That graph is misleading, or at least its annotation is. The physical light level (in lux) varies almost linearly over most of the eclipse, with no sharp dip. It's the subjective brightness that we notice that gives the rather logarithmic shape in that graph. A cube-root-law model fits the eye better, but the shape on a graph looks very similar to logarithmic.

From what I recall, if you don't know there's going to be a partial solar eclipse, even a near miss, you probably won't notice it at all. Even if you are outdoors in bright sunlight, you won't be looking at the face of the sun so as to observe its shape change. The dimming is very slow and subjectively it doesn't darken much. That's why a total eclipse can sneak up on you, until at the last minute the world suddenly goes all dark. That goes for birds too.

 

 
Are you thinking of King Solomon's Mines perhaps?

 
Nobody is mentioning the original War of the Worlds story 

 

What a day for you... Wednesday will provide almost the same depth of eclipse though at a different time of day, perhaps tell the rooks as 1999 will be a bit of a folk memory for them.

It's odd, the amount of light provided by a mostly obscured sun's disk. After the 1999 event, someone kindly provided me with a set of figures from a data logger that they'd set up at Carn Brea (the hill near Land's End rather than the one above Redruth). Despite, subjectively, the light levels dropping during a partial eclipse - while also gaining peculiar qualities - that plunge in light levels during the total phase then comes as more than a bit of a shock - and then, if partly cloudy, the abruptly dynamic appearance of the sky as the shadow tracks across...

Mark

 
A train to Plymouth organised by Pathfinder Tours that we picked up at Bristol. For the actual minute or so of totality, the clouds in the direction of the sun disgraced themselves - two minutes later they parted once more. However, obscured sun aside, the utterly unsettling appearance of everything else - and the behaviour of the wildlife - the eclipsed sun is only a smaller part of the experience and with a complex sky the lighting effects are overwhelming. After which we headed up to Gunnislake and back as that's pretty special too.

From the travel point of view the railway was... busy. A Network Rail helicopter on standby at Exeter, but the only disruption to the Pathfinders train was on the return as someone in the environs of Wellington saw fit to vandalise something (on another train) but management were on standby to sort issues so not much delay from that.

Mark

 
I took the family down to Penzance on Eclipse day 1999. We travelled down on the 06:25 from Exeter - normally a three car unit, but on that day, it was 11 Mark I coaches hauled by a Class 66. As history will tell you, it was cloudy and raining at Penzance, but it still went dark. Had we gone to St Ives or Newquay, the skies were clear!

 
On August 11th 1999, we completed the purchase of our first home in Melksham - No. 404, The Spa - an old semidetached 4 story Bath House from 1814 that was listed (grade 2) and we bought as a wreck.  We stood outside as it went dark in the middle of the day and listened and saw the rooks from the rookery in the neighbouring property start calling and with some concern as it became night-like for the m.

 
I recall seeing the 1999 eclipse from the cliffs very nearly at the southern most point in Devon.  I'm planning to view Wednesday's from somewhere near there too. 
Not being quite a total one, there's not the same level of hype and media lead doom mongering about the inability of the region to cope with the expected influx of visitors which ultimately didn't materialize (probably in part as a consequence of said media overkill). 
It'll be interesting to see how busy it gets where I am.

 
The isolating qualities of train travel aside, the Cornish main line might include nine miles of viaduct but I think we know what the train would be alongside at the crucial moment.

Mark

 
You'd do better looking to be travelling *towards* PNZ at a section with westerly views from the southern windows....between 1900 & 1930 - max at around 1913.

 
Details of the solar eclipse here: the map on this page allows you to pick a location and see precise timings etc (for british summer time, add an hour...).
https://eclipse.gsfc.nasa.gov/SEsearch/SEsearchmap.php?Ecl=20260812

**Raises hat to anyone who was involved in the railway's considerable provision to help bring people to Cornwall-and-a-bit-of-Devon for the 1999 eclipse.**

While this one's not total from there, and the eclipse is toward the end of the day rather than the middle, Land's End is about 300 miles off the path of totality, where the moon's shadow will be tracking along said path at over 2000 miles per hour.

People viewing this from Lands End will have the shadow on the upper atmosphere in plain sight - along with an element of absent reflected light from the ocean - though also looking in the direction of the 96% obscured-but-not-to-be-underestimated sun. Given a clear sky there are likely to be visual effects as the moon's distant umbral shadow passes beneath the deep partial eclipse. Visual effects in the form of a sense of motion, and this may give you thrills, and you may find that they're multiplying. Alas, I suspect that this will not be so noticeable from much further east in the UK, though perhaps...

Lands end being what it is, its worth bearing in mind that Penzance itself is tucked in its bay behind high ground. Away from the rail system, the Lizard is about the same distance from the path of totality and somewhere on its western coast... the environs of Poldhu perhaps... might well offer a better... visitor experience.

Turning to August 12th trains & looking to return the same evening, there are a couple of trains from Penzance up-country as far as Plymouth, but anything further would involve the sleeper. Thoughts extended to the people on the train that leaves at the moment of totality with connections as far as Bristol.... and Yeovil Junction.

Mark