingredient nitrogen combined with the familiar
hydrogen, carbon, and oxygen, with occasional other
elements, and these combinations assume enormous and
complicated architectural forms which we call proteins.
Some of the hydrocarbons contain scores of atoms to the
molecule, but a protein molecule may contain thousands.
For example, the stearic acid of our experiments is a
[191]
THE ADVANCING FRONT OF SCIENCE
representative fatty substance; its molecule consists of 56
atoms. But the molecule of a representative protein, the
familiar egg albumin, for example, consists of about 5000
atoms. And the latter complex substance is more typical of
the cell material than are any of the oils, fats, or other
hydrocarbons.
Langmuir and his associates have pushed their researches
recently into the field of the proteins. In 1937 they an-
nounced some preliminary experiments with egg albumin.
By a novel and original technique they have transferred
monomolecular layers of these large particles to solid
surfaces. And they have found it possible to alter the
permeability and other properties of the protein films by
making slight changes in the surrounding physical and
chemical conditions indeed simulating certain elementary
biological behavior.
But there are larger molecular structures than those of
egg albumin. The crystalline protein recently obtained by
Wendell M. Stanley from the juices of diseased tobacco
plants, and believed to be the virus of the tobacco mosaic
disease, has molecules consisting of 2,000,000 atoms
perfectly gigantic structures, chemically speaking. Early in
1937 Dr. Stanley provided Dr. Langmuir with some of this
virus protein, and it was found that when spread on
water the virus formed a layer one molecule thick. The
most amazing observation of these experiments, however,
was the relative thinness of the layer. Although the virus
molecule is atom for atom 400 times larger than the egg-
albumin molecule, a layer of the virus on water is no
thicker than that of the egg albumin. This may be ex-
plained, on the theory of Dorothy M. Wrinch, by assuming
that the huge spherical molecule of the tobacco virus may
unfold itself into a sheet which spreads out on the surface of
the water. However, many biologists believe that the mono-
molecular films formed from these huge molecules may in-
volve a breaking down of the molecular architecture from
[192]
A CHEMIST ON VACATION
complicated structures to smaller ones. Interesting tests of
the film phenomena are continuing, exploring new bypaths.
The studies of protein films are highly significant. They
advance the models of the chemist another step toward
approximating the conditions of the biologist. In the
protein experiments Langmuir has had the collaboration of
Vincent J. Schaeffer; and in certain interpretations of their
results they have been aided by Dr. Wrinch, biochemist of
the Mathematical Institute at Oxford University, Does it
not seem strange that an industrial research laboratory of
an electrical manufactory should join forces with a mathe-
matical institute to unshackle hidden meanings of life
phenomena ?
And so the busy vacation continues. Who could have
foreseen in 1909 that the mystery of the lamp would shed
light on the mystery of the living cell ? that glowing tung-
sten could bring authentic clues of sensitive protoplasm?
Surface chemistry is not only fundamental chemistry: it
may be fundamental biology.
[ 193 1
Chapter XI - LIFE AN D THE
(QUANTUM
this tremendous scene,
This whole experiment in green.
EMILY DICKINSON, XXXVIII
BIOLOGY is one of those intimate worlds which everyone
claims as his parish. An American novelist describes
the myriad reactions of consciousness as "cnemisms." A
philosopher and former premier of South Africa defines life
"not as an entity, physical or other," but "a type of
organization." Even in a book of astrophysics one may
encounter biological dogma. "Man," ventures an astrono-
mer of the Paris Observatory, "is only a colloidal oxynitro-
carbide of hydrogen with some admixture, chemically
speaking." Chemists are more analytical. They undertake
to break down the admixture into its traces of metals and
other infinitesimals, tab the results on a page, as one might
write the recipe for a pudding, and announce that the
chemical constituents are worth about 98 cents. Robots
should be cheap if we knew how to put the ingredients
together.
Aye, there's the rub! We know fairly well of what the
biological world is made, but we lack the fabricator's pat-
tern. The blueprint of life remains to be discovered. Until
it is found we may expect that such aberrations as cancer
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LIFE AND THE QUANTUM
and insanity will continue to pose their " infinite jests' 5 on
personality.
Protoplasm is both the nearest and the most remote
aspect of nature nearest because it is ourselves, the very
stuff that breathes and thinks and inquires; and yet, to the
investigator eager to unravel the secret of life, it sometimes
seems more inaccessible than any star. There are stars that
the eye cannot discern even through the loo-inch telescope,
but the more sensitive spectroscope and photographic plate
see and reveal them in such detail that it is possible to
classify the stars precisely and form some definite picture
of their inner structure. In certain fundamental aspects the
astronomer knows the invisible star more exactly than the
biologist knows the living cell.
But this comparison invokes the cosmic scale, and there
stars are the norm and protoplasm the rare exception.
More than 99 per cent of the visible matter of the Universe
exists as stars and nebulae in a state of high temperature,
incandescent, naked, completely gaseous, a comparatively
simple and obvious system of atoms which is explainable in
terms of physics and chemistry. A living cell, though al-
most inconceivably smaller, is far more complicated: a
heterogeneous aggregate of liquids, gels, and gases, a
comparatively chilly system which in spite of its low
temperature is the seat of powerful molecular and atomic
interactions that somehow spin their indefinable product,
life.
Life comes only from life, in our experience. But life is
also completely dependent on its nonliving surroundings;
and by changing the physical or chemical environment life
may be quickened and increased or retarded and destroyed
a fact which makes experimental physiology possible.
In 1912, at the Rockefeller Institute for Medical Re-
search in New York, Alexis Carrel opened a hen's egg that
was in process of hatching, removed the developing chick,
and cut out a tiny fleck of its beating heart. This bit of
1 195 1
THE ADVANCING FRONT OF SCIENCE
living tissue was transferred to a solution in a test tube.
And there, protected from germs, poisons, heat, and cold,
and provided with a never-failing supply of oxygen, sugar,
and other nutrients, it lived and flourished as no heart
cells in any living chick ever did. Indeed, it is doubtful if an
animal could provide its tissue with such completely
favorable surroundings; for in nature a heart as well as a
chick must work for a living. Freed from workaday strains,
the cells in the test tube proliferated so abundantly that it
was necessary to prune down the tissue daily to hold the
growth within bounds. Today, more than a quarter century
since the beginning of the experiment, this part of the part
of a chicken shows no signs of aging. On the contrary, there
is reason to expect that it may continue to live a hundred
years, a millenium, or until the Sun grows cold so long as
someone provides the necessary environment.
Dr. Carrel's experiment is a striking demonstration of
the complete dependence of the living on thejpot-living a
commonplace observation, but its implications go to the
root of our mystery. For when the chemist, sifting living
matter into its elementary parts, discovers nothing new,
nothing that is not already known in the rocks and the
stars
Finding their mould the same, and aye the same,
The atoms that we knew before
Of which ourselves are made dust, and no more,
the question arises : At what point and by what means does
inanimate matter pass over and become alive ?
Outside the cell are compounds containing carbon, hydro-
gen, nitrogen, oxygen, calcium, sodium all lifeless, familiar
elements, common to earth, air, and sea, "dust, and no
more." These diffuse through the ceil wall and are con-
verted into foods. The food products in turn pass over
into new combinations and enter a new category. They
become living matter: green chlorophyll, red hemoglobin,
LIFE AND THE QUANTUM
protoplasm! Thus endlessly the line of life marches on,
forever transporting star stuff into life stuff, moving by
some catalytic hiddenness that is the very bridge of life.
To find that bridge has become the grand quest.
Among the agencies which the new physics has brought
to the aid of biology in this search, none gives more promise
of success than the quantum theory of light and the new
implements and methods of generating, manipulating, and
measuring radiation. Light, which opened to the astrono-
mer the interior of stars and to the physicist the interior of
atoms, is becoming the physiologist's surest instrument for
exploring the delicate vital mechanism. Nor is it only an
instrument; light is also one of the chief subjects of modern
biological research.
For light is the great prime mover. Not long ago F. G.
Donnan, chemist of the University of London, suggested
a new holiday. He would have all city people make "a
pilgrimage to the tilled fields and green pastures once a
year, say when the first breath of returning spring brings
its fragrance to our nostrils, or when the Sun rises on mid-
summer's morn, and, falling on the bosom of Mother
Earth, offer thanksgiving for that bountiful conjunction of
Sun and Earth, of radiation and matter, which sustains
our life."
Such a festival might have a salutary effect on homo-
centric pretensions reminding a proud race of its com-
pletely dependent position, not only in the cosmic scheme
of things, but also among the living species. Whatever man
may be mentally, physically he is a spender. He is as
parasitic as any fungus, and in precisely the same way, i.e.,
he derives his energy from the degradation of organic sub-
stances provided by other living beings. With the exception
of a trifling fraction of power wrested from the harnessed
[ 197 1
THE ADVANCING FRONT OF SCIENCE
flow of water and wind, all the energy used by man the
fuel he burns in his furnaces and motors, and the food he
burns in his body is the product of a specialized type of
plant cell which has the faculty of trapping and storing the
energy of sunlight.
The importance of the plant's photosynthesis lies in this :
that it acts against the energy stream. Man and all animals,
the fungi and all parasitic plants, orchids and yeasts, move
with the current. And that current forever flows down-
stream, from hot stars to cool planets and on to the absolute
cold of interstellar space, ever falling to lower levels of
energy, toward stagnation, equilibrium, maximum entropy,
death. Against this universal waste the green plant sets a
valiant barrier. It is not strange, therefore, that many
biologists regard photosynthesis as the starting point for
the grand quest. Some of the most penetrating research of
modern biology has been in this field, and three of the recent
I Nobel prize men Richard Willstatter, Oto Warburg,
and Hans Fischer are distinguished for studies of chloro-
phyll or its processes.
This enigmatic green stuff of plants the trap that cap-
tures sunlight is today the focus of experimental work in a
score of laboratories, and an interest in hundreds of others.
Present researches stem from the classic experiments of
Willstatter, begun in 1902. It was in that year that the
young German chemist thirty years old left Munich,
where he had just worked out the difficult structure of
cocaine and other alkaloids, to accept a professorship across
the Swiss border in the University of Zurich. Here he
tackled a more difficult structure.
"I remember well the time of my first experiments with
chlorophyll," related Dr. Willstatter in a recent reminis-
cence. "I told my assistant to prepare a solution from grass
under specified conditions. When he asked, 'Shall I order
the grass from Mercks's ?', I took him to the window and
showed him the view from our old botanic garden. At our
LIFE AND THE QUANTUM
feet lay a meadow, which perhaps was much greener than
meadows appear to me nowadays."
But if Willstatter's studies took some of the greenness
out of meadows revealing that the chloroplasts always
contain, in addition to their green pigments, smaller but
quite definite proportions of yellow pigments they also
took some of the mystery out of the elusive sunlight trap.
He broke it down into its molecular parts. He showed that
chlorophyll is not one green substance, but two, each con-
taining the familiar carbon, hydrogen, nitrogen, oxygen,
and magnesium, but in slightly different arrangements. He
traced the two chlorophylls to their chemical origins, and
proved that the parent substance of the green stuff is closely
akin to, if not identical with, the parent substance of the
red blood pigment, hemoglobin. Thus, searching the secret
of light's mechanism within the plant, the explorer comes
upon a link with the animal kingdom. Hemoglobin is the
carrier of oxygen within the animal body. Chlorophyll is
the deoxidizer in the plant body. Their functions are
basically different yet blood and chlorophyll both own the
same ancestry. The intrinsic unity of nature beckpns to
us from the most hidden places.
The key problem is to explain how the green pigment is
able to bring together such mutually indifferent substances
as water and carbon dioxide and, together with light, forge
out of them a new compound, a substance of great energy
content sugar. For this is what photosynthesis does.
Whatever may be the inner processes, we know what goes
into the green cell and what comes out. The audit of the
exchange balances precisely:
Carbon dioxide + water -f- energy from Sun = sugar + oxygen
(6COi) (6HiO) (674 calorics) (CHijOe) (6Oi)
The six parts of molecular oxygen produced are released
and replenish the air. The one part of sugar is stored in the
[199]
THE ADVANCING FRONT OF SCIENCE
plant for food. And, mind you, it is life's basic food. Out of
it the cell builds the other carbohydrates, oils, and fats, and,
together with combinations of nitrogen, fabricates the
proteins. Sugar is the very fuel of life. It burns with oxygen
like any other combustible, and its combustion yields back
exactly the ingredients that went into its making: carbon
dioxide, water, and the 674 calories of chemical energy.
Any living being may set off this combustion process; in-
deed, it is continually occurring spontaneously. But only
the might of chlorophyll can reverse the reaction and
rebuild. And it must work with light.
Otto Warburg, at the biological laboratories of the Kaiser
Wilhelm Institute near Berlin, tried the experiment of
growing green algae under an illumination of weak light.
The water plants developed dark cells rich in chlorophyll,
and were powerful producers of sugar. It was found, how-
eVer, that the average efficiency of the chlorophyll de-
creased as the intensity of the illumination w^s increased.
The greater the input of light, the smaller was the output of
sugar per unit of light, which seemed somewhat of a
paradox until the discerning Warburg drew his picture of
what was happening in the cell.
The chlorophyll molecules, being colored, are the ab-
sorbers of the light. It is known that this absorption can
exist in each instance only a small portion of a second.
Indeed, in most gaseous reactions, the period is limited to
less than a millionth of a second. Therefore, whatever use
is made of the energy must be within that slender whirl of
time, and presumably it can be used only if the chlorophyll
is in contact with a molecule or other unit of chlorophyll. As
the process begins, this contact is 100 per cent; presumably
every chlorophyll has at hand a carbon dioxide waiting to
be reduced. As the intensity of the light is increased, the
chlorophyll unit quickens the process; more and more sugar
is manufactured; but presently the sugar is being produced
faster than the cell transport can carry it away. The on-
[200]
LIFE AND THE QUANTUM
coming carbon dioxide molecule now finds the assembly
line blocked; it is unable to reach a chlorophyll machine;
and so the works become clogged with their own over-
activity a demonstration from life of the evil of un-
balanced production and consumption.
In offering this explanation Warburg was one of the first
to apply the quantum theory to the photosynthetic
process. According to this quantum theory, light is not
emitted as a continuous flow of energy, like a stream of
water from a nozzle, but in discontinuous units or quanta,
like a stream of bullets from a machine gun. What the
chlorophyll unit receives, therefore, is the blow from a
bullet of energy shot out of some agitated atom of the Sun.
The impact may be said to displace one of the revolving
electrons within a chlorophyll molecule. In this process the
energy of the quantum is absorbed by the displaced elec-
tron; but when the electron returns to its stable state in
the molecule, the absorbed energy is released for use, again
in the form of a quantum.
But all quanta are not the same. The energy varies with
the wave length and frequency of vibration of the radiation.
Blue light, being of shorter wave length and higher fre-
quency than red, is packed with more energy. A quantum
of blue gives the absorbing body almost double the kick
that a quantum of red is able to deliver. And yet, chloro-
phyll does its most efficient manufacturing of sugar with
red light, and actually uses mostly red light.
Seeking an explanation of this apparent contradiction,
Warburg turned to the statistics of his experiments. He
found that when photosynthesis was accomplished with
blue light five quanta were necessary to reduce each mole-
cule of carbon dioxide; but when the process was activated
by red light, four quanta did the work. He was able to
derive a mathematical relationship which showed why this
must be so, namely, that four absorbed quanta were really
involved in both cases, but in the first case one was wasted
[201]
THE ADVANCING FRONT OF SCIENCE
in an incidental process. Another German biochemist,
T. Schmucker, has since completed a series of experiments,
using other methods, which confirm Warburg's results.
The yellow pigments, although present to only one-fifth the
extent of the green pigments, are very much stronger
absorbers of blue light; and the quanta they absorb appear
to be just so much wasted energy so far as photosynthesis
is concerned, for the yellow pigments seem to play no
productive part in the photosynthetic mechanism. It is
the green pigment that does the work, and the green selec-
tively absorbs red quanta to energize the photosynthetic
unit.
But what is the photosynthetic unit? Is it a single mole-
cule of chlorophyll, or many ? Two American biophysicists,
Robert Emerson at the California Institute of Technology
and William Arnold, then at Harvard, worked on that
question. They made use of a neon lamp which illuminates
the green algae with very bright intermittent light, twelve
flashes of light to the second, and each only one hundred
thousandth of a second long. With this device they found
that for every molecule of carbon dioxide reduced there
were present in the cell an average of about 2500 molecules
of chlorophyll. This does not mean necessarily that 2500
chlorophylls are active in the reduction of each carbon
dioxide. Indeed, it is difficult to visualize so many large
molecules (each containing at least 146 atoms) operating
on one small carbon dioxide molecule of only 3 atoms.
More plausible is the assumption that at each flash of the
light many chlorophyll molecules are not functioning, and
that the proportion of idle to active ones is roughly con-
stant and tallies some 2500 for each manufacturing unit.
It may be that the unit is a supermolecule. Harold Mestre
emphasizes in a recent paper that chlorophyll in the living
cell is rather different from the extracted chlorophyll which
we analyze in our test tubes. Absorption spectra and other
indicators show considerable differences. Extracted chloro-
[ 202 ]
LIFE AND THE QUANTUM
phyll has no power to make sugar. The meaning of the
2500 average is still under much investigation in an attempt
to choose the correct interpretation from various ones pro-
posed. The interpretation most favored at present involves
a very great physical improbability, and while physiologists
may accept it the physicists find difficulties which they are
trying to obviate. It will be interesting to see which wins
out, physiology or physics.
But the efficiency of photosynthesis in the living plant
may be increased by artificial means. Warburg used inter-
mittent light flashed from a rotating sector which divided
each revolution into equal periods of light and dark. With
this he found that when green algae were illuminated with
133 flashes per second, the rate of photosynthesis doubled
per unit amount of light. More recently Emerson and
Arnold used their flashing neon tube, adjusted to make
the period of illumination only a small fraction of the dark
period. With 50 flashes per second they were able to increase
photosynthesis per light unit by as much as 400 per cent.
Making five particles of sugar form where only one formed
before is an achievement and would seem to betray rather
close contact with life's most fundamental process.
It is not a single process, but is now revealed as a cycle
-in which at least two operations continually follow each
other. There is the photosensitive phase, actuated by visible
light, completed in the hundred-thousandth part of a
second. And there is a purely chemical phase, which is then
completed in the dark, and takes at least a thousand times
as long, i.e., a hundredth of a second or more. This dark
phase was predicted as long ago as 1905 by F. F. Black-
man, a British botanist, and is known as the "Blackman
reaction." The Emerson-Arnold experiments are convincing
evidence of the reality of the Blackman reaction.
How then, after all, does the green-plant factory operate ?
jjames Bryant Conant who was working on this prob-
lein when Harvard University called him to its presidency
[203]
THE ADVANCING FRONT OF SCIENCE
suggested from his extensive chemical studies of chloro-
phyll that the sugar is made in the dark phase. He thinks
this may be accomplished by a catalytic process of taking
hydrogen atoms from chlorophyll and combining them with
carbon dioxide in the pattern CeHiaOe, which is sugar. The
reaction in the light follows instantly, according to Conant,
and is a regenerative process to restore the sugar-making
mechanism to its productive phase; it may do this by re-
moving hydrogen atoms from water and using them to re-
pair the mutilated chlorophyll molecules, at the same time
setting the green stuff back to its former state packed
with the energy of sunlight, primed and ready to repeat the
cycle of manufacture.
Conant's theory is only one of many that have been
proposed to explain photosynthesis; and like the others, it
remains to be proved. All authorities are agreed that the
photosynthetic process is cyclical, though the steps within
the sequence may be far more complex tha$ any present
theory supposes. The Blackman reaction, for example,
may be not a simple interchange but a train of two or more
sequential operations. Recently Dean Burk and Hans Line-
weaver, of the United States Department of Agriculture,
proposed such a theory, whereby photosynthesis is analyzed
into four forward reactions: first, a dark reaction which
may take place in less than one-hundredth of a second;
next, the photosensitive reaction which takes place in the
light, and requires no more than one-hundred-thousandth
of a second; and then third and fourth, two successive
reactions in the dark, one building upon the other, these
two constituting the phase known as the Blackman reaction,
and together occupying about one-hundredth of a second.
Burk and Lineweaver find that each of the four reactions
is experimentally recognizable; each represents a step in
the process by which sugar is made and the " machine"
energized for the next reduction. The photosensitive reac-
tion, which comes second in the sequence, appears in
[ 204 ]
LIFE AND THE QUANTUM
some experiments to consist of several exceedingly rapid
reactions. Thus the picture grows more complicated; the
green-plant factory is no simple handicraft shop, but a
highly specialized industrialism.
Whatever the internal processes and subdivisions of labor
may be, we clearly distinguish the two phases, one using
light and the other requiring no light, which constitute an
unending cycle. Arnold has pictured the cycle in a simple
graph, from which we adapt the following:
MANUFACTURE OF SUGAR
The arrow B on the right represents the Blackman (or
dark) reaction or reactions; the arrow P, the photosensi-
tive reaction or reactions; together they constitute a turn-
ing wheel driven by the energy of light. It is the rotating
of this wheel, the two curved arrows following each other
in perpetual sequence, that moves the process as a whole
to manufacture sugar.
Whatever and wherever may be the bridge, surely here
is the wheel of life the whirling loom by which quanta
are woven with atoms and molecules into the peculiar forms
that nourish and make protoplasm.
3
But this universe of light contains more than visible
radiation. As we noted in Chapter V, the rays we see are
few and weak compared with the invisible light that is
pouring through space ultra-violet rays, x-rays, gamma
[205]
THE ADVANCING FRONT OF SCIENCE
rays, cosmic rays, to name only the high frequencies. In
addition to radiation, there continually move through the
air and surrounding space countless ions or electrified par-
ticles similar to the alpha and beta particles from radium.
These atomic particles dart in many directions at many
velocities, some at speeds approaching that of light.
Now, it is in the midst of this fantastic turmoil, of bom-
bardments and mutilations and rushings-about, that
protoplasm has emerged and spread its film of life over the
Earth. Did it do that in spite of the invisible radiations and
collisions ? or with their help ? What happens when one of
these projectiles smashes into a living cell ?
Science has known for more than 30 years that radiation
from radium and x-rays will destroy living tissue. Becquerel
discovered this by chance when he carried a small quantity
of radium in his coat pocket, and later suffered an ulcerating
sore in the flesh under the pocket. This accident suggested
the use of radium as a means of destroying cancerous tissue.
Through the years the cancer specialists have accumulated
considerable data on the biological effects of radiation.
They found, for example, that young rapidly growing cells
are more susceptible to its lethal action than are old cells.
The tissues too show varying resistence. Blood, spleen,
bone marrow, and other lymphoid cells are the most vul-
nerable, while nerve cells are the least. A body of empirical
knowledge of this kind has been built up in the course of
medical practice and is extremely valuable both to therapy
and to experimental medicine. But the biophysicists aspire
to apply exact quantitative methods to the phenomena,
and lately some significant results have been obtained both
in Europe and in the United States. A single series of ex-
periments, conducted by Ralph W* G, Wyckoff at the
Rockefeller Institute for Medical Research in New York,
will serve to illustrate the procedure and its disclosures.
Dr. Wyckoff selected bacteria as the subjects for his
studies. He proposed to bombard these minute creatures
[206]
LIFE AND THE QUANTUM
with high-speed particles and rays of various frequencies,
and measure the survival ratio. By applying the quantum
theory to the results he was able to arrive at some picture
of the changes brought about in living cells by these violent
intrusions.
The first experiment which was a joint project with
T. M. Rivers used a beam of electrons shot from a cath-
ode-ray tube at a speed of 148,000 miles a second. An elec-
tron is an ion, the negatively charged fragment of a smashed
atom; therefore these particles are comparable with the
ions which eternally dart through the atmosphere. Known
numbers of colon bacilli were spread in a single layer on an
agar plate and bombarded with electrons. Out of every 1000
bacilli, 311 were alive at the end of 12 seconds, and only
26 at the end of 28 seconds. Similar experiments with other
species of bacteria showed comparable results.
It is known that when an electron of this velocity is ab-
sorbed in matter, the effect is to release a large number of
secondary ions within a very small space. The impact of the
colliding particle sets off a veritable explosion, smashing
out parts of atoms, each of which recoils at high velocity
to wreak havoc wherever it strikes. Tests have shown that
an electron of this velocity will liberate about 10,000 ions
within a space of less than Mooo of a cubic millimeter a
space so small that about sixty such cubes would be re-
quired to cover the dot of ink which marks the end of this
sentence. It is this sort of atomic pandemonium that is
stirred up within the single cell of the bacterium. With
thousands of its molecules thus dismembered and pounded
into a frenzy of chaotic movements, the peculiar organiza-
tion of protoplasm is destroyed. The experiment indicated
two facts: (i) that a single electron hit can kill, and
(2) that every absorbed electron is fatal to its living
target.
For the second group of experiments Wyckoff used x-rays,
Here the bombarding projectile is not a charged particle,
[207]
THE ADVANCING FRONT OF SCIENCE
but something more penetrating a quantum of radiation.
Just as visible light has its range of energy proportionate
to the frequency of its vibration, so with x-rays. The bacilli
were bombarded with x-rays of five different frequencies,
in progressive order of energy. This interesting relation was
found: Millions of the rays passed through the bacteria
without harm, other millions were absorbed without fatal
effect, but when a death did occur it was the result of the
absorption of a single quantum. Of the bombardment with
the hardest or most energetic x-rays, about one bacterium
out of every four that were hit, died; while of the bombard-
ment with the softest rays, sixty were struck to one that
died. (The criterion of bacterial death was the cessation
of cell division; in the absence of simpler tests of life, Dr.
Wyckoff assumed that when a bacterium ceased to multiply
it had ceased to live.)
From the ratio of quantum absorptions to microbe
deaths, considering also the frequencies of the rays and
their ionizing powers, Wyckoff figured that th bacterium
must be a differentiated structure in which there is a rela-
tively small region sensitive to x-rays. It is as though a
man were vulnerable to a bullet only in his heart, and if
struck elsewhere would escape death. Wyckoff was able
from his statistical picture to compute the probable size
of this vital zone, and found that it measured about one one-
hundredth the volume of the living creature. And the
living creature, the colon bacillus, is a single-cell cylindrical
rod measuring about 2/1000 millimeter long by 5/10,000
millimeter in diameter. Divide that by 100 and you have
the size of the vital zone.
A third group of experiments used ultra-violet light. Al-
though this is less energetic than x-rays, it carries more
energy than visible rays. Using progressively five different
wave lengths of ultra-violet, Wyckoff found that of the
quanta absorbed by the microbes only about I in every
4,190,000 killed. Interpreted on the same basis as the x-ray
[208]
LIFE AND THE QUANTUM
results, this would mean that the sensitive region of the
organism is confined to the volume of a single large protein
molecule a conclusion which Wyckoff rejected as improb-
able. The fact that one bacterium can absorb millions of
ultra-violet quanta without destruction, while another is
killed by the absorption of a single quantum, is more rea-
sonably explained on the assumption that some individuals
among the bacteria are more susceptible than others to
this form of radiation.
Several years before Wyckoff began these studies, H. J.
Muller proved that it was possible to alter the inheritable
characteristics of living creatures by x-ray bombardment.
I have referred to these experiments in Chapter II, but
the subject is vital to our present discussion and additional
details will be interesting. Dr. Muller, a geneticist of the
University of Texas, used the fruit fly (Drosophila melano-
gaster) as the material of his experiments. Selecting care-
fully nurtured strains of normal stock, Muller placed the
flies in gelatin capsules, placed the capsules under x-rays
of measured intensity, and after subjecting the flies to given
periods of radiation, released them into larger bottles, where
they were provided with food and all the other comforts
of home. After several weeks had passed, and several
generations had bred, the progeny of the x-rayed insects
began to show strange deformities. Some of the offspring,
for example, were born with huge wings, others with trun-
cated wings, and many wingless. There were flies that grew
extra antennae; in a few the antennae came large and
thick; in one a leg grew out of its head in place of an an-
tenna. Variations showed up also in the behavior of the
insects. All these remarkable results are explained on the
hypothesis that the genes, or units of heredity in the germ
cells of the parent flies, had been struck by the x-rays or
their ions and thereby had been twisted or sliced into new
patterns. Comparing the slow rate of change in nature with
the results obtained by a few minutes of intense x-radia-
[209]
THE ADVANCING FRONT OF SCIENCE
tion, Muller reckoned that evolution had been speeded up
I5o-fold by the bombardment.
