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I wrote, about Frank Reed's claim, that the age-of-the-tide (interval
between New/Full Moon and spring tide) in Europe was 3 days-

>" Well, I simply ask Frank to supply some evidence to support his own claims
>about that three-day "age", on which he has built such a big argument."

Frank then responded to this request with a big argument about the words
"big argument".

And added this somewhat patronising paragraph-

>So George, do you know how to calculate the "age of the tide" from the
>harmonic constituents for a given port? Do you know how these numbers look for
>various places in Europe and for points in the Americas (which was the original
>relevance of my Bowditch question)? Should I describe how it's done? I've
>considered assembling a map, but it would be a bit time-consuming.

As for the evidence that I asked for; no evidence was forthcoming.

===============

I have tidal predictions for all of Europe (for some earlier years, not
this one) which include some harmonic constants. Being a simple-minded
fellow, I'm quite capable of averaging the interval between the moment of
new/full moon and the predicted spring tide, over a few tides, to get a
rough value for age-of-the-tide at a location, without reference to tidal
harmonics, thank you very much.

But I don't wish to go through that exercise for the whole of Europe, which
is a big place with a long and varied coastline, with very varied tides,
though seen from the USA it may not seem that way. I would be able to
confirm Frank's 3-day claim (or otherwise) if he tells us which parts (or
ports) of Europe it applies to. I don't wish to do the arithmetic for
places and then be told that his assertion didn't apply there.

It is true that in certain European ports a 3-day age of the tide applies.
It's a quantity that is required for calculating shallow-water corrections,
and so the admiralty tide tables quotes the age, but only for those ports
where shallow-water corrections are important. So I am able to tell Frank
that the age of the tide reaches 3 days for Avonmouth (up the Severn, for
Bristol), London Bridge (up the Thames), and Antwerp (up the Scheldt). Note
that these are all at the head of estuaries which contain a resonant (to
some extent) body of water which is likely to add its own lag, or "age". I
can't find any reference to 3-day ages elsewhere, but then the ages are not
stated for ports which are unaffected by shallow-water.

I am not claiming that Frank's assertion is wrong, though my own tidal
experience disagrees with it. All that I ask Frank to do is to tell me
which ports to look at, and I'll look.

Or otherwise explain what his assertion of 22 Dec was based on, as follows-

"In the case of northwest Europe, the result is that the solar tides lag the
lunar tides and Spring Tides occur about three days after New Moon and Full
Moon."

Or withdraw it.

George.

================================================================
contact George Huxtable by email at george@huxtable.u-net.com, by phone at
01865 820222 (from outside UK, +44 1865 820222), or by mail at 1 Sandy
Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
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