Objects from the top collection of Bert Degenaar in the Boerhaave museum
On 15 October 2021, Rijksmuseum Boerhaave opened the newly furnished rooms of Mighty Collections. Here, some of the objects from the extensive Zuylenburgh collection have been given a prominent and permanent place in the display. The museum and ‘gentleman dealer’ and collector Bert Degenaar have already signed up for this special collaboration, whereby it is arranged that the collection of scientific instruments is transferred to the museum after his death. Bert Degenaar’s collection is one of the largest private collection of scientific instruments in the world.
Scientific instruments from the seventeenth and eighteenth centuries differ from later instruments because they are all art objects. The Zuylenburgh collection covers the breadth of this period, with a strong focus on optical instruments, chronometers, navigation instruments, meteorology and mathematical instruments. The instruments have a mainly Dutch or English background, and are representative of the cross-border character of early modern science. These qualities are the result of the connoisseurship and selectivity with which the collection has been assembled. We explain a number of the instruments in more detail here.
An air pump by Francis Hauksbee (1709)
Hauksbee, who initially worked in the textile trade, started making air pumps in 1701 to participate in physics experiments. In 1703 he became an assistant to Isaac Newton and a member of the London Royal Society, the leading scientific society of the time.
Hauksbee’s air pumps contain clever improvements over previous versions of the air pump: they had two cylinders, making the vacuum pumping of the glass bell jar twice as fast. In addition, the force of one piston partially offsets the back pressure of the other, making operating the pump less arduous. As a bonus, the Hauksbee pump has a built-in barometer that measures the air pressure in the bell jar, so that the experimenter knew when the bell jar had been evacuated.
Eight Hauksbee pumps have survived, but some were made by his successors, who continued Hauksbee’s business after his death. However, Degenaar’s copy so closely resembles an illustration in a booklet that Hauksbee published in 1709, that we are probably dealing here with an inventor’s own product.
A microscope attributed to John Marshall (c. 1710)
John Marshall was an important maker of optical instruments (microscopes and telescopes) in London around 1700. Rijksmuseum Boerhaave owns a collection of microscopes that documents the development of the instrument from the mid-seventeenth century to the present. However, a representative microscope from Marshall is missing.
Marshall’s microscopes are usually of the compound type – i.e. with three lenses – and are characterized by the richly decorated tube (the microscope tube) in gold stamped leather and by the single stand with a provision to adjust the distance between the specimen and the objective of the microscope. to accurately adjust the microscope. These microscopes rarely come on the market, and when they do, it’s for amounts that usually exceed the museum’s purchase budget. However, the Zuylenburgh collection contains two Marshall microscopes. Boerhaave now exhibits both of them.
Clock with balance spring, Isaac Thuret (c. 1675)
In 1656 Christiaan Huygens invented the pendulum clock. The regular back and forth movement of a pendulum was used therein to regulate the mechanism of a clockwork. The result was a clock that ran many times more reliably than all timepieces up to that point. Thanks to Huygens, time measurement had become many times more accurate.
But the story didn’t end there. A pendulum clock cannot withstand sudden movements or shocks, making Huygens’ invention unsuitable for use in, for example, pocket watches or ship clocks. And the latter was certainly important. In fact, having a reliable onboard timer was essential for determining the ship’s longitude, and governments offered high rewards to anyone who would invent such a seaworthy timer.
Christiaan Huygens has devised several alternatives to the pendulum clock, all of which turned out to be unable to withstand the pitching movements of a ship on the high seas. But in 1675 he made an invention that brought him close to the solution: the balance spring. This is a spiral spring, which, coupled with the clock mechanism, has the same function as a pendulum, but which is hardly sensitive to disturbance by the movement of a ship. The Parisian clockmaker Isaac Thuret had already worked with Huygens around 1670, among other things on a clock that could be used for astronomical observations. Now Huygens contacted Thuret to build a clock with a balance spring.
This clock from the Zuylenburgh collection is probably a very early prototype of such a spring-balanced clock, made by Thuret in close collaboration with Huygens. It also seems to be a demonstration model: the housing is largely made of glass, so that the clock mechanism – with balance spring – is clearly visible.
The earliest pendulum clock by Huygens can already be seen in the permanent display of the Rijksmuseum Boerhaave, as well as the astronomical clock from 1670 and Huygens’ clock-driven planetarium from 1682. The Thuret clock from the Zuylenburgh collection is a valuable addition to the story.
Planetarium Zuylenburgh in Oud-Zuilen was completed in 2009. It is the second planetarium in Holland. The planetarium of Eise Eisinga in Franeker was set as example, although some new insights have let to a unique example of Planetarium Zuylenburgh tot een uniek voorbeeld van contemporary artisan work. The creation of Planetarium Zuylenburgh took three years to complete and is entirely built by hand.