These experiments have led to speculations on the role
of radiation as a factor in evolution. Mutations which pro-
duce new species of plants and animals may be accounted
for as results of stray collisions of germ cells with rays or
particles; though on statistical grounds it is argued that
there are not enough of these strays observed in nature to
account for the mutations that occur. Lately the geneticists
have been looking within the living cell itself for the activat-
ing mechanism of mutation. It may be that chemical in-
terchanges between the atoms and molecules of the genes,
or of the substances surrounding the genes, cause the strange
shiftings which later show up in the variants. It may be
that molecular or atomic activity within the cell is able to
produce an invisible radiation of its own, somewhat as the
firefly and luminous bacteria emit their visible radiation.
Life, whose wheel is driven by light, may also ^e a generator
of light. This is the amazing concept posed by a series of
experiments in a Russian laboratory.
4
The laboratory is the All-union Institute of Experi-
mental Medicine at Moscow. Here for several years Alex-
ander Gurwitsch has been at work with microscope studies
of living tissue cells. These grow by a process of division,
each cell reaching a stage when it splits and forms two cells,
each of which in turn repeats the process. Watching this
mysterious multiplication of life, Gurwitsch noticed that
the cell division frequently followed a definite rhythm. For
a year he concentrated on this study, and prepared a re-
port summarizing his experiments. But the manuscript was
lost in a censor's office in Leningrad, and most of these early
data are unrecorded.
From the order of the rhythm Gurwitsch concluded that
the cause must be physical. He suspected that it might
originate in neighboring cells. One of the tissues that had
[210]
LIFE AND THE QUANTUM
manifested the rhythmical division to a marked degree
was the tip of an onion root, so this obliging vegetable was
selected for the experiment. Several onion bulbs were al-
lowed to sprout in water. After the roots had grown five
or six inches long, the most symmetrical root was chosen
and all the others on the bulb were cut away. This selected
root Gurwitsch called the "sender." He proposed to use
it as a biological cannon. He mounted it in a thin tube,
setting it in a horizontal position that indeed suggested a
miniature short-range artillery piece. He pointed the tip
of this sender at another onion root, the "detector," which
was similarly protected in a tube, but with a small area of
its side exposed naked to the pointing tip of the artillery
piece. The idea was to see if the growth of its exposed area
would differ from the growth of other parts of the detector
root.
After three hours' exposure to whatever influence the
sender might have emitted, the detector root was sliced
into sections suitable for examination under the microscope.
And now, then, for the test! Gurwitsch counted the num-
ber of cell divisions on both sides, and found about one-
fourth more in the exposed area than in an equal area on
the opposite side. Apparently the biological gun had made
a difference.
He tried the experiment all over again, this time inter-
posing a thin sheet of quartz between sender and detector;
the result was unchanged essentially. But when he repeated
the experiment with a thin sheet of glass, or when the
quartz was coated with a film of gelatine, the effect ceased.
It is well known that quartz is transparent to ultra-violet
rays, while glass and gelatin are opaque to them. From
these and other considerations Gurwitsch concluded that
the influence might be an ultra-violet radiation generated
by the cells of the sender. Since it was the increased rate
of "mitosis," or cell division, of the receiving root tissue
that had betrayed the emissions, he named them mito-
genetic rays.
THE ADVANCING FRONT OF SCIENCE
Publication of these and later experiments evoked pro-
found skepticism among biologists and most of this atti-
tude persists, especially in England and the United States.
The wave lengths claimed for the mitogenetic rays are
shorter, therefore more energetic and powerful, than the
ultra-violet reaching us from the Sun, and it seemed in-
credible that living processes could generate such energetic
quanta.
In Paris, though, J. and M. Magrou repeated Gurwitsch's
experiments and reported similar results. Then T. Reiter
and D. Gabor, in the research laboratory of Siemens &
Halske Electric Company near Berlin, put the idea to the
test in a series of experiments. Their verdict is that the
rays are real. Others too reported confirmatory results,
while a smaller number of equally reliable and conscientious
investigators could detect no effects and were disposed to
dismiss the whole idea as illusory.
Meanwhile, in the Moscow laboratory, Barpn had found
that yeast cells are sensitive to the radiation; and, because
of the greater ease of handling, yeast took the place of the
onion roots as detectors. The effect on yeast was to accel-
erate the rate of budding by a factor of 25 to 30 per cent.
Later it was reported that bacterial growth was also stimu-
lated by the mitogenetic effect, and cultures of these
organisms have been used as detectors.
But biological growth is itself such an enigma that many
authorities balk at the idea of accepting it as proof of an
otherwise undetected radiation. Other causes might be in-
fluencing the growth. If the radiation really exists, argue
these critics, it should be measurable on a physical basis
like any other radiation. In accord with this idea, many
attempts have been made to photograph mitogenetic rays,
but always without success. It has been estimated that
because the quanta emitted per second are so few relatively,
an exposure of thousands of hours would be necessary to
obtain appreciable blackening of the most sensitive plate.
[212]
LIFE AND THE QUANTUM
This same limitation suggested that it might be impos-
sible to measure the radiation by its ionization effect. But
B. Rajewsky, working in Frankfurt, finally succeeded in
installing an extremely sensitive photoelectric cell in an
ionization chamber, and with this physicist's apparatus a
purely physical detection of mitogenetic rays was reported.
Other European investigators have confirmed Rajewsky's
results; but a careful campaign of experiments made with
a device of this same type was carried on in a Boston lab-
oratory by Egon Lorenz of the United States Public Health
Service, and his report is wholly negative. Lorenz was un-
able to detect any evidence of the radiation, though he
tried seven different living tissues, all of which had been
reported as good senders of mitogenetic rays. Even more
recently another search was made in the United States, a
study by Alexander Hollaender, conducted at the University
of Wisconsin and supported by the National Research
Council. Dr. Hollaender tried various methods of detection
on several reputed senders, and his report may be suc-
cinctly summarized as: Looked for and not found. But as
the great Warburg remarked recently, concerning these
rays, " In science one cannot prove that there are no ghosts."
The negative results are extremely disconcerting to one
on the side lines, however, especially in view of the wide
range of living material for which other investigators have
reported positive results. From the records of various suc-
cessful experiments I glean the following items. Young
cells radiate more strongly than old cells, root tips, dividing
eggs, and other germ cells being particularly active sources.
In mature animals, the working muscles, the cornea of the
eye, blood, and nerves are energetic senders. Healing
wounds give off rays, and it is claimed by some that the
healing process is hastened by mitogenetic radiation. The
blood of healthy rats gives off rays; the blood of starved
rats does not; but when a little sugar is added to the latter,
the radiation reappears. Illness seems to affect the quality
]
THE ADVANCING FRONT OF SCIENCE
and degree of radiation, and the Cornell bacteriologist
Otto Rahn reports that this has been observed of human
senders as well as of lower organisms. Many simple chemi-
cal processes, such as the combustion in a gas flame, the
digestion of proteins by pepsin, even the neutralization of
acid by alkali, are reputed to give off characteristic radia-
tions analagous to those of the mitogenetic effect.
Gurwitsch, on his part, is pushing the work into new
fields. Dr. Hans Barth, a pupil of the late Professor Willi
Wien of Munich University, has joined Gurwitsch's staff
in Moscow, and Barth the physicist is attacking the mys-
tery of the rays by purely physical means. Recently he
reported the successful detection of the mitogenetic effect
by a Geiger counter. The counter is an ionization device,
an electronic apparatus that has been much used to explore
cosmic rays. If other Geiger counters confirm Earth's re-
port, the case for the elusive effect will be very much
strengthened. A recent American visitor to^the Russian
laboratory found Gurwitsch completely convinced of the
reality of his discovery, and equally confident as to the
ultimate verdict of time.
Whatever that ultimate verdict may be, biological re-
search will continue to explore its shadowy borderlands by
the implements and methods and data of the radiologist.
Radiation assuredly provides the energy to drive our wheel
of life; demonstratedly it has provided a probe with which
to reach into the living cell and alter and test the mecha-
nisms of life; conceivably radiation is one of the products of
life, certainly so in the case of the luminous organisms.
Every year the techniques of the quantum physicists and
the quantum chemists become more accurate, more sure,
more penetrating, more available to the special needs of
biology. The future of biology lies in increasing the approxi-
mate exactness of experiment. And an important sector of
the future of biological experimentation, I venture to think,
lies in the strange and mysterious ways of radiation.
Qhafter XII WH E RE LIFE
BEGINS
Self kindled every atom glows,
And hints the future which it owes.
RALPH WALDO EMERSON, NATURE
OUR search for a bridge from the nonliving to the living
leads eventually to a search for a definition. What
does it mean to be alive? The physicist speaks of the " half-
life" of radium as being 1600 years, somewhat as the biol-
ogist speaks of the average life of man as being about 60
years. The electrician warns us against the harnessed
lightning bolt that is concealed in a "live" wire. The metal-
lurgist describes the "growth" of crystals, the "fatigue"
of metals, and the hysteresis or "memory" of certain
materials, and some years ago the French scientist Dastre \
published a paper on "The Life of Matter." Indeed, lifej
may be inherent in all matter, just as radioactivity and
magnetism are.
It is in. the massive chemical elements af the far end of the
periodic t%ble, vast bulky crowded atoms such as radium
and thorium and uranium, that we observe radioactivity
spontaneously occurring. But experiments early in 1934,
in both Europe and America, have shown that light ele-
ments, even such gases as nitrogen, become radioactive
under the battering of high-speed particles. Similarly, we
THE ADVANCING FRONT OF SCIENCE
associate the property of magnetism with iron and nickel
and cobalt and certain alloys of these metals; but the sensi-
tive detectors of the modern magnetic laboratory reveal
that all the elements possess a certain degree of magnetism.
We can apply these facts by analogy to our discussion of
life. Life is always associated with the element carbon, and
the carbon seems to require as close collaborators the ele-
ments hydrogen, nitrogen, and oxygen. But may it not be
that life, like magnetism and radioactivity, is a property
latent in all atoms, a something hidden, waiting for a pro-
pitious meeting of matter with energy to bring it into play ?
In truth, there is no single statement which the biologist
asserts of the elementary behavior of the living species
that cannot also be applied to nonliving matter. An or-
ganism reproduces itself, but so does a crystal of salt. A
broken tadpole will grow a new tail, but so too will a mu-
tilated atom repair itself. An amoeba responds to outside
stimuli; it shows irritability but an ionized gas molecule
also responds to outside stimuli, to the electric or magnetic
field, for instance. Both man and the paramecium breathe,
but there are nonliving organizations also which take in
oxygen and give off carbon dioxide. And, too, there are
certain bacteria which live in the absence of oxygen and
dispense with the function of respiration. There is no unique
criterion of life, and no combination of tests which fits all
cases. Perhaps, as a pragmatic device, in order to get on
our way, we may adopt the subterfuge employed by the
poet A. E. Housman when asked for a definition of poetry.
Housman, as he relates the incident in a lecture, told his
inquisitor that one "could no more define poetry than a
terrier can define a rat, but that I thought we both recog-
nized the object by the sympathy which it provokes in us."
All authorities, from terriers up, probably agree that the
rat is alive. Cut off the rat's legs, and the mutilated animal
will live. We can break down the whole yet more drastically,
remove its heart, suspend that organ in a perfusion ap-
WHERE LIFE BEGINS
paratus, and keep the part of the rat alive for months, per-
haps indefinitely. It is not necessary to remove the organ
* HWWtMftlfalwMwH***. * * W
whole. We may cut a small piece out of the heart, and by
immersing it in a nutrient solution and providing conditions
favorable to its welfare, demonstrate that the excised tissue
will live separated from its whole.
Under the microscope we see that the tissue is made up of
individual units, minute blobs of jellylike fluid held within
delicate membranous walls. Each of these cells is alive, and
it is reasonable to believe that each could be cultured in a
glass vessel if our techniques were sufficiently delicate to
care for an object so small. Indeed, we know that cells
live independently, for there are numerous species of one-
cell plants and animals which carry on within their single
room all the vital functions and tissue cells are simply
specialized individuals of the same general nature.
We may assert quite definitely, therefore, that life, this
thing of wholes, can be broken into organs, and the separate
organs will live. The organs may be cut into tissues, and
the excised tissues will live. The tissues may be divided
into cells, and the individual cells will live.
Is this the limit? Is it impossible for part of a cell to
carry on? Or can we dissect still more, break the cellular
whole and find some part that is more alive than the other
parts, some smaller unit which is the kindling spark of this
mysterious flame the place where life begins ?
It is a remote frontier that this question refers us to, but
a fascinating one. I shall attempt in this chapter to give a
brief account of several current discoveries which seem to
bear on the question, and of certain speculations which
have been ventured in interpretation.
Watch almost any living cell under a high-power micro-
scope. You look in on a world of ceaseless change. Within
the delicate membrane of the cell wall, the protoplasm
THE ADVANCING FRONT OF SCIENCE
churns and flows. Perpetually the living stuff is on the move,
and yet it maintains from moment to moment a certain
differentiation in which we may identify relatively stable
parts of the cell. Central, or nearly central, in this dynamic
structure is a region, generally spherical or oval in shape,
that appears more dense than its surrounding medium.
This interior protoplasm is the "cell nucleus," and the sur-
rounding thinner fluid is the "cytoplasm." All types of cells
but a very few, like bacteria and some algae and blood cor-
puscles, have an easily recognizable nucleus.
It is possible to puncture the cell wall without killing the
cell. It is possible to remove much of the cytoplasm without
killing the cell. Indeed, the loss will be made good by the
manufacture of new cytoplasm. The cell, like the tadpole, is
capable of a limited regeneration. But if you injure the
nucleus, the case is quite different. That inner zone is
vulnerable. It cannot long survive the removal of any part
of its substance.
The crucial role of the nucleus may be demSnstrated in
another way if we select for experiment those peculiarly
endowed units of protoplasm known as germ cells. These,
the egg cell of the female and the sperm cell of the male,
have through the evolutionary ages become specialized as
carriers of life. Some years ago it was discovered that by
treating the egg (that of a sea urchin, for example) with a
salt solution, or by pricking it with a needle, or by other
mechanical means, the cell could be artificially stimulated
to develop and produce a new sea urchin. You might cut
the egg in two, leaving the nucleus in one half. The half
containing the nucleus could be fertilized, but the other
half was sterile. In the case of some animals, in which the
nucleus is a very small part of the egg, the removal of the
nucleus left the egg nearly entire; but an egg so mutilated
had no power of reproduction.
Normally, in nature, fertilization is accomplished through
penetration of the egg by the sperm, which makes contact
WHERE LIFE BEGINS
with the nucleus and merges with it. The sperm cell is ex-
tremely small. It may bulk only a few hundredths the size
of the egg. It consists of a bulbous nuclear head and a short
thin trailing thread of cytoplasm. But small as it is, the
sperm cell carries all the pattern of characteristics of the
father which are to be inherited by the child. Might it not
also carry the spark of life to one of those bereft eggs of our
experiment the ovum from which the nucleus has been
removed ? This was tried, and it worked. When an egg frag-
ment consisting only of cytoplasm was exposed to a sperm
cell of its species, the sperm entered the fragment and by
this merger supplied the necessary nuclear material for
thereafter the fragment quickened, began to divide, and
grew into a new individual.
It is the nucleus, then, that is the captain of life. How
potent it is, how packed its small volume, is graphically
suggested by H. J. Muller in his book Out of the Night.
Dr. Muller computes that if all the human sperm cells
which are to be responsible for the next generation of the
human species, some 2000 million individuals, could be
gathered together in one place, they would occupy space
equivalent to that of half an aspirin tablet. The corre-
sponding number of egg cells, because of their larger com-
ponent of cytoplasm, would fill a 2-gallon pitcher. But since
it is the nucleus that carries the stuff of life, we may con-
sider only the nuclei of these eggs and reckon that they
would occupy no more space than the sperm cells. Thus, the
essential substance of both eggs and sperm could be con-
tained in a capsule the size of an aspirin tablet.
It is indeed difficult to believe, as Dr. Muller points out,
"that in this amount of physical space there now actually
lie all the inheritable structures for determining and for
causing the production of all the multitudinous character-
istics of each individual person of the whole future world
population. Only, of course, this mass of leaven today is
scattered over the face of the Earth in several billion sepa-
[219]
THE ADVANCING FRONT OF SCIENCE
rate bits. Surely, then, this cell substance is incomparably
more intricate, as well as more portentous, than anything
else on Earth."
Some of its intricacy can be made visible under a micro-
scope, by using suitable stains. Then we see the organs of
the nucleus, the minute sausage-shaped "chromosomes."
It is not only in the germ cells, but also in the somatic or
body cells, that the chromosomes are found, the structural
pattern being repeated in every cell. And the pattern is
specific. Every species of plant and animal has its typical
number of these nuclear organs, and for each there is a
standard shape, size, and arrangement. The cells of corn
/have twenty chromosomes; those of the lily, twenty-four;
\of the frog, twenty-six; of man, forty-eight; of the horse,
sixty. I have been curious to know the chromosomal equip-
ment of the elephant and the whale, but can find no record
that anyone has ever investigated the minute structure of
these largest of the beasts. The monkeys of Asia and Africa
have exactly the same numerical endowment as man, fojrty-
eight chromosomes; but the South American monkeys
apparently are more distant in their relationship with
/fifty-four.
One of the most productive researches of the twentieth
century is the tracking down of the relationship which these
microscopic nuclear bodies bear to the factor of heredity.
/The studies were focused on fruit flies. Thomas Hunt
[Morgan and his associates, working at Columbia University,
^ cultured the tiny insects (Drosophila melanogaster) in bot-
tles, provided the optimum of conditions for their growth
and reproduction, and kept exact pedigrees through many
generations. As new flies hatched out, the biologists ex-
amined the young individuals for possible changes in physi-
cal character. It was not long before they were finding
changes.
For example: the bulging eyes of drosophila are normally
red, but occasionally a white-eyed child would hatch out.
[ 220]
WHERE LIFE BEGINS
Morgan and his men were able to correlate this mutation
with a change in a certain region of one of the chromosomes
of the egg which gave birth to the fly. Later they found nine
variations in the wings, and following that came discovery
of scores of variations affecting practically every visible
characteristic of the fly physical changes which the inves-
tigators were able to relate to changes in the chromosomes.
These studies were reinforced by the radiation technique
first successfully used by Dr. Muller. Through his bombard-
ment of flies with x-rays, Muller showed that the rate of
mutation could be increased many times that spontaneously
occurring in nature. This confirmed the direct relation-
ship between definite areas of the chromosomes and physical
characteristics of the flies born of the chromosomes. The
crash of the rays into the minute cellular organs was both
destructive and constructive. In some cases part of a
chromosome was blasted out, to disappear. In some, the
fragment attached itself to the end of another chromosome,
thus forming a new structure of unusual size and shape.
In other experiments, chromosomes were sliced in two,
and the half of one was exchanged for the half of another
to form new combinations. All these chance alterations of
the nuclear structures showed up in physical changes in
the offspring of the bombarded flies.
By these and other experiments a new credence was given
to an idea that had long been held as an inference. They in-
dicate that the chromosomes are not simple continuous
wholes, but are complex patterns made of smaller inter-
:hangeable units. And these units are the "genes."
No one has ever seen a gene. It is too fine for even the
ultramicroscope to enlarge to visibility. But just as we
postulate invisible atoms to account for the chemical and
optical behavior of matter, so we find it necessary to postu-
late invisible genes to account for the developmental be-
havior of protoplasm. Genes are the unit structures, the
atoms of heredity.
[ 221]
THE ADVANCING FRONT OF SCIENCE
Nor is that all. Recent findings bring evidence of a still
more fundamental role. Experiments show that the injury
of genes may be a very serious event in the history of a
cell. The loss of certain genes means death. And this sug-
gests that the gene's function in the cell activities is not
merely to control heredity, but also to control life.
Discovery of the primary vital role of the genetic unit is
the work of M. Demerec, a geneticist of the Carnegie In-
stitution of Washington, member of its Department of
Genetics at Cold Spring Harbor, Long Island. For some
years Dr. Demerec has been watching the effect of muta-
tions on the reproductive capacity of drosophila. He was
impressed by some experiments completed five years ago
| by J. T. Patterson at the University of Texas. Dr. Patterson
found that out of fifty-nine mutations in three well-defined
chromosomal regions, fifty-one were what he called "lethals."
That is to say, when a fertilized egg carried these changed
chromosomes (in which certain genes were missing), the
egg developed only part way and died as an embryo. The
gene deficiencies were fatal to development, therefore lethal
to the fly.
Demerec followed this pioneer work with an intensive
search into the somatic or body cells of the flies. He found
that not only were the germ cells rendered incapable of
development, as Patterson's results showed, but the grow-
ing body cells, which by a special treatment had been made
deficient in these same ways, were rendered powerless to
grow. And the cells died though adjacent body cells,
which carried no deficiencies, showed no such effects.
Demerec's later work has demonstrated that more than
half of Patterson's lethals are cell lethals. And by further
extension of experiment and inference the Carnegie biolo-
gist arrives at the conclusion that some of these cell lethals
[ 222 ]
WHERE LIFE BEGINS
are chargeable to the loss of a very few genes, possibly only
one gene.
How large is this genetic unit? No one knows, and ap-
parently the only present way of approaching the problem
is to find out how many genes there are in the chromosomes,
divide the total length of chromosomal material by the
number of genes, and so arrive at an average value.
The number of genes may be assumed to correspond to
the number of places in the chromosomes at which changes
occur. By mathematical analysis of mutations it has been
figured that in drosophila there are about 3000 such places,
which means that each cell has at least 3000 genes.
Quite recently a new and more direct method of determin-
ing the number of genes has been introduced through the
work of Theophilus S. Painter, at the University of Texas.
The larva of the fruit fly, like man and other animals, has
salivary glands situated near its mouth, and in flies these
glands are made of giant cells. The cells are many times
larger than the other body cells, and the chromosomes are
about 150 times the size of the chromosomes of the germ
cells. This fact has been known for several decades, but
apparently no geneticist thought to search the chromosomes
of these giant cells for fine-structure details of mutations
until Dr. Painter took up the work in 1932. He found that
under a certain technique of staining and illumination, the
giant chromosomes revealed themselves as chainlike struc-
tures of varying width made up of transverse bands of
different sizes, each band showing a highly individual pat-
tern of yet finer parts. The band is not the gene no
geneticist claims that but it appears to be individual to
the gene, each is the holder of a gene, "the house in which
the gene lives," to quote Painter's picturesque phrase.
Therefore, by counting the number of bands, we should
arrive at the number of genes.
Here we are attempting to separate structures so fine
that they approach the limit of visibility under the most
[223]
THE ADVANCING FRONT OF SCIENCE
powerful magnification. Early counts showed about 2700
bands distinguishable, but recently Calvin B. Bridges,
using a more delicate technique, counted 5000 bands. There
may be more, and with further advances in microscopy we
may some day be able to see them one by one. Painter has
suggested a total of 10,000 as a guess. And some late specu-
lations of Muller open up the possibility of an even larger
total.
But, in order to be very conservative, suppose we take
Bridges' count as our basis. If there are approximately
5000 genes to the drosophila cell, then we may say that one
gene is not more than the five-thousandth part of the
chromosomal material. But the chromosomes, in turn, are
-probably not more than a hundred-thousandth part of the
average cell. The gene then figures roughly as not more than
one five-hundred-millionth of the total cell material. We
arrive at a picture of a mechanism so delicately balanced,
and of a unit so indispensable to the smooth running of this
mechanism, that although the unit represents only the five-
hundred-millionth part of the whole, its elimination is fatal.
What is the nature of this indispensable unit of life ?
A novel answer to that question was recently proposed
by Dorothy M. Wrinch. Dr. Wrinch sees the chromosomes
as made up of numerous filaments of protein molecules
linked end to end and bound together into long bundles by
a cross weaving of ringlike molecules of nucleic acid. On
this view, a gene is regarded not so much as a discrete par-
ticle, as simply a peculiarity in the chromosomal structure
arising out of the diverse overlapping and interweaving
of the two kinds of molecules, the warp and woof of this
protoplasmic texture.
The view more generally held among geneticists favors
the particle idea, however. Dr. Demerec pictures the gene
fas an organic particle, and suggests that it may be a single
large molecule. The observed instability of certain genes
seems evidence for this conception. Thus, it has been noticed
[224]
WHERE LIFE BEGINS
that the genie pattern responsible for wing formation,
which normally endows a fly with long wings, will some-
times change to a form producing short miniature wings,
and later shift back to the long-wing structure. These altera-
tions may be accounted for if we assume the gene to be a
large molecule which suddenly loses one of its subgroups
of atoms, and later recaptures and recombines the separated
parts. Other evidence adduced from the study of unstable
genes indicates that when a cell divides to form two cells,
the genes do not divide, but each is exactly duplicated by
the formation of a new gene next to the old one. This
method of reproduction favors the supposition that the
gene is a single molecule.
If it is a single molecule, it must be a large one. Organic
molecules of extremely complex structure are known to
chemists. Some proteins consist of thousands of atoms. But
these are too complicated, their structures too labyrinthine,
to attempt to represent them here. As suggestive of the
plan of a large organic molecule such as we may suppose
the gene to be, Demerec cited a comparatively small mole-
cule a structure compact enough to lend itself to dia-
gramming within the width of an ordinary book page, and
yet sufficiently complex to illustrate the principle the
compound known as thjmo-nucleic acid. It is one of the
products that we get from the chemical breakdown of
nuclear protein.
A molecule of thymo-nucleic acid consists of 59 atoms of
hydrogen, 43 of carbon, 32 of oxygen, 15 of nitrogen, and
4 of phosphorus a total of 153 atoms, with a molecular
weight of 1421 (in terms of hydrogen as i). The arrange-
ment of these atoms conforms to a certain architectural
pattern. A house of 153 rooms might be analyzable into
a central structure with attached wings and towers and
similarly we find the 153 atoms of this molecule organized
in a fixed sequence, with subgroupings and linkages, fol-
lowing the arrangement mapped on page 226.
THE ADVANCING FRONT OF SCIENCE
The map outlines a central structure flanked by four
smaller simpler structures. Each of these four subordinate
parts may also exist separately. There is a compound of
carbon, hydrogen, and nitrogen which the organic chemist
knows as "adenine," and so too there are "cystosine,"
"thymine," and "guanine." One may imagine a thy mo-
nucleic acid molecule in which the bond attaching an oxygen
atom of the thymine group is very weak. There might be a
tendency for this oxygen to break off. Such behavior would
be analogous to that of an unstable gene, in which a sudden
change occurs and causes a mutation.
O:P(OH), O:P(OH),
|C t H.N,0|
C,H,Or-0-C,H,Or-O-PO(OH) 0-C,Hi,04
<+* \ >* / 4 -%^ \ -' ^/ f
(Adenine) I 1 (Guanine)
(Cystosine)
/ Map of a Molecule of Thymo-nucleic Acid*
But conceivably some losses may be so serious as to in-
terfere with the functioning of the molecule. For example,
the thy mo-nucleic acid has 32 atoms of oxygen but only
4 of phosphorus. If something should happen to dislodge
or cripple one of the oxygen atoms, the loss would be only
a thirty-second part of the oxygen equipment and might
possibly be endured or repaired from the environment.
But the elimination of one phosphorus atom would be
more drastic: it would deprive the molecule of a fourth of its
phosphorus mechanism, and the loss might be irreparable.
This latter example suggests what may happen to a gene
in those mutations called lethal. The elimination of a single
atom may so change the gene structure that its duplica-
tion is rendered impossible. And when gene duplication
stops, cell division in many instances is blocked.
Thus we are led to a view of the protoplasmic world in
which a single small unit becomes critically important.
[226]
WHERE LIFE BEGINS
Deprived of this small unit the gene cannot function; de-
prived of the gene the chromosomes cannot function; and
with the paralysis of the chromosomes the functioning of
the cell is halted. Cell growth stops, reproduction ceases,
life comes to an end. If life comes to an end with the failure
of a gene, may we not infer that life begins with the func-
tioning of the gene ?
