A FEW winters ago - well, about thirty - I earned some pocket money by working a couple of weeks in the toy department of a big store. For some reason I was put in the electric train section.It's true that as an even younger person I had been an enthusiastic devotee of Hornby Double-O (a fine gauge of model railway with intricately beautiful rolling stock), spending hours helping my older brother put up the train set on the Ping-Pong table. From the controls, we'd make the trains rattle, generally much too fast, through cow pastures where painted lead cows and sheep grazed on grass made of green-painted sawdust. The trains would surge under bridges, rush daringly through a tunnel, screech un certainly to a halt at stop lights or stations, teeter dangerously at corners, and hazard life and limb at switching points. So when I, as a college student, came to sell to the Christmas public the latest in toy-train technology, I had a background which helped a little. But the thing that I could hardly avoid observing was that most of my customers were not small boys at all, but big ones: The average age was probably about 45. The average demeanor was shy. The average knowledge was staggering. A suited bank-clerk or a tweed-jacketed biology teacher would sidle up to the counter and ask, sotto voce, if we had the latest - and then he would give the complicated details, including obscure identification numbers and letters, of some classic long-distance engine which was so new that it had scarcely left the toy factory yet. He would register the most awful combination of critical distress and distraught incredulity if I was unable to satisfy his demand instantly, from stock. "What do you mean you 'll have to order it? How long will it take?" Here was a man in the grips of an all-absorbing passion. Age could not wither nor custom stale the infinite boy in him. Last weekend, taken by my wife to visit Harrods' toy department in London, I noticed, once again, that it is adults who are drawn to these emporiums supposedly sacred to the delights and desires of children. Around a table a small crowd formed to admire the antics of clockwork chickens hopping dementedly and battery-driven pigs whose noses wrinkled disconcertingly as they perambulated hither and yon, presumably in search of truffles. Not one member of the giggling, wide-eyed crowd was under 25. Behind us an assistant was demonstrating a paper aircraft that however determinedly he flew it away from him returned with boomerang precision to his hand. Two grown-up specimens of humanity were entranced while watching this aeronautic magic. It was with a slight feeling of relief that I eventually caught sight of a three year old careering (as if he too were driven by cunningly concealed clockwork) from one stand of teddy bears to another and showing every sign of being the typical tiny individual for whom all this toy making and toy displaying was actually intended. "Museums of Childhood" that exist in enlightened cities like Edinburgh (on the High Street), Stockholm (hard to locate), Munich (in a corner-tower), and London (at Bethnal Green), bear witness to the astonishing inventiveness that has, over centuries, been applied to toys. And not least among them are all the different kinds of toys that move under their own volition. IN our own age of micro-electronics, we ought, of course, to be blase about the primitive methods by which "automata" were in the 18th and 19th centuries - and in some exceptional cases right back to the years B.C. - made to assume the appearance of kinetic life. But what fascinates a child, regardless of age, changes surprisingly little. The age of clockwork may have long ago outlived itself, but the chickens in Harrods suggest that wind-up toys still have decided appeal. The age of molded plastic may have been with us now for years, but in my book no plastic toy could approach in naive and basic eccentricity a tin toy that I still remember with acute pleasure from my earliest time-wasting days. This was a twisted, undulating figure-eight, an up-and-over-and-under roadway, round and round which a succession of tiny metal cars ran - thou gh "ran" suggests something smooth and well-greased. This toy was wound up by key. I can even feel the key in my fingers now as I turned it, at first too easily, then with greater difficulty, finally with a heroic struggle against fierce resistance until I could turn it no tighter. Then I pushed the tiny metal release handle, and the cars instantly chased each other with zany, nervous celerity, at perfectly spaced intervals, making a noisy rattle, creak, and clatter unlike any other sound known to man. I'm sure I must have played with this toy hundreds of times. In museums of childhood I have encountered versions of it; in fact half the enjoyment of visiting these collections is that you are suddenly face to face (even if a sheet of glass intervenes) with small forgotten experiences. That 10 year olds apparently enjoy these museums as well, suggests either that nostalgia has a shorter time span now than ever or that they are simply enthralled by toys they haven't before encountered because they are no longer made. The glass cases full of toys that move are both fascinating and frustrating. Many of them have become rare and so delicate with age that to operate them might prove disastrous - and of course nobody could be permitted to touch them. There is a good case here, I believe, for the making of modern working replicas. The two "automata" shown on this page which reside in such a glass case in the Bethnal Green Museum of Childhood, London, are doubtless stilled forever. Yet who wouldn't love to see just how "The Great Billiard Player" (a clockwork mechanism made by the German manufacturer Kienberger in 1911) pots his tiny white ball, and whether it ever fails to go down one of the four holes at the end of the table. The hole near his cue-tip must be where the ball (or balls?) reappears, by some Archimedean device, ready for the next shot. And who wouldn't like to tilt the decorative box in which "The Wondrous Leotard," a French trapeze artist who lived from 1830 to 1870 (and who gave his name to a much used dance garment) and watch his indubitably fearless and weightless antics? Unable to touch this rare toy, I can only surmise that it operates on the same principle as other toys motored by falling sand. The hidden system is on the hour-glass principle: trickling sand bearing down on interrelated wheels. I feel certain that neither of the se old toys have lost any of their original magic and that no modern child has seen anything quite like them. Or modern adult, come to that. IN Edinburgh's Museum of Childhood, a similar array of once animated toys is on display. There is a monkey that could be made to climb up strings, a water pumper operated by elastic band, and birds in a cage that sing when the bellows below them is worked. There are all sorts of balancing toys - a paddle steamer, various birds, and a high-wire trapeze performer. Figures arranged on a scissors mechanism. A wooden hen who pecks when a button is pushed. A rocking cow. A push-up toy donkey. (I remember him! His legs are impossibly wobbly and double-jointed!) There are toys that were - when they were subjected to energetic use in some now defunct playroom - made to move by turned handles, by the movement of mercury, by water, by steam, by a rubber bulb that, when pressed, fills them suddenly with air, by articulation (a snake), by momentum and gravity, by metal spring, by static electricity, by a string-pull spinning-top mechanism, by magnets, by weights, and even by being so spindly light of leg that when placed on a piano lid, they would dance as the instru ment was played. And there - I almost missed it - was a tank made from a spool of thread. Good grief - how could I forget? We used to make these at school. A spool, some steel panel pins, a matchstick, and an elastic band through the hole. Twist the elastic until it buckles and bunches and then release your tank - today you're one of the Germans - on the floor or a table top. Come on! Achtung! Here goes all the military might of Rommel's Army in the Desert Campaign! In chaotic competition, the entire class's tanks are jerking and spurting towards the finishing post the Allies versus the Third Reich ... . Oh NO!!! Mine has veered violently to the left and died. No bang. No whimper. Just demise. Vot hes gone wrong? Has zee elastic ge-broken? Have zee pins come loose von zeir moorings? Ach vell! Nussing vor eet - beck to zee dumkopf drawving boart, ya voll, nein, ya?