Tides and moons in July 1917

luckat

I'm trying to find out about the high tides in Dublin (specifically Skerries) in July 1917, and haven't had a lot of luck.

However, I know that nowadays when the moon is full, the high tide in Dublin is roughly at noon and midnight.

I've found a record of phases of the moon but - and this will seem a horribly ignorant question to anyone with any knowledge of science - is the moon full at every part of the earth at the same time?

If I'm looking at a full moon in Dublin, is someone in Australia also looking at a full moon? (Leaving out the question of daylight, obviously.)

And *is* there anywhere online that has records of the Dublin tides going back that far?

boneless

Newspapers publish the information on tides. Check the issues for the periods in question? National Library holds them.

luckat

I had already tried the Irish Times archive and the tides weren't published then.

boneless

Oh... that's not so good then. I wonder if the Lloyds of London shipping lists contain tidal information? It may be worth a try. Remember though, the First War was on at the time so there may have been restrictions.

Good luck with the research.

tricky D

You can get the tides for Boston MA from this link.

http://tidesandcurrents.noaa.gov/data_menu.shtml?stn=8443970%20Boston,%20MA&type=Historic%20Tide%20Data

Input the date range, select the Six minute WL and click the View Data button. You'll get the tide heights at each six minute interval in the right hand column. Work out when High Tide was for the date/time you're interested in. Then all you have to do is figure out the time difference between Boston and Skerries from the local papers, which should still be more or less the same today as it was 90 years ago.

luckat

Heh, thanks. Boston MA is not that near Skerries, unfortch.

Turns out the Dublin Port archives are now held by a private company, and some of those data may be online at some stage.

tricky D

Read the last sentence.

Find the difference in High Tide times for today from the papers (taking time zones into account) and use that to work out the historical Skerries' HT times from the historical Boston times.

luckat

Tricky D, how would I do that, please? (I'm absolutely hopeless at maths, I should explain - to the extent that I usually pay for things by holding out a handful of change and saying "Take what it costs.")

I did try looking at a week from last year in Boston, thinking "I can go to the Irish Times and see what time the high tide was in Dublin, compared to what it was in Boston", but I couldn't at all understand the spiky diagram that appeared. I'm sorry about this - I didn't study science (they wouldn't let me into the class because I couldn't do decimals) and don't know how to read these data.

I tried changing the settings - for instance, changing to 'Monthly water levels' - but it didn't make things any easier.

All I need to know is what time the high tide was in Dublin on July 9 1917; it's amazing how difficult it is to find out something so simple.

tricky D

No prob. I have you at a disadvantage knowing tides from growing up beside the sea, have lotsa maths and am an engineer so should know how to work this stuff out.

The high tides in Skerries on those days were:

1917 07 10 10:01
1917 07 09 21:37
1917 07 09 09:04
1917 07 08 20:49

That's in British Summer Time which was then in use.

Take away 5 mins for Dublin port.

Method:
Get the old tides for Boston
Compare today's times for Boston and Skerries and estimate time difference
Add the difference to the old tides
Correct for Summer Time
That's the short version

Note that this is only an estimate so I'd allow for 15 mins each way. Tides have so many variables e.g. Boston Harbor today might be a different shape affecting the tide times, the moon might be in a different phase,.. etc.

However the times should be good (hopefully) for your purposes.

hth
\r

brianthebard

Can you not get an old moore's almanac from the archives?

luckat

brianthebard, I don't know who would hold Moore's - or if it goes back to 1917. (Or rather, if it does for Ireland.)

Thanks very much, Tricky. Hmm. That throws my theory a bit. If the high tide was at nine, at 4.30pm it must have been at low tide and turning, which *should* mean that you could actually walk out to Shenick Island. Hmm.

Going on the phase of the moon, I'd taken it that the tide would be at the full and just turning at 4.30pm.

Pgibson

luckat wrote: »

If I'm looking at a full moon in Dublin, is someone in Australia also looking at a full moon? (Leaving out the question of daylight, obviously.)

PERFECTLY simultaneously only if the Earth were made of transparent glass.

As the earth spins around the moon will seem just as full to an Australian's naked eye a few hours after(or before) an Irish person sees it.


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Pgibson

Pgibson wrote: »

PERFECTLY simultaneously only if the Earth were made of transparent glass.

As the earth spins around the moon will seem just as full to an Australian's naked eye a few hours after(or before) an Irish person sees it.

CORRECTING MYSELF !

The comment above applies to New Zealand...but NOT to Australia!

A quick glance at my globe shows me that an Irish person can see a full moon rising (and be fairly high off the Eastern horizon) at THE EXACT SAME MOMENT as an Australian can see it sinking towards the Western horizon in Australia.

"The Great Admit Their Errors."

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