Float and Sink; Light

It took me ages to understand the Archimedes principle; I don't think I really got the hang of it until I started using a hydrometer for wine-making, by which time I was far from young. So the devotion of close on 30 pages to presenting this most basic of ideas to beginners deserves at least careful scrutiny and - as it turns out - commendation too. For Maria Gordon provides a well organised sequence of notions and experiments introducing the concepts of relative density and specific gravity in easy terms. Particularly useful is the classic plasticine ball/bowl experiment to show that, as she puts it, 'dense things can float if you change their shape'.

This simple way with words is effectively used in Light too - for instance 'Light is a sort of energy - we call it energy because it make things happen.' Here we examine various light sources and the rectilinear nature of light waves, and if this is somewhat less entertaining than Float it's probably because the brief is intrinsically easier, though the basic tenets are just as valuable.

The texts are abetted throughout by Mike Gordon's pictures; at first glance rather effetelooking, these actually deliver more than they promise and back up salient points very helpfully.

And of course each volume has a couple of pages of text-related 'notes for adults' but these do little to dull the shine of this pleasant duo from a series which also promises Air and Sound.