Table Of ContentThe Powell and Lealand "No. 1" microscope. This instrument
represented perhaps the height of microscope design and craftsman-
ship in this country during the last century.
The Evolution of the
MICROSCOPE
by
S. BRADBURY, M.A., D.Phil., F.R.M.S.
Fellow of Pembroke College,
Lecturer in Human Anatomy,
University of Oxford
P E RG AM ON P R E SS
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Copyright © 1967
Pergamon Press Ltd.
First edition 1967
Second Impression 1968
Library of Congress Catalog Card No. 67-18485
Printed in Great Britain by Λ. Wheaton & Co. Ltd., Exeter
08 003143 9
To my Parents
In commendation of ye Microscope
Of all the Inventions none there is Surpasses
the Noble Florentine's Dioptrick Glasses
For what a better, fitter guift Could bee
in this World's Aged Luciosity.
To help our Blindnesse so as to devize
a paire of new & Artificial eyes
By whose augmenting power wee now see more
than all the world Has ever doun Before.
HENRY POWERS 1664
PREFACE
OF ALL the instruments used by the scientist, the microscope is perhaps
the one which most aptly symbolizes this profession to the non-
scientist. It is a tool which finds application in research (both in biolo-
gical and non-biological fields), in teaching, and in a multitude of
industrial and other applications. In fact wherever there is need to
supplement the rather mediocre performance of the human eye, and to
make the details in a small object visible, then the microscope in
some form or other will be used. One suspects that very few of the
many users of this instrument are more than vaguely aware of the
interesting stages through which the microscope has passed during
the course of its long development. This present book has been written
in an attempt to present, in a readable form, some of the features
of this history, an acquaintance with which often helps in under-
standing the rationale of the design features found in current
microscopes.
Much more research remains to be carried out into the development
of the microscope. It is strange that such an important symbol of our
technology has hitherto been very largely overlooked by the historians
of science. There are, of course, some notable exceptions to this and I
have drawn to a great extent upon their work. In particular for the
earlier period the History of the Microscope by R. S. Clay and T. H.
Court has been invaluable; much help has also been obtained from the
Cantor Lectures on the microscope delivered by J. Mayall, and from
Harting's classic work Das Mikroskop. Later writings on this subject,
especially those of A. Hughes and E. Frison, have also been extensively
drawn upon. Much of the information concerning the stages in the
development of the electron microscope is taken from the work of
E. Ruska and T. Mulvey.
Many interesting changes may be discerned in the development of
the microscopes used for various specialized purposes, especially in the
physical sciences. The story of the polarizing microscope and the
metallurgical microscope remain to be told at some future date. In
the present book, however, it proved impossible to cover these topics
ix
χ Preface
and do them full justice so that, very reluctantly, it was decided to
restrict the scope to the microscope as used in biology.
It is probable that some factual errors have been perpetuated, for
which I apologize, but whenever possible I have gone back to the ori-
ginal sources, particularly when illustrating a specific point by means
of an actual quotation.
Acknowledgments
I am most grateful to G. L'E. Turner of the Museum of the History
of Science, Oxford for many helpful discussions, and to Alan Todd of
Micro Instruments (Oxford) Ltd. for information on the design
features of current microscope stands. I wish to extend my thanks to
Miss Christine Court who prepared many of the drawings and to the
photographic staff of the Department of Human Anatomy, Oxford for
their willing assistance; I am also indebted to Mrs. G. Fodor who typed
the final manuscript. Last, but by no means least, I wish to express my
thanks to my wife Sheila not only for her forbearance during the writing
of this book but also for reading and correcting the first draft of the
manuscript.