Of that functioning we know only three results surely:
(i) that in the process the gene is exactly duplicated, (2)
that the gene occasionally mutates, x (3) that genes some-
how control and pass on to the developing organism the
physical characteristics which distinguish it. But all these
operations are manifest only in groups of genes. Indeed,
we know genes only as they function in the closely related
teamwork of the chromosomes. But suppose a gene should
get separated from its fellows. Imagine one of these living
molecules adrift in the cell fluid, or a wanderer in the body
plasma. Could it function independently? If so, with what
effect ?
Several years ago B. M. Duggar, of the University of
Wisconsin, speculated on tfiis possibility. Dr. Duggar sug-
gested that a lone gene might be a destructive agent. He
pointed to the filtrable virus. Might not the virus be simply
a gene on the loose ?
3
The virus has been known for more than 40 years. It has
long been a candidate for recognition as the most elemen-
tary living thing, and Duggar's suggestion offers presump-
tive argument for such rating. But first let us review what
is known of the virus. Recent research can help us, for
within the last 2 years an exciting discovery has been made.
Wendell M. Stanley is the discoverer.
Dr. Stanley is an organic chemist. A graduate of Earlham
College, he spent postgraduate years at the University of
Illinois working on leprosidal compounds, then studied in
[227]
THE ADVANCING FRONT OF SCIENCE
Germany on a fellowship from the National Research
Council, and in 1931 joined the staff of the Rockefeller
Institute for Medical Research in New York. In 1932 the
Institute opened additional laboratories near Princeton,
and Stanley went there with definite designs on the virus.
The nature of the virus is one of the key problems of
pathology. Such destructive diseases as infantile paralysis,
influenza, parrot fever, rabies, "St. Louis " encephalitis or
sleeping sickness, yellow fever, and certain types of tu-
morous growths are propagated by these invisible carriers;
therefore virus investigation is a major project for medical
research. Pathologists and other biologists have specialized
on biological aspects, and have turned up many important
facts about the physiological effects of the virus and its
response to various agents. Stanley the chemist was asked
to specialize on chemical aspects to find out, if he could,
what a virus is in terms of molecules, and what the molecules
are in terms of atoms: how large, how massiye, how com-
posed, how reactive ?
He chose for his inquiry the oldest known virus, that
which causes the tobacco mosaic disease. This is a pestilence
dreaded by tobacco growers, for if one plant in a field con-
tracts the disease, the infection usually spreads through
the entire acreage, stunting the plants, puckering their
foliage, and causing the leaves to assume the mottled ap-
pearance of a mosaic. Back in 1857, when mosaic disease
was first recognized, it was confused with a plant pock
affliction, and not until 1892 did the botanists realize that
the two diseases are different. This discovery was made
by the Russian investigator Iwanowski, and he startled
the bacteriologists of his day by announcing that the juice
of infected tobacco-mosaic plants remained infectious after
it had passed through a Chamberland filter.
Now a Chamberland filter is a porcelain affair with pores
so fine that if a pint of distilled water is placed in the filter,
many days will elapse before the liquid percolates through,
[228]
WHERE LIFE BEGINS
unless strong suction is applied. There was no known bac-
terium that could get through such minute holes. And yet,
the agent which communicated the tobacco mosaic disease
readily passed. Other experimenters confirmed Iwanowski's
findings, and six years later the first filtrable carriers of an
animal contagion were discovered in the foot-and-mouth
disease. Since then scores of afflictions affecting plants,
animals, and man have been identified as virus infections.
Of all the viruses, tobacco mosaic virus is conspicuous in
its possession of properties which enable it to be worked i
with easily. Furthermore, it has long been regarded as
typical and representative.
On the acres near Princeton, Stanley grew thousands of
tobacco plants, infected them with the disease, later ground
up the dwarfed, puckering, mottle-leafed plants, pressed
them to a pulp, and collected the juices. Somewhere in the
gallons was the virus. You could not see it, you could not
accumulate it in a filter, you could not culture it in agar
or in any of the soups used to grow bacteria. You knew
it was there only by its destructive effect. For if you took
a drop of the juice and touched it to a healthy plant, within
a few days the leaves showed the unmistakable signs of
mosaic. The virus was there. But how to get at it chemically ?
The known ingredients of protoplasm may be grouped in
five classes: metal salts, carbohydrates^ hydrocarbonsj^lipoids
or^fatty compounds, "and proteins these last the most
complex of all. There are certain enzymes which break up
proteins. Protein splitters, or protein digesters, they are
called. Pepsin, for example, does precisely that in the
stomach, and will do the same in a test tube. What would
it do to the virus ?
Stanley put some of the infectious tobacco juice in a test
tube, poured in pepsin, kept the mixture at the temperature
and in the other conditions favorable for pepsin digestion,
and at the end of the experiment tested the solution for
infection. It had none. Rubbed on the leaves of healthy
[ 229 1
THE ADVANCING FRONT OF SCIENCE
tobacco plants it showed no power to transmit the disease.
Obviously the pepsin had destroyed the infectious principle
in the juice. But pepsin digests only proteins it has no
effect on lipoids, hydrocarbons, carbohydrates, and salts.
From this it seemed reasonable to conclude that the virus
material is protein.
There are chemicals which precipitate proteins. These
were tried on the virulent tobacco juice. Immediately cer-
tain substances dropped down as solid precipitates, and
it was found that thereafter the juice had no power to in-
fect. But when some of the precipitate was added to neutral
liquid, the solution immediately became infectious. This
plainly said that the disease carrier resided in the protein
precipitate, and Stanley now began a campaign to trace
the carrier down to its source.
He dissolved the precipitate in a neutral liquid, and added
an ammonium compound which has the faculty of edging
protein out of solution without changing th^ protein. A
cluster of crystals began to form at the bottom of the test
tube somewhat as sugar crystals form in syrup. But these
might not be a single pure stuff, so Stanley sought to refine
them. He removed the crystals, dissolved them in a much
larger volume of neutral liquid, and with the help again
of the ammonium compound brought this more dilute solu-
tion to crystallization. His next step repeated the process,
but with still greater proportion of the liquid. In this way,
by increasing the dilution each time, the chemist carried
his material through ten successive fractionations and re-
crystallizations. One would assume that by now the sub-
stance was pure, that all extraneous materials had been
separated out, also that all living matter had been elimi-
nated for we know no plant or animal, no bacterium, no
protoplasm, that can undergo crystallization and remain
the same. So the experiment seemed ripe for a supreme test.
Stanley took a pinch of the product of that tenth recrys-
tallization, dissolved it in a neutral fluid more than 100
[230]
WHERE LIFE BEGINS
million times its bulk, rubbed a drop of the solution on the
leaves of a healthy tobacco plant, and awaited the result.
The test was conclusive. Within the usual time the plant
showed all signs of an acute outbreak of the mosaic disease.
Surely in the crystals we have the virus. And since, by all
rules of chemistry, the crystals have been refined to the
pure state and may be accepted as an uncontaminated
single substance, it seems reasonable to believe that the
crystals are the virus.
I have watched them through the microscope: a mass of
white needlelike structures bristling in every direction. It
is not supposed that each needle is a virus. Just as each
crystal of sugar is made of numerous molecules of sugar,
so it is presumed that each of these crystalline spikes is a
cluster of millions of molecules of the protein, and that
each molecule is a single virus.
Stanley's chemical analysis shows that the virus molecule
is composed of carbon, hydrogen, nitrogen, and oxygen.
Unlike many other physiologically active proteins, it con-
tains no sulphur and no phosphorus. Just how many atoms
of each element are present, and the arrangement of the
atoms in molecular architecture, are details still in process
of investigation. But the evidence indicates that the mole-
cules are enormous.
Ingenious physical measurements of the molecules were
recently made by The . Svedberg, at the University of
Upsala, and by Ralph W. G. Wyckoff, at the Rockefeller
Institute, using centrifuges of the ultra type. The apparatus
is a whirling machine capable of doing better than 100,000
revolutions per minute. Dr. Svedberg's apparatus is made
of steel, and is driven by a stream of oil pumped at high
pressure. Dr. WyckofPs apparatus is made of an aluminum
alloy, and its turbine is driven by compressed air. In both
machines, the rotating part is housed in a chamber made
of 3-inch armor-plate steel a safeguard to protect the
operator in case of explosion. If a dime is placed in the
[231 1
THE ADVANCING FRONT OF SCIENCE
ultracentrifuge, and the apparatus is rotated at a certain
velocity, the centrifugal force is so great that the dime
presses out with an effect equal to the weight of half a ton.
The purpose, however, is not to perform trick stunts with
dimes, but to separate mixtures of molecules, using a prin-
ciple long familiar in the dairyman's cream separator. In
the ultracentrifuge this principle is harnessed to the ut-
most degree of control. Under the accelerated fling of
centrifugal force generated by the rotating mechanism,
molecules in solution are separated, each is thrown out
with a speed proportional to its mass, and by timing the
period required for its separation the molecular weight and
size of any constituent may be determined. Dr. Stanley
sent Professor Svedberg samples of his crystals, and at
the same time supplied specimens to his colleague Dr.
Wyckoff, and to the test of this indirect weighing and
measuring machine the substance was subjected.
The results are in remarkable agreement. Both Svedberg
and Wyckoff independently reported that the weight of
Stanley's crystalline protein is approximately 17,000,000
(in terms of hydrogen's atomic weight of i). The largest
molecule known up to this time was that of the animal pro-
tein called hemocyanin (which is the pigment of earth-
worm blood), with a molecular weight of about 5,009^000.
Thus Stanley's find is more than three times heavier. In
size it appears to be egg-shaped with a diameter of about
; 35 millimicrons. The corresponding dimension of the hemo-
cyanin is 24 millimicrons. And a millimicron is 1/25,400,000
inch.
The tobacco mosaic protein thus provides the chemists,
the molecular architects, the microcosmic adventurers, with
a perfectly enormous molecule for their exploration: a
structure many times more massive and complex than any-
thing heretofore analyzed. It must consist of hundreds of
thousands of atoms, possibly of millions.
WHERE LIFE BEGINS
It provides the biologists with an indubitable specimen
of the invisible stuff that is responsible for so many hu-
man ills, and if we can learn in intimate detail the ways of
the tobacco mosaic virus we may get some important
flashes of information on the ways of the virus of the com-
mon cold and other hidden enemies of mankind. Many
points of correspondence have recently been found, prop-
erties in which the plant virus shows characteristics similar
to the animal virus. Thus, it is known that the common
cold affects many species of animals. Similarly, the tobacco
mosaic virus affects tomato, phlox, and spinach plants, as
well as tobacco. H. S. Loring, one of Stanley's coworkers,
recently extracted a crystalline substance from the juices
of diseased tomato plants, and the substance was found to
be a protein identical with that extracted from the juices
of the diseased tobacco plants. The protein has also been
isolated from mosaic-diseased spinach and phlox plants.
Another point of similarity between the tobacco mosaic
virus and the virus of animal diseases lies in this: that both
may be inactivated and rendered harmless. Thus Pasteur
found that by drying the spinal cords of dogs which had
died of hydrophobia, he obtained a material which was
harmless; and yet it seemed to contain the principle of the
hydrophobia carrier, for a person inocculated with the
material gained a certain immunity to the disease. Stanley
has found that by treating his crystalline protein with
hydrogen peroxide, or formaldehyde, or other chemicals,
or by exposing it to ultra-violet light, he causes its virulence
to vanish. When the virus is rubbed on the leaves of healthy
plants, no ill effects follow. And yet the crystals appear to
be the same as those of the virulent untreated protein.
When they are analyzed by x-ray bombardment they show
the same diffraction pattern, when weighed they show the
same molecular weight, and, most important of all, when
injected into animals they produce an antiserum which
[2331
THE ADVANCING FRONT OF SCIENCE
when mixed with solutions of active virulent virus is able
to neutralize or render inactive such solutions. There are
slight chemical differences, however, and it is Dr. Stanley's
idea that the effect of the treatment is to alter certain ac-
tive groups of the huge molecule to switch certain towers
or ells of its architecture, as it were but to leave the struc-
ture as a whole unchanged. These experiments with inac-
tivation of the tobacco mosaic protein seem to promise
results that will be helpful to the human pathologist search-
ing the frontiers of immunization.
Additional support for the idea that the tobacco mosaic
protein is a virus was obtained early in 1937 by Stanley and
Wyckoff. They found that, instead of depending on chemical
means to isolate the virus, they could accomplish the result
mechanically with the ultracentrifuge. By whirling a solu-
tion of juices from the diseased plants, repeating the process
with the heavy precipitate thereby obtained, and doing
this over and over again, they found it practicable to sepa-
rate the activating substance from the mixture. In this
way Stanley and Wyckoff isolated the molecule of another
;plant virus, the infectious ring-spot disease. By the same
method they isolated the activating agent of still other
vegetable diseases, potato mosaic, severe etch, cucumber
mosaic; finding that the concentrations of these viruses in
the host differed widely. Most important of all is their
demonstration that the activating substance of each of
these highly contagious plant diseases is a heavy protein
molecule similar in general to the first found, the tobacco
mosaic protein of Stanley's pioneering chemical experiments.
But man, whose virus diseases are of animal nature, wants
to know of the virus that affects animals. Has any research
progress been made in that direction? Yes, an interesting
beginning, just announced. There is a highly contagious
animal disease known as "infectious papillomatosis"
which affects rabbits. It causes warty masses to grow on
the ears and other parts of its victims, and has been at-
WHERE LIFE BEGINS
tributed to a filtrable virus carrier. This disease was first
described by R^E^j^Shope; and recently Wyckoff and J.W.
Beard obtained some of the warty tissue from Dr. Shope,
ground it up, made a solution of it, and subjected this
solution to the new technique of the ultracentrifuge. In
this way they isolated a heavy protein which when tested
on healthy rabbits immediately communicated the disease.
But rabbits frequently develop warts which are not in-
fectious, and so as a further test the investigators obtained
some of this noninfectious warty tissue, and subjected it
to the same treatment. They were unable to obtain from
this solution any heavy protein, though repeated trials
were made. Apparently the giant molecules flung out of
the solution of the infectious tissue are a virus which is not
present in other warts. And by weight and measurement
the wart virus proves to be a tremendous molecular struc-
ture weighing something more than 20,000,000 and measur- ;
ing about 40 millimicrons in diameter. Thus the first animal
virus to be isolated is a larger, more massive, and presum-
ably a more complex molecule than that of the first dis-
covered plant virus, the carrier of tobacco mosaic. But all our
evidence points to many similarities among these various
disease-carrying substances, and very many lines of research
are now being pushed with the tobacco mosaic protein on
the idea that it is not only a virus but a representative
species of the whole virus family, both plant and animal.
Is it alive ? Stanley reminds you that it can be crystallized,
a property that we think of as purely inanimate and wholly
chemical. He points to the additional fact that it has not
been cultured in a test tube. This would seem to say that
it is not a bacterium. A few bacteria placed in a nutrient
soup will rapidly multiply into uncounted millions, but the
crystalline protein shows no growth behavior in a glass
vessel, no metabolism, no reproduction.
And yet, observe what happens when it comes in con-
tact with the inner tissue of a tobacco plant or other vege-
[235]
THE ADVANCING FHONT OF SCIENCE
table host. Instantly the molecules begin to multiply. An
almost imperceptible particle of a crystal will infect a
plant, and in a few days the disease will spread through a
field, producing an amount of virus millions of times that
of the original. It exhibits a fecund ability to propagate it-
self, to extend its occupancy of space and time at the
expense of its environment. Is not this a characteristic of
living things ?
Perhaps the virus is a molecule of double personality,
alive and yet not alive animated by its environment when
that environment is specific to its nature, but passive in
any other environment. The discovery of this substance
and the elucidation of its properties is one of the most im-
portant biological advances of our century. In 1936, when
Dr. Stanley presented his comprehensive paper reporting
the research to the American Association for the Advance-
ment of Science, the Association esteemed the report the
most important on its agenda and awarded Stanley its
$1000 prize.
4
The tobacco mosaic protein has certain apparent points
of correspondence with the gene. The two appear to be of
approximately the same order of size. Both are molecules
that in certain surroundings undergo duplication. Both
suspend this reproductive faculty over long periods of time
without losing the capacity to call it into action when
conditions are favorable. The quiescence of genes in an un-
fertilized egg or in the cells of a resting seed, and the in-
activity of the virus when stored in a bottle, are examples
of the last-mentioned characteristic.
There is still another parallel. The gene, as we know, is
sometimes unstable. Stanley has found a somewhat similar
behavior in his crystalline protein. The common form of its
disease is known as " tobacco " mosaic, and produces a
green mottling of leaves. Recently there was discovered
[236]
WHERE LIFE BEGINS
another strain of the disease which has been named
"masked," and a still more virulent form known as "acuba"
which shows a yellow mottling. The crystals of acuba
strain are larger, its solution is more silky and opalescent,
its solubility is lower, and the ultracentrifuge shows that
its molecules are actually larger than those of the common
tobacco mosaic they weigh nearly as much as the giant
molecules of the rabbit wart disease, approximately 20,-
DOO,OOO. Now the strange finding of recent experiment is
this: a tobacco plant suffering from the common form of
the mosaic disease may suddenly change to the more viru-
lent acuba form. Apparently something happens by which
the smaller molecules of 17,000,000 weight attach other
molecular groups to themselves to form particles of 20,000,-
DOO weight, and these combinations take place between
just the right groupings to produce the acuba effect. In a
sense, it is a synthesis. Also it suggests the important
property M of Individuality. Just as each gene, or at least
certain genes, seems to carry an individual pattern to con-
trol the future development of its organism, so does the
molecule of the mosaic disease possess a personality, a
nature individual to its structure being in some instances
of the "masked" strain, which is so mild in its symptoms
as to be almost unrecognizable; in other instances of the
"tobacco" strain, which is serious; in other, of the "acuba"
strain, which is highly dangerous; and in still other, of the
" lethal" strain, which invariably causes the death of
the plant. It seems likely that a single virus molecule may
in the course of its history appear in each of the four roles,
mutating from strain to strain as it loses or gains features
3f molecular structure. In these behaviors we recognize a
:urious suggestion of the mutation of unstable genes.
Oscar Riddle, of the Department of Genetics of the
Carnegie Institution of Washington, noting some of these
parallels, is inclined to believe that in one respect the gene
represents a higher order of organization than the virus.
[237]
THE ADVANCING FRONT OF SCIENCE
He points to the teamwork of the genes in the chromosomes
as apparently an essential relationship. All the evidence
goes to show that the gene must be in association with its
fellow genes in order to duplicate, and Dr. Riddle doubts
if a single gene alone can perform any function. Indeed, he
questions if an isolated gene can be called alive which is
precisely what Stanley questions of his crystalline protein.
But this leads to another question. How "live" is alive?
S
There is a bacterium known as azqtobagtpr, an organism
nearly as large as a yeast cell. It lives in the soil, it breathes,
it takes in food from its surroundings, it grows and mul-
tiplies all authorities agree that azotobacter is alive. In-
deed, it possesses a remarkable faculty which the majority
of other species of living things lack the capacity to fix
gaseous nitrogen. The azotobacter is continually taking
free nitrogen from the air, and by combining it with certain
organic matter absorbed from the soil, it is making am-
monia or the equivalent, fabricating that into amino acids,
and out of the acids building protein. This faculty is indis-
pensable to life as we know it, for without protein it is
impossible to have protoplasm. The ability to form pro-
teins is a test of life.
Recently, at the Academy of Sciences in Moscow, three
Russian chemists collaborated in a series of experiments
with azotobacter. A. N. Bach, Z. V. Yermolieva, and M. P.
Stepanian were the experimenters. They cultured a pure
group of the bacteria in a glass vessel, feeding them sugar,
and obtained a small output of ammonia. Then the chemists
took the teeming microbes, crushed them, ground them,
and pressed out the juices. This bacterial fluid could be
filtered free of any trace of cell matter. To the clear filtrate
the Russians added sugar and bubbled a mixture of nitrogen
gas and oxygen gas into the liquid. According to their re-
port, the filtrate produced ammonia. Something in the
[238]
WHERE LIFE BEGINS
lifeless juice was doing what the living bacteria had per-
formed as their unique function.
Professor Bach and his associates explain that the nitro-
gen fixation in the living azotobacter is accomplished by
an enzyme. An enzyme is a catalyst, i.e., a chemical sub-
stance which activates and promotes the combination of
other substances into new compounds but itself remains
unchanged in the process. It is the Russians' idea that their
crushing and filtration procedure separates out this organic
catalyst, and they point to their experiments as proof that
the catalyst is just as potent to perform the synthesis in a
test tube as in the living creatures. Indeed, they claim, it
is more effective in the test tube, and they cite records
which indicate that the yield of ammonia from the filtrate
is fifty times greater than that from the living bacteria
when fed an equivalent amount of sugar. This very strik-
ing difference is explained on the supposition that the living
organisms consume much of the sugar to sustain growth
and other vital processes, whereas the free enzymes in the
filtrate, being "mere" chemicals, have no vitalistic burdens.
So they stick to business and turn out a maximum yield.
An interesting series of experiments in this field is now in
progress in America. Dean Burk, chemist at the United
States Department of Agriculture, visited the Moscow
laboratory, spent several weeks in consultation with the
Russian investigators, watched their technique, and on his
return to Washington set up a similar apparatus to repeat
the investigation here. His results will be awaited with
keen interest. Confirmation of the Moscow findings by an
outside laboratory would mean another step into the dim
borderland between the living and the nonliving.
Perhaps the nearest we can come to a definition is to say
that life is a stage in the organization of matter. The
ascent of life, from azotobacter to man, is a hierarchy of
organizations continually becoming more complex and more
versatile. And so with the ascent of matter, from the single
[239]
THE ADVANCING FRONT OF SCIENCE
electron or proton to the numerous and enormously compli-
cated colony of electrical particles which make up the
bacterium it too is a hierarchy of continually increasing
complexity, of relationships, of organization.
Protons and neutrons, with their encircling electrons,
associate together to form atoms, but their organization is
too primitive to permit any behavior recognizable as life.
The atoms, in their turn, group to form molecules of simple
compounds water, salts, carbon oxides but again the
grouping is too limited to operate in ways that class as
animate. From these simple molecules more complicated
ones are synthesized in nature's unresting crucible, sugars
and other carbohydrates, fats and more intricate hydro-
carbons. And somehow, in the melee, atoms get joined
together in the distinctive patterns known as catalysts, of
which the enzymes are a special class. The primitive cata-
lysts may fabricate the first amino acids. Out of these
essential acids they build the first proteins, sinyple ones at
first. Proteins associate with other proteins, eventually
they join as subgroupings of larger molecules to form what
we imagine to be the first genes, and chains of these giant
molecules line up or interweave and interlink as chromo-
somes. And so specialization develops, coordination evolves,
the ability to duplicate the pattern, to divide, to multiply,
to enter into a dynamic equilibrium of continually moving
material and forces life!
Just where life first appears in this supposed sequence is
beyond charting. But perhaps it is not far amiss to think
of the turning point as being reached with the emergence
of the protein-building catalyst. The gene may be the most
primitive living unit. The virus may be the most primitive
predator on life. But the presumption is strong that neither
of these organizations antedates the selective, assembling,
organizing presence of the enzyme. The enzyme may not
be life, but it seems to be a precursor of life. And wherever
it becomes active may be the place where life begins.
[240]
Chapter XIII MACHINES WHICH
IMITATE LIFE
What am I, Life? A thing of watery salt
Held in cohesion by unresting cells
JOHN MASEFIELD, SONNETS
HERE is a curious behavior which has interested many
persons who have seen it. A drop of chloroform is in-
troduced into a beaker of water. You take a fine glass rod
and try to puncture the chloroform drop. It resists. But
if you coat the tip of the rod with shellac the rod is avidly
sucked into the drop. The chloroform acts as though
shellac were its food, and as soon as it has fed, i.e., as soon
as the shellac is dissolved, the drop manifests its former
antipathy to the glass and ejects the rod as so much waste.
A living amoeba behaves in much the same way,
But the amoeba can multiply itself. After growth has
reached a certain stage its single cell of protoplasm divides
into two, and each becomes an individual amoeba capa-
ble of independent action, continued growth, and repeated
cell division. This is life: activity, growth, reproduction,
the continuous passing on of the torch. But there are purely
chemical setups which perform in much the same way.
For example, a drop of oil may be suspended in water. If
you touch it at opposite sides with two small pieces of soda
the surface tension of the drop is lowered at the two points
1 241 ]
THE ADVANCING FRONT OF SCIENCE
of contact; consequently the surface tension at its equator
becomes relatively greater, and the drop neatly divides
into two droplets. There are other combinations of material
in which inorganic bodies spontaneously bud and proliferate
in seemingly lifelike behavior. The action of a drop of
yellow prussiate of potash when suspended in a water solu-
tion of blue vitriol is an example among several that are
known.
The chloroform, the oil, and the yellow prussiate of
potash are familiar chemical compounds, and their reac-
tions to the glass, the shellac, the soda, and the blue vitriol
are readily explainable in physical terms. There are laws
of solution, of surface tension, osmosis, and chemical
affinity which fully account for the behavior of these inani-
mate combinations. Protoplasm is more intricate. Its mem-
bers are more complex and more varied, and its reactions,
therefore, are more complicated than anything we know in
the test tube. But may we not suppose that they are phys-
ical and chemical changes throughout, that all the essen-
tial behavior of life is ruled at bottom by the same laws
which govern the drops of chloroform, oil, and prussiate
of potash ?
It would be a presumption to answer this question with
a straight Yes, but the accumulating results in the labora-
tories steadily point that way and give a hopeful bias for
such an answer. I say hopeful because any other answer
would be discouraging, not only to biological research, but
also to medical practice and to mankind's frail fight for
time. If the toll of disease has been cut down and the
average longevity of human life extended, it is largely
because modern experimenters have believed with sixteenth
century Paracelsus that "the body is a conglomeration of
chymical matters; when these are deranged, illness results,
and naught but chymical medicines may cure the same/*
Sir Frederick Gowland Hopkins, a discoverer of vitamins,
tells of the remark of a distinguished organic chemist of
[242]
MACHINES WHICH IMITATE LIFE
the i88o's commenting on his decision to pursue biochem-
istry. "The chemistry of the living? That is the chemistry
of protoplasm; that is superchemistry; seek, my young
friend, for other ambitions." But Hopkins and other pio-
neers of his generation held to their conviction that life
is physically reasonable, and the fruits of their research
today are eloquent endorsement of the Paracelsian doctrine.
If the hydrogen, carbon, oxygen, nitrogen, and other
elements which compose the living body are the same as
the hydrogen, carbon, oxygen, nitrogen, and other ele-
ments which compose the air, the earth, and the sea, it
should be possible to set up chemical and physical arrange-
ments which will duplicate the results of living processes.
This has actually been done in several laboratories. No one
has been able to construct a mechanism which will exhibit
all the kinds of behavior of even the simplest organism, but
there are many types of biological behavior which have
been isolated and simulated separately. This fact is addi-
tional testimony perhaps to the elaborate complexity of
protoplasm. Professor Henry A. Rowland used to say to
his Johns Hopkins students that he did not know what
an atom was like, but, he added, it must be at least as
complicated as a grand piano. On this basis we might ven-
ture to postulate the microscopic amoeba as "a conglomera-
tion of chymical matters" at least as complicated as a
symphony orchestra or, perhaps better, a convocation of
symphony orchestras. Dr. Clark L. Hull, in whose labora-
tory at Yale I saw demonstration of many different types
of machines which imitate thinking processes, admitted
the primitive crudity of these gadgets. They are simplifica-
tions, analogues, groping approximations but they do
demonstrate the fact that it is possible for nonliving mat-
ter to execute results of a kind which we are accustomed to
associate only with the living. And that, no matter how
feeble the effect nor how limited its range, is a gain a step
toward the unmasking of living protoplasm.
