THE OPTICAL EXHIBITION
IHAVE come away from the Exhibition arranged' by the Optical Convention at South Kensington (which closes to-day, Saturday.) feeling that my eyes and the region behind them have had a very pleasant and rather unusual morning's exercise. - The Imperial College of Science and Technology has always seemed a forbidding, rather desolate place, but there is more in it than meets the eye ; doubtless it - serves a useful purpose ordinarily, and extraordinarily it has provided in this instance a scientific exhibition and popular entertainment nicely and discriminatingly blended. The experiment is to be heartily recommended and I hope it will be repeated.
I saw here the telescope that Nelson placed to his blind eye at Copenhagen and a beautifully embossed Russia leather instrument with which Galileo scanned the sky. In the evening a Phonofilm—that is to say, a talking cinematograph—of Sir William' Bragg was shown, and although I did not have the pleasure of seeing the illusion of that eminent scientist on the screen or of hearing the illusinn of his voice, there were wonders enough of other kinds to fill a very delightful morning.
Downstairs there was a room completely full 'of spectacles, a bewildering forest of opthalmology to the layman—but showing none the less that British makers are more than holding their own in respect of visual appliances. Upstairs were such things as a corneal microscope, automatic skioptometer, refractometers, and . —more intelligible perhaps—fascinating instruments for predicting frost and charting the next day's weather. A daily programme of lectures on optical problems was given,' while some of the special exhibits of optical firms were undoubtedly of interest not only to the man of science but to-other classesOf people as Widely separated as the aeronaut and the shopkeeper. For instance, a new form of a wide-angle aeronautical-photograph sighting telescope, the Aldis, attracted my attention. This remarkable instrument brings within a sharply defined range objects seen below an aeroplane within an angle of 70 degrees, an angle much greater, of course, than that of human vision. Lines indicating the margin of the plate, the central drift line and the photographic axis are seen simultaneously in sharp focus, while the instrument is linked with an indicator in the pilot's cabin so that there can be perfect co-operation between the man flying and the man taking pictures.
The amateur cinema camera of Horton and Butcher for 12 guineas, taking a hundred feet of full-size film, interested me. I wonder more people don't take moving pictures of their children month by month, so that in after years the children will, literally, be able to watch themselves growing up.
But it was naturally the display of optical illusions that interested me most. I am not a scientist nor an inventor, but like everybody else I enjoy seeing my face strangely mirrored with one central Cyclopean eye, or provided with three eyes, or fantastically elongated. And in the room where Mr. Theodore Brown displayed his inventions, I found an ingenious device for exhibiting signs in shop windows so that they hang glittering in mid-air, apparently summoned from the circumambient ether. Here also was a fascinating children's story book which comes to life when looked at through a cardboard disc, so that Jack actually climbs the beanstalk and Little Boy Blue summons his sheep from the meadows.
What a world of delights is this, of illusion incarnate, of the Eastern Maya made almost palpable, yet clinging to that veil which may after all be the ultimate reality ! A bundle' of £1 notes was displayed, with a notice " Please take one," but though visible to mortal eyes they were as evanescent as £1 notes usually are, and the outstretched hand grasped nothing but air and reflexions.
But it was the Intangible Lady who symbolized and summed up for me the meaning of this little world of objects which are rarely what they seem, She looks at you through the proscenium of a Punch and Judy show, a very real and attractive girl with laughing eyes that held me so that I stood rooted to the spot, although I knew in fact that she was not there at all, but somewhere else. I kept returning to this radiant, creature as puzzled and as " vamped " as any cinema character. By creeping round the edge of the box and making my neck elastic, I detected a mirror and in it a reflection of the lower half of the Intangible Lady's face; enormously magnified, but none the less charming. The mystery of her presence I did not discover ; she remained reinote, as our ideals usually are.
Sir Frank Dyson and all concerned in this exhibition are to be much congratulated on providing entertainment and instruction for " high-brows " and " low-brows " alike. It is always a good thing for the world when scientists, without abrogating any of their high purposes, consent to speak so that the uninitiated can understand ; they have a duty to the public like everybody else, and in this case they have amply and generously fulfilled it. I hope the fairies, spectacles, skioptometers and Intangible Lady will be seen in London again next
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