Table of Contents

• THE ROMANCE OF THE MICROSCOPE
  • CHAPTER II SOME EARLY MICROSCOPISTS
  • CHAPTER III THE ACTION OF LIGHT
  • CHAPTER IV THE COMPOUND MICROSCOPE
  • CHAPTER V ANIMAL LIFE IN THE PONDS AND STREAMS
  • CHAPTER VI PLANT LIFE IN PONDS AND STREAMS
  • CHAPTER VII THE MICROSCOPE AND PLANT LIFE
  • CHAPTER VIII ANIMAL LIFE AND THE MICROSCOPE
  • CHAPTER IX THE STUDY OF THE ROCKS
  • CHAPTER X THE MICROSCOPE AS DETECTIVE
  • CHAPTER XII MEDICAL WORK WITH THE MICROSCOPE
  • CHAPTER XIII THE MICROSCOPE AND AGRICULTURE
  • CHAPTER XIV THE MICROSCOPE AND INSECT LIFE
  • CHAPTER XV THE MICROSCOPE BY THE SEASIDE—ANIMAL LIFE
  • CHAPTER XVI THE MICROSCOPE BY THE SEASIDE—PLANT LIFE
  • CHAPTER XVII THE MICRO-TELESCOPE AND SUPER MICROSCOPE
  • CHAPTER XVIII CHEMISTRY AND THE MICROSCOPE
  • CHAPTER XIX THE USE OF THE MICROSCOPE IN MANUFACTURES
  • CHAPTER XX THE MICROSCOPE AND CAMERA ALLIED
  • CHAPTER XXI HOW THE GLASS USED IN MICROSCOPES IS MADE
  • CHAPTER XXII THE CHOICE AND USE OF APPARATUS AND ACCESSORIES

THE ROMANCE OF THE MICROSCOPE

By the courtesy of Messrs. F. Davidson & Co.

An Example of a Micro-Telescopic Photograph

“Nanda Kot.” Height, 22,510 feet; distance, 60 miles. The trees at the lower right-hand corner are only 20 yards from the photographer. A remarkable photograph, showing the great depth of focus of the micro-telescope.

THE ROMANCE OF
THE MICROSCOPE

AN INTERESTING DESCRIPTION OF ITS
USES IN ALL BRANCHES OF SCIENCE,
INDUSTRY, AGRICULTURE, AND IN THE
DETECTION OF CRIME, WITH A
SHORT ACCOUNT OF ITS ORIGIN,
HISTORY & DEVELOPMENT.

BY

C. A. EALAND, M.A.

AUTHOR OF “ANIMAL INGENUITY OF TO-DAY,”
“INSECTS AND MAN,” &C., &C.

WITH 39 ILLUSTRATIONS & NUMEROUS DIAGRAMS

LONDON
SEELEY, SERVICE & CO. LIMITED
38 GREAT RUSSELL STREET
1921

UNIFORM WITH THIS VOLUME

THE LIBRARY OF ROMANCE

Extra Crown 8vo. With many illustrations. 6s. nett.

“Splendid Volumes.”—The Outlook.

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^{By Prof. G. F. SCOTT ELLIOT, M.A., B.Sc.}

