A hydrometer is a device for measuring a density (weight per unit volume) or specific gravity (weight per unit volume compared with water). It was also called an aerometer, a gravimeter or a densimeter.
On 1 June 1784, Nicholson wrote to his good friend Mr. J. H. Magellan with: ‘A description of a new instrument for measuring the specific gravities of bodies’.
According to Museo Galileo, hydrometers date back to Archimedes and the Alexandrian teacher Hypatia, but the second half of the nineteenth century saw the design of several types which were well-used in industry of which “the better-known models include those developed by Antoine Baumé (1728-1804) and William Nicholson (1753-1815)”.
Nicholson’s paper, which does not seem to be accompanied by a drawing, was published the following year in the Memoirs of the Manchester Literary and Philosophical Society (London: Warrington, 1785) 370–380, and can be accessed via Google Books
In the first edition of Nicholson’s A Journal of Natural Philosophy, Chemistry and the Arts, Nicholson wrote an article about the hydrometers invented by Baumé – one for spirits and one for salts - which had never been used in this country, but never mentioned his own earlier invention.
In June 1797, Nicholson published a translation of a paper that had been read in France at the National Institute by Citizen Louis Bernard Guyton de Morveau (1737-1816), and then published in the Annales de Chimie. Nicholson points out that ‘this translation is nearly verbal’ as he finds himself writing about his own invention.
Comparing Nicholson’s hydrometer with that designed by Fahrenheit which he described as ‘not fit for the hand of the philosopher’, Guyton de Morveau says:
“The form which Nicholson gave some years ago to the hydrometer of Fahrenheit, rendered it proper to measure the density of solids. At present it is very much used. It gives, with considerable accuracy, the ratio of specific gravity to the fifth decimal,water being taken as unity. … It does not appear that any better instrument need be wished for in this respect.”
Of all of Nicholson’s inventions, this one still bears his name and is called Nicholson’s hydrometer today. Examples can be found in several museums, and it is possible to purchase a modern version for use in school experiments for just a few dollars.
The Oxford Museum of the History of Science kindly showed me their Nicholson’s hydrometer from 1790.
Others can be found at:
Sadly, I couldn’t find a video online with a demonstration of Nicholson's hydrometer being used. If anyone knows of one, or feels the urge to produce one, I would love to share it on this website.
Image Michal Jarmoluk on Pixabay
Well done to the group of art historians who wrote to The Times on 6 November:
“The fees charged by the UK’s national museums to reproduce images of historic paintings, prints and drawings are unjustified, and should be abolished. Such fees inhibit the dissemination of knowledge that is the very purpose of public museums and galleries. Fees charged for academic use pose a serious threat to art history: a single lecture can cost hundreds of pounds; a book, thousands.”
A full copy of the letter (and more recent developments) can be found on the website www.arthistorynews.com.
As someone who uses images as a daily basis for marketing, I am used to being able to licence stock images (photographs or drawings) from websites such as Istockphoto or Shutterstock for a reasonable fee, and was shocked to find out how much some museums wished to charge, how complicated the fee structure can be, and how inconsistent the pricing structure is across various national institutions.
Initially, I had been keen to include a large number of illustrations in my modern biography of Nicholson - hoping to bring some potentially dry scientific subjects to life - but I soon had to modify my aspirations.
By way of example, when writing this blog on Nicholson’s clock, which is in the British Museum but not on public display, I was only allowed to include the three images provided by the Museum under the Commons, Attribution-NonCommercial-ShareAlike 4.0 International licence, “an internationally recognised licence recommended by one of the Directives we are expected to follow as a public sector body.”
However, the museum did not have photographs of some interesting and unique aspects of the clock including a close up of the inscription “William Nicholson / 1797” and a side view showing the fusee mechanism.
While I was permitted to take photographs, and video, for my personal use during the visit – I was not allowed to use these on the blog, as
“… you can certainly use your own images for ‘private and non-commercial purposes’ but I’m afraid you are not permitted to publish these images.
This allows us to maintain the quality of representation of our objects, keep a record of what is used and avoid any complications regarding future copyright.
