Tide by Hugh Aldersey-Williams

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Reviewed by Terence Jagger

I live close to the tidal Thames, and often walk by the sea – and have never quite understood the tides. Yes, I was taught at school that the moon pulled the water up with gravity, but never really grasped why the high tide should not be at the same time every day, or why there is such a difference between high high tides (springs) and low high tides (neaps), and why some places in the world have massive tides and others have none or negligible ones, and what high tide is measured against … and so on. These are interesting questions, not just because sometimes beaches flood to the cliffs and urbanites get cut off, or landlubbers leave their cars on a dry road near me and find them door deep and electrically dead a few hours later, but also because of their importance for trade and for wildlife – the world’s greatest birdfood buffet is between the high and the low tide marks.

So I turned to this book with great interest and great anticipation. It is a slightly indulgent wander through time, starting with 12 hours and 40 minutes just watching the tide ebb and flood through the creeks of Norfolk, covering myth, history, and increasing scientific understanding, with a smattering of discursions into poetry, natural history and anything else that appeals to the author. The chapters – which are unnumbered – have titles like Beyond the micromareal, Shores of ignorance, A place of resonance. A dry, academic book this is not, and I can’t imagine any reader not finding much to interest and entertain. In Aldersey-Williams’ own words:

In weaving these strands together, strict chronology is occasionally sacrificed for the sake of a thematic connection. The science is, I hope, made simple but not simplistic. This is not a textbook about the tides. It is a book of stories and journeys. I hope you find yourself able to go with the flow. It is always unwise to fight the tide.

So he covers the wise King Canute (the common wading bird, the knot, is called canutus because it walks at the water’s creeping edge and fails to stop the tide) and tidal bores, and he covers gravity from the moon (and the sun), and he writes about increasingly sophisticated tidal forecasting, and he explains why there are ‘amphidromic points’ around which tidal movements revolve, but which have no tides themselves – Messina in Sicily is one, and there are others in the middle of many seas and off many coasts. He talks of Bede, Grosseteste, and Newton and Galileo. He covers the famous and dangerous walk across the sands of Morecambe Bay with a local guide, the Thames Barrier and the acqua alta in Venice, tidal power in Canada and the Maelstrom in Scandinavia. In fact, its hard to think of much he doesn’t cover, so the book is constantly surprising and enlightening.

Here he is, talking about watching a tidal bore on the Shubencadie River in Nova Scotia:

A full moon last night has increased my sense of anticipation … driving [here] I have passed tidal inlets very different from East Anglia with their smooth mud. These channels are vigorously carved out of sand and sandstone, steep-sided and sharply corrugated. We are early – we all know the tide does not wait for man – and an expectant babble has started up. I soon learn there are tidal bores, and there are tidal bore bores. Already chocolate coloured water is swirling at the bridge supports, making whirlpools the size of vases. [As the bore passes] … new sandbars are emerging, their arrival advertised by a flurry of surf as the water falls away. Three eagles … come to catch the striped bass flung up by the bore wave. How do they know it is coming?

And in his concluding chapter, he visits Shingle Street in Suffolk (where I shall be walking on Saturday), a small hamlet where:

Across the pointillist grey and orange and black of the shingle runs a line of bleached whelk shells, one whelk wide, all the way from the water to where the marram grass finally finds a purchase, and the land can be said to begin … who made it, how long has it been here … what is its story? It is interesting to me now because it helps illustrate … the fact that the shingle is not a featureless expanse, but is arranged in seemingly endless stony waves [which] may be read a little like tree rings … each is evidence of a major storm. The place seems haunted. It is history-in-geography laid out in the horizontal sequence of these shingle banks.

As you can tell, this is a generous, full book, which I greatly enjoyed reading and would recommend warmly. But I did have two niggles: in a book which deals sometimes with tricky issues about how the moon and sun relate to the earth and each other, and other complex shapes of land and seabed, why is there not a single map or diagram to help? And why is this romantic, speculative, engaging book illustrated with such muddy and grainy black and white photographs?

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Terence Jagger grew up and still lives within a few minutes walk of tidal water, and would do no other.

Hugh Aldersey-Williams, Tide: The Science and Lore of the Greatest Force on Earth (Viking, 2016). 978-0241003367, 384pp., hardback.

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