THE ADVANCING FRONT OF SCIENCE
The heart is a pump. But is there any imperious necessity
that it be a living pump ? Early in the nineteenth century
the French physiologist C. J. J. LeGallois suggested that
"if one could substitute for the heart a kind of injection
... of arterial blood, either natural or artificially made
. . . one would succeed easily in maintaining alive indefi-
nitely any part of the body whatsoever." It is a rather
telling footnote to the magnitude of this "if" that more
than 100 years passed before an inventor was able to sur-
mount the difficulties of the requirement and produce an
apparatus that would substitute for the heart as an engine
of circulation. In the interim, various brilliant feats with
severed organs were attained, solutions capable of sustain-
ing life were compounded and used as media for such
transplantings; but in even the most successful of these
experiments the separated organ survived only^a few hours.
It was not until the year 1935 that the program proposed
in 1812 by LeGallois was realized. In June of 1935 a brief
scientific paper, signed by Alexis Carrel and Charles A,
Lindbergh of the Rockefeller Institute for Medical Research,
announced the remarkable results obtained from a perfu-
sion pump of Colonel Lindbergh's design, "a model that has
for the first time permitted an entire organ to live outside
of the body."
Anything connected with either Lindbergh, the hero of
transatlantic flight, or Carrel, America's first winner of the
Nobel Prize in Medicine, was good for a headline, and this
news of the laboratories immediately jumped from the
inconspicuous inner pages of the weekly journal Science
on to the front pages of the daily newspapers. But when the
editors and reporters tried to shape the story, puzzled by
the connection of the aviator with this technical medical
business, they found that the research itself, rather than
[244]
MACHINES WHICH IMITATE LIFE
the personal anecdote of the inventor which they vainly
sought, was the big news.
A thyroid gland had been removed from a cat, installed
in a glass chamber, and for more than twenty days this
excised organ, perfectly protected against bacterial infec-
tion, had lived an apparently normal life in its artificial en-
vironment. Its arteries pulsed, its cells grew and multiplied,
its secretions flowed, all the usual functions of life con-
tinued thanks to the unfailing regularity of the perfusion
pump. So long as this artificial heart circulated its artificial
blood, sending life-giving nutrients and oxygen to the im-
prisoned organ, the gland flourished. And so with other
organs. There were twenty-six experiments in all, using
kidneys, hearts, ovaries, spleens, and suprarenal glands, in
addition to thyroids, and in each case the perfusion pump
proved itself competent for the task. There are many rea-
sons to believe that LeGallois's full conception may now
be realized: that science at last has at hand an apparatus
for maintaining alive indefinitely any part of the body
whatsoever.
This means that those parts concealed within the mantle
of flesh may now be brought out into the transparency of
the glass tube and there be followed through every detail
of functioning. Three fairly obvious applications suggest
themselves as possibilities.
First, the normal organ may be studied to see how it
operates, how it is affected by changes of diet, by drugs
and other stimuli, and what conditions are optimum to its
well-being. In experiments with a thyroid Dr. Carrel dem-
onstrated the feasibility of this technique. By changing the
content of the circulating fluid he showed that he could
change the behavior of the transplanted organ which it
irrigated. When the fluid was diluted the thyroid responded
to this starvation treatment by losing weight progressively;
but when the fluid was enriched by generous additions of a
THE ADVANCING FRONT OF SCIENCE
growth-producing medium the gland grew rapidly. These
results suggest endless possibilities for experiment with
normal organs.
Similarly, a diseased organ could be installed in glass and
watched through the course of its malady, to discover
the nature of the disease and explore the possibilities of a
cure. It might be possible to remove a diseased viscus, such
as a kidney or a thyroid, and by cultivating the thing in
vitro learn more in one experiment than could be uncovered
in years of groping in the dark of pain-racked human bodies.
Diseases of the arteries, which account for so large a sec-
tion of the death roll, should lend themselves to experiment
in the transparent environment of the glass chamber.
Still a third practical application would be the use of the
perfusion pump to cultivate glandular organs for the sake
of their secretions. During thousands of years man has
practiced this exploitation of the submissive cow, cultivat-
ing the whole animal for the reward of the secretions from
her lactine glands; it should require, therefore, no wrench
of the imagination to picture the more specialized practice
here suggested. The pancreatic gland produces the indis-
pensable hormone known as insulin which aids the animal
body in its utilization of sugar. When the human pancreas
.fails, the victim of this lack dies unless the necessary in-
sulin is supplied from some other organism. Today there
is a considerable industry which makes a business of ex-
tracting insulin from the pancreas of freshly killed sheep
and other animals and marketing it for the benefit of per-
sons suffering from diabetes. But with the technique pro-
vided by the Carrel-Lindbergh research, the pancreatic
gland may be transferred alive to an assigned glass com-
partment and there be maintained in perfect health by the
continuous flow of the rich fluid circulated by the per-
fusion pump yielding meanwhile an output of insulin as
standardized as the output of milk is from a scientifically
managed dairy. The current practice of insulin extraction
MACHINES WHICH IMITATE LIFE
may be for the present more practicable commercially, but
the picture here suggested is possible theoretically, and
may in time be realized.
It would seem, therefore, that there is no imperious neces-
sity that the heart be a living pump. Lindbergh's mechanical
pump made of glass, actuated by the pressure of com-
pressed air, which pressure is released into the pump in
pulsating sequence through a revolving valve operated by
a diminutive electric motor does just as well so far as the
bare necessities are concerned. The living heart, hidden
within the flesh and activated by its own living mechanism,
is more compact and more convenient; but the mechanical
heart has demonstrated that it can do the job. It can cir-
culate a fluid (free from bacteria) which will sustain life,
and there is every reason to believe that it can continue
such a process indefinitely.
Biological models are of two kinds. There are, first, those
like the perfusion pump, which are designed as working
substitutes for living organs whose operation is fairly ob-
vious. The second type of biological model springs from a
different motive. Here the attempt is not to provide a
practical substitute for an essential organ, but rather to
explore and understand the mystery of the organ itself.
In the first type the model is auxiliary to a research on
some other problem. In the second type the model is the
problem; it embodies the biologist's theory of what he is
trying to understand, and indeed the main purpose of the
model is to test the theory.
For example: in the living organism the observer en-
counters a process which seems comparable to that of
water running uphill. Briefly, it is this. Protoplasm exists
as a jellylike liquid that invariably gives an acid reaction,
whereas the blood stream which ceaselessly irrigates the
cells is alkaline. The acidic protoplasmic interior of each
[2473
THE ADVANCING FRONT OF SCIENCE
cell is separated from its alkaline surroundings by only a
thin membrane, and through this membrane nutrients are
continually diffusing inward from the blood into the proto-
plasm, and waste products are continually diffusing out-
ward from the protoplasm into the blood. In spite of these
interchanges, the acid of the protoplasm and the alkali of
the blood never seem to meet and neutralize each other
though a normally high affinity between acid and base is
one of the most universal and powerful relations known to
chemistry.
The situation is still more emphasized by the accumula-
tion of certain substances. Every living cell shows a tend-
ency to take in potassium, though blood and other media
which feed the cell are habitually poor in potassium. The
blood is rich in another element, sodium, which is similar
in general properties to potassium; this exists there mostly
in the form of sodium chloride (which is responsible for
the salty taste of blood). But the protoplasmio stuff inside
the cell will accept little in some cases none of this
wealth of surrounding sodium. It takes potassium, from an
environment that is meagerly provisioned with potassium,
and excludes sodium, though its all-embracing medium is
teeming with that prolific element; and it continues to do
this throughout its entire process of growth. In some in-
stances the potassium concentration within the cell is forty
times that of the medium outside, and yet the flow of
potassium continues persistently from outside to inside. It
suggests something of a paradox: as though a head of
water which was gauged at a pressure of 100 pounds to
the square inch should steadily flow upward to a tank
where the pressure was 4000 pounds to the square inch.
This strange capacity of the living organism for working,
as it were, against the energy gradient has long preoccupied
the attention of biologists and philosophers.
Philosophers pointed to it as evidence of the presence of a
"life force." It goes to show, they said, that in the cell there
[248]
MACHINES WHICH IMITATE LIFE
is something outside the sway of chemistry and physics,
something that can outwit the second law of thermody-
namics and attain upstream motion in a world where the
order of energy changes seems everywhere downstream.
Biologists looked to their experiments. By what "con-
glomeration of chymical matters" could such a system
operate a system in which "to him that hath shall be
taken away even that which he hath" ? In other words, by
what chemicophysical arrangement could the selective
permeability of the cell be explained ?
Theories were proposed. It was suggested that the potas-
sium enters the cell in soluble form, and when inside com-
bines with other elements to form an insoluble compound
which, because of its indiffusible nature, cannot escape. An-
other explanation called into use the Donnan equilibrium,
a complicated law of chemical energetics which might ac-
count for the apparent paradox. Neither of these theories
was derived from experiment. They were offered simply as
hypothetical explanations, awaiting test.
3
For one of the most successful attacks on this riddle we
turn again to the Rockefeller Institute for Medical Re-
search, to the work there of W. J. V. Osterhout and his
associates. Dr. Osterhout came to the institute several
years ago from Harvard University, where he was professor
of botany; and perhaps his past experience predisposed
him to go to the plant world for the most fitting subject
for his search into the chemical mechanism of life. Most
protoplasmic cells, both plant and animal, are of micro-
scopic size. Special techniques have been worked out for
the microdissection of these minute units, some of them of
marvelous and ever-fascinating deftness; but protoplasm
is so sensitive that one can never be sure of the integrity
of the ruptured cell. The content of injured protoplasm
cannot be assumed to be the same as that of normal proto-
[2491
THE ADVANCING FRONT OF SCIENCE
plasm. Osterhout wanted to take samples of the interior
fluid and analyze them; he wanted to introduce different
conditions into the cell and see how it reacted; he wanted,
in effect, to get inside this complicated living machine
without injuring it; and for this kind of venture he needed
a big machine.
There is a marine plant known as valonia. It is of the
algae, one of that innumerable horde whose most common
representative is the green scum which floats on ponds;
under the microscope the scum shows itself to be made of
minute cells joined one to the next in long filaments. The
valonia cells, however, are not so sociable. Each lives its
life apart and each attains gigantic size for a cell. A full-
grown valonia may be larger than a pigeon's egg. And yet
it is a single cell of living matter a unit organism, like
an amoeba, and not a composite, like a man. Its general
structure is easy to describe: (i) a firm outer wall of cellu-
lose, inside of which is (2) a thin layer of protoplasm cling-
ing to the cellulose surface like paper on the wall, and
(3) sap filling the interior cavity. Valonia lives in the sea,
and an environment of sea water appears to be as indis-
pensable to it as an environment of blood is to the cells of
the human body. Therefore, to represent the complete
establishment we must add the final element, (4) sea water
outside the cell.
Osterhout and his aides found this marine plant a pliant
subject for their study. Hundreds of valonia cells were ob-
tained from the favorable waters off Bermuda and installed
in vessels of sea water in the laboratory. To gain access to
a cell interior the experimenter punctured its wall and
protoplasmic membrane with a fine glass tube that had
been ground to a needle point. In a related alga, halicystes,
two tubes were inserted and left in unused until the cell
had recovered from the invasion, repaired the wound, and
resumed its normal functioning. Then a series of experi-
ments began. Through these diminutive tunnels it was
[250]
MACHINES WHICH IMITATE LIFE
possible to draw out samples of the sap; indeed the entire
contents of the vacuole were removed in some experiments.
It was possible to introduce other solutions, to dilute the
sap, or to replace it entirely.
But the significant discovery, from the point of view of
our discussion, was disclosed by analysis of the sap of
valonia. It was found to contain accumulated potassium,^
in the proportion of forty parts in the sap to one part in^
the sea water. This accumulated potassium, moreover, was
not locked up in the form of insoluble compounds, but was
dissolved in the watery sap. Nor were the proportions those
of the Donnan equilibrium. Experiment thus demonstrated
that both of the proposed theories of this queer selectivity
were mistaken, and it was evident that some other means
of accounting for the behavior must be sought in the cell
structure or composition.
The cellulose wall was dismissed from consideration, for
it proved to be permeable in either direction; apparently
it is simply an outside skeleton to provide a supporting
structure for the coating of protoplasm inside. In the proto-
plasm, therefore, must be the agency that determines what
enters and what is excluded.
The protoplasm of valonia, as I have mentioned, is a
thin layer less than the two-hundred-and-fiftieth part of
an inch in thickness. Despite this, the layer shows stratifica-
tion: first a film of lipoid or oily material constituting its
outer surface, then a thicker region of watery material,
and inside another surface film of lipoid.
Tests showed that it was the surface of the protoplasm
that played the dominant role in this biochemical drama.
When the oily skin was broken, all the electrical effects
of the cell ceased, all its power of selective permeability
disappeared, the accumulated potassium flowed out into
the surrounding sea water until the sap within contained
precisely the same dilution as the water without, andjthe
cell died. It was not necessary to break through the full
THE ADVANCING FRONT OF SCIENCE
thickness of the protoplasm. The slightest rupture of its
almost impalpable lipoidal film was sufficient to disrupt
the finely balanced machinery and destroy its capacity for
trapping some substances and excluding others.
The valonia cell, thus dissected, may be diagrammed in
cross section roughly as follows:
SEAWATER(ALKALINE)_ZT- ~
'/'.CLLL-
I 'SAP )'
PROTOPLASM (NON-AQUEOUS SURFACE)
The living cell
Would it be possible to imitate this living apparatus?
Dr. Osterhout's studies of the cell had led him to formulate
a physicochemical theory of its operation, ancf if true the
theory should be demonstrable. There is no need here to
elaborate the theory in its entirety but we may note a few
salient points.
In the first place, it was known that potassium, sodium,
and other electrically active elements move in an aqueous
solution as dissociated atoms that is, as ions, each bearing
an electric charge and, therefore, each constituting a mov-
ing unit of the electric current. But oils, fats, lipoids do
not conduct the electric current, and experiments with the
protoplasmic surface showed that this is true of that par-
ticular lipoid. Electrolytes, therefore, must penetrate this
surface in some form other than as dissociated atoms or
ions.
But potassium and sodium exist in the sea in alkaline
compounds (as well as in the familiar salts) and Osterhout
turned his attention to these. If there were an acid in the
protoplasmic surface it might combine with alkalis of the
[252]
MACHINES WHICH IMITATE LIFE
sea to form salts of potassium and of sodium, and these
salts might permeate the oily film and pass through as whole
molecules.
However, the rate of transport varies from element to
element. It is well known that certain solutes move more
readily than others. This quality depends on their "parti-
tion coefficients," and the partition coefficient depends in
turn on the ionic radius of the element the greater the
radius the more rapid is the motion. It happens that the
ionic radius of potassium is greater than that of sodium.
We thus arrive at a purely chemical explanation of the
"preference" of the cell for potassium.
The potassium passes through the protoplasmic layer in
the form of a potassium salt, but as soon as it reaches the
interior and comes in contact with the sap it changes again.
The sap contains carbonic acid, for which the potassium
has stronger affinity. So the potassium drops the atoms
which it took on from the protoplasm and contracts a new
union to form potassium hydrocarbonate, a salt which im-
mediately dissolves in the watery sap. Thus the carbonic
acid of the sap is continually being neutralized by the in-
flowing potassium; and if this were the whole story the
process would be short-lived.
But there is another operation continually at work. The
cell is respiring, that is, taking in oxygen and sugar and
burning them to release energy and form carbon dioxide.
Some of this carbon dioxide (also known as carbonic acid
gas) is continually uniting with water in the sap to form car-
bonic acid, and thus the acidity of the sap is steadily renewed.
In consequence there is always acid within to combine with
the entering potassium. Indeed, the acid may be pictured as
a sort of chemical magnet attracting the potassium, or,
better still, as a chemical pump sucking it in. The acid would
react just as effectively with sodium, if the sodium were
quick enough to get through the lipoidal film in sufficient
numbers. But the peculiar nature of potassium gives it
r
THE ADVANCING FRONT OF SCIENCE
greater penetrating power, and thus a higher ratio of
accumulation.
The test of this theory was a model. In the living appa-
ratus there were three essential phases: (i) the sea water,
(2) the cell sap (both aqueous solutions), and (3) the proto-
plasmic surface (a nonaqueous phase separating I and 2).
Clearly, the model must contain parts corresponding to
these three phases. It was not necessary, however, to con-
struct a hollow globule the size of a pigeon's egg in order to
simulate the mechanics of the cell. All that was required
was to concoct an artificial sap and an artificial sea water
and separate them by an artificial protoplasmic surface.
To simulate the protoplasmic surface Osterhout selected
two well-known carbon compounds, guaiacol and p-cresol.
He mixed them in proportions 70 per cent of the first and
30 per cent of the second. The result was a heavy oily liquid,
nonaqueous, impervious to water, and containing an acid.
To simulate the sea water he dissolved equal amounts of
caustic potash (potassium hydroxide) and caustic soda
(sodium hydroxide) in distilled water. Since both com-
pounds are alkalis, the solution was alkaline.
To simulate the cell sap he bubbled carbon dioxide
through distilled water. Some of the gas combined with the
water to form carbonic acid, and thus the solution, like
the sap, was acidic.
We now have three artificial liquids. To make our model
we must separate the acid solution from the alkaline solu-
tion by the nonaqueous oily fluid. A simple arrangement in
a glass beaker accomplished this. Into the beaker Dr. Os-
terhout first poured the guaiacol-p-cresol solution, sufficient
to cover the bottom to a depth of two or three inches.
Then he lowered a short section of a large glass tube into
the beaker, and supported it there permanently with the
lower end of the tube protruding slightly into the guaiacol-
p-cresol solution. Into this inner tube he poured the acid
solution, into the beaker outside the tube he poured the
[254]
MACHINES WHICH IMITATE LIFE
alkaline solution, and thus the model was complete. The
wall of the glass tube prevented any direct intercourse
between the artificial sap within the tube and the artificial
sea outside. The only possible communication was through
the artificial protoplasm. If any of the alkalis of the arti-
ficial sea could combine with the acid of the artificial proto-
plasm (as postulated by the theory) then some of the
electrolytes of the "sea" ought to pass through the non-
aqueous liquid and up through the open end of the tube
into the "sap." The model may be outlined in cross section,
thus:
ALKALINE -^^Z^Zr^l ARTIFICIAL
SOLUTION "
The artificial cell
This artificial cell worked. Just as in the living cell, so
here in this nonliving model potassium and sodium accu-
mulated in the sap, and the potassium concentration in-
creased more rapidly than the sodium concentration. By
lowering a small glass tube into the "sap" and continually
bubbling carbon dioxide gas through it, the acidity of this
internal fluid was maintained. Eventually the artificial cell
reached a steady state at which the concentration of potas-
sium and the lessened concentration of sodium attained
a fixed ratio to the water content of the sap which is
precisely what happens in the living valonia cell. A purely
physicochemical model of a living process !
4
The model just described simulates one general property
of the living organism namely, its permeability. But in a
[ 255 ] r v /
THE ADVANCING FRONT OF SCIENCE
live cell many other processes are operating at the same
time. Each seems to depend on a train of physicochemical
reactions, and by separating the functions and isolating
them in individual models, biochemists have been able to
imitate many of these processes in other artifacts.
In experiments conducted at the Desert Laboratory of
the Carnegie Institution of Washington several years ago,
D. T. Mac J>ougal made artificial cells of cellulose capsules,
lined them with jellylike mixtures, and filled them with an
acid sap. These cells maintained their acidity for days in
alkaline solutions, and exercised selective absorption of
sodium, potassium, calcium, chlorine, and nitrates from
soil solutions activities similar to those of living root
hairs.
At another Carnegie Institution laboratory, that of Plant
Biology in California, H. A. Spoehr has set up a cell model
which respires. It takes in oxygen and sugar and combines
these materials to form carbon dioxide and water, which is
precisely what the living cell does. In the living cell, iron
is present and is believed to serve as the catalyst which
facilitates the breakdown of sugar and its oxidization to
water and carbon dioxide at ordinary body temperature,
without the chemist's usual aid of heat or strong acids.
Similarly, in his model, Dr. Spoehr includes an iron com-
pound for the same purpose, and the reactions take place
under comparable conditions of body temperature and
absence of strong reagents an impressive analogue in a
glass cell of the basic act of metabolism.
At the University of Chicago, in its laboratory of general
physiology, Ralgj^. Lillie is working with a model of the
nerve cell. His model consists of an iron wire immersed in a
strong solution of nitric acid a purely inorganic chemical
system. But Dr. Lillie finds that the response of this strip
of passive iron to various stimuli such as touching it with
a base metal, jarring it, bending it, or scraping it with a
piece of glass is very similar in its conditions and general
[256]
MACHINES WHICH IMITATE LIFE
features to the response of a nerve or other sensitive proto-
plasmic system. The irritability of the nerve shows itself
when an electric current is passed through it, and similarly
the wire shows a closely analogous type of responsiveness
to the electric current. In both cases there is a trigger effect.
The stimulus must reach a certain magnitude before any
response is given, but when it is given the response is com-
plete. That is to say, both the living cell and the nonliving
wire behave in the " all-or-none " manner characteristic
of nervous action. Experiments show that when the wire
is first placed in the acid a thin surface film immediately
forms which is analogous to the surface film of protoplasm.
In both cases the film is impermeable, electrically polariz-
able, and chemically alterable. Dr. Lillie attributes the
irritability of the iron and of the protoplasm alike to phys-
ical and chemical changes which occur in their respective
surface films.
The oil films on water with which Irving Langmuir has
been experimenting, as reported in Chapter X, provide
still another model of the living setup. Here the film is made
to approximate very closely the surface conditions within
and without the cell, and permeability seems to be related
to the density of the monomolecular layer ranging from
the impermeable state of a two-dimensional solid to the
very permeable state of a two-dimensional gas. There
seems to be endless opportunity for experiment with these
models.
5
But a model does not have to be an actual physical ap-
paratus or a system of chemical materials in vessels. The
physicist has long been familiar with paper-and-pencil
studies of physical systems; and with the application of
mathematical techniques to biology, the same practice is
becoming increasingly helpful in exploring the fundamentals
of living systems. An outstanding example of this is pro-
l *S7 1
THE ADVANCING FRONT OF SCIENCE
vided in the work of another scientist at the University
of Chicago, a mathematical biophysicist, Nicolas Rash-
evsky. Dr. Rashevsky is one of a small group oif pioneers
who have essayed the task of building "a complete and
consistent system of mathematical biology," approach-
ing this formidable undertaking by means of paper-and-
pencil models of the cell.
The living organism is so complex that at first thought
this would appear to be a hopeless task. Forms, sizes, and
structural details vary widely, from the huge valonia cells
to the microscopic bacteria, from the long nerve cells to
the floating red corpuscles of the blood stream. Essentially,
of course, all cells are systems of protoplasm, and most of
them are characterized by two general features: an inner
structure, the nucleus, surrounded by the cytoplasm. But
the nucleus, as we have seen, is a complex of chromosomes,
which in turn are made up of smaller units, the genes; and
similarly, under the microscope, the cytoplasm exhibits
differentiation, vacuoles, fat globules, mitochondria, all in
ceaseless motion, bubbling, flowing, living. By what mathe-
matical magic may the physicist hope to approach this
restless intricacy and sort out its phenomena into their
physical sequences ?
/' By the well-known strategy of absti#ction, answers Dr.
Rashevsky; that is, by picking out the essential features
and centering attention on them, ignoring for the time the
other phases. This is the method by which physics mastered
other complexities. Thus Newton's law of gravitation was
derived from a study of the problem of two bodies. He con-
sidered the motion of a planet in the Solar System as though
the planet and the Sun were the only gravitating bodies
in the sky, and from that abstraction, that simplification
of the complicated pattern of many encircling planets, the
great generalization was arrived at. With the fundamental
principle expressed in a law, it was possible for later mathe-
maticians to compute the mutual disturbances of the other
MACHINES WHICH IMITATE LIFE
planets very precisely indeed with such exactitude that
the existence of unknown planets was thereby disclosed,
and their positions indicated so definitely that when
searched for in the heavens the predicted bodies were found.
These results were a triumph of precision, and yet the
method rests in the first place on a simplification which
ignored many obvious features.
The mathematical attack on the living cell proceeds by
the same method. Just as Newton adopted the relation be-
tween the one planet and the Sun as the " essential " in a
complex of many relations, so the mathematical physicist
must select from among the myriad aspects of living matter
those that rate as the " essentials" of the simplest possible
system.
Of the multitude of features which enter into a descrip-
tion of the living substance, which shall we take as the ir-
reducible minimum ? Some cells have walls, others do not
so we shall not require a cellular wall in our model. Most
cells have nuclei, but a few varieties do not therefore we
need not include the nucleus as an essential. And so with
the vacuoles, chloroplasts, and other differentiations of the
cytoplasm as they are not in all cells, we leave them off
the list of requisites. Retaining only those features which
are common to all, Dr. Rashevsky draws up his bill of
essentials as follows:
"We conclude that a cell is essentially a small liquid sys-
tem, a drop, in which occur some chemical reactions that
result in growth. The necessary substances for these reac-
tions diffuse into the cell from the outside, with some of the
products of the reactions diffusing from the inside out. This
growing drop, whenever it reaches a critical size, divides
in two, each half growing again, and so on. Moreover,
division is the only method by which new drops may be
produced. No drop is formed spontaneously, although all
necessary substances may be present in the surrounding
medium. Omna vivum e vivo; omnis ccllula e cella [all life
[259]
THE ADVANCING FRONT OF SCIENCE
comes from life; all cells from cells]. We are thus led
to a physico-mathematical theory of such droplets as a
first approximation to a theory of the cell. And this is no
longer a hopeless task."
The task is to justify within the laws of physics the ob-
served behavior of these simplified cells. Can such drops
show growth behavior and reproduction behavior? Yes,
concludes Dr. Rashevsky, if we admit certain fundamental
assumptions.
We must assume (i) a drop immersed in a liquid medium,
like a cell of protoplasm afloat in the sea. We must assume
(2) that the surrounding medium contains in solution the
materials which react and recombine to form the sub-
stance of the drop. We must assume (3) that this drop sub-
stance, however, is not soluble in the surrounding liquid;
or else that the drop is surfaced with a film impermeable
to the interior substance but easily permeable to mate-
rials outside, which enter by diffusion and participate in the
internal reactions.
If these postulates are accepted it can be shown that
differences in concentration of materials will immediately
be set up. Certain materials (corresponding to the food of
the living organism) are continually passing into the drop
and being utilized to increase its substance, while certain
other materials, by-products of the internal reactions (and
corresponding to the secretions of waste from the living
cell) are continually flowing out of the drop. In general,
the "food" concentration will be greatest in the outside
medium, and greater inside near the surface of the drop
than at its center. Corresponding conditions for the "waste
secretions " will be in reverse order that is, these by-prod-
ucts will be most concentrated at the center of the drop, less
concentrated at its surface, and least concentrated in the
medium outside.
The differences in these concentrations are highly impor-
tant. Indeed they are the controlling factor in the behavior
[260]
MACHINES WHICH IMITATE LIFE
of the drop. If the diffusion of food materials inward is
more rapid than the diffusion of waste secretions outward,
then the drop increases in size, i.e., grows. With growth
comes increase in the difference between the concentrations.
The differences become greater as the size of the drop be-
comes greater, and the effect of these disparities is to set
up forces which tend to divide the drop, to break it into
smaller units, and thus reduce the magnitude of the differ-
ences. When a certain size is passed, these forces of disrup-
tion get the upper hand and the drop automatically bisects
into two drops, i.e., reproduces.
What determines this critical size ? Many items enter into
the tug of war diffusion constants, permeability rates,
temperature, surface tension, rate of internal reactions
(metabolism) all well-known quantitative physical enti-
ties. Thus we have reached a purely mathematical basis for
growth and reproduction.
While each of the foregoing entities is expressible in
terms of exact measurement, the task of measuring all of
them(and drawing an instantaneous mathematical picture
of the entire system of even a single dropMs beyond the
power of human intelligence. However, to test the theory,
this complete analysis is not necessary. The modelmaker
may take the outstanding feature respiration, for ex-
ample, since in many living cells we observe that the
respiratory rate far exceeds all other forms of metabolism.
^Reckoning thus, Dr. Rashevsky finds that the critical size
of the drop is of the order of a globule with a radius of % oo
millimeter (about the three-thousandth part of an inch).
And when we turn to living material we find that the critical
size thus derived theoretically is well within the observed
range. Living cells rarely are larger than one-tenth, or
smaller than one-thousandth, millimeter radial measure-
ment, in spite of wide differences in their physical make-up.