My thanks are due to Messrs. J. A. Churchill Ltd. for permission to
quote extracts from Carpenter and Dallinger's The Microscope and Its
Revelations and for the use of a figure from this work (Fig. 5.15), and
to Dr. S. H. Robinson for permission to quote from his address on
Powell and Lealand to the Lincolnshire Natural History Society. I also
extend my thanks to the following who supplied illustrations and gave
permission for their reproduction: Messrs. A.E.I. Ltd (Figs. 8.6; 8.9;
8.10; 8.12); Messrs. Degenhardt (Fig. 7.7A); Studio Edmark, Oxford
(Fig. 4.12); Messrs. Leitz (Fig. 7.15B); The Museum of the History of
Science, Oxford (Figs 3.1; 4.12); The Royal Microscopical Society
(Figs. 1.11; 1.14; 1.15; 2.11; 3.8; 3.10; 3.12; 4.1; 4.5; 4.8; 4.9; 4.11;
4.14; 5.2; 5.6; 5.7; 5.8; 5.14; 6.2; 6.4); The Science Museum, London
(Figs. 2.5; 2.12; 4.2; 4.10; 5.5); Messrs. Siemens, Germany (Figs. 8.8,
8.11 A & B); The Wellcome Trustees (Fig. 4.3).
CHAPTER 1
THE FIRST MICROSCOPES
PEOPLE are naturally curious about their surroundings. Their bodies
need detailed information about the world around them in order that
they may adapt smoothly to the demands and processes of living. More
important, in human beings the search for information is carried much
further than the bare requirements for existence in order to satisfy our
innate desire to understand the world in which we live. We are pro-
vided with various receptive mechanisms or senses to help gather such
information: of all these senses, the most important by far is that of
sight. It is natural, therefore, that we are constantly using our eyes to
tell us where we are in relation to obstacles, and to provide us with
information about the properties of objects around us. The disabilities
suffered by anyone who is blind, such as the difficulty which they
experience in carrying out simple everyday tasks, the uncertainties
attached to moving around, and the aesthetic losses from which they
suffer, bring home the importance of sight to us very forcibly indeed.
It seems natural, therefore, that when we want detailed information
about some part of our surroundings we first take a very close look at
it. Such visual examinations are normally perfectly adequate for the
day to day processes of living, but we must remember that the visual
gathering of detailed information relating to our surroundings, and the
classification and study of such knowledge forms a large part of the
discipline known as "natural science". For such purposes the human
eye often proves to be a very inadequate tool indeed, excellent though
it may be for the normal needs of existing in our world; this is because
the amount of detail which it can reveal to us is very limited.
From the days of the earliest civilizations, such as those of the Baby-
lonians and the Egyptians, through Greek and Roman times up to the
so-called "Dark Ages" in Europe, scientists and philosophers, astrono-
mers and medical men have all been observing and collating natural
phenomena. Much valuable information was obtained, but the whole
world of structure which was smaller than the limits of resolution of
l
2 The First Microscopes
the sharpest eyes remained completely unknown, though not unsus-
pected. During the Dark Ages serious study was almost at a standstill,
except for the Arabian world, in which the knowledge of the Ancient
scholars was carefully preserved and augmented. When eventually
the writings of the Greeks were translated from Arabic into Latin, the
European scholars tended to spend their time commenting upon them
and attempting to reconcile them with the doctrines of Christianity
and the teachings of the Church. Such attitudes proved distinctly
discouraging both to the observation of the natural world and to ex-
perimental study, although isolated figures such as the Oxford scholar
Roger Bacon proved to be notable exceptions to the rule.
With the European Renaissance in the fifteenth century, scholars
began to revolt against the dogmatic interpretation of the early
writers such as Aristotle and the physician Galen; this change of
intellectual climate proved significant, as it led to the stimulation of
the processes of observation and experiment, which in turn placed
the natural sciences on a sound footing. The development of observation
in science gradually led to a dissatisfaction with the relatively poor
resolution of the naked eye and this paved the way for the development
of optical aids to vision.
The first successes of the new studies were in astronomy and mech-
anics, but there was soon a spread to the biological and medical fields.
One of the landmarks in this latter field was undoubtedly the publi-
cation of the superb anatomical studies of Andreas Vesalius, in 1543,
which were known under the title De humani corporis fabrici. This
work, with its accurate illustrations of structures which can be seen
with the naked eye, refuted many of the doctrines which had been
accepted uncritically since the days of Galen 1300 years before, and
it set the standard and provided the inspiration for the future. Scientists,
such as Gabriele Fallopio, Bartolommeo Eustachii, Francis Glisson,
Thomas Wharton and many others less well known, followed the lead
given by Vesalius and began the detailed study of anatomical structures.
