A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Pillar sextant: what's in a name?
From: George Huxtable
Date: 2007 Oct 26, 20:34 +0100
From: George Huxtable
Date: 2007 Oct 26, 20:34 +0100
First, I will try to summarise the discussion so far, about whether the usage "pillar-sextant" by E J White referred to a double-frame sextant, separated by short pillars, or to a stand-sextant. I've chosen those names to avoid prejudging the matter. Frank Reed, in [Navlist 3534], Lunar distance accuracy, started this off by referring to the paper from E J White, in the Proceedings of the Royal Society of Victoria, Vol 1 June 1889. It can be found at- http://www.clockwk.com/lunars/ejwhite ==================== and I commented, in navlist 3547- "White uses a Troughton "pillar-sextant" from the early 1800s. That term has been used elsewhere in two different contexts. Occasionally, it's been used for a handheld sextant in which, to save weight, the frame was made from two thin brass sheets, spaced apart by short brass pillars, which should more properly have been called a double-frame sextant, and usually was. Otherwise (and this is the meaning that seems to be relevant here) it's a sextant firmly mounted on a pillar stand, for use on land, not at sea. It is usually arranged so that the whole sextant can be easily rotated about a polar axis, parallel with that of the Earth, just as a telescope can. In this way the two views from the sextant can be aimed appropriately at the two objects (such as Sun and Moon) and then the instrument can be slowly rotated about the polar axis to keep them in view, for as long as desired. That allows the observer to perfect the alignment of the two bodies taking as much time as he wishes, and then time the result, without being constrained by the lasting-power of his arm muscles. It aso allows the sextant itself to be larger and therefore heavier that a handheld instrument could be. It would have been intended for measuring precise longitudes from on land (just as Evans was doing) in exploration, and perhaps also for measuring star-to-star distances in sky surveys. One would expect the ultimate in precision when using it. " ====================== Frank Reed  replied- "You mention that the phrase "pillar sextant" sometimes referred to a sextant mounted on a stand. And I don't think that's true in the first place. I haven't found a single case of this usage in the lit. Do you know of one? As a corollary, is it possible that it's only you (and maybe a local museum in Oxford which you mentioned once before) that refer to a sextant on a stand as a "pillar sextant"? In the period, the term was used for the well-known double-frame design, originally patented by Troughton. For example, in Lecky's sextant buying suggestions, he writes, "Give the preference to a "pillar" sextant over one whose framework is cast all in one piece" (Lecky's Wrinkles in Practical Navigation, 1884, via Google Books). " ==================== My reply (navlist 3574), included this, about a stand-sextant- "I can't recall having seen such an instrument in a textbook, so if anyone discovers such a reference, or a picture, I would be pleased to learn about it. Perhaps they can be found in museum catalogues, if we can discover the name they are listed under (which is the problem we're trying to solve). I will consult a helpful expert at Greenwich. For our present purpose it would be useful to consult a contemporary Troughton sales catalogue, if such a thing exists. I will ask if it does. So I return to Frank's comment "I haven't found a single case of this usage in the lit." . Does he know of ANY such reference in the literature to such an adaptation of the sextant on a stand, under any other name, then? I would like to discover more. There is no doubt such instruments existed, as I have seen two of them. And we can deduce what they were probably intended for, simply by looking hard at them. They could have been more common in that nineteenth-century heyday of exploration." and referring to that quote from Lecky, I conceded- "Well from those words of Lecky's in that earlier edition, his meaning of the term becomes quite clear." and also conceded- "And if that design was patented by Troughton, under the name "pillar sextant", then White's meaning is also clear, and my interpretation of his words was wrong." However, in the light of additional evidence (see below) it now seems likely to me that my original interpretation of White's meaning, when he wrote pillar-sextant, may indeed be correct. ========================= Wolfgang Köberer, in navlist 3571, gave a pointer to the stand-sextant, held in the Science Museum, London, at- http://www.sciencemuseum.org.uk/objects/astronomy/1931-95.aspx The picture of it is attached here. and Michael Daly perceptively noted, in 3587, "Ah yes - a double frame (pillar) sextant on a stand (pillar) - that ought to clear things up! :-)" ============================== The Science museum describe it on their webpage as- "Double A-frame sextant of 12-inch radius, 1788-1803." The same instrument is described elsewhere on their website as- "English sextant with pillar stand, 1788-1804." In both cases it's attributed to the Troughtons. And you will notice that the only use of the word "pillar" is in relation to the stand, not the frame. White used these words- "The instrument was a pillar sextant, Troughton No. 1139, it was made at the beginning of this century, and has been in my possession nearly forty years ..." The fact that it's a Troughton instrument doesn't help a lot, because we see that Troughton was responsible for production of BOTH double-frame sextants and stand-sextants, as that picture shows. We have to fall back on the context. Those words came, not from a mariner, but from an astronomer, writing a paper in a scientific journal, about on-land observations. He uses the word "pillar" as though it's relevant: if it just referred to how the frame of his sextant had been assembled, it would have been irrelevant to that readership. In two museums, similar instruments to our stand-sextant have the word "pillar" attached, and indeed, when you look at the instrument itself, pillar is just the word that comes to mind. And White was writing from a young colony, in which just such instruments would have been carried about by surveyors in the serious business of mapping that new territory from the beginning of the century, the date of his own instrument and that in the Science Museum. To me, that evidence seems pretty strong, and the fact that Lecky chose to use the same word for something different seems irrelevant. We need stronger contrary evidence than that. George. contact George Huxtable at george---.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 unsubscribe, send email to NavListemail@example.com -~----------~----~----~----~------~----~------~--~---