If the theory be correct, we should expect to find that
with high rates of metabolism should be of smaller
[ 261 ]
THE ADVANCING FRONT OF SCIENCE
size than those of low. This seems to be borne out in living
forms. In the human body, the cells of the liver are slow
takers of oxygen, and they are among the largest cells. In
the brain the lower cortical layers are made of large cells,
and the higher cortical layers of small cells; evidence seems
to show that these small brain cells have a higher rate of
oxygen utilization than the large cells.
From the simplified case of the one-phase drop the mathe-
matical biophysicist proceeds to more complicated sys-
tems: to two-phase drops (corresponding to cells having
nucleus and cytoplasm) and then to colonies of drops. The
tendency of cells to group together, to colonize into a
composite like a fish or a man, seems to be associated with
irritability; the greater the degree of irritability of the cells,
the more pronounced is their communistic tendency. And
irritability, in turn, is associated with permeability, that
physical factor through which the environment of the
moment exerts its influence. ^
There is, however, something not wholly of the moment:
it is the property that physicists call hysteresis. It is the
property exhibited by a metal wire which has recently
been twisted. The twisted wire will behave differently
from a fresh wire, apparently " remembering " its experi-
ence, but if you wait long enough it may " forget" and not
behave so differently. The same "memory" faculty enters
into the behavior of the liquid drops.
This is suggested by the fact that if the environment of
the drops is changed the behavior of the drops will change
but the same environmental change may produce differ-
ent response changes, depending on the present configura-
tion or state of the drops, which in turn depends on what
has happened to them in the past.
As Dr. Rashevsky explains it: "The reactions of such a
system to the same environmental change will vary. They
will depend on its 'history,' or, to be still more anthropo-
morphic, on its 'previous experience/ In a formal way,
[262]
MACHINES WHICH IMITATE LIFE
however, this is a characteristic of the behavior of all
organisms, particularly of the higher ones 'endowed' with
a highly developed brain. This dependence of reaction on
previous experience we attribute to learning. And, from
a purely formal point of view, learning is nothing more
than a particular kind of hysteresis. Thus our systematic
mathematical study of biophysical phenomena has led us
in quite a natural, we may say almost synthetic, deductive
way, from the elementary general properties of unicellular
organisms to a mathematical study of behavior of higher
animals and man!"
The test of theory is experiment. If learning is nothing
more than a particular kind of hysteresis, and hysteresis is
a common property of material systems, it should be pos-
sible to construct models which will learn. Several experi-
menters have been working with this idea, and claim a
modicum of success for their mechanisms as will appear
in our next chapter.
[263]
Chapter XIV THINKING
MAC HINES
If an army of monkeys were strumming on typewriters
they might write all the books in the British Museum.
ARTHUR 8. EDDINCTON, THE NATURE
OF THE PHYSICAL WORLD
How many monkeys would be required, how many years
they would take, how many tons of paper they would
waste before hitting the right keys these are not specified
in the bond, and we may guess that the number in each
item would be almost incredibly great. But one feature of
the picture is specific, and that is the accidental nature of
the process. In their monkeying with the keys the animals
just happen to hit off Hamlet, the Ode on a Grecian Urn y
Sir Isaac Newton's Principia, and the other works which are
treasured in Britain's greatest library. In the imagined
situation the monkeys may be regarded as so many forces
of the environment, like sunshine and the rain. Indeed, a
prolonged fall of hailstones whose masses were sufficient
to depress the keys without demolishing the typewriter
mechanism should do just as well as the monkey strum-
ming. Thus it might happen that nonliving matter provided
the actuating control of the typewriter. Logically we could
say that the typewriter itself composed Hamlet in response
to the changing configuration of the environment. We might
[264]
THINKING MACHINES
even describe the changing configuration as the stimulus or
inspiration of the writing.
From such " nonsense " and it seems implicit in the
modern obeisance of the physical sciences to the law of
probability we are led to the presumption of the thinking
mind as the reacting mechanism in a perpetual give-and-
take between itself and outside forces. Just as the chance
strumming of the monkeys on the typewriter might pro-
duce Hamlet, so the chance strumming of external nature
on Shakespeare may have produced Hamlet in the first
place. The peculiar physicochemical instrument which we
call the man Shakespeare was necessary to the production
of the poetic and dramatic effects resulting from nature's
impacts, just as the peculiar mechanical instrument which
we call a typewriter is necessary to the production of the
typed effects resulting from the monkeys' strumming. The
monkeys could produce no manuscript from sewing ma-
chines, though they might in a multibillion years produce
a useful suit of clothes in the Prince Albert style. Similarly,
nature could get no verses from Isaac Newton, but it did
draw the Principia.
Some years have passed since the English philosopher C.
D. Broad thought to blast the claims of the mechanists with
his verclict: "If a man referred to his brother or his cat as
an ingenious mechanism, we should know at once that he
was either a fool or a physiologist." If Professor Broad
were to pontificate today he might add the biochemist and
the psychologist to his list of alternatives.
The biochemist proceeds on the hypothesis that mecha-
nism is the basic principle of nature. It may be a fiction,
but it is a useful fiction, indispensable to a chemist and
so he proceeds to apply the law of cause and effect as if
it were true. The behavior of salts, acids, and alkalis in
the test tube follows as if the law were true: then may
not the same law govern the behavior of living salts, acids,
and alkalis in the bodies of plants and animals? Much
[265]
THE ADVANCING FRONT OF SCIENCE
evidence points that way. Biological behavior includes
many properties, such as circulation, respiration, digestion,
irritability, growth, and reproduction, which have been
imitated quite successfully in the laboratory by nonliving
models, as we have seen. But biological behavior includes
also certain other processes, such as thinking, which seem
to belong in a different category. Are these mental phe-
nomena different are they outside the rule of chemical
formulae, beyond dominion of its " great, eternal, iron laws " ?
"At one time I thought so," answers the Cambridge Uni-
versity biologist Joseph Needham, "and doubted whether
biochemistry and physicochemical study of life could have
anything to say about phenomena usually regarded as es-
sentially not physicochemical. It seems to me now that after
its own manner it may have everything to say. Let us take,
for purposes of exposition, a thoroughly extreme case. Some
day some group of biochemical investigators may prove
.that a deficiency of sulphatide phosphorus and a high oxi-
dation-reduction potential in a certain area of the cerebral
cortex is invariably associated with the creation of great
poetry. Obviously such a suggestion is as wild as can be,
but it is nevertheless a legitimate extrapolation from facts
already known/ 71
The psychologists are less unified than the biochemists,
both in method of approach to mental phenomena and in
the variety of their interpretations; but their outlooks are
predominantly mechanistic. One leading school, the psy-
choanalysts, infer a subjective mechanism in which certain
subconscious desires and impulses are the mainspring of
conscious thinking. The reality of mind is not denied, but
its rational elements are everywhere under the drive of its
irrational forces, leaving very little if anything to the free
will of the individual.
1 The quotation is from The Sceptical Biologist, an exciting book in which
Professor Needham explains his qualification "after its own manner" in inter-
esting detail.
[266]
THINKING MACHINES
Quite in contrast with this subjectivism of the psychoan-
alysts is the wholly objective technique of another group
of psychologists, sometimes known as the behaviorists.
These objective psychologists do not bother to investigate
thoughts, dreams, desires, consciousness, the subconscious
all those items dear to the psychoanalyst. Their ideal is
the modern physicist's attitude of considering only "ob-
servables"; and since thoughts and subjective states can-
not be seen, they confine their analysis to the behavior of
the individual. How does he act? how does he react to
certain events? how does his reaction change when the
stimuli change? in a word, how does he behave? When a
button is pushed and the automatic elevator stops at the
floor indicated by the button, we do not say that the ele-
vator thinks out the problem of selecting the floor. It stops
because its mechanism is set to stop. Similarly, says the
objective psychologist, with human behavior. A certain
sound, a certain sight, a certain odor are as so many
push buttons to the living mechanism, and the response
of the man is as mechanical as the response of the
elevator.
But the elevator response is completely standardized.
It never varies from a fixed pattern, whereas human be-
havior exhibits the concept of choice. Pushing button 16
always results in a stop at the sixteenth floor, but waving
a red flag within sight of a human being does not always
produce the same effect. The red signal may cause him to
stop short and look and listen, sensing danger ahead. Or
it may cause him to run forward joyously and welcome the
"comradely" symbol of communism. Or it may evoke curses
and scowls and cause him to advance menacingly and seize
the "hated" flag. In the Harvard Stadium the crimson
banner would inspire still different patterns of behavior.
Over an auctioneer's door it would carry yet another mean-
ing and call forth other responses. Can the mechanists
build a machine that will not only respond to red, but learn
[267]
THE ADVANCING FRONT OF SCIENCE
the different meanings of red, and respond appropriately
according to the significance of the symbol ?
Yes, I believe we could, answers the behaviorist.
Then you could actually build a mechanical mind one
that would exhibit emotions of fear, sentiments of loyalty,
thoughts of aggression and acquisitiveness, all the roll call
of mental responses evoked by the symbolical use of red ?
Call it what you will, answers the behaviorist, we should
be inclined to call it a habit machine, a mechanism operat-
ing according to the laws of the conditioned reflex.
The principle of the conditioned reflex has been recog-
nized since the time of Plato, but its current applications
to psychology stem from the work of the Russian physiolo-
gist Ivan PayjQV. Many years ago Pavlov began to investi-
gate wHat happens in a dog's body when fooc^is offered it.
The mere sight of a chunk of meat causes the gastric juices
to flow, and by means of delicate operations Pavlov gained
access to the stomachs of dogs and made measurements of
the quantities and velocities of these flows under various
conditions. Then he hit upon a more obvious and less diffi-
cult technique. The sight of food also causes the mouth to
water; why not observe and measure this ? So Pavlov turned
to the new criterion, and his recent and more famous work
has been in what an inelegant commentator calls "the
science of slobbering."
It is unnecessary to recount in detail the story of these
Russian experiments. They have formed the theme of
writings and discussions almost innumerable, and my
readers, I feel sure, are well acquainted with the process by
which the physiologist showed the purely automatic nature
of the dog's responses. Since, however, certain parallels are
to be pointed out in this chapter, it will be helpful to recall
very briefly a few of the fundamental definitions. The
[268]
THINKING MACHINES
offering of the food to a hungry dog, Pavlov calls an "un-
conditioned stimulus"; the flow of saliva in response to
this, he calls an "unconditioned reflex." The process of
ringing the bell simultaneously with the offering of the
food, he calls "conditioning." The sound of the bell is a
"conditioned stimulus," and the mouth-watering which
responds to a conditioned stimulus is a "conditioned reflex."
An agreeable stimulus, such as the food offering, is "ex-
citatory," while an unpleasant one, such as the taste of
disagreeable food, is "inhibitory." The brain is the clearing-
house into which continually flash these messages of the
senses, some of them excitatory, some inhibitory. Whatever
is learned, thought, imagined, felt, or forgotten is the result
of this perpetual interplay of excitations and inhibitions.
"I write best while wearing a checkered waistcoat," con-
fesses a certain popular author. But do not call it artistic
temperament, say the behaviorists; the gentleman has
simply been conditioned to the plaid vest it might just
as well have been a helmet and buckler or silk pajamas. He
is like the man in John Locke's story who learned to dance
in a room where an old trunk stood; thereafter his dancing
was conditioned to that stimulus and he never could dance
well except in the presence of a trunk of similar appearance.
Many idiosyncrasies are explained by this Pavlovian hy-
pothesis of the brain as the automatic switchboard of a
completely automatic machine.
And not only idiosyncrasies, but also such faculties as
reasoning, insight, purpose are resolved by this same hy-
pothesis into conditioned reflexes. Though the difference in
degree must be measured in units comparable to light-years
in magnitude, this behavioristic interpretation holds that
Beethoven's composition of the Ninth Symphony and
Leverrier's discovery of the planet Neptune are processes
of the same kind as the dog's salivation at the sound of the
bell. Since the dog's reflexes appear to be mechanical, the
objective psychologist argues that man's more compli-
[269]
THE ADVANCING FRONT OF SCIENCE
cated intellectual and emotional activities similarly are
mechanical,
"It is only a question how the material is organized that
determines how it will behave," explained Clark L. Hull,
professor, of psychology at Yale University, when I asked
for simple analogies to make clear this point of view. "If
material is organized in a certain way, it will fly like an
eagle; if it is organized in another way, it will fly like an
airplane. There was a time when the property of aerial
locomotion was associated only with organic life. Suppose
there had been a system of philosophy which asserted that
aerial locomotion must necessarily be associated with a
mysterious something called life ? Such an attitude is com-
parable to that of the vitalist who holds that it is impossible
for a thing to think unless it is alive. Leonardo da Vinci
doubted the first supposition; the Wright brothers also
doubted it and today airplanes fly automatically under
the control of gyroscopic mechanisms. Equally some of us
doubt the second supposition. In experimental support of
our doubt we can point to certain man-made machines
which reproduce some of the rudimentary behavior of the
conditioned reflex."
Several years ago Dr. Hull was conducting a seminar in
psychology. The class met in the evening, a group of gradu-
ate students for the most part, and discussion was lively,
ranging the frontiers of psychological thought. For several
sessions the seminar had been considering the conditioned-
reflex experiments, and one evening, as the discussion
closed, Dr. Hull gave his class a jolt. " If the mechanistic
theory is true it should be demonstrable," he proposed.
"One week from tonight I want each of you to bring in a
model which will display the characteristic behavior of the
conditioned reflex."
[270]
THINKING MACHINES
He said that as a gesture more than anything else, in an
effort to stimulate the students to think concretely on the
subject. But the following Wednesday three models were
brought to class, and all of them worked. Two were rather
crude arrangements of wooden levers, but one was fairly
ingenious the design of a young physiological chemist
who had come to the seminar to please his wife. She was
a member and had persuaded her husband to attend.
" Perhaps our theoretical speculations bored him," re-
marked the professor, "but my suggestion that a model
might be made to test the theory appealed to his scientific
imagination, and he worked the thing out on the basis of
electrochemical principles. "
This guest of the seminar was H. D. Baernstein. A search
through the psychological journals shows that several
earlier trials in the field of simulating mental processes
had been published, but Baernstein was not aware of them.
And as his model is the first of a series of several originating
from this chance suggestion, we may regard it as a land-
mark. Some newspaperman heard of it and published a
story describing the thing as a mysterious mechanical
brain. The news item, picked up and reprinted by others,
went over the country, and resulted in a number of letters
of inquiry. The Baernstein device was publicly exhibited
for the first time in May, 1929, at the meeting of the Mid-
west Psychological Association in Urbana, Illinois.
What the psychologists saw was an arrangement of wires,
batteries, glass tubes, heat coils, two electrical switches,
and a small incandescent lamp all mounted on a flat
wooden base. It was explained that the two switches repre-
sented two different stimuli in an analogue of Pavlov's
conditioned-reflex experiment, while the lamp was intended
to provide the response.
The demonstration was simple. First, push switch A.
The lamp instantly glows a behavior corresponding to the
mouth-watering of Pavlov's dog at the sight of food. Ap-
1 271 1
THE ADVANCING FRONT OF SCIENCE
patently there is a direct connection between switch A and
the battery which energizes the lamp. If you push switch J?,
however, the lamp does not glow. Its inaction corresponds
to the dog's indifference to the ringing of the bell. You
assume that switch B has no connection with the battery
and the lamp. But now close both switches, and hold
them down for several seconds. After a few of these simul-
taneous closings, you abandon switch A. You press switch B
alone and the lamp glows! Press it again and again; it
lights up repeatedly just as the dog's mouth waters re-
peatedly at the sound of the conditioned bell. Switch B has
become "conditioned" to switch A, for the lamp now will
respond to either stimulus. But if you keep pressing B alone
for several trials, there comes a time when the lamp does
not light. The conditioned reflex has suffered what Pavlov
calls "experimental extinction." However, a few moments
of repeated conditioning will restore the tendency, and
thereafter the machine will recognize and respond to its
conditioned stimulus quite as persistently as the dog reacts
to his dinner bell.
As a preliminary to the explanation of Baernstein's mech-
anism, let us consider first a simpler type of thinking ma-
chine which was designed later by another of Dr. Hull's
students, R. G. Krueger. Krueger was a young electrical
engineer before he took up psychological studies, and he
seized on the storage battery (or polarizable cell, as it is
also called) as the key to his conditioning apparatus. The
arrangement which he set up may be diagrammed as
follows :
CHARGED
ELECTRIC
BATTED
ft,
SWITCH A
LAMP
SWITCH B
Simple type of thinking machine
[272]
THINKING MACHINES
The hookup is simple. When switch A is closed, the
entire left half of the diagram becomes a closed circuit;
the current from the charged battery flows through the
lamp and causes it to glow. Similarly, when switch B is
closed, the entire right half of the diagram becomes a closed
circuit with the lamp; but there is no energy in the un-
charged storage battery; therefore the lamp gives no re-
sponse. When both switches are closed simultaneously, the
current from the charged battery not only flows through
the lamp, but it also flows through the uncharged cell, and
some of its energy is stored there. Thus the process of
conditioning consists of charging the storage cell, and after
this is accomplished Switch B alone can invoke the light.
Prolonged pressing of B will exhaust the stored energy,
thus accounting for the "experimental extinction." But
if you leave the exhausted cell passive a few minutes a cer-
tain chemical readjustment will take place, a "spontaneous
recovery " such that if you now press switch B the lamp will
glow feebly a mechanical analogue of memory.
Krueger's working model included not only the condi-
tioned stimulus represented by switch #, but a whole series
of them. Thus, after conditioning B to A^ it was possible
to condition a new circuit C to By and after that a circuit
D to C, and so on for a considerable sequence. This pro-
vided a chain of reactions comparable to those of Pavlov's
experiments in which, after conditioning the sound of the
bell to the showing of the food, Pavlov conditioned a flash
of light to the sound of the bell, and then the sight of a
luminous disk to the flash of light, and so on. The heart of
the Krueger model is the uncharged storage cell with its
capacity for accumulating energy (a process analogous to
learning), and its capacity for exhausting its energy (ex-
perimental extinction), and its capacity for spontaneous
recovery (remembering).
The Baernstein model is more complicated, but the dis-
tinguishing feature of its mechanism may be described as a
THE ADVANCING FRONT OF SCIENCE
valve actuated by heat control. The essential features of
this are sketched in cross section as indicated.
HEAT
CONTROL
VALVE.
WIRES TO
RELAY
CONTROLLING
THE LAMP
WIRES
BATTERf
Control valve of thinking machine
The valve is in the B circuit, and, since the circuit is open
until the two wires in the right arm of the valve are con-
nected, the mere pressing of switch B will have no effect
on the lamp. But when both A and B switche^ are pressed,
the connection thus made allows current from the battery
to pass through the heat coil shown to the left of the valve.
(In the apparatus, the heat coil surrounds the toluene
chamber.) As the coil gets warm, its rising temperature
heats the toluene. This toluene is a liquid which expands
rapidly with a moderate rise of temperature. As it expands,
the toluene forces the mercury down into the U-tube. The
mercury rises in the right arm of the tube until finally it
touches the ends of the two wires in that tube, and thus
makes contact between them. Thereafter switch -ff, through
this mercury connection, is able to send a current from the
battery to the lamp. But after a while the toluene cools
and contracts, the mercury "assumes its old level, and the
connection between the two wires is broken. Then we may
say that the machine has forgotten.
These two mechanical-electrical arrangements each
quite different and yet both alike in that each provides its
apparatus with a means of changing its internal setup in
[274]
THINKING MACHINES
response to an outside stimulus furnish a clue to the un-
derstanding of all thinking machines. In each of them there
is some provision like the polarizable cell of Krueger's
model or the thermostatic control valve of Baernstein's
model a provision for adjusting the mechanism to what
it experiences, or, as the objective psychologist bluntly puts
it, for learning.
Learning is interpreted as an effect of a trial-and-error
process. In 1934 Dr. Hull published a paper in one of the
technical journals in which he set forth in detail a theory
of the animal mechanism of trial-and-error learning. A stu-
dent at Miami University in Ohio, D. jC-JEllson, chanced
to read this treatise and it inspired him to try to reproduce
the theoretical system in a mechanical model. He set up a
series of three electromagnets in circular arrangement, and
suspended an iron bar so that it was equally distant from all.
The magnets were of different degrees of strength: one
measured 100 magnetic units, another 70, the third, 30.
The strength of these electromagnets in each case was de-
termined by the number of electrically active turns of
wire surrounding its core. And there were internal switches
providing for the automatic cutting out of a certain number
of turns, thus reducing the magnetic strength, or, alter-
natively, for the cutting in of a certain number of turns,
thus increasing the magnetic strength.
Suppose you wish to teach the iron pendulum to move
to a certain magnet, to the weakest magnet, Z. You set a
certain relay to indicate this goal, and close the electrical
circuit which actuates the mechanism. The pendulum,
under the pull of magnetism, moves first to the strongest,
which is magnet X. But that is not the choice you have
indicated as the goal, and the mechanism is so set that
when the pendulum reaches the point of contact with mag-
net X y the electrical connection for that magnet is switched
and automatically 30 of its 100 turns of wire are cut out.
Its strength is reduced by 30 per cent, and in the tug of
[275]
THE ADVANCING FRONT OF SCIENCE
war among the magnets Y now assumes the control. The
pendulum moves to Y. But as Y is not the goal called for
by the setup, the same automatic process occurs here: cer-
tain coils of the wire surrounding the Y core are shunted
out, leaving the dominance to magnet Z. The pendulum
immediately moves to Z, and, as this is the goal, a reward
in the form of increased induction is given for one must
use rewards to teach magnets and pendulums as well as
dogs. What happens is that the contact at Z causes a switch
to close, and this cuts in additional turns of wire, thus
insuring that on the next trial Z will be stronger than it was.
X and Y are weaker now, and Z is stronger; but X is still
the strongest, and Y is next in strength. On the second trial
the pendulum again moves first to X, then to Y> and finally
to Z but this time it performs the sequence more rapidly.
It is learning. At the end of the second trial, additional
turns of the wire have been cut out of X and F, and, cor-
respondingly, additional turns have been cut in to Z.
Eventually, after five trials, the pendulum wftstes no time
in experimenting. Magnet Z is now the strongest, and the
iron bar proceeds directly to its goal. It has learned by
trial-and-error behavior. Nor is the machine standardized
to Z; the goal may be set as Y or X according to the will
of the operator. The machine can be taught to move to
either of them by the same process.
Still another episode in this narrative has its setting in
the Pacific Northwest. It seems that the newspaper account
of Baernstein's model of 1928 caught the attention of a
young man in the state of Washington, Thomas Ross.
Ross had been working on an idea for an automatic type-
writer, thought that the thinking machine might suggest
some useful features for his invention, and so he wrote for
particulars. Dr. Hull answered the letter and the boy came
back with another. Thinking machines interested him: he
thought he would make one himself. Eventually there
arrived in New Haven, by express from the remote North-
[276]
THINKING MACHINES
western village, a carefully crated package. It was Ross's
thinking machine: a device of springs, levers, pinions,
electromagnets, a protruding arm (like the boom of a toy
derrick), and a vertical "maze" (a series of metal shelves
suggesting a miniature cupboard). Odd scraps of material
had gone into its making whatever was available but
the thing is said to have worked.
Set the tip of the protruding arm at the entrance to the
bottom passage of the maze, and start the machine operat-
ing. The tip pushes along the passage until it comes to the
dead end. It can go no farther, and the pressure of the
dead end actuates a switch in its mechanism which causes
it to reverse. It retraces its steps, and moves upward to
the entrance of the second passage. Here the exploratory
process is repeated: the arm moves along the second pas-
sage until the blind alley's closed end on the right stops it,
actuates a switch as before, and so causes it to reverse and
retrace its way out of the second passage just as it did out
of the first. By a similar procedure, it explores the third
passage. In this way, by trying every path, it comes at
last to the end of the maze and so to the goal. The course
of its journey through the maze is indicated by the dotted
line:
GOAL
Maze of learning machine. Starting from left is the path traversed by the arm
of the machine in first reaching the goal.
It would require a complicated array of diagrams to
picture the various circuits, switches, electromagnets, and
other essential parts of the mechanism which drives and
[277]
THE ADVANCING FRONT OF SCIENCE
controls the movement of the protruding arm along this
path through the maze. The machine is electrically driven,
and the tip of the arm carries metal points which make
contacts with the metal slots of the maze and communicate
an electrical current. As this electrically sensitive tip travels
the circuitous route outlined by the dotted path, and ex-
periences the blind alleys, these encounters cause certain
switches in the actuating mechanism to be changed. The
switches cut out certain circuits and cut in other circuits,
as a result of which the arm is held to a more direct route
on its second journey through the maze. This shorter path
of the machine, after the conditioning, can be made clear
by revising the dotted path in our diagram, thus :
1
GOAL
After the machine has learned. Its path to the goal now is more direct.
With further refinement of mechanism, says the inventor,
it would be possible so to condition the machine that it
would proceed by the shortest possible path, i.e., vertically
upward in a straight line from the starting point to the
opening of the upper passage, and then horizontally to the
right to the goal.
Since this early experience Ross has proceeded to college,
and during the last three years has been working in psy-
chological research under Dr. Stevenson Smith at the
University of Washington in Seattle. For several years
Dr. Smith had had in mind an idea for a maze-learning
machine which would travel a track, and now he put Ross
to work on the job. Within a few months they had made
[278]
THINKING MACHINES
and were able to demonstrate a mechanism which news-
paper writers promptly named "the robot rat."
Rats are favorite subjects for the experimental psy-
chologist, and are particularly apt at learning the twists and
turns and obstacles of mazes. So too with the Smith-Ross de-
vice. It might be mistaken for a toy electric locomotive: a ve-
hicle a little more than a foot long and about seven inches wide,
loaded with motor, solenoids, gears: all the equipment
necessary for actuating and directing its movements. The
mechanical rat travels a grooved track from which fork
off at irregular intervals twelve open sidetracks leading to
dead ends. These are equivalent to the blind alleys which
the living rats encounter in their maze running. When the
mechanical rat takes a siding and bangs into the dead end,
a switch is turned within its mechanism which causes the
motor to reverse; so the machine backs up, gets onto the
main track again, and then moves forward, this time passing
the fork. It has learned to avoid the useless turn. And so
with each fork; the machine bumps and learns. The sig-
nificant detail is that this process of conditioning alters
arrangements only within the mechanical rat nothing is
changed in the track. The environment remains unaltered;
but after it has experienced the environment the machine
has been so conditioned and trained by this environment
that it will travel the track from beginning to end without
making a false turn.
"It remembers what it has learned far better than any
man or animal," said Dr. Smith. "No living organism can
be depended on to make no errors of this type after only
one trial."
But how does it learn, and how remember ? The thing is
electrically activated, propelled by a motor, and its choice
of route is determined by a rudder wheel which travels the
grooved track. Before learning, the machine is set so that
this rudder wheel will follow the right-hand branch of every
fork. Every time it takes a side-track and bangs into a
[279]
THE ADVANCING FRONT OF SCIENCE
dead end, not only is the motor automatically reversed, but
one flange in the edge of a twelve-flanged "memory disk"
is depressed. The depression of this flange allows a rocker
arm to fall into a hole, the dislocation of the rocker arm
causes an electrical contact to be made and another con-
tact to be broken, thus connecting one solenoid and discon-
necting the opposite solenoid. It is these solenoids that,
by their magnetic influence, steer the machine. They pull
to one side or the other a lever which controls the rudder
wheel, and after the first collision the flange is so depressed
that thereafter the rudder wheel must take the lefthand
branch of that particular fork. In passing the next section
of the track, two levers in the machine brush against sta-
tionary outside posts and cause the memory disk to turn
forward one division. But here at this new division of the
disk the flange is still upright, and the effect of its being
turned forward is to lift the rocker arm back to original
position and again set the rudder wheel for a right turn at
the next fork. In this way, as it moves through the maze,
always turning right at the first trial, the record of its col-
lisions with dead ends is indelibly written into the memory
disk. If in any instance the right-hand turn proves to be
the main-line path, the machine will encounter no collision
and, therefore, will not alter the flange and the position
of the rocker arm in that twelfth of the memory disk. After
the machine has traversed the twelve sections of the maze
the memory disk will have revolved to the original starting
point. But it is so marked by the experiences of its first
journey that thereafter it infallibly guides the rudder wheel
past all false turns. The living rat learns by experimenting
that is, by experiencing and so does the machine.