^{The Romance of Savage Life}

^{The Romance of Plant Life}

^{The Romance of Early British Life}

^{By EDWARD GILLIAT, M.A.}

^{The Romance of Modern Sieges}

^{By JOHN LEA, M.A.}

^{The Romance of Bird Life}

^{By JOHN LEA, M.A. & H. COUPIN, D.Sc.}

^{The Romance of Animal Arts and Crafts}

^{By SIDNEY WRIGHT}

^{The Romance of the World’s Fisheries}

^{By the Rev. J. C. LAMBERT, M.A., D.D.}

^{The Romance of Missionary Heroism}

^{By G. FIRTH SCOTT}

^{The Romance of Polar Exploration}

^{By CHARLES R. GIBSON, F.R.S.E.}

^{The Romance of Modern Photography}

^{The Romance of Modern Electricity}

^{The Romance of Modern Manufacture}

^{The Romance of Scientific Discovery}

^{By CHARLES C. TURNER}

^{The Romance of Aeronautics}

^{By HECTOR MACPHERSON, Junr.}

^{The Romance of Modern Astronomy}

^{By EDWARD BENNETT}

^{The Romance of the Post Office.}

^{By ARCHIBALD WILLIAMS, B.A. (Oxon.), F.R.G.S.}

^{The Romance of Early Exploration}

^{The Romance of Modern Exploration}

^{The Romance of Modern Mechanism}

^{The Romance of Modern Invention}

^{The Romance of Modern Engineering}

^{The Romance of Modern Locomotion}

^{The Romance of Modern Mining}

^{By EDMUND SELOUS}

^{The Romance of the Animal World}

^{The Romance of Insect Life}

^{By AGNES GIBERNE}

^{The Romance of the Mighty Deep}

^{By E. S. GREW, M.A.}

^{The Romance of Modern Geology}

^{By J. C. PHILIP, D.Sc., Ph.D.}

^{The Romance of Modern Chemistry}

^{By E. KEBLE CHATTERTON, B.A.}

^{The Romance of the Ship}

^{The Romance of Piracy}

^{By T. W. CORBIN}

^{The Romance of Submarine Engineering}

^{The Romance of War Inventions}

^{By NORMAN J. DAVIDSON, B.A. (Oxon.)}

^{The Romance of the Spanish Main}

^{By H. O. NEWLAND, F.R.Hist.S.}

^{The Romance of Modern Commerce.}

SEELEY, SERVICE & CO., LIMITED.

CONTENTS

LIST OF ILLUSTRATIONS

The Romance of the Microscope

CHAPTER I
THE EARLY DAYS OF THE MICROSCOPE

It is certain that lenses were used as early as the thirteenth century, and it is probable that they date back to far earlier times. The ancient gem cutters probably used spheres of glass filled with water as magnifiers, their work could hardly have been accomplished without some artificial aid. We know, from early writings, that burning glasses were used by physicians in their work, and Seneca, the author, who wrote in A.D. 63, says: “Letters, however small and dim, are comparatively large and distinct when seen through a glass globe filled with water.”

Euclid, whose name at least is familiar to everyone, was, as shown by his writings, perfectly well acquainted with the fact that curved mirrors may be used to magnify objects, and that was so long ago as the third century B.C. Convex glasses, used as spectacles, were first mentioned by Bernard de Gordon, about 1307, but, as far as we know, they were never used for the purpose of studying minute living objects.

To Leonardo da Vinci belongs the honour of seriously investigating, for the first time, the properties of concave and convex lenses, and several alchemists, as the early chemists were called, used flasks filled with water, concave mirrors or glass balls to gather together the rays of the sun. “Long before the dawn of the seventeenth century, the principle of the lens was both comprehended and applied to scientific matters by the Englishmen, Leonard Digges and his son Thomas, and by the Italian, Giambattista Porta.”

Towards the end of the sixteenth century and the early part of the seventeenth century, interest in the minute structure of natural objects appears to have developed. As early as 1590, Thomas Mouffet used magnifying glasses in studying small mites, and in 1637 Descartes invented a single lens microscope in which the rays of light were reflected on to the object by means of a concave mirror. This method of illumination, it is interesting to note, is still used in some forms of pocket magnifiers. Most of the early discoveries were made with single lenses, for in the compound microscopes which were first made, it was only possible to view such a small portion of an object at one time that the advantage lay with the less complicated instrument.

The earliest microscopes were simply short tubes of any material which would not admit light; at one end there was a lens, at the other a glass plate on which the object to be examined was placed. Because these crude instruments were chiefly used for the examination of insects they were known as “Vitrea pulicaria” or “Vitrea muscaria.” Later they were called “Engyoscopes,” and, after the invention of compound microscopes, they were described as “Microscopia ludicra,” as opposed to the latter instruments, known as “Microscopia seria.”

