Answering the public

Where’s Kevin? He went on holiday and never came back. Nick at Work is mystified. It is all very odd. Perhaps I will find out at some future date. Stay tuned for further developments.

Today was mostly about a query from a member of the public. Nick at work had received an email from Eric, who knows his lifting screws. He was concerned that the image of a particular object did not match the description. As described, the object referred to a patent (11,036 of 1843) but, when the patent was studied, it didn’t appear to match the image.

Nick would have loved to have dealt with it but he was too busy with more mundane tasks so he forwarded it to me. And so I spent most of the day unravelling the discrepancy.

The patent described (and illustrated) a screw lifting device that sat proud of the stern, beyond the rudder while the photograph depicted a boxed in lifting screw which, clearly would have sat forward of the rudder, going through the deck.

Eric pointed out that the model could have been of a specially designed lifting device for an ill-fated Arctic expedition. Two ships had been fitted out and made ready for the particular conditions the ships would experience in the frozen wastes. Most telling was the fact that the lifting mechanism would have to be in some sort of housing in order to protect it from freezing and, subsequently becoming inoperable.

I should explain that when ships started having steam engines, they still retained their sails. The engines were seen as a supplemental source of propulsion for when the winds died. The sails would be furled, the engines stoked up and the propeller (screw) would take over. Early ships (and a number of marine engineers) indicated that a ship under sail would be hindered for speed by the drag produced by the propeller. And so some sort of lifting device was required.

Early lifting devices would have to be lifted by hand but, very quickly, the chains were attached to an auxiliary engine.

Another consideration was the position of the screw relative to the rudder. Obviously, the blades of the screw would need to spin without fouling the rudder that sat, dominant on the stern of the vessel. Like all new technology, a lot of shipwrights and engineers wanted to be able to adapt existing ships as well as create them from new.

Joseph Maudslay (of Maudslay, Son and Field) invented one such lifting screw in 1843 and submitted the invention for patent protection. A few years later, the Arctic exploration was mounted and the adaptation of the two older vessels started. Given the conditions that the expedition would encounter, the Maudslay screw lifting process would not have worked and so a shipwright working at the Royal Dockyard, Deptford, created a housed system. And that, as described, was far more like the model at the museum.

So Eric was correct. The photograph didn’t match the patent. Having verified his claim, my problem was to ascertain why.

The model had the object number painted on it so it wasn’t a case of the wrong image being attached to the wrong record. This means that the error was made when the object was first received at the museum. The object as described had come from the Patent Museum, which used to be on the site of the Science Museum. When the Patent Museum closed, all of the objects were ‘inherited’ by the newly formed Science Museum and given their own object numbers. This particular object record was initially created in 1861.

One of the many paper-based records held at the museum is the set of books from the Patent Museum which describe the objects, when they arrived and from whom. The records do not contain the new numbering system, making cross referencing a bit laborious but then what can you expect from pre-computer days.

Anyway, long story thankfully short, it would appear that the object was incorrectly assigned to the original patent record. Which means Eric was correct.

I sent Nick at Work a long, detailed email with the results of my research (which took most of the day) and then explained it all to him.

This might sound quite dull but it was very enjoyable and invaluable in terms of the museum records. I’d like to thank Eric for pointing it out.