3
The skeptical bystander, watching a demonstration of
one of these arrangements, is not fooled. "Truly an ingen-
ious machine," he may remark, "but not a rat."
[280]
THINKING MACHINES
The psychologist agrees. The apparatus has been de-
signed to simulate only one kind of rat behavior the
behavior of learning the most direct route through a maze.
"But your robot blindly bangs into obstacles, and by
these collisions sets prearranged switches in its electrical
control system which thereafter turn its wheels in prear-
ranged ways, and by mechanical direction steer clear of the
sidetracks," persists the amateur critic. "That is not think-
ing that is merely turning switches and resetting relays."
It is merely turning switches and resetting relays, agrees
the behaviorist, but how do you know that learning and
thinking are not the same thing essentially? All we see of
the living rat's procedure is that it follows blind alleys at
first, collides with dead ends, retraces its steps, and eventu-
ally, after a series of experiences, it makes the trip through
the maze without repeating these mishaps. If it is behavior
that we are judging, and if our study is confined to "ob-
servables," where is the difference, in principle, between
what the machine does and what the rat does ?
Admittedly the maze-running machine is not a rat, just
as the airplane is not an eagle. It is only an analogue cap-
able of simulating one limited type of rat behavior. And
so with other models. The glowing of the incandescent
lamp in Baernstein's model is not the same operation as the
dripping of saliva from the mouth of Pavlov's dog, but
the functional relationships between stimulus and response
in the dog are of the same order as the sequence which
conditions the lamp response. It is possible that a model
might be built which would actually salivate at the sound
of a bell, but so complicated a construction is not necessary
to provide a test for the psychologist's theory. And that,
we remember, is the practical justification of model build-
ing: to test theory. If a mechanical artifact can be made to
reproduce the conditions of the theory no matter how
crude or elementary the reproduction evidence is thereby
adduced for the reasonableness of the theory.
[281]
THE ADVANCING FRONT OF SCIENCE
"But we are not deceiving ourselves," said Dr. Hull.
"The model provides a test for the internal logic of our
theory, but it does not absolutely prove the truth of the
theory. If we have a mechanical hypothesis of thinking, and
if we build a mechanical model following this hypothesis,
and if our model executes behavior of a kind analogous to
that which in the living animal we call mental behavior, then
we can fairly claim that a machine can think though we
may be sure that the living organism is not the same kind
of machine. Thus models check the reasonableness, though
they cannot prove the truth, of the theory."
The construction of model psychic mechanisms is a
fascinating diversion; perhaps some would call it a weak-
ness to be indulged only occasionally. For the most part
the psychologists study the living organism itself. In his
laboratory Dr. Hull has under way a huge program of re-
search with living material. The theory of the conditioned
reflex is being investigated and tested here through experi-
ments on the habits of men as well as on thfose of white
rats, dogs, and monkeys. Already a large body of data
has been gathered, and it has considerable significance in
practical life but this subject matter is too voluminous
to be introduced incidentally here.
Hull has never made a model. Stevenson Smith waited
for a young prodigy at mechanism to come along before
he undertook to materialize his idea of the mechanical
rat. Most of the thinking machines have been built by
students, many of them by engineering students. At the
Massachusetts Institute of Technology a young electrical
engineer, N. B. Krim, devoted his graduation thesis (by
which he completed his qualifications for the engineering
degree in 1934) to an exposition of thinking machines. He
made a simple working model. And in his thesis, Krim
provided blueprints for fourteen different electrical cir-
cuits, each designed to reproduce adaptive behavior, some
of them promising responses of a high degree of complexity.
[282]
THINKING MACHINES
A conclusion one derives from observing these machines
is the amount of mechanism needed to provide even the
most elementary behavior. The mechanical rat is equipped
to learn a maze, and its thinking stops there. But a living
rat is equipped to learn hundreds of different tasks. "To
make a model which would reproduce all the behavior of
a rat would require a mechanism probably as large as the
Capitol at Washington," said Dr. Hull. To make a model
which would discriminate among the various symbolical
meanings of the color red, and respond to the emotional
patterns characteristic of human responses to this symbol,
would require a far larger array of mechanism. What
would it take to reproduce the whole behavior of a man
of an average, typical ordinary man-in-the-street ? On the
same scale such a machine might occupy a whole county
or spread over an entire state, so intricate and almost
infinite in number are the cross connections, the associa-
tions, represented by ordinary human behavior.
In a preceding chapter I have discussed the mathe-
matical approach to biology which has been undertaken by
Nicolas Rashevsky, and suggested the nature of his models
of the living cell. Dr. Rashevsky has not confined his
method to elementary processes of primitive life. He has
published the general specifications for a machine which
he claims will exhibit " purpose," and in particular will
"tell a lie" which "may be described as purposeful." The
actual construction of the machine has not been attempted,
It "will be a matter of tremendous expense and labor,"
Dr. Rashevsky admits, but of its possibility he has not
the slightest doubt. Anyone who has the inclination, the
mathematical acumen, and the necessary where-withal,
will find all clues freely revealed in Rashevsky's paper in
the Journal of General Psychology (1931).
Questions of biological mechanism came up for discussion
at a meeting of the American Philosophical Society held
at Philadelphia a few years ago. After hearing various argu-
[283]
THE ADVANCING FRONT OF SCIENCE
ments on both sides, Dr. Cyrus Adler threw out this
challenge:
"If the mechanistic theory were carried to the extreme
and there were produced, as I understand there can be
produced in the laboratory, a robot that could in every
way duplicate the acts of what we call man, it has been
suggested, and I regret that I cannot take credit for this
suggestion, that the acid test as to the identicalness of the
real man and the mechanistic man is whether the latter
would ever engage in the search after truth."
Would the machine ever develop a curiosity as to its
nature, its origin, its destiny?
What say the psychologists, the biochemists, the bio-
physicists, the modelmakers? "Stands Scotland where it
did?"
[284]
Chapter XV C H E M I S T RY AND
THINKING
The cells of a human brain continue to act because the
blood stream brings to them chemical free energy in the
form of sugar and oxygen. Stop the stream for a second
and consciousness vanishes. Without that sugar and
oxygen there could be no thought, no sweet sonnets of
Shakespeare, no joy, and no sorrow.
F. G. DONNAN, THE MYSTERY OF LIFE
WHATEVER we may infer from nonliving mechanical
analogues as to the nature of the mind, its close
physical relationship to the brain is everywhere confirmed.
And the direct dependence of the brain upon the chemical
interchanges of the body is equally a matter of universal
observation. It is not only that substances foreign to the
body, such as a few drops of alcohol, a few whiffs of an an-
esthetic, or microscopic granules of a narcotic, may pro-
foundly affect the organ of mind, but that the health and
very life of the organ depends from moment to moment,
as indeed does that of every organ, upon the ceaseless flow
of the blood stream and the constancy of its cargo of nu-
trients. The brain appears to be peculiarly sensitive to the
physicochemical equilibrium. When that equilibrium is
upset the brain and its nervous system are the first to feel
the shock. In experiments with dogs at the Rockefeller
Institute it was found that if circulation were interrupted
only 5 minutes, the dogs were easily resuscitated to appar-
THE ADVANCING FRONT OF SCIENCE
ently normal condition; if the interruption lasted 8 minutes,
the dogs were resuscitated but with impaired intelligence;
if the interruption of blood flow were as long as 10 minutes,
resuscitation was difficult and when accomplished the dog
was blind and paralyzed and in other ways gave evidence
of serious brain injury. When death comes to the body,
the brain is the organ that dies first.
Is it possible to gauge, not only the brain's living, but
also its thinking and other mental functioning, by the na-
ture and rate of the body's chemical interchanges ? There
is, quite obviously, a chemistry of living. Is there also a
chemistry of thinking ?
A person lying in bed in the early morning before break-
fast, having taken no food since the previous night's dinner,
awake and yet in a state of repose, his muscles lax, his
mind at ease, is a thermodynamic machine t or near its
lowest ebb of activity. Just to keep the heart beating, the
lungs pulsing, the other organs in tone and functioning,
requires a certain minimum of energy. This energy is con-
tinuously supplied by a chemical reaction or series of reac-
tions in which some of the fuel taken in as food is combined
with the oxygen breathed in as air. By this process, literally
a burning, heat is generated and energy is made available.
Individuals differ as to their needs, but on the average the
requirement for an adult is about I calorie a minute, 60
calories an hour an energy rate equivalent to that repre-
sented by the combustion of two lumps of sugar in an hour.
This energy level is basic. It measures the cost of merely
keeping alive. Any increase in bodily activity calls instantly
for an increased burning of fuel. Merely sitting up raises
the energy requirement by about 5 per cent; standing, by
about 10 per cent; and walking briskly may at once treble
the need, and speed the calorie output by 200 per cent.
[286]
CHEMISTRY AND THINKING
The energy requirements of the body in repose and in
action have been the subject of prolonged study at the
Nutrition Laboratory in Boston, one of the research centers
of the Carnegie Institution of Washington. Here Fraricis
G. Benedict and his colleagues have measured the metab-
olism of man and other animals under a variety of condi-
tions, seeking always to find a correlation between such
measurables as oxygen consumption, carbon dioxide out-
put, heat production, and the activity of the organism.
An airtight, heat-tight room was constructed at the lab-
oratory, so arranged that several persons may live in it for
days without discomfort and carry on all the ordinary
activities of eating, sleeping, working, playing, while sensi-
tive apparatus measures their intake of air, their output
of waste, the heat generated by their living processes. Dr.
Benedict found that the intake of oxygen is a precise index
to all the other factors, so his later studies have centered
on this single indicator. He has devised an airtight helmet
and other portable apparatus for measuring oxygen con-
sumption, and with this has been able to go into the field
and measure the metabolism of elderly persons in their
homes, of workmen at the bench, of women at the ironing
board, and by such means has accumulated a wide range
of data on the energy requirements of the human machine
at work and at play.
He finds that a person engaged in a sedentary occupation,
a desk worker, for example, requires about 2500 calories^
daily to supply basal needs and provide the energy neces-
sary to sustain his work. For manual workers the needs are
greater. A farmer requires on the average about 3500 calo-
ries daily, while a lumberman, engaged in the more laborious
tasks of sawing, chopping, and lifting logs, uses about
7000 calories. A professional bicycle racer, who obligingly
submitted to the scientists' measuring device, developed
the enormous requirement of 10,000 calories approxi-
mately four times the rate of the desk worker.
[287]
THE ADVANCING FRONT OF SCIENCE
I cite these representative cases out of thousands of
measurements that have been made. The evidence is com-
pletely consistent in showing that the more active a person
is physically, the higher is his rate of oxygen intake, the
greater is the combustion of fuel in his cells, and the larger
is his output of energy. Every lifting of an arm, every
speaking of a syllable, every quiver of an eyelid, costs
energy which must be supplied by the burning of an addi-
tional portion of fuel,
If physical activity demands its toll and shows its costs
so unmistakably in the increased chemical activity of the
body, what of mental activity? Who that ever solved a
tough problem in mathematics, or worked through a 3-hour
examination at school, or participated in an extended con-
ference calling for close attention to many details and the
decision to act in a critical situation, can forget the feeling
of fatigue which follows these mental exercises ? Surely
the labor of the brain is no less exhausting than the labor
of the muscles. *
Since this is abundantly affirmed by experience, we may
ask, what are the energy requirements of mental effort?
If a sedentary desk worker who is engaged in routine duties
requires 2500 calories daily, how many additional calories
are needed when that same desk worker has to apply his
brain to a knotty problem ?
Such questions led Dr. Benedict to a searching experi-
ment.
The physiologist was aided in this study by his wife,
Cornelia Golay Benedict, his collaborator in many pre-
vious studies. They selected as subjects one woman and
six men. The woman had been a professional accountant,
five of the men were university trained, and two were of
professorial rank. Presumably each was capable of sus-
tained intellectual effort. All were in good health.
[288]
CHEMISTRY AND THINKING
The experiments were carried forward during a series of
forenoons, the subjects arriving at the laboratory at about
8:30 without breakfast. The instant food is taken into the
body the rate of chemical activity rises automatically,
since energy is required for digestion. Therefore, to avoid
this complication, the seven willingly fasted each day until
about noon. During the 3 or 4 hours each wore the helmet
continuously, though the actual testings of the effect of
mental effort were limited to periods of 15 minutes and
were relieved by periods of rest.
For each day the program was about as follows. The sub-
ject was seated comfortably, in a position involving the
minimum of muscular tension or strain, a posture that was
maintained so far as possible throughout the series of meas-
urements. The idea was to obviate extra energy demands
due to physical requirements. In this early stage of relaxa-
tion and mental repose, the metabolism was measured.
That gave a sort of base level with which to compare
changes. Then the subject was called to a state of mental
attention, and again the metabolism was measured. Finally,
the person was told to solve a mathematical problem, and
during this intellectual activity the metabolism was meas-
ured. Usually the problem was to multiply a two-digit
number by another two-digit number. For example, what is
the product of 37 multiplied by 29?
No paper and pencil were provided, for the use of writing
materials would call finger muscles into play, and physical
effort would be added to mental effort, thus confounding
the result. No, the whole computation must be carried on
in the head. And when the problem was solved, the answer
must not be announced orally. Speaking would bring into
action the muscles of the vocal organs and add their toll
on energy. So the subject was asked merely to touch a
sensitive electric switch which lay at hand and thereby
signal the conclusion of the problem, whereupon the ex-
[289]
THE ADVANCING FRONT OF SCIENCE
perimenter would take the signaler's word for it that the
problem was solved, and would propound another.
After a morning of these mental gymnastics, there was
not a one of the seven who did not feel fagged. Each was
glad of the opportunity for a change, oppressed by a sense
of exhaustion, and inclined to believe that sawing wood or
sweeping floors might be preferable to three hours of sus-
tained mental labor.
There was no question about the feelings of the subjects
of the experiment. The thinking did take something out
of them. But what about the records of the unemotional
instruments the measuring devices which unerringly
write down the rises and falls of the body's chemisms ?
Surprisingly, the measurements showed scarcely any
difference between the energy requirements of the body
in mental repose and those of the body in mental activity.
The rise in oxygen consumption for the latter was only a
trifling 3 or 4 per cent.
There were also slight increases in the fates of heart
beat and respiration and in the ventilation of the lungs,
changes which require a corresponding acceleration in
muscular activity; and, according to the Benedicts' inter-
pretation, these increases in the activity of heart and lung
muscles might well account for the increased use of oxygen.
Even if the entire 4 per cent increase be attributed to the
extra demands of the thinking brain, the toll is amazingly
slight approximately 4 calories an hour, an amount of
energy equivalent to that supplied by eating half a peanut!
But the energy released by the combustion of half a
peanut may be relatively enormous if we consider the
small proportion of body material involved in the thinking
process. This was emphasized by the Viennese physiologist
Arnold Durig in a communication to Dr. Benedict. Pro-
fessor Durig estimates that the number of brain cells which
, function in an act of mental effort can weigh hardly more
than 7 grams (^ ounce) proportionately about one-hun-
[290]
CHEMISTRY AND THINKING
dredth part of I per cent of the average human body weight.
For this small mass of cells to be responsible for the 4 per
cent increase in body metabolism which the Benedicts de-
tected, it would be necessary for the brain cells to have a
metabolic activity four hundred times greater than that
of the average body cell, says Durig. Metabolism/or mental
effort is one thing; metabolism due to mental effort is quite
another.
We may say with confidence that there is a metabolism
necessary for mental effort, because, to repeat the idea with
which this chapter began, any interference with the stream
of blood which continually pulses to the brain, any tam-
pering with its freights of oxygen, sugar, and other essen-
tials, is quickly reflected in mental infirmities. In his Terry
lectures at Yale, Sir Joseph Barcroft told of some rather
drastic experiments that he performed upon himself in
pursuit of this problem. In one test he spent 20 minutes in
a sealed room whose air was diluted with more than 7 per
cent carbon dioxide gas. This meant that he was breathing
and putting into his blood more carbon dioxide than is
normal. The effects showed in symptoms of mental fatigue:
"An inability to concentrate on or even listen to conversa-
tion without effort; the tendency to take up a newspaper,
read a few lines of one paragraph, preferably something
quite unimportant, then a few lines of another, without
finishing anything." This inability to concentrate and
Sir Joseph points out that it was an impairment of the
higher qualities of the brain lasted about two days. In
another experiment he spent only 5 minutes in air contain-
ing the higher mixture of 10 per cent carbon dioxide, and
"when I came out I was retaining my grip on things only
with an effort."
From many experiences and observations Barcroft con-
cludes: "The thoughts of the human mind, its power to
solve differential equations, or to appreciate exquisite
music, involve some physical or chemical pattern which
[291]
THE ADVANCING FRONT OF SCIENCE
would be blurred in a milieu itself undergoing violent
disturbances."
3
This physical or chemical pattern also displays electrical
properties. Certain areas of the brain are undergoing con-
tinual changes in electrical potential, and the resulting
differences in potential between one area and another give
rise to minute electrical currents. Recently it has been
found possible to cause these microcurrents to write their
records of pulsations. The result is the attainment of a new
index to the ceaseless energy flux of the organ of mind, the
so-called "brain waves."
The existence of electrical activity in the brains of ani-
\mals has been known since 1875, but systematic study of
the effect in man dates only from 1929. In the latter year
the neurologist Hans Berger, at the University of Jena,
borrowing a device from the radio engineer, attached wires
from opposite sides of a man's skull to a powerful vacuum-
tube amplifier. The delicate currents from the brain were
thereby stepped up, magnified by a factor of millions, and
when led off into an oscillograph they showed a wavelike
pattern. Among this pattern Berger discovered a certain
predominant rhythm with a vibratory frequency of about
jio a second, and these pulsations he called " alpha waves."
There was another rhythm, less pronounced but often
detectable, which was of shorter wave length and higher
frequency, and these he named "beta waves. " Later in-
vestigators have identified other pulsations of irregular
wave length and uncertain rhythm.
The pattern of waves, if pattern there be, is complex and
of a language difficult to decode. But the fact that at last
man has an instrument which can pick up and respond
to the delicate activities of the thinking mechanism is of
the greatest encouragement. Today brain waves are the
subject of study in a dozen leading laboratories of Europe
CHEMISTRY AND THINKING
and America. Important advances in this new field have
been made by E. D. Adrian at Cambridge University; by
M. H. Fisdier and A. E. KornmueUer at Berlin. In the
United States, Brown University, Harvard, and the Loomis
Laboratory among others have contributed valuable
studies.
The waves which are recorded from outside the skull
seem to originate in the cerebral cortex, that ensheathing
bark of gray matter in which reason and creative thinking
have their home.
"It has required upward of twenty million years of evolu-
tionary history to fabricate the architecture of this cortex
out of the simpler nervous structure of the brain stem,"
points out C. Judson Herrick, psychologist at the Uni-
versity of Chicago. "The larger outlines of this history can
be read, yet we are still profoundly ignorant of how it per-
forms its miracles of production that we know it does pro-
duce. But these mysteries are not insoluble, and the last
quarter century has contributed more toward the solution
of the problem how the brain thinks than all the pre-
ceding centuries of scientific research yielded. We have new
instruments oscillographs with radio-tube amplifiers
and new points of view that promise as great a revolution
in the physiology of the nervous system as the invention
of the microscope effected in the field of anatomy."
The microscope can work best with restricted things,
small colonies of tissue or individual cells, and often the
material has to be stained, that is to say, injured and even
killed, for its details to become visible through the lens.
But the electroencehalograjgh (as the technicians call the
brain-waveHetecting and recording apparatus) has no such
limitations. It works with the whole organ, the living brain
in place, and without interfering with its normal function-
ing. It is not even necessary to puncture the skin. Present-
day instruments are so sensitive that two metal electrodes
in contact with two different areas of the scalp will pick up
[293]
THE ADVANCING FRONT OF SCIENCE
the flow of electricity passing from a brain area of high
potential to one of lower, and this can be done without dis-
comfort or annoyance to the person submitting himself to
the experiment. Indeed, any discomfort or annoyance will
be reflected in the pattern of waves ; therefore it is impor-
tant that the subject be at ease and without apprehension.
At the Harvard Medical School a small cubicle has been
paneled off at one side of the laboratory; it has been fitted
with a couch on which the subject lies during the experi-
ment; and frequently one or two preliminary periods are
run in advance of the actual test as a means of making the
apparatus and procedure familiar, thereby relieving anxi-
ety. Once confidence is established, the comfort of the couch
and the warmth and peace and twilight of the closed room
have a soporific effect, and in many experiments it has been
a problem to keep the person awake. This is necessary, for
the wave patterns during sleep are different from those
during wakefulness, while those of the awake but passive
brain with eyes closed are different from thos^of the seeing
brain or the thinking brain.
These effects were easily demonstrated. The subject re-
clined at ease in the closed cubicle, the two electrodes ad-
justed to his head and connected with wires. The wires
led outside through a series of amplifiers to a tiny electro-
magnet which actuated a pen on a moving strip of paper,
a tape not unlike the ticker tape of Wall Street. The man
on the couch inside had been instructed to "keep your
eyes closed until we tell you to open them, and just take
it easy." As soon as the switch was pressed, completing
the circuit, the pen began to write a wavy line. The waves
were fairly regular, and came about ten a second a record
of alpha waves.
"Keep your eyes closed, and multiply eighteen by
eleven."
Immediately the pen changed its antics. The bold lei-
surely strokes ceased, and in their place came a series of
[294]
CHEMISTRY AND THINKING
smaller waves, some barely perceptible. Apparently the
mobilizing of mental faculties from idleness to work had
affected the currents which our apparatus was able to pick
up, and now the pulsations were feebler. This period of
smaller waves lasted several seconds, but after a while the
waves began to lengthen and the pen grew bold again,
writing out the oscillations of the alpha rhythm. The experi-
menter knew then that the brain had solved the problem
and was relaxed once more. But the relaxation was tem-
porary, for in another instant the pen resumed the narrow
less-defined strokes, as though the brain were returning to
its task. And so it was; for, as the subject later explained,
after multiplying the numbers and getting an answer, he
was disquieted by the thought that it was a wrong answer.
Accordingly he repeated the multiplication to a satisfying
conclusion. After that, more alpha waves.
There are other means than mental arithmetic for smooth-
ing or suppressing this ground swell of alpha waves, as our
experimenter now demonstrated.
"Don't open your eyes," he warned.
The alpha rhythm ceased. The effect of this call to atten-
tion was very transitory, however, for presently the alpha
waves resumed.
"Now open your eyes," and at the command the experi-
menter turned an electric switch which lighted a lamp on
the wall inside.
Quickly the alpha pattern changed, reverting again to the
weaker pattern. And the new pulsations persisted for some
time, demonstrating that the act of seeing has a profound
effect on the electrical output of the brain.
The experiments cited are typical, and their results cor-
respond to those obtained in many other laboratories,
though it must be said that there are wide variations in the
responses of different individuals. A few persons among
those tested show no alpha rhythm. Some show irregular
patterns, large waves interspersed with small. But many
THE ADVANCING FRONT OP SCIENCE
give a fairly recognizable rhythm, though the wave length
varies slightly from individual to individual.
In general we may summarize findings thus: Those per-
sons whose brain potentials characteristically reveal an
alpha rhythm, cease to show it (i) when the brain is em-
ployed in conscious mental effort, or (2) when the brain is
called to attention, or (3) when the eyes are opened in a
lighted room. By other experiments it has been shown that
alpha waves are more pronounced when one of the elec-
trodes is placed at the back of the skull over the visual area
of the cerebral cortex, the brain region which is receptive
to messages from the optic nerve. In some way, we do not
know why, alpha waves are related to the sense of sight.
4
Results so far described refer to experiments with the
subject awake. Interesting variations show when the ma-
chine is set to record the currents given by a sleeping brain.
This is a project that has engaged the interest of Alfred
L. Loomis, E. Newton Harvey, and Garret Hobart at the
L6bmTs^Labof^toiy w in"^Tuxedo Park, New York. Here a
bedroom has been equipped with special apparatus to in-
sure controllable conditions. The room is electrically
screened to guard against stray currents from the outside;
it is equipped with a sensitive microphone to record all
noises heard within the room, and with a photoelectric
device to record the movements of the bed in response to
the sleeper's restlessness. Sleep records from many different
persons, ranging in age from 1 1 days to 75 years, have been
taken while a device ceaselessly wrote the history of the
brain's electrical rhythms. Finding that in a night the
customary apparatus would turn out half a mile of paper
tape, the Tuxedo Park investigators constructed a revolving
drum 8 feet long on whose paper surface the pen may write
an entire night's waves in an advancing spiral. Moreover,
they devised an arrangement by which three circuits of
[296]
CHEMISTRY AND THINKING
electrodes are used at the same time, and three pens simul-
taneously record the waves from three pairs of opposing
areas on the same head. Records of every heartbeat, every
pulsation of the lungs, every movement of the body, are
also inscribed. These several messages travel electrically
through shielded cables to the control room 66 feet away,
and there are entered by automatic pens in different colored
inks on the spacious paper of the revolving drum.
The purpose of these accessory hookups is to determine
whether or not there is any correlation between brain waves
and the rates of heartbeat, respiration, and other muscular
movements. The investigators found no synchronism with
heartbeat and none necessarily with respiration, though at
times a definite change in the wave occurs with each
breath. Regular snoring shows no correlation, but an occa-
sional isolated snort may start a series of alpha waves.
The Tuxedo Park experiments show three types of waves
to be characteristic of sleep. First are the "trains" of alpha
waves (10 a second) which appear in the first stage of falling
asleep and reappear during light sleep. Second are the
"spindles," short bursts of waves of rapidly increasing and
then rapidly decreasing amplitude, with a frequency of 14
a second. Finally, there are irregular waves which Loomis,
Harvey, and Hobart call "random."
In general, spindles and random waves are associated
with deep sleep, and the trains occur during interrupted or
light sleep. Often a sudden change from the random type
to regular trains resulted from merely speaking to the
sleeper. Interestingly, too, noises of an accustomed nature,
such as the honking of an automobile horn, frequently
have no effect, while anything that indicates the presence
of another person may cause spindles and random waves
to give place abruptly to trains. A cough, a whisper, a faint
footfall, the rustling of paper these slight noises have in
many cases produced sudden trains of alpha waves, when
loud noises and bright lights brought no response from a
THE ADVANCING FRONT OF SCIENCE
sleeper. "We are inclined to believe that the starting of
trains by sound is not a direct result of the sound stimulus,
but is connected with a change in the normal level of brain
activity/ 1 report Loomis and his associates.
When brain waves are being received from two different
areas of the head, from a back area and a front area, for
example, each may send pulsations of a quite different order.
There may be spindles coming from tfie back brain and
none from the front, or there may be spindles from both
but with no correlation in time or wave length, or the pat-
terns from each may be entirely random in an individual
way. But if a sudden noise disturbs the sleeper, the sound
of a voice or the closing of a door, instantly the pattern
from both areas changes to trains. Tests show that these
noises which initiate trains in a sleeping person have no
effect on his wave pattern when he is awake.
Insomnia victims, who find that when they try to make
their surroundings very quiet their difficulties increase, may
perhaps derive a helpful clue from these experiments. The
more quiet a bedroom is the greater is the likelihood for a
sleeping person to hear slight noises, footfalls, whispered
conversation. But if the bedroom is subject to a constant
loud noise of a soothing nature, such as the throb of an
ocean liner, the sleeper cannot hear the faint human sounds,
and so rests undisturbed. Experiments indicate that the
electrical wave patterns are much less disturbed under the
latter condition.
Suppose you hypnotize a person. Will his brain waves
be those of sleep or of wakefulness ? DavidjSlight of McGill
University brought a man to the Loomis Laboratory for
this test. His electrograms were recorded awake and during
normal sleep, and showed characteristic and different pat-
terns for each condition. Then Dr. Slight hypnotized him.
A sustained condition of cataleptic rigidity ensued. He ,
appeared to be sleeping. And yet, the trains of alpha waves \
characteristic of the man awake remained throughout the ]
[298]
CHEMISTRY AND THINKING
hypnosis. At no time did any spindles or random waves
'appear. It would seem that the hypnotic state is not sleep,
if brain waves may be taken as a criterion.