The next stage in the development of the microscope consisted in the introduction of lenses of very short focal length, and, in 1665, Robert Hooke used small glass balls, formed by fusing threads of drawn glass, for this purpose.

It was Antony van Leeuwenhoek, however, who perfected these instruments. He brought an extraordinary skill and industry to bear on the grinding and polishing of minute lenses of short focal length. Already in 1673 Regnier de Graaf wrote to the Royal Society in London that Leeuwenhoek was making glasses far superior to those of the great Italian lens maker, Eustachio Divini. Leeuwenhoek’s success was largely due not only to his method of grinding, but also to the skill with which he mounted his lenses, which were accurately fitted into a minute hole in a metal plate. The object to be examined was firmly held in a stand and adjusted by means of a screw movement. By this means, and by the use of hollow metal reflectors, he succeeded in availing himself of transmitted light in the case of transparent objects. Leeuwenhoek was able to make immense advances with these instruments, the minute pond animals he could see with ease, and by 1683 he had even attained a sight of the bacteria. His researches represented the high-water mark of work done with the simple microscope, most of the later work was carried out with the compound instrument.

The earliest history of the compound microscope is difficult to separate from that of the telescope and, in any complete account, the two instruments must be considered together. It appears that the first scientist that conceived the idea of using a series of lenses, rather than a single lens, was Leonard Digges, whom we have already mentioned.

In a book by Porta, a writer who though not himself original, was gifted with great curiosity and industry in the collection of the ideas of others, we read: “How to make plain a letter held far away by means of a lens of crystal,” and also that “with a concave lens you see things afar smaller but plainer, with a convex lens you see them larger but less distinct. If, however, you know how to combine the two sorts properly you will see near and far both large and clear.”

Shortly after the publication of Porta’s book the method of combining two lenses into a microscope or telescope was discovered, quite accidentally, by a Dutch boy named Zacharias, who worked in the shop of his father, a spectacle maker. The event was described by Willem Boreel, Dutch Ambassador to France, in a letter written in 1655. He wrote: “I am a native of Middleburg, the capital of Zeeland, and close to the house where I was born, there lived in the year 1591 a certain spectacle maker, Hans by name. His wife, Maria, had a son, Zacharias, whom I knew very well, because I constantly as a neighbour and from a tender age went in and out playing with him. This Hans or Johannes with his son Zacharias, as I have often heard, were the first to invent microscopes, which they presented to Prince Maurice, the governor and supreme commander of the United Dutch forces, and were rewarded with some honorarium. Similarly they afterwards offered a microscope to the Austrian Archduke Albert, supreme governor of Holland. When I was Ambassador to England in the year 1619, the Dutchman Cornelius Drebbel of Alkomar, a man familiar with many secrets of nature, who was serving there as a mathematician to King James, and was well known to me, showed me that very instrument which the Archduke had presented as a gift to Drebbel, namely, the microscope of Zacharias himself. Nor was it (as they are most seen) with a short tube, but nearly two and a half feet long, and the tube was of gilded brass two fingers’ breadth in diameter, and supported on three dolphins formed also of brass. At its base was an ebony disc, containing shreds or some minute objects which we inspected from above, and their forms were so magnified as to seem almost miraculous.” So this was the first compound microscope!

Although Zacharias invented the microscope, it was Galileo who introduced it to the scientific world. He published a book in 1610 in which he wrote: “About ten months ago a rumour reached me of an ocular instrument made by a certain Dutchman, by means of which an object could be made to appear distinct and near to an eye that looked through it, although it was really far away. And so I considered the desirability of investigating the method, and reflected on the means by which I might come to the invention of a similar instrument. I first prepared a leather tube at the ends of which one placed two lenses each of them flat on one side, and as to the other side I fashioned one concave and the other convex. Then holding the eye to the concave one, I saw the objects fairly large and nearer, for they appeared three times nearer and nine times larger than when they were observed by the naked eye. Soon after I made another more exactly, representing objects more than sixty times larger. At length, sparing no labour and no expense, I got to the point that I could construct an excellent instrument so that things seen through it appeared a thousand times greater and more than thirty-fold nearer than if observed by the naked eye.” Galileo had his enemies, who accused him of having picked Zacharias’s brains; he admitted that he had taken his idea from the Dutchman’s invention, but further than that he would not go; in fact, he replied that the invention of Zacharias was a mere accident but that his own instrument was discovered by a process of reasoning.

