Sunday, 18 February 2018

An Oxford Perspective

On Saturday 17th February I visited Oxford to see two exhibitions. One about manuscripts at the Weston Library (https://www.bodleian.ox.ac.uk/weston) and the other almost directly opposite on Broad Street in the Museum of the History of Science (http://www.mhs.ox.ac.uk). Both exhibitions were free to visit although donations were appreciated.  The biggest attraction in the MHS has to be a blackboard that Albert Einstein used to deliver a lecture at Oxford University in May 1931. After his lecture the blackboard was unscrewed from the wall and preserved for future generations. When I was at school most blackboards were simply wiped clean at the end of a lesson ready for the next class!

In addition to Einstein's blackboard the museum houses Brunel's sextant, some of Lewis Carrol's photographs and many old astrolabes, nocturnals, several radio transmitters from Marconi's collection, antique laboratory glassware and of course many telescopes. One interesting observation I made was that many old telescopes are highly decorated with patterned leather sleeves rather than the polished metal or enamelled metal that is common nowadays.


Item 6 in the Orrery Collection is of interest to this blog. It is a 1" objective perspective telescope from 1725.  An image can be found on line at the MHS website but here is the photo I took yesterday.
The perspective, or small telescope, dates from 1725 and has a concave eye-lens as Galileo used. The perspective is made from pasteboard covered with Vellum and the lens holders are made from Ivory. In the cabinet the perspective was no more than 6 inches in length but when extended would have been 9 or 10 inches in length and just over an inch in diameter. A small telescope of this nature is most probably what Ben Johnson is referring to in his masque about Britain's New Bourse Of course by 1725 much better telescopes would have been available for serious study of the night sky but this instrument probably represents something like the early Dutch Trunke that was used by Harriot to observe the Moon. A Dutch Trunke like this was also obtained by Galileo and then improved to make his observations reported in Sidereus Nuncius.  According the to MHS description a perspective is a small telescope and this description would also cover the Digges-Bourne perspective glass or any hand held optical magnification device for distance viewing.
The MHS gets very busy so its best to get there early when it opens at noon to get an unrestricted view of the fascinating items it houses some of which like backstaffs and quadrants which were used as navigational aids by sailors and would certainly have been familiar to William Shakespeare and his audiences (See Merchant of Venice Act II, Scene 5). 

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