Overview: Where When What How


At a glance

Where  The Netherlands: Delft
When   The 1600's: The Golden Age of the Dutch Republic
What    The Microscopic World: Protozoa and Bacteria
How     Magnifying Glasses: Tiny Single Lenses


The Netherlands
Delft is about 20 miles south of Amsterdam
The Netherlands lies in the low country along the northwestern coast of continental Europe about 200 miles (320 km) east northeast of London, across the North Sea.
Delft is in the middle of the Randstad, the urban conglomeration that made Holland, in the Golden Age and still today, the most densely populated area in Europe. Geographically, it is in the marshy flat delta where the Rhine and Maas (Meuse) rivers flow into the North Sea.
Without the extensive Dutch water control system, Delft would be under water, along with the nearby cities of Leiden 11 miles (18 km) to the north and Rotterdam 8 miles (13 km) to the south.


the 1600's, the Golden Age of the Dutch Republic 

The Batavia

This ship of the Dutch East India Company (VOC) was built in Amsterdam in 1628. The Batavia was shipwrecked on her maiden voyage. This replica of the ship is in Lelystad, Netherlands.
From the end of the Spanish armada in 1588 until the rise of England in the early 1700's, the Dutch Republic was the most prosperous and most powerful country in Europe economically, especially in world-wide trade. Half the ships of Europe's combined navies were built in Dutch shipyards and Amsterdam was Europe's financial center.


The Microscopic World

He had, and was willing to use, a microscope much more powerful than anyone had ever had. Thus, everything that Leeuwenhoek saw, he was the first human ever to see. They had no names, so he called them diertjens, little animals. While certainly some bacteria are the enemies of human life, most bacteria, as Leeuwenhoek seemed to understand, are our friends.
rotifer, a protozoan
Protozoa: Rotifer
His personal showcase was a microscope that revealed the circulation of blood through the capillaries of a live eel. However, looking back after three hundred years, we see discoveries that turned out to be more important than Leeuwenhoek could have imagined, being so far ahead of his time. On the short list now: protozoa, bacteria, sperm, and red-blood cells.
What astonished him most was how these animals could be so small yet have such intricate moving parts. The rotifer pictured here has rotating parts and a darting movement through the water. Millions are them are swimming around unseen in a few drops of canal water. Leeuwenhoek called that number unbelievable. It was, however, true.


Tiny Single-Lens
Magnifying Glasses

specimen stuck on the pin
Specimen-side view
These are the little hand-made devices, most often brass, all a little different, that easily fit into Leeuwenhoek's palm. With them, he discovered a whole new world that no one even suspected.
your eye has to get very close to the tiny lens
Eye-side view

The specimen was impaled on or stuck to the pin. The screws moved the specimen into focus.

Because the lens was so small, about two millimeters in diameter, the specimen and Leeuwenhoek's eye had to be that close to the lens.

This made the microscope very hard to use and, in fact, made its single-lens design a dead-end in the history of the microscope.