It would serve no good purpose to tell the story of all the scientists who have helped to bring the microscope to its present state of perfection, although many of their descriptions of objects and apparatus are as quaint as the latter. Scheiner, for example, who wrote in 1630, mentions “that wonderful instrument the microscope, by means of which a fly is magnified into an elephant, and a flea into a camel.” To Kircher belongs the credit of being the first worker to construct an instrument with coarse and fine adjustment and with a substage condenser, which could be used either for concentrating the sun’s rays or those from a lamp. With an instrument of this pattern Malpighi saw the circulation of blood in a frog’s lung. By 1685, when instruments with four and six lenses were being used, the compound microscope was firmly established as a help to scientists, and the simple lens was used thereafter as an adjunct but not a rival to the newer instrument.

History makes a strong appeal to many people, and those who are fascinated thereby will find endless amusement in reading old books on the microscope and its objects. In the preface to Mouffet’s Insectorum Theatrum, one of the earliest books on insects, we read the following quaint lines: “If you will take lenticular object glasses of Crystal (for though you have Lynx his eyes, they are necessary in searching for atoms) you will admire to see the Fleas that are curasheers, and their hollow trunk to torture men, which is a bitter plague to maids, you shall see the eyes of Lice sticking forth, and their horns, their bodies crammed all over, their whole substance diaphanous, and through that, the motion of their heart and blood. Also little Handworms, which are indivisible, they are so small, being with a needle prickt forth from their trenches near the pool of water which they have made in the skin, and being laid upon one’s nail, will discover by the sunlight their red heads and feet they creep withal.” The creatures called Handworms are itch mites, which tunnel in the human skin.

In our chapter on Nature Study and the Microscope we refer to the brown patches to be found on the backs of fern fronds; it is interesting to note that so long ago as 1646 Sir Thomas Browne had quite a good idea of their structure. Describing them, he said: “Whether these little dusty particles, upon the lower side of the leaves be seeds we have not yet been able to determine by any germination. But, by the help of magnifying glasses we find these dusty atoms to be round at first and fully representing seeds out of which at last proceed little mites, almost invisible, so that such as are old stand open, as being emptied of some bodies firstly included, which though discernible in Hartstongue, is more notoriously discoverable, in some differences, of Brake or Fern.”

Two years earlier a noted scientist, Hodierna, had made a special study of the eyes of insects and, considering the crude instruments with which he must have worked, his descriptions are wonderfully accurate. Of the house fly he wrote: “The head is all eyes, prominent and without lids, lashes or brows. It is plumed with hairs like that of an ostrich and has two little pear shaped bodies hanging from the middle of the forehead. The proboscis which arises from the snout can be extended freely and stretched forth to suck up humours and can afterwards be directed back through the mouth and taken into the gullet. This instinct nature has given the creature according to its need, for it is without a neck and cannot stretch forth its head to obtain its food, as is also the case with the elephant.” The author’s knowledge of the house fly was evidently greater than his knowledge of the ostrich, for the bird has anything but a plumed head. The eye of the insect he compares to a white mulberry.

Another of these early workers, writing about the same time, gives a concise account of cheese mites, heading his description “On the creatures which arise in powdery cheese,” he wrote: “The powder examined by means of this instrument (the Compound Microscope) does not present the aspect of dirt, but teems with animalcula. It can be seen that these creatures have claws and talons and are furnished with eyes. The whole surface of their body is beautifully and distinctly coloured in such sort as I have never seen before, and which indeed, cannot be seen without wonder. They may be observed to crawl, eat and work and are equal in apparent size to a man’s nail. Their backs are all spiny and pricked out with various starlike markings and surrounded by a rampart of hairs, all of such marvellous kind that you would say they are a work of art rather than of nature.”

