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.”