A National Poetry Day contribution


Visitor notice: We are pleased to announce that Royal Museums Greenwich is reopening. To find out more about which sites will be open and how to plan your visit, click here.

Today is National Poetry Day, which has 'stars' as its theme this year, so it seemed rather appropriate to offer up a 'poem' (more or less) that was published in Lloyd's Evening Post in 1764 (in the edition for September 12-14). The poem is about the 1763-4 sea trials to Barbados to test John Harrison's sea watch (H4), Tobias Mayer's latest tables for determining longitude by lunar distance, and Christopher Irwin's marine chair for observing Jupiter's satellites.

I've not included the footnotes from the original, but it's a nice summary of at least one person's view of what was going on at a crucial time for the history of longitude at sea:

The TRIPLE-SCHEME for finding the LONGITUDE at SEA, truly stated: Or, REMARKS on Mr. HARRISON'S TIME-PIECE, and late VOYAGE to BARBADOES.
Humbly addressed to the PUBLIC.

To aid true judgment, which he thinks no crime,
He thus, for shortness, makes remarks in rhime.

Was e'er this Watch's equal motion prov'd.
From Stars revolving, uniformly mov'd?
It's gain in eight days by th'unequal Sun,
Proves not it's equal gain in ev'ry one:
Nor does it's gain or loss in eight days space,
Prove the same gain or loss in diff'rent place;
Without which equal motion first be shown,
No Longitude can certainly be known.
-- Unequal, if it goes too fast or slow,
The Longitude, in error, must be so.
Various effects, it's equal pace with-hold.
Shocks, gravity, wet, dry, and heat and cold;
Sometimes too slow it goes, and then too fast,
That Longitude, by chance, is found at last.
-- How vain prediction, from each Port, accords
With Longitudes, as taken on mens words!
As those and Latitudes are dark or clear,
At Ship and Port, their distance will appear;
For Longitude for nothing ever serv'd,
But where the Latitude was well observ'd,
From both we shew how far the Port's a-part,
The Navigator's, not Time-keeper's art.
The Seaman in the Latitude steers right
Due West or East until his Port's in sight;
Then running three leagues off, and lying to
'Till morning light, he hits the place most true;
As, in our voyage, we were us'd to do.
So, in return, another might behold,
And make the Lizard, as the brig foretold.
But as to what was done at Surry-stairs,
The public must be judge from what appears;
The Watch examin'd with a friend's regard,
Was found within the Longitude-reward:
-- Tho' this, and others made, must go the same,
On ev'ry voyage --- else the project's lame!
-- If such a Watch will time, at home, decide,
The time, on board, another must divide,
From day to day be often rectified.
The diff'rence of which times, when you descry,
Is the Ship's Longitude to ev'ry eye.
But a Watch-maker must with these be sent,
To keep in order, or cure accident:
For, if these miss the Longitude at Sea,
(While num'rous Ships, for num'rous Watches pay)
The Nation's care and cost are thrown away!
But, if you more prefer the Lunar scheme,
As Maskelyne, and Speculatists seem;
Some gaping for the mammon more than praise,
Exciting wonder, as our mirth they raise!
Two minutes, in degree, if these mis-spy,
(And who can peep out Latitude so nigh?)
Two miscompute-twice two, in time, those crost,
Then all their credit, time, and gain, are lost!
-- But rivals, will each other still offend,
And for a shadow often will contend;
Each vying with the other to be great,
And each one's scheme the other wou'd defeat!
See Irwin's Chair exalted for a while,
O'erpower'd by interest, now is in exile!
Tho' recommended by a noble Lord,
To whom it truth, and pleasure did afford.
An easy, cheap, and certain, simple thing,
That can't above two minutes error bring;
As Jove's first Satellite will give you proof,
Whose known Eclipses are seen oft enough;
Which observations, when improv'd with care,
To thirty miles will tell you where you are.
-- But Truth and Fashion vary like the Times,
Virtues to-day, to-morrow may be crimes!
And what avails it Art or Truth to know,
Without a Friend in Pow'r to prove it so!