At about this period the microscope was used for the first time for medical work and, as far as can be ascertained, Pierre Borel was the first to use it for this purpose, and he learned a great deal about the structure of flesh and the appearance of blood.

Of all the early writers on microscopy the man who spread abroad his knowledge of the instrument and its capabilities, more than anyone else, was Kircher, who died in 1680. He was an energetic writer, and wrote on a large number of subjects. His books dealt with magnetism, designs for a calculating machine, light, sound, history of plague, the philosopher’s stone, Egyptian antiquities, a history of China and a grammar. To all who read his book on the plague, it is clear that he had a good idea of infection; he was, in fact, the first writer who suspected it, though the microscope he used could not show him bacteria. In his book he wrote: “Everyone knows that decomposing bodies breed worms, but only since the wonderful discovery of the microscope has it been known that every putrid body swarms with innumerable vermicules, a statement which I should not have believed had I not tested its truth by experiments during many years.” The experiments he performed to prove his statement are so quaint that we give them in his own words.

Experiment I.—“Take a piece of meat which you have exposed by night until the following dawn to the lunar moisture. Then examine it carefully with the smicroscope and you will find the contracted putridity to have been altered by the moon into innumerable wormlets of diverse size, which, however, would escape the sharpness of vision without a good smicroscope. The same is true of cheese, milk, vinegar and similar bodies of a putrifiable nature. The smicroscope, however, must be no ordinary one, but constructed with no less skill than diligence, as is mine which represents objects one thousand times greater than their true size.”

Experiment II.—“If you cut up a snake into small parts and macerate with rain water, and then expose it for several days to the sun and again bury it under the earth for a whole day and night and lastly examine the parts, separated and softened by putridity, by means of a smicroscope you will find the whole mass swarm with innumerable little multiplying serpents so that even the sharpest eyes cannot count them.”

Experiment III.—“Many authors claim that unwashed sage is injurious, but I have discovered the cause of this. For when, by means of the sun, I minutely examined the nature of the plant, I found the back of the leaves completely covered by raised work as with the figure of a spider’s web, and within the water appeared infinitesimal animalcules, which moving constantly came out of little buds or eggs.”

Experiment IV.—“If you examine a particle of rotten wood under the sun, you will see an immense progeny of tiny worms, some with horns, some with wings, others with many feet. They have little black dots of eyes. What must their little livers and stomachs be like?”

In the light of modern discovery much of the writing of these early microscopists seems absurd. Kircher’s experiments, for example, prove nothing, and he is often hopelessly vague and sometimes incorrect in his statements. We must not be too critical, however, for some of this early work was excellent, the microscopes in use would not be tolerated at the present day, and without these pioneers microscopy would not have reached the stage it has. Rather than laugh at their efforts, we should marvel that they did so well.

CHAPTER II
SOME EARLY MICROSCOPISTS

Of the early British microscopists, Robert Hooke must not pass unnoticed. He was appointed Curator of the Royal Society two years after its formation, and the terms of his appointment were somewhat one-sided. He was required to “furnish the Society every day they meet with three or four experiments”; for this no pay was to be his till the Society accumulated sufficient funds to reward him.

Although compound microscopes had been invented in Hooke’s day, it is noteworthy that he remained faithful to the single lens, in fact it was not till very many years later that the simple lens was supplanted, in general use by the more complicated, if more perfect instrument.

