Have you ever read A Shropshire Lad, by A.E. Housman? If not, you haven't lived. This collection of poems combines the rural sentimentality of The Deserted Village and Gray's Elegy with a Welt- schmerz born of bitter-sweet experience - as in the case, for example, of the young farm lad whose homeward way proved very hard to wend:
Oh I have been to Ludlow fair/And left my necktie God knows where/And carried half way home, or near/Pints and quarts of Ludlow beer.
Late one foggy night in the early 1930s young Percy Shaw found himself in such a situation.
As he wandered homeward along a country road, he was almost hit by a motor-car approaching from behind.
Because of fog, the car had difficulty keeping to the road, but clearly through the mist in front of him, young Percy spied two bright eyes; it was a cat - and it was the germ of an idea. The eyes of a cat have a very special quality.
Light rays from a distant source entering the animal's eye are brought to a focus on the retina, the surface at the rear of the eye which is, as it were, a screen on to which the images of what it sees project.
Now in the case of some animals, and in particular the cat, the spot illuminated on the retina acts itself as a secondary source of light; light emanating from that spot passes back through the lens of the eye and heads off in the direction whence it came, back towards the distant source.
The cat's eye, when it behaves like this, is not acting like a mirror.
A mirror reflects light in a direction which depends on how the mirror is orientated.
However, in the case of a cat's eye, its spherical construction gives it the unusual property of sending the light back directly towards the source, regardless of the orientation of the eye, or indeed the cat itself.
Percy's brainwave was to replicate cats' eyes in glass, and to implant the devices in roads as an aid to motorists in foggy weather.
His idea was patented in 1934, when he was only 23, and it made him a substantial fortune.
Besides their convenient optical properties, and the attraction that they use no fuel, cats' eyes as designed by Shaw had another feature that was delightful in its sheer simplicity; the protective rubber covering, when depressed by a passing car, slides down like eyelids over the glassy spheres and keeps them clean.
Percy Shaw, inventor of cats' eyes, died 25 years ago tomorrow, on September 2nd, 1976.