5
But science is just beginning its exploration of this field,
and present discussion of brain waves can be little more
than an enumeration of interesting phenomena. The results
are so many-sided one might say, so heterogeneous that
as yet the laws of mental activity which these changing
electrical potentials obey are unknown. The thing that
impresses all investigators is the ceaseless continuity of the
activity. This was not expected. "Many of us/' as Hallowell
Davis recently expressed it, "have thought of the nervous
system as a great silent network of neurons activated only
in response to sensory stimulation. We must now enlarge our
thinking by assuming a constant background of preexisting,
and probably spontaneous, activity."
What is this activity? Apparently the effect that is
caught by the electrodes and transmitted through the wires
is an overflow from a ceaseless interchange of electrical
energy generated in the brain cells. The main activity is
within. The delicate apparatus picks up only the fragments
that spill over from this vast hookup of billions of living
chemical batteries. It seems reasonable to assume that co-
incidences occur in the electrical discharge of these cells.
Perhaps thousands or even millions discharge simultane-
ously many times each second, and their coincidences ap-
pear in our detectors and recorders as a pattern of waves.
The increase or decrease in the number of cells thus coin-
ciding in their electrical activity may be the factor that
determines the changes in frequency and wave length, the
disappearance and the recurrence, of the waves.
Whatever their origin, it can hardly be doubted that
waves may reveal changes in the mental state of the indi-
THE ADVANCING FRONT OF SCIENCE
vidual. F. A^Gibbs and his associates at the Harvard
.. n * ""' r
Medical School have studied many cases of victims of
epilepsy, and they find that certain types of brain waves
are associated with epileptic seizures, and that in many
cases preliminary waves appear to signal the onset of a
seizure in advance of any other outward sign. Moreover,
somewhat similar changes of wave pattern can be artificially
stimulated. Dr. Gibbs had twelve men breathe pure nitro-
gen to the point of unconsciousness, and the brain waves
they gave off during their ordeal were in general of a type
similar to those characteristic of certain epileptics. Four
other subjects agreed to a treatment which lowers the blood
pressure to the extent that blood is unable to reach the
brain in normal volume; and again, their changes in wave
pattern roughly suggested those of an epileptic. A final
test, in which ten subjects overventilated their lungs with
air, a procedure which depletes the blood of carbon dioxide,
gave similar results. And the interesting sequel is that when
ten epileptic patients volunteered for these tests, and were
subjected to a nitrogen atmosphere, to a condition of
lowered blood pressure, and of overventilation of the lungs,
usually the artificially induced condition brought on an
eplileptic seizure with its typical waves.
Are brain waves something individual, characteristic of
each person like his face or his voice? Hallowell Davis
thinks they may be, and is now in the thick of an exciting
exploration of this question at the Harvard Medical School.
He has found it possible to classify the alpha waves into
four general types, and he observes that while the pattern
'varies from individual to individual, it is fairly constant
for each. That is to say, John Brown's rhythm is different
from Jack Robinson's, but under the same standard condi-
tions Brown's alpha waves always show the same dis-
tinguishing features, and similarly Robinson's are standard
for Robinson. Dr. Davis, in collaboration with his wife
Pauline Davis, has repeatedly recorded the electrical pat-
[300]
CHEMISTRY AND THINKING
terns of thirty-five persons, and thus far they have found
no exception to this suspected rule.
Moreover, they have recorded the electrical wave pat-
terns of eight pairs of identical twins, ranging in age from
eighteen years to fifty-eight. One pair had a very strongly
dominant alpha rhythm, another pair showed no rhythm,
and between these extremes the other six pairs showed many
variations of wave form which Dr. Davis was able to classify
under his four general types. But in every one of these
peases both members of the pair showed the same rhythm.
The fastest alpha rhythm that these investigators have
ever recorded thirteen vibrations a second was found in
one pair of identical twins, and both twins had it. On the
other hand, brothers and sisters who are not identical twins
do not always show the same pattern. The evidence suggests
that the alpha rhythm reveals inborn characteristics of
brain organization qualities which may be hereditary.
It is all very exciting, very fascinating, and as yet very
tantalizing. "Here is a key fashioned by physiology out of
radio," said the Davises in a report to the Harvard Ter-
centenary Conference. "Has neurology a lock which the
key can open ?"
There is another key, an older one, which physiology
stumbled upon in chemistry: a marvelously sensitive con-
trol centered in the endocrine glands. Not only are the
popeyed comedian, the bearded woman, the dwarf, the
giant, and the fat lady of the circus victims of defective
endocrines; but also many mental cases, the feeble-minded,
the idiot, the pervert, and, some may wish to add, the
crank and the genius, appear to be among the casualties of
abnormal flows of hormones. The human body has seven
ductless glands, or seven sets of them: (i) the pineal, hid-
den in the brain; (2) the two-lobed pituitary, also in the
head at the base of the brain; (3) the thyroid, in the throat,
THE ADVANCING FRONT OF SCIENCE
touched on either side by (4) the parathyroids, four in
number; (5) the pancreas, adjoining the stomach; (6) the
two adrenals, close to the kidneys; and (7) the two gonads.
Of these seven, all but the first and the fifth have given
evidence of being connected with mental states.
I am using the term mental states to cover a wide range
of behavior. It would be simpler if we could restrict dis-
cussion to the consciously directed efforts of the brain, and
consider only such intellectual operations as were tested
by the Benedicts in the metabolism experiments. But the
mind not only thinks, it also feels. It is rational, but also
emotional. Somehow there are generated or received in the
brain the feelings of rage, fear, hate, love, and the rest.
Each of these emotions may be curbed by thoughts which
also are formed or received in the brain, or, contrarily,
each may veto reason and take the helm. It is a matter
of common observation that the second alternative is the
more frequent occurrence. *
Michael I. Pupin once asked Foster Kennedy if the medi-
cal men had yet found the part of the brain which governs
emotion. Dr. Kennedy, as he told the story 1 in a recent
lecture at the New York Academy of Medicine, surprised
the physicist by answering, "Yes, in the hypothalamus."
"Ah, but can you pull the switch ?" inquired Pupin.
"No," replied the Cornell neurologist, "but another
hundred years of peace, and we will be able to! And then
the governments of the Earth will establish switching posts
throughout all countries, and there will be a great Day,
when mankind will come to be switched into happiness.
But," continued Dr. Kennedy, "there will be one man in
perhaps every two hundred million who will hang back
in uncertainty and discontent. Six months after the switch-
*Thi$ account is from Dr. Kennedy's lecture "The Organic Background of
Mind" which forms a chapter in the book Medicine and Mankind^ edited by lago
Galdston (1936).
[302]
CHEMISTRY AND THINKING
ing, these doubting Thomases will together be lords of the
Earth; but six months later still they will have found there
is no Earth worth being lords of for their subjects will
not work, they will be only shepherds of sheep. And to make
man once more discontented and human, the lords of the
Earth will take all the doctors and load them into scows
and tow them into the middle of the Atlantic and sink
It was Walter B. Cannon and his collaborators who
showed the importance of the hypothalamus for emotional
reactions. Dr. Cannon further demonstrated that this
ancient part of the brain it can be traced through fossil
fish for a thousand million years operates in close associa-
tion with the adrenal glands. Suppose an animal sees or
hears something which angers him, or frightens him it
makes no difference which, for in either event the thalamus
responds the same. It sends a series of impulses through
the nervous system. When this excitation reaches the ad-
renals, the medulla of these glands discharges a hormone
into the blood stream, the substance we know as adrenalin.
When particles of this adrenalin, carried through arteries
and veins, reach the liver they cause it to release into the
blood some of its stored-up sugar. Thus the animal, be he
man or fish, is swiftly provided with the extra fuel needed
for fighting or fleeing. Whether he stays and faces the foe,
or runs to fight another day, he will need energy and by
such means the body has keyed its chemical mechanism to
supply the fuel at an instant's notice. But the same effect
may be attained artificially. The injection of adrenalin into
a placid animal or man will induce these same bodily
changes, including an ill-defined emotional state. As before
the liver will release sugar; the blood through changes of its
pressure will be partly withdrawn from the skin and diges-
tive organs and be sent in greater volume to muscles and
brain.
I 303 1
THE ADVANCING FRONT OF SCIENCE
A dramatic example of this chemico-mental sequence in
action was related by James Bertram Collip, the Canadian
biochemist and former coworker with Banting in insulin
research. It seems that a diabetic patient took an overdose
of insulin, and did not discover his condition until he was
walking on the street. Too much insulin depletes the blood
of its normal sugar content, and the brain, which must
have its fuel, cannot long endure the short rations. The
consequences are faintness, incoherence of speech, a con-
vulsive seizure, eventually unconsciousness. Most diabetics
carry a bit of sweet in their pockets, and a nibble will soon
restore the blood equilibrium. When this person of Dr.
Collip's story felt himself getting dizzy he hurried to a
near-by drugstore to buy a bar of sweet chocolate, but
arrived in such a wobbly state that he was unable to make
his wants known. The clerk supposed the fellow was drunk,
and threw him out of the store. This act enraged the choco-
late seeker. His rage got in its work; his adrenals poured
adrenalin into the blood, the adrenalin activated his liver
to release sugar, and thus resugared the gentleman re-
gained control sufficiently to proceed to another drugstore
and make his purchase. 1
As the adrenals serve the emotions through their control
of sugar, so in their ways the parathyroids seem to serve
by their control of the calcium content of the blood. Too
much calcium may result in a hyperexcitable state of the
nervous system, together with the muscular rigidity asso-
ciated with tetany; too little has been known on occasions
to bring on languor and mental torpidity. Dr. Collip told
of a patient in a stupor who could be roused only with
difficulty and whose speech was incoherent. Test showed
that his blood calcium was only half the normal amount.
Appropriate hormonal treatment was given, and "his
1 Our story would be incomplete if I did not add that the nervous system can
bring about equally well all these emergency reactions, releasing blood sugar
and changing the blood pressure, without calling upon the adrenals. The adrenals
provide reserve equipment, to reinforce the nervous system when necesiaiy.
[304]
CHEMISTRY AND THINKING
rapid return to normal, both mentally and physically,
was truly remarkable."
The gonads, or sex glands, are the manufactories of
hormones which exercise profound control over mental
states. "The contrast between a virile dominating person-
ality and that of a weak whining emasculate is all-illumi-
nating/' as R. G. Hoskins points out in his book The Tides
of Life. The late Sir Frederick Mott and others traced an
apparent parallelism between dementia praecox and defi-
ciency of this hormone. Indeed there are cases on record
in which patients suffering from this mental disease showed
marked improvement following medication with the missing
hormone but it is also true that many improved without
the treatment. "Altogether," concludes Hoskins, "the re-
lation of the male sex glands to insanity still remains one
of the thousands of unsolved problems in endocrinology."
Perhaps the most clearly defined and broadly inclusive
control of mental states by endocrine secretion is that
identified with the thyroid gland. Children born with de-
fective thyroid equipment show defective intelligence; the
extreme consequence is the form of idiocy known as cre-
tinism. When the thyroid output becomes impaired in
adult life, the victim's mental activity slows down, initia-
tive wanes, concentration and consecutive thought become
impossible. Excessive functioning of the thyroid also is a
disease: here the patient is irritable, restless, sometimes
obsessed by pathological fears, sometimes swept by hysteria.
One of the triumphs of biochemistry was the attainment
of the thyroid hormone in pure state. In a brilliant research
at the Mayo Clinic, E. C. Kendall isolated a highly active
crystalline derivative. Several years later C. R. Harington,
working at Cambridge University, extracted this product
more efficiently and in its natural form, identified it accu-
rately, and proved its chemical composition by synthesizing
it. Others too had part in this important advance, and today
thyroxin is built up in the laboratory like many other
THE ADVANCING FRONT OF SCIENCE
chemical compounds. To thousands of humans this stuff
of carbon, hydrogen, oxygen, nitrogen, and iodine has been
a true elixir of life, and, what is more important, of sane
balanced life. "Not the magic wand of Prospero or the
brave kiss of the daughter of Hippocrates ever effected
such a change as that which we are now enabled to make
in these unfortunate victims," said Sir William Osier, re-
ferring to the baby victims of thyroid deficiency, "doomed
heretofore to live in hopeless imbecility."
But supreme among the hormone producers is the pitui-
tary gland. Indeed, the pituitary appears to be a master
organ which sets the level of life for the other glands. It is
known that the front lobe of the pituitary secretes hormones
which serve as messengers to the thyroid, the gonads, and
the adrenals, and thereby control their growth and direct
their functioning. It is difficult to separate the direct physio-
logical consequences of pituitary defects from those result-
ing from the failure of the other glands which in turn are
dependent on pituitary control, but there are diseases which
appear to be in the former category. The form of giantism
known as agromalgy has been traced to an overactivity of
the pituitary. Its victims may show marked mental dis-
turbances and personality changes, ranging from melan-
cholia to manic-depressive insanity and that curious disease
of split personality known as schizophrenia. Collip deprived
a wolfhound puppy of its pituitary gland. At once it be-
came extremely stupid and timid, and continued so for
months. Then he began to treat the animal daily with a
pituitary extract, and within a few days it had become
bold, aggressive, inquisitive, quite like a normal dog of its
breed.
Nor is courage the only moral quality that seems to get
its stamp from this distinctive lobe of tissue. Perhaps mother
love, the solicitous care of the parent for its child, the home-
making and nest-building instinct, also derives from a
minute chemical activator which is fashioned here. Oscar
CHEMISTRY AND THINKING
Riddle has discovered that a remarkable influence does issue
from the front lobe of the pituitary gland, a hormone which
he named prolactin.
Recently, in his laboratory at the Carnegie Institution's
Station for Experimental Evolution, I watched Dr. Riddle
perform an experiment. He reached into a cage in which
a mother rat was nursing her seven youngsters, and took
out three of the baby rats. There were rows of many other
cages, each containing a rat and labeled with a card which
noted essential data of its occupant. Some of the rats were
lacking in thyroid glands, some in pituitary, some in other
organs; some were males, some females. Dr. Riddle selected
three cages at random, and placed one infant in each. Then
we stood back in the shadow and watched.
In one cage the rat gave no attention, hardly a glance,
to the helpless babe. In another the occupant immediately
approached the little fellow, smelled it, and passed on, not
interested. In the third the rat showed immediate interest,
nosed the baby for several seconds, then picked it up hur-
riedly, carried it to the nest, and cuddled it solicitously.
Now the extraordinary fact is that this third rat was a
male, and the other two were females. Ordinarily males
show no solicitude for the young, not even for those of their
own household. But this male had been injected with pro-
lactin, and the hormone so dominated him that character-
istic maleness was overruled to conform to the maternal
behavior decreed by prolactin. Half a dozen other rats
were tried in the same way, and the results were similar.
The rats being treated with prolactin were interested and
solicitous; those in which the hormone had not been in-
jected were indifferent.
Dr. Riddle and Robert W. Bates prepared this hormone
from the pituitary glands of cattle, and found that it ex-
cites mammary glands to produce milk. Hence the name.
Later it was demonstrated that the hormone affects nerve
tissue as well, inducing a brooding instinct in fowls and
[307]
THE ADVANCING FRONT OF SCIENCE
parental solicitude in rats. After treatment with prolactin,
virgin rats build nests over young and care for their adopted
little ones. If there are no baby rats available, they will take
baby mice as wards, or even newly hatched pigeon squabs.
And herein appears a mighty reversal of instinct, since
under normal conditions a baby pigeon is the natural
prey and food of a healthy rat. No change in human nature
could be more radical than this demonstrated change in rat
nature.
A curious interrelation which Riddle observed is that
full effects of prolactin depend upon a previous action of
the two gonadal hormones acting in a fixed sequence. "Thus
we here find I believe for the first time in the psychic
sphere a normal development of response which rests
upon a succession or chain of normal actions. "
7
Assuredly much more than sugar and oxygen are required
to sustain the competent brain. Possibly there are sequences
of control yet to be uncovered, versatilities in hormone
activation which we do not suspect today. The fact that
the injection of minute quantities of thyroxin, a chemical
compounded in the laboratory, can transform a child from
a gaping idiot into a rational human being, is powerful
evidence for the chemical foundation of mind. We may
paraphrase and extend: Without that sugar and oxygen
and thyroxin and other essential hormones there could
be no thought, no sweet sonnets of Shakespeare, no joy,
and no sorrow.
Very very minute are the quantities of endocrine sub-
stances that serve the body; this fact emphasizes the po-
tency of the chemical control. The electrical potentials
of the brain, as they are detected by the electroencephalo-
graph, are tiny millionths of a volt. Half a peanut supplies
the extra energy for an hour of mental effort but relatively
that is colossal. The hormones that ride the blood stream
[308]
CHEMISTRY AND THINKING
on their merciful errands of binding and loosing are vanish-
ingly small portions of matter. One fourth of a grain of
thyroxin suffices for the entire human body.
To have detected that dilution, to have isolated its mole-
cule, weighed it, broken it down into its atoms, and then
built the thing anew in a test tube, is a demonstration of
the adeptness and sureness of our modern techniques.
Similar feats are occurring all along the biochemical front
today. They strengthen our faith that the chemist of the
future will be one of the chief allies of the neurologist, and,
perhaps, of the psychiatrist.
[309]
Chapter XVI -CAN WE LIVE
LONGER?
Man will never conquer death. For death is an essential
characteristic of our self. But he will not tire of seeking
youth. Medicine and hygiene have already considerably
reduced the number of premature deaths. . . . Some
day, almost every individual may reach senescence, and
die of old age. Can we progress farther?
ALEXIS CARREL, THE MYSTERY OF DEATH
IN the Athenian Mercury -, that curious weekly miscellany
of questions and answers published in London in the
seventeenth century, I came upon this query propounded
by a reader 247 years ago: "Whether may a Man preserve
his life to extreme old Age, without diminishing of his
Senses, or interruption of Health, either by Pains or
Sickness ?"
"It's reasonable in the Theory/' answered the editor,
"but difficult in the Practice Part to obtain such an immor-
talizing Quintessence to preserve or renovate all sorts of
Persons." A list of prescriptions follows: the use of diets,
consultation of the herbal, the resort to astrology, reading
of the stoics, partaking of milk from the rays of the Moon,
or a golden elixir from the rays of the Sun, or a broth brewed
of the influence of the stars medicines difficult to procure,
the candid editor admits, but "that there are such Medi-
cines is out of Controversy true."
CAN WE LIVE LONGER?
Through the centuries has run a persevering faith in the
belief that "there are such Medicines." Perhaps most of
it is wishful thinking, aided and abetted by the wiles of
quacks, but honest science also has encouraged the idea
that the years of a man's life are not necessarily limited
to the psalmist's formula of threescore and ten. From early
philosophers, down through astrologers and alchemists, the
idea has come at last to the test of the research laboratory
which calmly experiments. Here chemists, physiologists,
endocrinologists, and other biological adventurers are try-
ing various arts and medicinals to see if they can add any
days, months, or years of lucid flame to life's brief candle.
Candles and men are subject to accident and may be
snuffed out. Both are subject to the laws of thermodynamics
and, even if no accidents befall, they burn out. The acci-
dents to which human bodies are liable range all the way
from encounters with automobiles to encounters with
germs. If an elephant tramples a child we list the cause of
death as accidental. If that same child should escape the
elephant and encounter a bacterium, and die in a paroxysm
of choking, the cause might be recorded as diphtheria but
actually the attack of the invisible microbe is no less acci-
dental than the attack of the massive elephant. Both are
external, both are elements of the environment which by
chance happen to make contact with the child, and both
extinguish a living flame which but for their presence
would continue. In this view we may class all contagious
diseases, all those biological disturbances which are com-
municated by a bacillus, a virus, or other agent, as
accidents.
Germs and other carriers communicate disease to organs
which are open to contact with the external world. At least,
these first-to-be-encountered systems would be the ones
most liable to attack. I refer to such as the lungs and other
organs of respiration (in continuous contact with air from
outside), the digestive organs, and others. At Johns Hop-
THE ADVANCING FRONT OF SCIENCE
kins University, where for many years Raymond Pearl and
his associates have been making a systematic study of the
records of human longevity, Dr. Pearl uses a scheme for
classifying the parts of the body into two groups: first,
those organs which are exposed to external contacts, and
second, those like the heart, arteries, and veins, which are
closed systems and normally have no outside contacts.
Recently Dr. Pearl took the records of the 5,985,833 deaths
which are registered as occurring in the United States dur-
ing the five years 1923 to 1927, classified the causes of death
in terms of the organs which were diseased, and found this
suggestive comparison:
Diseases of organs of the first group were responsible for
most of the deaths which occurred between the ages of
twenty and twenty-four years, and, to a lesser extent, for
most of those occurring up to age forty-five; whereas
Diseases of organs of the second group were responsible for
most of the deaths which occurred after age yxty-five, and
particularly at age ninety and beyond. (There were 85,-
039 deaths at ninety and beyond, sufficient to provide a
fair statistical sampling of extreme old age.)
In short, it appears from this analysis that most of these
young people in their twenties and thirties, and those whose
lives were just beginning at forty, died of diseases of organs
exposed to contacts with the outer world presumably a
considerable proportion were victims of chance encounters
with germs and other accidents; while the ninety-year-olds,
with stronger constitutions or greater immunity or better
luck, resisted these external foes only to die at last from
failure within.
The crucial task in the study of aging is to determine the
nature of this failure within.
Do organs irrevocably wear out, overuse their inborn
capacity to endure, eventually exhaust their resources in
some such inevitable sense as the candle burns up its store
of hydrocarbons in the wax ?
CAN WE LIVE LONGER?
Or, is organic failure itself an accident, the result of
conditions that might be remedied if we knew their causes
or perhaps a consequence of burdensome accumulations
in the body mechanism which might be avoided, or of
neglect of repairs which might be self-corrected if the body
were continuously provided with repair material ?
These questions suggest two radically different theories
of the aging process. If the second alternative be true, it
seems reasonable to expect that a life might be indefinitely
prolonged by supplying the body with the necessary where-
withal assuming, of course, that we can discover what
that prime essential is. But even if it should turn out a false
clue and we are left with only the first alternative, we still
may inquire whether by any means the inborn capacity
to endure may not be utilized more effectively, be hus-
banded, rationed, made to last longer, and so be stretched
over a greater span of years.
The experiments with which investigators are pursuing
these questions are necessarily limited to the lower organ-
isms. It would be more convincing to have a demonstra-
tion made on human subjects, but men and women are
not available as laboratory material for tampering with
the life span. And so the researchers turn to creatures more
amenable to their disciplines. They try out their theories
in carefully controlled experiments with rabbits, rats, fish,
fruit flies, even the lowly water fleas and the nerveless
cantaloupe plants, as samples of the living fire which glows
also in the sacred frame of man.
That there is an inherent constitutional endowment, an
inborn capacity for longevity, has long been accepted on
the evidence of human statistics. Family histories show that
nonagenerians are usually the descendants of long-lived
parents and grandparents. And experiments indicate that
the capacity for longevity is handed down from parents to
THE ADVANCING FRONT OF SCIENCE
children with a mathematical precision corresponding to
that with which eye color, hair texture, and other physical
characteristics are transmitted in the hidden chains of
heredity.
Dr. Pearl established this by a series of experiments with
the fruit fly. Starting with a single pair of flies as the se-
lected ancestors of his stock, and following their progeny
through many generations, he obtained the life histories
of thousands of individuals. As each generation emerged
from its pupa state (corresponding to birth) he noted the
date, transferred all members of the new generation to a
new bottle plenteously provisioned with an agreeable
banana mash and surrounded by the optimum conditions of
air, temperature, and humidity, and awaited their mor-
tality. Some died young, some lived to middle age, a few
survived to old age and it was found that in general a
fruit fly lives about as many days as a man lives years.
Thus, a forty-day-old fly corresponds in maturity of its
life to a forty-year-old man in human life. A ninety-day-
old fly is an extremely elderly individual, usually decrepit
and feeble.
Among the thousands of individual insects studied in
this way there were many of abnormal physiques. They are
what the geneticist calls mutants, i.e., changelings or sports.
And among the several known types of sports there is one
whose distinguishing characteristic is a dwarfing of the
wings. The tiny wings look like mere vestiges of the long,
broad, overlaid, transparent wings of the normal flies;
therefore flies of this mutant type are known as " vestigials."
Geneticists had observed previously that they are less ro-
bust than flies of the normal type and have a higher death
rate, and Pearl's studies now provided an accurate life
table. He found that on the average the vestigial flies live
less than a third as long as the normal flies.
The next step was to take a female of the normal strain
and mate her with a male of the vestigial strain. Some of the
[3141
CAN WE LIVE LONGER?
descendants of this crossing were short-lived vestigials and
some were long-lived normals, and the distribution of the
two types in each generation followed closely the ratios
called for by Mendel's laws of inheritance. In repeated
trials and variations of this experiment, Pearl showed that
the life span is related to constitutional organization that
what is in the egg, the minute arrangement of its genes or
protoplasmic units, decrees not only that the fly hatched
from that egg shall have dwarfed wings but also that it
shall have dwarfed days.
Prior to this work at Johns Hopkins, two biologists of the
Rockefeller Institute had observed another line of results
from a different series of experiments. Here Jacques Loeb
and John H. Northrop were interested in observing the
effect of heat on duration of life. They took a number of
newly laid eggs of fruit flies, divided them into several
groups, and placed each group of eggs in a glass flask plugged
with cotton. Every precaution had been taken to guard
the experiment against infection. The flies from which the
eggs came were aseptic; the flasks and the food within them
were sterilized; all conditions except one were kept the
same, and that single exception was temperature. Each
flask was installed in an incubator held at a different tem-
perature, and the experiment was to see how long the flies
would live in each of these climates.
The results disclosed a close correlation. Flies in the
clime of 3OC. (86F.) lived on the average 21 days; those
in the more temperate zone of 2OC. (68F.) averaged 54
days; and those in the chilly world of ioC. (5OF.) sur-
vived for an average of 177 days.
There were, quite likely, various mutants among these
flies, possibly short-lived individuals along with those con-
stitutionally predisposed to longevity. The significant dis-
closure of the experiment is the progressive order of the
temperature effect. In each case, the colder the climate the
longer was the average duration of life. Heat is used by
[315]
THE ADVANCING FRONT OF SCIENCE
the chemist to speed up reactions in the laboratory, and
apparently heat has a similar accelerating effect on the
chemical reaction which is life.
"If it were possible to reduce the temperature of human
beings, and if the influence of temperature on the duration
of life were the same as that in the fruit fly," wrote Dr.
Loeb, "a reduction of our temperature from (its normal)
37MC. to about i6C. would lengthen the duration of our.
life to that of Methuselah; and if we could keep the tem-
perature of our blood permanently at 7%C. our average
life would (on the same assumption) be lengthened from
threescore and ten to about twenty-three times that
length, i.e., to about nineteen hundred years."
It is difficult to imagine the human longing for life being
satisfied at the cost of the discomfort and inactivity which
refrigeration would entail. But assuming that some persons
would be willing to put up with a hibernating existence, it is
superlatively doubtful, as Dr. Loeb was careful to point out,
that this method of life extension can ever be applied to the
human species. For, unlike insects, reptiles, and other cold-
blooded animals, man does not assume the temperature of
his surroundings. Whether he be in an icehouse or a furnace
room, a living man's body temperature remains fairly
constant around 37C. Whether some means might be
found to induce a state of suspended animation, halt the
metabolic processes, and later start them again, is a ques-
tion that Alexis Carrel discussed in a recent lecture at the
New York Academy of Medicine. He suggested the pos-
sibility that " Animals could be put into storage for certain
periods, brought back to normal existence for other periods,
and permitted in this manner to live for a long time."
Whether the term animals includes man is not specific in
the published form of the lecture.
But temperature is only one of many conditions that
change with environment. Suppose the flies were crowded
into congested communities, what then ? Dr. Pearl arranged
CAN WE LIVE LONGER?
a numerous series of i -ounce bottles, stocked them with
food, and installed various numbers of insects placing
in one group of the bottles 2 flies each, in another 5, in
another 10, and so on, increasing the population each time
until in the last vials he installed colonies of 500 each. The
flies were all the same age, just hatched, and all of the same
normal type, but they died at different rates which varied
with the degree of crowding. Thus, of 1000 flies which
started in bottles with an initial density of 200, half were
dead in 7 days, but of 1000 which started with an initial
density of 35, 45 days elapsed before half the population
had died.