So far, during all the years from the earliest times up to the end of the
sixteenth century, studies of the structure of natural objects had been
performed with the unaided eye. Studies of both objects at great distances
such as the stars, and very minute objects and structural details of larger
objects were limited by the capabilities of the human eye. As more
and more scientists took up such studies the need for supplementing
the human eye became apparent; when the method of combining
lenses to obtain an enlarged image was discovered at the end of the
The First Microscopes 3
sixteenth century its possibilities were rapidly realised. The needs of the
scientists stimulated rapid progress in microscopy and this, in its turn,
gave immense benefits and impetus to the work of the scientists.
Before the development of the microscope in its early days is described
in detail, however, we must see what developments in optics led up
to it, and consider what artificial aids to vision were available up to the
end of the sixteenth century.
It cannot be decided with certainty whether the ancient world was
aware of the magnifying properties of simple convex lenses. From the
writings of the Romans it seems that they knew that such lenses could
converge the sun's rays and act as a burning glass. Indeed, from the
writings of Pliny we have good evidence that this was actually used in
medical practice for the cauterization of wounds, when he says
I find that among doctors it is thought that nothing is better when any
part of a body is to be burned than to use a crystalline sphere placed in
the sun's rays.
Several other sources confirm that the ancient world was aware
of the action of the burning glass, although it is certain that they
did not understand how the phenomenon occurred, as at that time
the laws of refraction of light by a crystalline sphere were not known.
One famous passage which occurs in the writings of Seneca may be
translated as
Letters, however small and indistinct, are seen enlarged and more clearly
through a globe of glass filled with water.
In another chapter of the same work he states that fruit appears larger
if it is floating in water. The conclusion is drawn that as all objects seen
through water appear larger than they are, the enlargement is due to
the water; the geometrical shape of the object containing the water
is not involved in the process. One may conclude that although the
phenomenon of the refraction or bending of light rays on their passage at
an angle from one medium to another had been observed, there was
no conception of the action of a lens-shaped transparent body in the
production of a magnified image. There is certainly no mention in
Pliny's works, or indeed in those of any other writer of this period, of
the use of lenses to correct or compensate for defects in the human eye,
such as long or short sight. The use of lenses in this way would have
certainly been mentioned had their effects been known; references in
writings of the fifth century A.D. to short sight (and again as late as the
4 The First Microscopes
thirteenth century) specifically state that this condition is uncurable.
Spectacles appear to date from the last years of the thirteenth century;
evidence for their use to correct defects of vision is provided by the
writer of a Florentine manuscript dated 1299 in which he says
I find myself so pressed by age that I can neither read nor write without
glasses which they call spectacles, newly invented, for the great advantage
of old men when their sight grows weak.
Many examples of engraving on gems and precious stones have
survived in our museums; some of these carvings show extremely
minute detail which, it has been objected, could not have been executed
without some form of magnifier. This has been used as an argument to
support the contention that the magnifying action of a convex lens
was known to the early engravers. It seems unlikely, however, that
this was the case, as no account of the use of artificial aids has survived
in any of the classical writers. In particular, Pliny, who was deliberately
attempting to chronicle all the existing technological knowledge of his
day, would surely have mentioned this important detail had it been a
custom. He goes into great detail about gem-engraving, and mentions
that the workers looked at or through emeralds or other green stones
in order to strengthen or rest their tired eyes, but there is no hint of the
use of a glass sphere or any other possible magnifier. Almost certainly
the secret of such detailed engraving must have been in the high degree
of visual acuity of the workmen. There is much individual variation
among different people as to the amount of detail visible in an object;
short-sighted people, in particular, when they place an object very
close to their eyes can see detail which would be almost invisible to a
person with normal sight. Such ability, together with the long and
careful training of an engraver could quite well account for the minute
detail found in many examples of their work without supposing the
availability of any artificial aids to vision.
An interesting example of the exceptional visual acuity of some
engravers is furnished by the entry for August 10th, 1664, in the
famous diary of Samuel Pepys :
Abroad to find out one to engrave my tables upon my new sliding rule
with silver plates, it being so small that Browne that made it cannot get
one to do it. So I find out Cocker, the famous writing master, and get
him to do it, and I set an hour by him to see him design it all : and strange
it is to see him with his natural eyes to cut so small at his first designing it,
and read it all over, without any missing, when for my life I could not,
