Van Leeuwenhoek's Microscopes

46 Chapter 4

Chapter 4 Van Leeuwenhoek’s Microscopes

While I am writing this letter, I have 8 or 10 magnifying glasses lying about, which have been mounted in silver by me; and although I never received any instruction in working in any metal with a hammer or a file, still I mount my glasses, and my tools have been fitted in such a way that master goldsmiths say that they cannot emulate me.

In a letter comparing his ability to see sperm with the results claimed by Nicolaas Hartsoeker (see chapter 6), Antoni van Leeuwenhoek wrote to the Royal Society about how well he made his simple microscopes. It is frequently said that he invented the microscope, but this is not true. He improved the single-lens microscope enormously, but the manufacture and use of magnifying lenses began much earlier.

The First Microscopes: A Brief History

Magnifying lenses of one type or another have been in use for thousands of years. The oldest known lenses – made of polished crystals, usually quartz – date from 700 BC and were found in the Assyrian empire, and later in Egypt, Greece and Babylon. The Greek comic playwright Aristophanes (446–386 BC) wrote that burning glasses for the starting of fires were on sale in the shops of Athens. It is believed that the necessary magnification for the delicate work of cutting precious stones in antiquity was done using glass flasks filled with water. The Roman Stoic philosopher, Seneca (± 4 BC–65 AD), wrote that small letters, however small and unclear they may be, became large and clear when viewed through a glass bowl filled with water. Pliny the Elder (23–79 AD), the Roman amateur scientist, reported the use by physicians of burning glasses for cauterising wounds. He also wrote that the Emperor Nero (37–68 AD), who was very short-sighted, used to watch gladiator fights through a telescope with polished emerald lenses. The Greek astronomer Ptolemy (87–150 AD) of Alexandria wrote a work on the properties of light, including a table of the refraction of rays of light when they penetrate glass at different angles. This text later became a source of inspiration for Ibn al-Haytham, also known as Alhazen (965–1049AD), who was

Figures 4.1, 4.2 The astronomer and mathematician Abu Ali al-Hasan ibn al-Haytham, Alhazen, Father of Optics. A crater on the moon was named after him in the 18th century.

experimenting with light, mirrors and lenses in Egypt. He is regarded as the father of optics. A scientific renaissance in Europe began at the end of the 16th century, and academies sprang up everywhere. These centres for the discussion of philoso- phy, mathematics, medicine and astronomy fostered an interest in studying stars and planets, and generated a need for improved optical instruments. At the same time, magnifying lenses were being used to magnify and study different materials. For example, in 1590 the English naturalist and physician Thomas Muffet (1553–1604) used magnifying glasses to study scabies (an infectious skin disease caused by the mite Sarcoptes scabei) and published his findings in his Insectorum sive Minimorum Animalium Theatrum.