Topic: What are these Molineaux Webb glass balls for?

[Anne]

The biggest problem with them being balls from the Campbell-Stokes type sunshine recorders is the size, as the smaller the ball the smaller the card the data is burned onto, so I would think it calls into question the accuracy of any readings if they are too small.

I've found the specs from versions still being made and that gives the size of the sphere as 101.6mm (i.e. exactly 4") diameter, the same as the ones in David's Chance advert, and those offered for sale today say they are made to a British Meteorological Office specification (so in this instance I think size does matter Christine  :24:

However, searching through the Science Museum online stuff I found a page here: http://www.ingenious.org.uk/media/4.0_SAC/webimages/1031/1/10311940_3.jpg which shows a variety of instruments from an exhibition in 1885, one of which might have a smaller ball: see image, second item from left top row. Sadly the writing is too fuzzy to read the caption underneath this item.

It might be worth Neil contacting the NMSI and asking if they have a higher resolution copy of this image and what that second item is... and it'd be also worth asking the Manchester Art Gallery if their balls are attached to those stands or if they are separate.

[David E]

Having just revisited this topic, as there were so many different sizes, going down to 'powder' (almost), then they could have been what became known as Ballotini beads. These had a wide range of uses, such as a coating for reflective road signs, cinema screens, and the largest known were used for storing blood plasma - not sure what size these were, but I imagine the idea was to prevent coagulation.

Sizes quoted on the original patent of 1943 (US2334578, R H Potters) were 0.008-in to 0.055-in*. However, all this is superfluous as it  post-dates the Molineaux Webb spheres, unless MW never patented their idea?

*In Monopoly money that's 0.2032 to 1.397mm