Now for something completely different from British television: science lectures for children on the subject of light.

Beginning this afternoon on Channel 26 at 3 o'clock is a 12-part series called "The Natural History of a Sunbeam."

If you own a video recorder, this series is: a) impossible to understand completely without viewing more than once and b) worth taping anyway. It is full of entertaining bits, and moves so fast it can smear the eyeballs, so you won't mind looking at it a second time. All the rest of us will be devoutly wishing we had a recorder, or at least a slow-motion knob that would slow things up.

The show has some pith, and the lecturer's speed is something just shy of supersonic.

As lectures go, this set has far more than most. It has sleight of hand, historical experiments, clear illustrations and a script spiced with humor and lively quotation.

But if these lectures are for children, first we must redefine "children."

Children in this case must mean curious people who have had some basic science classes in school, especially those curious people who, in books or classes, caught only snatches of what was going on and would like better demonstrations of the ideas.

In this lecture, ideas become graphic and clear (if you can follow the lightning speed of a point as it passes by). The lecturer, Sir George Porter, is the director of the Royal Institution in Britain, where the lectures are an annual Christmas event. He punctuates his speech with jokes, magic tricks, little experiments.

Real children of, say, age 8 to 14, however, may be lost immediately even by this lively lecturer. He moves too fast and makes handfuls of references per minute -- to Shakespeare, to historical problems in science, to facts that are unlikely to be known to the American viewer. It is possible that children will like the magic and the experiments, and perhaps catch a point or two even if they can't follow the full explanation.

But WETA made a serious error in scheduling when it put this series on at 3 o'clock in the afternoon. Who is home to watch TV at 3? Only mothers who are likely to be too busy to concentrate on the lectures, as their preschoolers are either diving from furniture or using indelible markers on the walls.

An interesting series of lectures is likely to be lost to all but the tape machine owners.