What is this longevity factor which overcrowding may
change and temperature may alter ? Is it an inherent store
of vitality with which each individual is peculiarly endowed
at birth? To question that idea, Pearl placed newborn
flies in bottles without food. This left them entirely on their
own, each individual completely dependent on its inherent
vitality and the flies lived an average of 44 hours. He
repeated the starvation test with flies at different densities
of population but crowding made no difference, for death
came in about 44 hours for all communities at all densities.
He placed flies of the short-lived vestigial strain in one food-
less bottle, and flies of the long-lived normal strain in an-
other but genetic differences gave no advantage now, for
in both groups death came in about 44 hours. Apparently
the inherent vitality of the individual is not the only funda-
mental factor which influences longevity, else the two types
should show marked differences in survival under the
starvation test.
The problem has been further investigated with canta-
loupe seedlings. Carefully selected seeds, all taken from the
same melon, weighed and graded so as to insure equality
of starting conditions, are allowed to absorb all the moisture
they can in a three-days' soaking. Then each seed is laid
on the surface of a gel of agar in a glass tube, and the tube
[3171
THE ADVANCING FRONT OF SCIENCE
is placed in an incubator running 86F. The incubator is
closed and dark within, so no energy of light can reach the
seed and aid its growth. The agar is not nutritious and con-
tains no plant food. It merely provides a medium for the
roots to grow into, and presently the seed sprouts, sends
down a rootlet, pushes up a stem. It grows in a normal way
for several days, developing a considerable root system,
the stem climbing upward in the darkness and carrying
the cotyledons with it, until a maximum growth is attained.
Then the seedling remains without visible change for a
number of days, not growing but still living, with cells
in full turgor, carrying on their normal metabolism: the
seedling is in a state of suspended animation.
All this active period of growth and this quiescent period
of suspended animation are independent of the environ-
ment, speaking nutritionally. Like the fruit flies in the
starvation experiments, the seedlings must live on their
own resources, on whatever was in the seed a the beginning.
Gradually the cotyledons shrivel as their stored-up materials
are more and more exhausted, until a time comes when they
can no longer support even the restrained chemisms of
suspended animation. Then the stem begins to wither with
the onset of death.
For some seedlings death comes earlier than for others,
but for each of them it was found that the total length of
life was directly related to the period of growth. When the
period of growth was long, the period of suspended anima-
tion also was longer than the average. When the period of
growth was short, the period of suspended animation was
shorter, and the seedling hastened to early death. A case
of wasting its substance in riotous living?
This relation of growth to longevity may be tested also
by measuring the amount of carbon dioxide given off by the
plant, since this waste is a direct index to the rate of living.
There were seedlings that lived 14 days, others 15, still
others 16, and it was found practicable to measure the
CAN WE LIVE LONGER?
carbon dioxide produced daily by each of these tiny plants*
The daily output for all was averaged, and this was arbi-
trarily taken as 100 per cent. When the average output for
each of the three groups was reckoned in terms of this
average for all, the carbon dioxide rate showed as follows:
For plants that lived 14 days, 104 per cent
For plants that lived 15 days, 102 per cent
For plants that lived 16 days, 81 per cent
It is not only a notion we have gained from observation
of prodigal sons, but a rather fundamental rule of nature:
the faster a body lives, the shorter will be its life.
But the output of carbon dioxide is not the only indicator
of rate of metabolism. The consumption of oxygen is an-
other index. The consumption of food is yet another and
here we come to a factor that is of great personal interest
and should be directly under man's control.
The subject of diets and their probable influence on
length of life has been a topic of speculation through the
years, both before and since Francis Bacon proclaimed his
generalization: "The cure of diseases requires temporary
medicines, but longevity is to be procured by diets." This
Baconian thesis of more than three centuries ago is engaging
the attention of some of the best thought and skill of the
biochemical laboratories today. And results are beginning
to tell.
At Cornell University, for example, C. M, McCay, W. E.
Dilley, and M. F. Crowell came upon a significant outcome
while making a study of the nutritional needs of brook
trout. It seems that in nature there is a peculiar vitamin
essential to trout life factor " H" it is called. The Cornell
scientists were interested in seeing just what dietary rela-
tionship exists between the level of this H, which supplies
catalyzing agencies for the fish's living processes, and the
THE ADVANCING FRONT OF SCIENCE
level of protein, which supplies calories for its growth.
So they designed a series of diets which were uniformly
deficient in the H factor but of varying protein content
the diet for one group of trout being 10 per cent protein,
that for another group 25 per cent protein, another 50, and
a fourth 75 per cent. The uniform deficiency of H doomed
all the fish to premature death, but the experimenters
wondered if the different amounts of protein would have
any effect.
It was known that food containing less than 14 per cent
protein is insufficient to provide the fuel necessary for
growth, though it will sustain life if all other essentials are
present. The experiment confirmed this. For the group
whose diet contained only 10 per cent protein did not grow
another perceptible gram, whereas the fish in the other
three groups all grew, and, despite their varying rations
of protein, all grew at the same rate. Also they all died at
about the same rate, in 12 weeks. But the >rout in the first
group, those that had failed to grow, lived on the average
twice as long. These results suggest that there is, to quote
Dr. McCay, "something consumed in growth that is essen-
tial for the maintenance of life." He and his associates re-
solved to investigate that "something" and uncover its
effects in a higher order of animals.
They chose as the subject for their new inquiry the white
rat. Perhaps no other animal has been so variously experi-
mented upon, and of hardly any creature below man is
there so much factual knowledge of its biological nature.
The nutritional requirements of the rat are similar to those
of man; therefore for food experiments a colony of rats sub-
stitute very well for a colony of human beings, and with
advantageous economy both of provisions and of time.
The rat experiments at Cornell were conducted jointly by
McCay, L. A. Maynard, and Crowell. They took 106 baby
rats, born of parents closely akin genetically and, therefore,
presumably of the same general heredity, and as soon as
the animals were weaned divided them into three groups.
I 3*0]
CAN WE LIVE LONGER?
Group I, consisting of 14 males and 22 females, were
provided with a completely balanced diet containing also
extra calories to sustain rapid growth, and were fed this
rich food throughout their lives* Before 1200 days had
passed all were dead.
Group II, 13 males and 23 females, were provided with
meager portions of the same diet. On these spare rations
they grew very slowly but showed a capacity for growth at
practically all ages. After 28 months of this parsimonious
feeding they were placed on the abundant fare of Group
I and throughout the rest of their lives were free to eat all
they desired. After 1200 days of the experiment, 8 of this
group were still alive.
Group III, 15 males and 19 females, were fed abundantly
for the first 2 weeks, the same as Group I. Thereafter they
were restricted to the short allowance of Group II until
28 months had passed, when all were put back on full help-
ings and permitted to feast at will. After 1200 days 5 were
still alive.
In all three groups some individuals died early, some in
middle life, and, as is true of human society, more females
than males survived to old age. The oldest male lived 1321
days, the oldest female 1421 days, and both were of Group
II. When all results were averaged for each group, they gave
these values :
Average span of life
Males
Females
Group I
483 days
820 days
894 days
80 1 days
775 <*ays
826 days
Group II
Group III
The tabulation shows that the male rats whose early
growth had been retarded lived nearly twice as long as
those that had known no restraint. For the females the
averages are not conclusive. Ordinarily they have a life
[321]
THE ADVANCING FRONT OF SCIENCE
expectancy about 10 per cent greater than that of males:
but why the females of Group I should outlast the males
of the same group by almost another lifetime seems inex-
plicable. The low average for the females of Group II may
possibly be accounted for by the death of two young lady
rodents during a spell of hot weather early in the experi-
ment, and these premature losses distort the data. But de-
spite the relatively low average of the females of Group II,
5 of them were alive after all of Group I had died.
In general the full data strongly suggest the presence in
Groups II and III of some factor which tended to promote
longevity and whose effect was more marked with males
than with females. Nor is the number of days the only
index to the operation of this unknown factor. Age for age,
the rats of the retarded groups looked younger than those
of the group that had matured rapidly. Their fur remained
soft, silky, and thick well into the third year, in striking
contrast with the coarse, unkempt, scraggy hair of the
equally aged animals of Group I.
These results seem in accord with Pearl's findings from
the cantaloupe seedlings. Further confirmation is lent by a
series of investigations lately reported from Brown Uni-
versity. Here Lester Ingle and Arthur M. Banta have been
experimenting with the large water fleas known as daphnia
really not fleas, but a species of small crustacean. They
find that when these creatures are fed full rations of food
throughout their lives from birth to death their average
life span is about 29 days; whereas those fed half rations
for the first 14 days, and thereafter given full fare, live
about 50 per cent longer to an average span of 42 days.
A regimen of frugal eating would appear to be a funda-
mental requisite for long life if we are to take at their face
value the results of these ingenious trials of cantaloupe
plants, water fleas, and white rats.
The Cornell experimenters do not regard their search as
concluded. They are pushing forward with a new program
CAN WE LIVE LONGER?
in which they plan to repeat the experiments, using larger
colonies of rats, and also at the same time to pursue some
promising bypaths which their earlier studies opened. For
example: post-mortem examination of the hearts, livers,
bones, and other internal organs of the subjects of their
former experiments showed certain changes following the
limited diets. The new study will seek the meaning of these
changes whether any of them have to do with the retention
of physical and mental vigor into old age. Another bypath
to be explored is an inquiry into the value of physical ex-
ercise whether exercise after middle life hastens or delays
senile changes. For the complete program of old-age re-
search a 6-year schedule, already begun in 1936, has been
laid out.
3
Meanwhile, at Columbia University, Henry C. Sherman
and his associate Harriet L. Campbell have been investigat-
ing dietary effects to determine the ingredients of food that
contribute to length of life. They have found unmistakable
evidence that calcium is a factor, and Vitamins A and G
are also indicated as probable factors. The experiments
are still under way, but the results already attained are so
convincing to Dr. Sherman that he is applying them in his
own eating. He believes that by including in the daily
diet of a lifetime a liberal allowance of food rich in calcium
and in the two vitamins, 6 or 7 years may be added to
"the period of the prime."
This Columbia work grew out of an investigation begun
in 1918, when the shortage caused by the World War made
it important to know what food combinations would stretch
farthest without risk of undernourishment. Specifically,
Sherman took the two most common foodstuffs, wheat and
milk, and undertook to find what is the smallest proportion
of milk that will supplement wheat to form a nutritionally
adequate diet. He used hundreds of white rats for the test,
[3*3]
THE ADVANCING FRONT OF SCIENCE
feeding each group a different combination of milk and
wheat, allowing all to eat at will and as much as they
pleased, and then watched the course of their health and
general vitality under these different feeds.
Diet A consisted of five-sixths ground whole wheat
mixed with one-sixth dried whole milk. Diet B contained
twice as much milk, the proportions here being four-
sixths and two-sixths. It was found that diet A supported
normal growth and health, that it was adequate, therefore
a permissible diet; but that diet B gave an even higher
average result. When he tested this higher average further
in terms of length of life, Sherman found that the animals
on diet B lived about 10 per cent longer than those on
diet A.
Why?
The explanation must lie in the milk, since the only
difference between the two diets was in the proportions.
The problem became one of identifying th^ component of
milk that carries the longevity promoter.
Milk is a fluid of exceeding complexity. It embodies
proteins, carbohydrates, fats, all the known vitamins, and
several mineral elements. Any complete analysis of this
complicated mixture, and trial of its substances one by
one, would be an almost interminable task. But there are
certain ingredients that are prominent or that for various
biochemical reasons may be considered suspect, and the
Columbia chemist went after them first. Calcium, for
example, the well-known metallic constituent of lime which
is necessary to bone building, is a prominent constituent
of milk. Dr. Sherman took diet A, with its five-sixth wheat
and one-sixth milk, and added to it a carefully measured
quantity of lime a quantity just sufficient to provide the
calcium that would be carried by an additional one-sixth
of milk. Thus he attained a combination that was diet A
in all ingredients but one: in calcium content it was the
same as diet B. When he tried this calcium-enriched food
CAN WE LIVE LONGER?
on a large group of rats, feeding a control group on unen-
riched diet A at the same time, he found that the calcium
eaters lived on the average longer than the diet-4 eaters.
Milk is rich also in vitamin A, while wheat contains very
little. Butterfat too is rich in vitamin A; and by adding to
it a measured portion of butterfat, diet A was made as
rich as diet B in vitamin A without introducing the other
significant components of milk. Thus it became practicable
to test the influence of a double portion of vitamin A in
food, and the results gave strong presumptive evidence
that this vitamin is a longevity promoter. By similar
methods, circumstantial evidence was found pointing to
vitamin G as a third agency that contributes to length
of days.
The three longevity factors calcium, vitamin A, and
vitamin G are absent from, or very meagerly present in,
cereals and many other foods. But they are all present in
milk. The two vitamins, and to a lesser extent the calcium,
are present in fresh fruits and vegetables. Dr. Sherman
therefore advises those who aspire to long life to make milk,
fresh fruits, and vegetables important members of their
daily diet. As a practical formula for insuring ample por-
tions of the longevity factors, he suggests that at least
one-fifth of the family food budget be spent on milk and
cream, and not less than one-fifth on fresh fruits and green
vegetables. This leaves three-fifths for meat, bread, butter,
eggs, tea, coffee, and condiments, including all sweets.
Animals on the diet enriched by calcium not only lived
longer, but their rate of growth was more rapid than that
of those on diet A\ while those on the low-calcium diet
grew to maturity more slowly and died earlier a result
which seems quite the opposite of the Cornell result. But
Dr. Sherman doubts if the two sets of experiments are
necessarily in conflict. The starting point of the Cornell
studies was a diet rich in practically all food components,
and especially so in proteins; and the results show that re-
THE ADVANCING FRONT OF SCIENCE
straint is desirable. The starting point of the Columbia ex-
periments was an abstemious diet, a "poor man's fare"
such as most people must live on; and the results show that
certain small improvements in this relatively inexpen-
sive diet have a beneficial effect both on growth and on
longevity.
As a crude analogy we may liken the life cycle to the
path of a projectile launched into space with an initial
propulsion that may send it a certain maximum distance.
But the distance may be shortened by wind resistance.
The initial force is analogous to the genetic constitution or
heredity which imparts momentum to the life and deter-
mines how far it may reach. The loss of momentum through
wind resistance is analogous to the shortening of a life
span by an overrapid rate of living. But, Dr. Sherman
points out, there is another possible element in the picture.
There are some projectiles, torpedoes, and rockets which
are not wholly dependent on the impetus jof the initial
force. They generate additional propulsive power during
flight, and so are able to go farther. We are to think of the
protective foods as supplying additional propulsion, as
neutralizing to some extent the forces of degeneration and
death, and so as prolonging the life cycle.
There is another approach to this problem. We observe
that certain forms of life never grow senile. Leo Loeb has
pointed out that cancer cells may be called immortal,
since they outlive many times the natural life of the mouse
in which they originated and have continued to live through
successive transplantings with every reason to believe that
the sequence may be prolonged indefinitely. The "death-
less" chicken cells at the Rockefeller Institute were twenty-
five years old on January 17, 1937, and I have no doubt
that long after our generation has passed some historian
1326]
CAN WE LIVE LONGER?
will be recording their hundredth anniversary. It is our
complexity that dooms us: the multiplicity of specialized
mechanisms that must be in step, in synchronization, con-
tinually interacting in the complicated teamwork of inter-
dependent organs. Perhaps no one dies of old age; it is the
failure of a gland to secrete an indispensable hormone at a
critical moment, the drying of the tissues, the heightening
of blood pressure, the thickening and hardening of the
arteries. Nor is it only the veterans of eighty and beyond
that are victims of these diseases.
"If we take as our criteria the usual specifications for
old age used by the medical profession arteriosclerosis,
hypertension, tissue dehydration, and the rest we find
that numerous people die of 'old age' anywhere between
forty and one hundred and forty years, " said William
Marias Malisoff. "This indicates either a very unstable
state of affairs, or the wrong definition of old age. On the
first alternative the span of life cannot be said to be 'fixed.'
'On the second, no one can be said to have lived out his
span. There are at least 5000 people in the centenarian
range in the United States. They are evidence that 'cen-
tenariness' is a persistent thing, else it would have bred out
quite thoroughly long ago through intermarriage.
"We look for clues. The outstanding correlation be-
tween a physical characteristic of the body and the age of
the body is a deposition of lipoids in the arteries, notably
in the large aorta. If that is primary, surely we can inter-
fere with old age. If it is secondary, we have many clues
from diseases, such as diabetes, which may put us on the
trail of the primary process, which process in turn probably
depends on a hormonal disturbance or is a hormonal dis-
turbance. Our problem may reduce to one of supplying
hormones or their equivalent. There is increasing evidence
that all hormonal substances eventually will yield to syn-
thesis, either to chemical synthesis in a test tube or to
biological synthesis outside the human body as, for ex-
[327]
THE ADVANCING FRONT OF SCIENCE
ample, adrenalin, insulin, and thyroxin are now being
synthesized. Thus it becomes possible that old age may be
alleviated by supplying the missing factors."
Can that possibility be tested and its probability be de-
termined ? Dr. Malisoff, a physical biochemist working first
at the University of Pennsylvania and now at the Monte-
fiore Hospital in New York, has been studying the problem
of aging from the point of view just outlined. Lipoids are
insoluble substances such as fats and the solid alcohols
known as sterols, and among these sterols is a white mate-
rial which the early chemists found in bile. They named it
"cholesterol," meaning bile solid. Afterward the analysts
identified cholesterol in a variety of animal material. It is
an ingredient of egg yolk, of nerve tissue, and of brain cells,
it clots in certain organs to form gallstones, it deposits on
the eye to form a cataract, and its gradual accumulation
in the wails of the blood vessels is a mark of arteriosclerosis.
Accepting this effect of cholesterol accumulation as one
of the most important indices of what occurs in aging,
Malisoff interprets it as related to a general diminishing
of the oxidation processes of the body. The dumping occurs,
apparently, at points of least resistance. But why does it
occur ? Probably because of the absence of something which
can oxidize cholesterol something which is abundant in
youth but scarce in old age.
Cholesterol is insoluble in water. But Malisoff demon-
strated that by a vibration of sound waves he could cause
a solid mass of cholesterol to break up and become finely
dispersed through the liquid. Later, working with F. A.
Stenbuck, he made a finely dispersed solution of cholesterol
and subjected the mixture to short electric waves, of 5
meters wave length. The effect of these electrical vibrations
pulsing through the solution was to cause a dilution of the
material by about 25 per cent. Apparently the electric
waves caused the particles of cholesterol to cluster, to
coarsen, and thereby to reduce the total surface of material
1 328 j
CAN WE LIVE LONGER?
in solution, giving an effect of dilution. Chemists call this
process "aging." It seems to be well named.
The foregoing studies were made in glass beakers, not in
living material; but in 1936 Malisoff began a series of ex-
periments with rabbits, following a trail that was blazed
in Russia many years ago. There, in the old St. Petersburg,
a physiologist Ignatowski found that when rabbits were
denied their customary vegetable food and made to live
on a diet of eggs, beef, and milk, they developed hardening
of the arteries. Later investigators showed that the meat
and the milk had hardly any effect in this direction, but
that a diet of egg yolks alone would induce the disease
also a diet of brains. Both egg yolk and brains are rich in
cholesterol. Later two other Russian experimenters, Anitsch-
kow and Chalatow, fed straight cholesterol to their rabbits
and found it even more effective in bringing on the arterial
hardening.
An animal accustomed to an herbiverous diet may be ex-
pected to have less adequate means for coping with un-
accustomed ingredients of a carniverous diet, so we are
not to conclude that because yolk-eating rabbits develop
hardening of the arteries yolk-eating men and women
are courting the disease. Not necessarily. The point is
that this experiment provides the research scientist with
a means of inducing the condition of arterial hardening at
will, and thus facilitates inquiries into the nature and cure
of the disease.
It is believed that the thyroid gland is one of the body's
defenses against arteriosclerosis. Two Japanese investi-
gators, Marata and Kataoka, found that thyroid extracts
administered to rabbits were moderately successful in
combating the disease. H. Unger, at the University of
Jerusalem, tried iodine and found that it had a neutralizing
effect on cholesterol accumulation. MalisofPs experiments
at the Montefiore laboratory are an attempt to test and
extend these ideas. He picked at random twelfre young
[3*9]
THE ADVANCING FRONT OF SCIENCE
adult rabbits from a thoroughbred group, and by surgery
deprived each rabbit of its thyroid gland. The rabbits were
allowed to eat their green vegetables and other customary
food at will, but in addition each rabbit was fed daily a
pellet of pure cholesterol, the pellet being wrapped in a
cigarette paper and soaked in sugar to make it palatable.
Thus deprived of their thyroids and dosed with cholesterol,
the rabbits might be expected to develop hardening of the
arteries, unless some defense against the disease were pro-
vided artificially.
The defense which Malisoff had selected to try was the
powerful KCNS, potassium thiocyanate. This compound
is a very effective dispersing agent, is found in body fluids,
and is not poisonous. It operates by furnishing thiocyanate
ions, whose negative charge is important in dispersing
cholesterol. To four of his rabbits Malisoff gave each day
60 milligrams of the thiocyanate; to another four he ad-
ministered the lesser dose of 20 milligrams ^laily; and the
remaining four were fed no thiocyanate, but left on their
own resources entirely, as a control group.
At the end of about 60 days the twelve rabbits were
killed. The four that had received no thiocyanate all showed
very pronounced conditions of arteriosclerosis, with de-
posits of cholesterol both in the aorta and in the kidneys.
The four that had received 20 milligrams of the thiocyanate
showed the disease in a milder form. The four that had
received 60 milligrams of the drug showed no hardening.
Apparently the effective dose for the rabbit lies somewhere
between 20 and 60 milligrams. And the experiments seem
to indicate that potassium thiocyanate exercises a protec-
tive action against the deposition of cholesterol in rabbits.
But rabbits are not men, and their diet is normally quite
different from human diet. So Malisoff is now planning to
push his research into higher levels of life, to try the effect
of the drug on animals nearer to man. Also he is trying other
substances to test his other theory that the cholesterol
1330]
CAN WE LIVE LONGER:
deposition is a consequence of the failure of the body's oxi-
dation processes.
"A theory is only a guide to the searcher," explained Dr.
Malisoff. "This one says to me, 'Look for oxidation pro-
moters, especially of cholesterol/ These promoters, if found,
may help the body to regain its youthful potential, rate,
and quality of oxidation. At any rate, like insulin in a
diabetic, they may help to postpone a showdown for a long
time. The argument will be materially strengthened if the
oxidation products of cholesterol should turn out to be
substances which normally decrease in old age such sub-
stances, for example, as the sex hormones. "
5
The approaches to our problem are many, the methods
are diverse, the results are yet to be correlated. To all our
hopes and encouragements we have to add the qualifica-
tion, not proved; perhaps, with faith, we may say, not yet
proved. Many realists question whether effects which are
demonstrated in lower forms of animals are necessarily
true of man. It may be, though, as Max Rubner suggested
years ago, that length of life is a function of evolution. Dr.
Rubner made a study of the metabolism of a wide range of
organisms, and found a certain ratio existing between the
size and metabolic rate of animals and their characteristic
life span. Thus, for a large group of warm-blooded animals,
including the horse, cow, dog, cat, and guinea pig, he ob-
served that after reaching maturity the animal expended
about 200,000 calories of heat energy for each kilogram of
body substance, and then died. But when he came to man
the ratio was quite different. During an adult human life,
extending from age twenty to age eighty, Rubner reckoned
that 775,000 calories per kilogram of body weight are ex-
pended before the machine gives way. If these calculations
are correct it would seem that man has attained a superior
position in the race with time. If haphazard evolution has
THE ADVANCING FRONT OF SCIENCE
done that much for us, what might be accomplished if man
took the all-important business of evolution into his own
hands ?
A biologist has already considered that question in pub-
lic. I quote from J. B. S. Haldane's Possible Worlds: "In
the rather improbable event of man taking his own evolu-
tion in hand in other words, of improving human nature
as opposed to environment I can see no bounds at all to
his progress. Less than a million years hence the average
man or woman will realize all the possibilities that human
life so far has shown. He or she will never know a minute's
illness. He will be able to think like Newton, to write like
Racine, to paint like Fra Angelico, to compose like Bach.
He will be as incapable of hatred as Saint Francis. And when
death comes, at the end of a life probably measured in
thousands of years, he will meet it with as little fear as
Captain Gates or Arnold von Winkelried. And every minute
of his life will be lived with all the passion*>f a lover or a
discoverer. We can form no idea whatever of the exceptional
men of such a future/'
"Less than a million years" is indefinite and sounds re-
mote, but science has a way of accelerating its fulfillments,
and possibly in our groping experiments today we are laying
the foundations of such a future. In the search for a Methu-
selah formula many clues must be sifted. The aging process
needs to be studied with something of the comprehensive-
ness of the research that has focused on the processes of
growth. Significant are the studies of the physiology of old
age recently carried on at the Nutrition Laboratory in
Boston by Francis G. Benedict and his associates. We
may expect other specialists to explore further the bio-
chemistry and the biophysics of the human body in its
transformations with time, in its sequences from heredity,
in its reactions to vitamins, hormones, and other elixirs.
For "that there are such Medicines is out of Controversy
true."
I 332 1
epilogue -THE PROMISE OF
SCIENCE
Oh science, lift aloud thy voice that stills
The pulse of fear, and through the conscience thrills
Thrills through the conscience with the news of peace
How beautiful thy feet are on the hills I
W. H. MALLOCK, LUCRETIUS ON LIFE AND DEATH
THERE is another sense in which the frontiers of science
and of the sciences are borderlands the sense in which
Petrarch, from the vantage point of the Renaissance, sur-
veyed the human scene. Turning his gaze to the past,
wrapped in its graveclothes of history, he saw the dark ages
of drift and blind struggle, centuries of eclipse and blun-
derous groping when but for the dim torch of learning
kept alive here and there, in monastery, in university, and
in alchemist's cell, it would seem that the human spirit
must have lost its way. And then, looking to the future,
veiled in its mists of destiny, Petrarch glimpsed the aura
of the coming civilization. "Here stand I as though on a
frontier that divides two peoples, looking both to the past
and to the future." And so it may be with us. These border-
lands of research divide more than knowledge from ig-
norance. They can, if man's will and effort are alive to their
opportunity, divide hope from despair, achievement from
frustration, a new humane civilization from the old jungle
of laissez faire.
[333)
THE ADVANCING FRONT OF SCIENCE
As an indicator, compare the treatment of disease today
with the medical practices of our forefathers. In 1732, when
George Washington was born in Virginia,, the average life
expectancy of a baby was about thirty eight years. Today
an infant can look forward to about sixty years. Washing-
ton was luckier than average, for he lived to be nearly
sixty-eight, but even then he seems to have died unneces-
sarily soon. Recently Creighton Barker of the Yale Medical
School examined the records of Washington's last illness
at Mount Vernon, and from all the evidence Dr. Barker
diagnoses the disease as septic sore throat. The former
President had the best medical skill of his day. During the
24 hours of his illness the physicians bled him four times,
thus needlessly weakening him, and Washington died (says
Dr. Barker) of a virulent streptococcus infection. In the
corresponding month of 1936, just 137 years later, a son of
the President of the United States was stricken by the same
disease. The medical men who attended hirfi drained away
none of his blood, but instead fortified it by the injection
of a newly discovered chemical compound, and the young
man rallied to a rapid recovery. The directness and pre-
cision of the 1936 treatment compared with the fumbling
empiricism of the 1799 treatment emphasize the change
which has come in our therapy. They suggest that the
revolution which is reshaping medical science is not merely
a fight against death, but also a fight for life, with all the
implications both economic and social which emerge from
science's successful lengthening of the life span. The society
which fosters research to save human life cannot evade re-
sponsibility for the lives thus extended. Its science must
go farther: not merely conserve life, but conserve living.
Indeed, our techniques are yet in their infancy. What we
know may be as only a few shells picked from the shore
when compared with the vast sea of our ignorance, but
what we know is colossal compared with the knowledge we
have put to use. "The great scientific revolution is still to
[334]
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