In his book on Microscopy, entitled Micrographia, Hooke gives a quaint account of the making of a microscope. “Could we make a microscope,” he writes, “to have only one refraction, it would cæteris paribus, far excel any other that had a greater number. And hence it is, that if you take a very clear piece of a broken Venice glass, and in a Lamp draw it out into very small hairs or threads, then holding the ends of these threads in the flame, till they melt and run into a small round Globul, or drop, which will hang at the end of the thread; and if further you stick several of these upon the end of a stick with a little sealing wax, so that the threads stand upwards, and then on a whetstone first grind off a good part of them, and afterward on a smooth Metal plate, with a little Tripoly, rub them till they come to be very smooth; if one of these be fixt with a little soft wax against a small needle hole, prick’d through a thin Plate of Brass, Lead, Pewter, or any other Metal, and an Object, plac’d very near, be look’d at through it, it will both magnifie and make some Objects more distinct than any of the great Microscopes.”

This early worker was noted for the variety of his investigations rather than for the depths of his learning. Amongst the so-called Observations, in his book are many that are not connected with microscopic work. The following are interesting and, in the curious old book Micrographia, there are an extraordinary number of well executed illustrations. Early in his book Hooke compares various man-made objects, such as a razor edge, the point of a needle and a piece of cloth, with various natural objects, and always to the detriment of the former. He examined Foraminifera with his microscope, and was probably the first man to draw these beautiful little creatures. Petrified wood and charcoal also came under his notice. When he studied cork, he observed that it was made up of “little boxes or cells,” and the name cell has survived to this day despite the fact that it is by no means an appropriate term. That Hooke’s knowledge was not very deep is shown by the fact that he presumed cork to be a fungus growing on the bark of trees.

Many of the objects we have described in our pages were described and illustrated by Hooke more than two hundred years ago. The sea mat, despite his accurate observations, he mistook for a seaweed, as many later naturalists have done. The stinging hairs of nettle he made out in every detail. Fish scales, bee stings and birds’ feathers all came under his notice. The foot of a fly he described with wonderful accuracy; the scales of a butterfly’s wing and the head of a fly were all studied and described in detail. On the life history of the gnat he made many blunders, but he saved his reputation by remarkable observations upon the Chelifer, a curious parasite of the fly which we mention in our pages, and upon the silver fish, a little creature which frequents sugar and starch. Neither of these organisms had been described before. Fleas, lice, vinegar-eels and spiders were also studied by this indefatigable worker, a worthy collection indeed, but Hooke, like others of his time, was an observer first and foremost. As a methodical, scientific worker he was of little account.

Living about the same time as Hooke, the celebrated Italian, Malpighi, laid the foundations of much of our present-day knowledge of plant structure. Various romantic stories have been told concerning certain imaginary events which led Malpighi to take up the study of plant structure, but the scientist himself refuted these picturesque stories. Suffice it to say that his book on the subject, Anatome Plantarum, though imperfect in many respects and, as might be conjectured in so early a work, often inaccurate, contains a large number of astonishingly good drawings; many of the original drawings, by the way, executed in red chalk, are in the possession of the Royal Society.

It is interesting to note that this botanist compared the falling of leaves to the shedding of an insect’s skin, in this respect at any rate he had advanced no further than Aristotle, who compared leaf-fall to the moulting of a bird. On the other hand, the Italian was the first scientist to describe the pores (stomata) of leaves, though he never discovered that they occurred on all leaves. He, first of all men, showed that nectar was formed by the flower and not transferred thence from other sources as had previously been believed; he too explained accurately for the first time the process of germination in the seed. It was not alone as a botanist, however, that Malpighi was celebrated. He elucidated the various changes which take place during the hatching of an egg; he was the first man to give an accurate account of the structure of an insect, and this he did in his work on the Anatomy of the Silkworm. Using a simple microscope for his investigations, he contracted an eye affliction during this period from which he suffered more or less severely all the rest of his life. He discovered the breathing tubes of insects and that when they are covered with grease the insect will die “in the time that one can say the Lord’s Prayer”; the heart, the silk glands, the development of wings and legs were all discovered for the first time by this untiring worker, aided by his simple microscope.

