Read the text and check your ideas in Ex. 16

simple microscope was merely a tube with a plate for the object at one end and, at the other, a lens which gave a magnification less than ten diameters — ten times the actual size. They became known as "flea glasses" as they were mostly used to view fleas or tiny creeping things.

About 1590, two Dutch spectacle-makers, Zaccharias Janssen and his son Hans, while experimenting with several lenses in a tube, discovered that nearby objects appeared greatly enlarged. This became the forerunner of the compound microscope and of the telescope. In 1609, Galileo (1564–1642), father of modern physics and astronomy, heard of these early experiments, worked out the principles of lenses, and made a much better instrument with a focusing device.

The father of microscopy, Anthony Leeuwenhoek of Holland (1632–1723), started as an apprentice in a dry goods store where magnifying glasses were used to count the threads in cloth. He taught himself new methods for grinding and polishing tiny lenses of great curvature which gave magnifications up to 270 diameters, the finest known at that time. These led to the building of his microscopes and the biological discoveries for which he is famous. He was the first to see and describe bacteria, yeast plants, the teeming life in a drop of water and the circulation of blood corpuscles in capillaries. He also used his lenses to make pioneering studies on an extraordinary variety of things, both living and non-living and reported his findings in over a hundred letters to the Royal Society of England and the French Academy.

Robert Hooke (1635–1703), the English father of microscopy, reconfirmed Anthony van Leeuwenhoek's discoveries of the existence of tiny living organisms in a drop of water. Hooke made a copy of Leeunwenhoek's microscope and then improved upon his design.

Later, few major improvements were made until the middle of the 19th century. Several European countries began to manufacture fine optical equipment but none finer than the marvelous microscopes built by the American, Charles A. Spencer (1813–1881), and the industry he founded. Present day instruments, little changed from these early microscopes, give magnifications up to 1250 diameters with ordinary light and up to 5000 with blue light.