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This is a resend of a resend.

Joel Jacobs states that his recent messages to Nav-L have failed to get through, and that seems to
have happened to me also, in my response, followed by a repeat, to Ken Gebhart's posting about
Sumner. And yet, another posting from me about Sumner, responding to Fred Hebard, sent this morning
at 11:19 GMT, has been successfully posted. What is going on?

Below is the message that I sent at 10 33 GMT this morning, once again, hoping that third time will
be lucky.

xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

| Yesterday, 2 Feb, at 15:46 GMT, I posted a reply to Ken Gebhart's question about Sumner's line.
|
| I can always rely on getting such a posting reflected back to me as an email message from Nav-L,
but
| this time it didn't happen.
|
| Chuck Taylor has since sent a posting on that topic, and from that I judge that he didn't receive
a
| copy of my posting either. I wonder if anyone did. Perhaps it has been somehow interpreted as spam
| by the Nav-L input filter. I wonder if Dan Hogan can comment.
|
| Anyway, best I can do is to send it again, as follows-
|
| =====================================
|
| Ken Gebhart wrote-
|
| I am looking for help in understanding something about Thomas Sumner's event during which he
| discovered his line of position.  Space does not permit recounting the details of his situation,
nor
| a drawing of the navigational plot of his attempt to find Small's light.  However, this is covered
| in detail in Bowditch and many other navigational books.  At the very end of the recount it says"
| The DR position was found to be in error by 8 min too far south, giving a longitude of 31 min, 30
| sec too far west.  The result to the ship might have been disasterous had this wrong position been
| adopted". My question is howso?
|
|
|
| Can anyone tell me from historical insight of navigational procedures what course Sumner would
have
| set had he not questioned his first position?  In other words would he have turned to go straight
| through St. George's Channel, or would he have turned to acquire Small's Light first? I can see
that
| the latter choice might have been more dangerous because he would have gone south of Small's
light,
| and his eta would have been upwards of 2 hours late, catching him off-guard when land (or rocks)
| appeared. But there were the Saltees Rocks light and the Tusker Rock light off the coast of
Ireland
| which would have given him some protection had he opted to go straight for the Channel.
|
|
|
| This is not just a pedantic question I have.  I talk about this situation in my seminars to show
how
| his line of position was discovered, but thankfully no one has questioned me about exactly how a
| disaster was averted.  Any comments are welcomed.
|
| ====================
|
| Response from George.
|
| First, Ken should acquire a copy of "Line of position navigation" subtitled "Sumner and
| Saint-Hilaire, the two pillars of modern celestial navigation", by Michel Vanvaerenbergh and Peter
| Ifland, Unlimited Publishing, 2003, $13.99, ISBN 1-58832-068-5. Peter is a member of our list and
| occasional contributor, and also author of that wonderful book about navigational instruments,
| "Taking the stars". His book about the position-line contains, in good facsimile, the complete
text
| and plates of Sumner's original article of 1843, with intelligent explanatory notes, and a host of
| stuff about St-Hilaire's improvements on Sumner.
|
| Please forgive a bit of pedantry to start with. The light Sumner needed to see (well, the
lightHOUSE
| actually, as it was daytime) was not "Small's light", as both Sumner and Ken refer to it, but "The
| Smalls light", named after the lethal group of low rocks and reefs that it protects against.
|
| Sumner's passage was from Charleston (South Carolina) to Greenock (Western Scotland, on the
Clyde),
| via St George's Channel (between Ireland and Wales). He was coming from the general direction of
the
| Azores, and had no observations since about 1500 miles back, except for a single sounding,
| presumably South of Ireland. So, he was relying on his dead reckoning. Sumner had a nice beam
wind,
| from a SouthEasterly direction, but that would have made the SouthEast corner of Ireland, with its
| Tuskar Rocks, a nasty lee shore. Presumably, then, he would wish to keep to the Welsh side of St
| George's Channel, to preserve his freedom to act in an emergency.
|
| Sumner describes the weather as boisterous, and very thick. This is important. The hidden Smalls
| Rocks lie on the Welsh side of the passage, but a ship can readily keep clear of them as long as
she
| can see the lighthouse tower in time. However, if the weather is too thick, unless a vessel is
| heading straight toward that lighthouse, she might sail past without seeing it, and get into the
| middle of those rocks before realising it. There are also other rocks too, further East, off that
| coast.
|
| What Sumner's 10 am position line told him was the exact course to keep to reach the Smalls light.
| As long as he trusted that observation, he could sail straight toward it and be sure he would
reach
| the light before he was in danger from the rocks around it. And so it turned out. The Smalls
| lighthouse was seen "close aboard" (so only just in time). Then, Sumner knew exactly where he was,
| and the rest was easy.
|
| Ken wrote-
| "At the very end of the recount it says" The DR position was found to be in error by 8 min too far
| south," giving a longitude of 31 min, 30 sec too far west.  The result to the ship might have been
| disasterous had this wrong position been adopted". My question is howso?"
|
| It's strange, but I can't find those actual words in Sumner's account. Did he write it out
| elsewhere, I wonder? Or are those Bowditch's's words, perhaps?
|
| Sumner actually wrote- "The Latitude by dead reckoning, was erroneous 8 miles, and if the
Longitude
| by Chronometer had been found by this Latitude, the ship's position would have been erroneous 31
1/2
| minutes of Longitude, too far W, and 8 minutes, too far S. .." The next sentence, that Ken
| attributes to Sumner,  (and may be somewhat over-dramatic) seems to be absent from Sumner's own
| text.
|
| Sumner was describing a common state of affairs round our coasts (as he points out), with bad
| visibility near the horizon but taking advantage of a momentary glimpse of the Sun.
|
| Ken asks what he would have done had he not been able to deduce that "Sumner Line". I think he
would
| have tacked about, standing off and on, to mark time (as he had done the previous night), holding
| position until the weather cleared enough to allow him to tackle the St. George's passage with
| comfidence. I doubt if there was any great imminent danger.
|
| That's my own view, but others may put a different slant on it. It will be interesting to see
what's
| offered.
|
| ==================(end of copy of earlier message)
|
| Chuck Taylor's reply is to-the-point, and we appear to agree completely.
|
| He usefully wrote-
|
|| Sumner's own comments on the situation may be found
|| in his book, reproduced courtesy of the University
|| of Michigan, at
||
|| http://www.hti.umich.edu/cgi/t/text/text-idx?c=moa;idno=AAN0447.0001.001
|
| I was unaware of that copy, and have since taken a glance at it, without downloading the whole
| thing. Perhaps I will do that at a time of cheaper phone rates, as I am on a dialup line.
|
| It doesn't seem identical to the copy printed in full in the Vanvaerenbergh - Ifland book, in that
| (at least) the page numbering seems to differ. Perhaps they are copies from different editions.
What
| I have is a copy of the 1843 edition.
|
| Chuck and I have agreed that the comment-
|
| "The result to the ship might have been disasterous had this wrong position been adopted".
|
| was over-dramatised, and I wonder if he or Ken can tell us where those very words can be found, as
I
| can not locate them in my copy of Sumner.
|
| 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.
|

   

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