Pages could be filled with accounts of Malpighi’s other scientific work on the structure of the lung, the liver and kidney, the life of the liver fluke and a hundred and one other subjects. Though undoubtedly a great and clever microscopist, the general estimate seems to be that his work had little influence upon the scientific world. The main reason is that he was ahead of his time; men of the day concluded, for instance, that in his Anatomy of Plants he had said the last word on the subject, that there was no more to be learned. An English worker, Nehemiah Grew, carried the Italian scientist’s studies of plant structure a little further and his Anatomy of Plants contains many new and often accurate observations. His studies also led him to discover the structure of the ridges and sweat pores of the human hand, in fact Grew may be looked upon as the originator of the study of finger prints.

A Dutchman, Jan Jacobz Swammerdam by name, and a contemporary of Grew, was undoubtedly the most accurate observer amongst these old-time microscopists. Despite ill health, his enthusiasm was unbounded, and a friend wrote concerning him: “Swammerdam’s labours were superhuman. Through the day he observed incessantly, and at night described and drew what he had seen. By six o’clock in the morning in summer he began to find enough light to enable him to trace the minutiæ of natural objects. He was hard at work till noon, in full sunlight, and bareheaded, so as not to obstruct the light, and his head steamed with profuse sweat. His eyes, by reason of the blaze of light, became so weakened that he could not observe minute objects in the afternoon, for his eyes were weary.” If only for the fact that the Dutchman made clear the processes involved in the transformations of insects, his name would be famous. He described the structure and habits of the hive bees, male, female and drone with wonderful accuracy, and illustrated his work with plates which “would do credit to the most skilful anatomists of any age.” Swammerdam was sarcastic at times; he had shown that the facets of a bee’s eye are six-sided and, as so commonly happened in those days, some naturalists jumped to a conclusion, in this case that the fact explained the six-sidedness of the cells in the honey comb. By the same reasoning Swammerdam remarked that men, having round pupils, should build round houses. It is not only for his study of the minute structure of insects that this microscopist is noted, he worked upon the tadpole and the snail. He it was who discovered the red blood corpuscles of the frog, and he described his discovery in the following terms: “In the blood I perceived the serum in which floated an immense number of rounded particles, possessing the shape of, as it were, a flat oval, but nevertheless wholly regular. These particles seemed, however, to contain within themselves the humour[1] of other particles. When they were looked at sideways, they resembled transparent rods, as it were, and many other figures, according, no doubt, to the different ways in which they were rolled about in the serum of the blood. I remarked besides that the colour of the objects was the paler the more highly they were magnified by means of the microscope.” Of the snail he made a number of strikingly accurate studies, in all of which he was aided by his lenses, so that it is the more remarkable that he considered snails to be insects.

Leeuwenhoek, another Dutchman, he of all men brought the simple microscope to its highest state of development. His instruments were one of the sights of Holland, and many eminent personages made a point of seeing them. Though he had not the advantage of any scientific training and spoke no other language than his own, he made some remarkable additions to the scientific knowledge of the time. Like Hooke, he was not a methodical worker, he was impelled by an unbounded curiosity. “When we are inclined to disparage Leeuwenhoek’s hasty methods it is well to recollect that he initiated biological inquiries of the greatest interest, e.g., the parthenogenesis of aphids and the revivification of dried microscopic organisms, while he gave the first notices, or the first worth mention, of rotifers, Hydra, infusorians, yeast cells and bacteria.”

We may here explain the meaning of the term “parthenogenesis of aphids.” The female aphids or green flies are able to bring forth generation after generation during the first two-thirds or so of each year without the assistance of males. This form of increase, which by the way accounts for the extraordinary numbers of green fly, is known as parthenogenesis.

Leeuwenhoek thought that no one but himself could use his lenses properly, in consequence, when he sent any interesting object to a friend for him to examine, a lens was always affixed in place so that the object could be seen to the best advantage. He gave a set of his lenses and objects to the Royal Society, and described his gift as “a small black cabinet, lackered and gilded, which has five little drawers in it, wherein are contained thirteen long and square tin boxes, covered with black leather. In each of these boxes are two ground microscopes, in all six and twenty; which I did grind myself, and set in silver; and most of the silver was what I had extracted from minerals, and separated from the gold that was mixed with it; and an account of each glass goes along with them.”