The Museum’s Visitor Regulations regarding personal photography is:
8. Film, photography and audio recording
8.1 Except where indicated by notices, you are permitted to use hand-held cameras (including mobile phones) with flash bulbs or flash units, and audio and film recording equipment not requiring a stand. You may use your photographs, film and audio recordings only for your own private and non-commercial purposes.
The image rights team kindly offered to “easily arrange new photography for £85 + VAT (30 day turnaround but often much faster)”. How they might incur such costs was a mystery to me, and I did not bother to ask whether this was per photograph.
This seems to go against the British Museum’s object of:
The Museum was based on the practical principle that the collection should be put to public use and be FREELY accessible.
Given that Nicholson’s clock is not on public display, one might have thought they would see the benefit of some broader exposure online – at no cost to the public purse.
In thinking about what to include in book, I am faced with this pricing structure for scholarly and academic books:
Total combined print run and download units (prices per image ex-VAT):
Up to 500: £30
501 – 1,000: £40
1,001 – 2,000: £50
2,001 – 3,000: £60
My initial plan to include up to eight images, in order to properly detail the design and mechanics, would set me back £400 if the print run is between 1,000 and 2,000. Somehow, I doubt that Neil MacGregor has this problem when choosing his next set of 100 hundred objects.
There is a big difference between the commercial value in the photograph of Nicholson’s clock’s fusee and an iconic sculpture such as the Discobolus, of which the British Museum sells replicas for £2,500.
I should think that the trustees of the British Museum would have a better understanding than most of the fact that many niche historical books have only a limited customer base, but are nonetheless extremely valuable in terms of the spread of knowledge and understanding.
Images copyright British Museum
The British Museum was founded in 1753, the year of William Nicholson’s birth. I have evidence of at least two of his visits to the museum. The first was as part of his research for the 1783 edition of A Critical Review of the Public Buildings, Statues, and Ornaments, in and About London and Westminster. Then in January 1790, Nicholson deposited the journals of the Count de Benyowsky with the museum for safekeeping. He might have been rather delighted to know that one of his own creations would end up there too.
In 1958, one of Nicholson’s clocks was acquired by the British Museum as part of the Ilbert Collection - the most important collection of horology ever achieved by a private collector.
Courtenay Ilbert (1888-1956) was a civil engineer and he acquired the clock from a dealer called Clowes on 17 March 1938. He paid £20 for this 1797 regulator clock, a sum at the top end in comparison to the prices that Ilbert paid for other clocks from that period.
I recently enjoyed a visit behind the scenes with a curator of horology, Oliver Cooke, who had very kindly got the clock working for me. Previously I had seen the picture of the Nicholson’s clock on the British Museum website but had not registered the dimensions, and was surprised at how large it is.
Height: 57 centimetres
Width: 30.75 centimetres
Depth: 17.3 centimetres
The clock is described in David Thompson’s book Clocks as “an interesting example of a rather unassuming case which in reality conceals a movement of a most unusual and interesting design.”
The British Museum describes it as " SATINWOOD CASED EIGHT-DAY BRACKET TIMEPIECE WITH GRAVITY ESCAPEMENT AND CENTRE-SECONDS. Bracket timepiece; eight-day; gravity escapement; round silvered-metal dial with centre-seconds; satinwood case with moulded arched hood; glazed panels to front and sides surmounted by brass flaming vase finials. TRAIN-COUNT. Gt wheel 180" Click here for the full description.
The delicate mechanism for this 8-day clock rests upon a rather unprepossessing lump of steel which acts to stabilise the clock and to support the pendulum and the movement.
The plain steel pendulum rod would expand or contract with changes in temperature, but at the top Nicholson has built an ingenious mechanism with bi-metallic strips to compensate for the changes in temperature.
“Nicholson’s big solid design is going in the right direction – and it is good to see someone outside the clock-making tradition trying something different,” said Oliver Cooke. “It was clearly an attempt to make a precision timepiece, and you can see original thinking – even if Nicholson has not got it quite right.”
Nicholson’s name is engraved on the dial where the name of the commissioner/designer would usually appear: Wm Nicholson f 1797
More information can be found in:
Clocks by David Thompson, British Museum Press, London 2004.
Precision Pendulum Clocks, The Quest for Accurate Timekeeping, by Derek Roberts, Schiffer Pub Ltd, Atglen, Pennsylvania, U.S.A., 2003