NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: the Shovell Disaster
From: George Huxtable
Date: 2007 Nov 14, 18:04 -0000
From: George Huxtable
Date: 2007 Nov 14, 18:04 -0000
Responding to comments from Michael Daly, about Newton's reflecting instrument, Ken Muldrew wrote- | | In 1676 Newton said, "I will resolutely bid adieu to (science) externally, | excepting what I do for my private satisfaction or leave to come after me; | for I see a man must either resolve to put out nothing new or to become a | slave to defend it." This was over his dispute with Hooke over who | deserved the credit for various findings in optics, but it does show that | Newton was not universally held in awe by his contemporaries (at least he | didn't think so). Note from George- If Newton said that in 1676, he was a bit premature, having another 50 productive years ahead of him. And his octant didn't appear until over 20 years later, at its one-and only public mention, noted in the Royal Society's Journal Book for 1699, when Newton referred to it as having been used at sea by Halley. There are many curious aspects to this business of the Newton instrument, discussed in the recent book "Astronomical Minds", by Ted Gerrard. For example, Halley never even mentioned what instrument he used to obtain such precise latitudes, in his three voyages, though it must have been something special, to achieve the results he did. Ted ascribes it to a demand for secrecy from the Admiralty, to keep such knowledge from England's enemies. But it's hard to see the point of also keeping such knowledge from England's instrument-makers and navigators. One aspect that I had hadn't appreciated until reading Ted's book is this: The engraving of the Newton instrument, which is to be found in any book about the history of navigation, was not based on any first-hand knowledge of what that instrument actually looked like. It was an imagined reconstruction, based on a note which Newton had left with Halley, referring to a diagram which no longer exists, of an instrument which had probably not yet been constructed when that note was written.. Indeed, the engraving was based on a drawing that had been made for the Royal Society, based on that note, long after Newton' death, and Halley's too. There are discrepancies between the Newton note, the drawing, and the engraving. So the engraving can't necessarily be taken at face-value; it has to be taken with a pinch of salt, because so many hands have intervened in its production. However, Newton's note itself is very clear, in describing an instrument that has all the necessary features of the double-mirror octant, and its application to lunar distances. It has only one statement I would question, quoted in Appendix 10 of "Astronomical Minds", where he writes- "...to make the observation true, let the star touch the Moon's limb, not on the outside of the limb, but on the inside". George. contact George Huxtable at george@huxtable.u-net.com or at +44 1865 820222 (from UK, 01865 820222) or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To , send email to NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---