Kircher was overwhelmed with the notion that various living creatures are generated from non-living matter. Fleas, for example, he was certain, came from dirt, and it remained for Leeuwenhoek to prove that they arise from eggs and grubs, in the manner now so well understood.

He carefully studied the structure of a garden spider, and for the first time explained its wonderful feet, its jaws and poison gland, its spinnerets and silk. He studied Hydra first of all men, and said that, under the microscope, its tentacles appeared to be several fathoms long. Although sadly at sea over the correct position of his snails in the animal world, he was clever enough to include Volvox amongst the plants and fortunate enough to see the young forms escape from the parent colony.

Concerning this microscopist’s early studies in bacteriology we may quote from Professor Miall’s The Early Naturalists, a book by the way of the greatest interest to those who would learn something of the struggles of the men who laid the foundations of our present-day biological knowledge.

Professor Miall says: “In 1683 Leeuwenhoek wrote a letter to the Royal Society which contains the first mention of bacteria. He had been writing and speculating upon saliva, and had searched the saliva of the human mouth for animalcules without finding any. It then occurred to him to ask whether the teeth might lodge animalcules discharged from the salivary ducts. He tells us that, though his own teeth were scrupulously clean and particularly sound for his age (about fifty), the lens revealed a white deposit upon them. This deposit was found to contain minute rods, some of which showed either a steady or gyratory movement. Others were very minute, of rounded form, and moved with remarkable velocity. The largest of all, which were either straight or bent were motionless. The teeth of an old man, which were never cleansed, contained among others large rods which exhibited snake-like undulations. Rubbing the teeth with strong vinegar did not kill the moving bodies, but they became quiescent when detached and placed in a mixture of vinegar and saliva, or vinegar and water. Nine years later Leeuwenhoek returned to the subject. Living particles were no longer met with in his teeth, and he was at a loss to explain why, until it occurred to him that he was accustomed to drink hot coffee every morning. This, he thought might have killed the animalcules, and his conclusion was confirmed by finding that on the back teeth, which were less exposed to the hot drink, plenty of them were still to be found. In 1697 he tells how he pulled out a decayed tooth, and found that the cavity abounded in moving particles.” Nearly a hundred years elapsed before anyone else took up the study of bacteria.

From the time of Leeuwenhoek onwards, scientific discoveries were announced in rapid succession, so that in one short chapter it is impossible to keep pace with the progress that was made. Among the great men who owe much of their success to the microscope we may mention the Frenchman Réaumur, whose memory is kept green for all time by his thermometer; as a worker upon problems of insect life he was indefatigable; the Swede, Linnæus, to whose early efforts we owe the orderly arrangement of living creatures and plants, known as classification. This arrangement has been considerably modified, more modern ideas have upset much that he initiated, yet he remains the parent of orderly arrangement.

Buffon, a great naturalist, was followed by Cuvier, the first serious student of fossils; by Humboldt, naturalist and traveller; by Robert Brown, the founder of modern Botany; by Darwin and by Pasteur in turn. How much these men owe to the microscope can never be known; certain it is that without its assistance our world, the world we know and can see, would have been smaller than it is to-day.

CHAPTER III
THE ACTION OF LIGHT

It is hardly necessary to remark that the wonderful properties of the microscope depend upon light. Without light, lenses would be useless, objects could not be illuminated and we could not see them. In this short chapter we propose to give a brief outline of the action of light; if our words appear to savour of the school-book, we shall try to avoid it, but, we repeat, if they do so we would remind our readers that the more one knows of the action of light the better use one can make of one’s instrument. As a well-known microscopist has remarked we may be able to afford a costly harp or a costly microscope, but although we may be able to strike a few notes on the former and examine a few objects with the latter, we can only make the best use of either by thoroughly understanding and practising upon it.