Van Marum's large electrostatic generator 

I’m a sucker for old-school machines (like this beauty – here, here and here – made by Jezze & co), so when I saw the one above in the Teylers Museum in Haarlem recently I was mesmerised. I don’t need to know what they do or how they work to find them fascinating, especially when they’re this finely crafted!

That said, I did read the exhibit’s label (although didn’t necessarily understand it all), and can tell you that it’s an Electrostatic Generator. It was made in 1784 by John Cuthbertson (an English instrument maker who settled in Amsterdam) after a design by Dutch scientist and teacher Martinus Van Marum. Van Marum used the machine for over a decade in his various electro-chemical and electro-physical research experiments.

Apparently, with its 1.65 meter diameter discs, it is the largest plate generator ever built and could produce a spark with a record-length of 61 cm, which implies a voltage of
330 000 volts. Smokin’!

large electrostatic generator, detail

“Each disk is rubbed by four friction pads of waxed taffeta pressed to the glass by leaf springs. The central portions of the disks are coated with resinous material to absorb the vibrations when they are in motion”

large electrostatic generator, detail

“The disks are rotated by a double crank in a frame fixed to the top of a table, on which two men stood to work the machine”
(woodwork designed by architect Leendert Viervant)

large electrostatic generator, detail

“Combs ‘transport’ the charge to the conductors”

large electrostatic generator, detail

“The arrangement contains a battery of Leiden jars, the earliest type of condenser”

(text in italics is quoted from the exhibit’s label)

The Teylers Museum is filled to the brim with other intriguing and exquisitely crafted scientific instruments, and also houses (in what appear to be the original 18th Century wooden cabinets!) a huge collection of fossils, bones, crystals, rocks, paintings, drawings and prints.

They also serve a mean chocolate cake in their cafe. You should go… you’d like it :)